| 单词 | glaciation |
| 例句 | Every foot of the landscape from here on north would be scored and scarred with reminders of glaciation—scattered boulders called erratics, drumlins, eskers, high tarns, cirques. A Walk in the Woods 1997-11-01T00:00:00Z At the peak of the last glaciation, the modern human population was hit hard, but we survived. Humans may notice a chill in the air 2012-09-29T23:05:01Z If the Wisconsin glaciation buried Manhattan, how much ice would we have been standing under here? When Manhattan Was Mannahatta: A Stroll Through the Centuries 2020-05-13T04:00:00Z If polar bears manage to cling on, there'll be much more room for them in the next glaciation. Humans may notice a chill in the air 2012-09-29T23:05:01Z It’s hard to know for sure about early glaciations because later glaciers rearranged everything, but traces remain. When the Bronx Was a Forest: Stroll Through the Centuries 2020-08-05T04:00:00Z For warm-loving species, the south may provide an important refugium during a glaciation, but a few small populations may also be able to hang on in pockets of suitable habitat in the north. Humans may notice a chill in the air 2012-09-29T23:05:01Z The deep canyons were scraped away during long periods of glaciation. When the Light, Shadow and Stars Aligned: Standing Where Ansel Adams Stood 2023-03-13T04:00:00Z Every age sits in the trough of transition. washed away by the current of change into unknown future, yet shaped by the cirque revealed by past glaciation. ‘The Crown’ Episodes 1 and 2: Stiff Lips, Warm Heart 2016-11-04T04:00:00Z The ridges are gneiss and schist; the valleys, marble, worn down through various glaciation events. When the Bronx Was a Forest: Stroll Through the Centuries 2020-08-05T04:00:00Z For any animals adapted to a temperate climate, glaciations posed something of a challenge. Humans may notice a chill in the air 2012-09-29T23:05:01Z Some time in the past 300,000 years, a population of brown bears clung on through a long glaciation in an isolated northern refugium – perhaps in Ireland. Humans may notice a chill in the air 2012-09-29T23:05:01Z Even for those populations of plants or animals living in a habitable area – or refugium – in the south, survival right through a glaciation is far from guaranteed. Humans may notice a chill in the air 2012-09-29T23:05:01Z But Weidensaul's exhaustively researched and entertainingly written history goes back well before the era of exploration and settlement, all the way to the last period of North American glaciation. 'The First Frontier': the bloody centuries before America's revolution 2012-02-15T22:17:06Z I would have assumed it couldn’t be that old because the cycles of glaciation would have wiped it out, but I guess it’s just so big. Chris Hadfield meets Randall Munroe: ‘Are we alone in the universe?' 2015-11-28T05:00:00Z The paper suggested the Pleistocene era before the Wisconsin glaciation, so perhaps 1.5 million years ago. When the Bronx Was a Forest: Stroll Through the Centuries 2020-08-05T04:00:00Z So just imagine the impact on plants and animals of these switches from long, wintry glaciations to brief, summery interglacials. Humans may notice a chill in the air 2012-09-29T23:05:01Z Battle-scarred by successive waves of glaciation, the hills here are unique in Scotland, enshrined within its first geopark, which was given Unesco status in 2006. Scotland’s best Highland bothy weekend adventures 2020-02-29T05:00:00Z Massive ice sheets covered wide swathes of the continent - reaching as far south as Illinois - amid extensive glaciation. New tests confirm antiquity of ancient human footprints in New Mexico 2023-10-05T04:00:00Z It could have to do with the dynamics of glaciation and sea level change. 'Spirit Whales and Sloth Tales' tracks Washington fossils and their stories 2023-09-15T04:00:00Z It’s not clear what drove our species to the brink of extinction, but Pan and Li suggest long periods of glaciation, cooling sea surface temperatures, or droughts may have played major parts. Human ancestors may have survived a brush with extinction 900,000 years ago 2023-08-30T04:00:00Z The trend held up in a further analysis of dozens more plant genomes, which revealed additional waves of whole genome duplication during periods of climate change or glaciation. Cells with extra genomes may help tissues respond to injuries—and species survive cataclysms 2023-08-23T04:00:00Z As the Paleozoic progressed, glaciations created a cool global climate, but conditions warmed near the end of the first half of the Paleozoic. Fundamentals of Biology 2015-01-01T00:00:00Z These are often called ice ages, and each has included multiple glaciation periods during which glaciers grew on the land. World History: to 1500 2023-04-19T00:00:00Z A new study bolsters the idea that the global glaciation wasn’t all encompassing. Life may have survived far north of equator during ‘Snowball Earth’ 2023-04-04T04:00:00Z Subsequent chapters discuss glaciers and glaciation, take readers on a visit to the ultra-sacred Mount Kailash, and describe the work of various Indian, Tibetan and European scholars and explorers. Review | 2 wonderful new books take armchair travelers to the Himalayas 2023-01-12T05:00:00Z That contributed to a stable climate over the past 10,000 years by counteracting trends of declining carbon dioxide levels that might have triggered another glaciation event. Population growth, climate change create an ‘Anthropocene engine' that's changing the planet 2022-11-16T05:00:00Z Such hot spots align with rare regions of Mars that could have remained ice-free for large swaths of the planet’s ensuing history despite a near-global glaciation from a worldwide cooling event. Life on Mars May Have Been Its Own Worst Enemy 2022-10-28T04:00:00Z That this movement occurred during the start of the most recent glaciation period suggests that climatic changes may have been a motivating factor. World History: to 1500 2023-04-19T00:00:00Z The Balzan citation noted their joint and complementary work on the dynamics of glaciation and ice sheets which has helped to create “more reliable projections of ice sheet behavior related to changes in sea level.” Balzan Prizes honor work in humanities, science 2022-09-12T04:00:00Z Boreal landscapes have thin soils, scraped bare in the last glaciation, that even in a warmer world could scarcely support crops. Review | How to deal with climate refugees? Probably not like this. 2022-09-09T04:00:00Z The main hypothesis for its cause is a period of glaciation and then warming. Biology for AP Courses 2022-06-09T00:00:00Z “Their evolutionary history is pretty much associated with historical climate change and glaciation,” said Dr. Vianna, who recently led similar research but was not involved in the new study. How Penguins Beat the Heat and Went South 2022-07-19T04:00:00Z As sea levels rose following peak glaciation, the water covered these routes in the same way it covered Beringia. World History: to 1500 2023-04-19T00:00:00Z The late Proterozoic “Snowball Earth” glaciations were thought to be sufficiently intense to affect the entire planet. Physical Geology 2015-01-01T00:00:00Z Note that the greatest upward movement occurs in regions affected by recent glaciation, isostatic rebound. An Introduction to Geology 2017-01-01T00:00:00Z It is well known that the North American, and to some degree Eurasian, megafauna, or large animals, disappeared toward the end of the last glaciation period. Biology for AP Courses 2022-06-09T00:00:00Z Inevitably, the eye is drawn to the map’s north and south running lines, which represent the gouging effect of northward-retreating fingers of glaciation. When modern science detects a Seattle Earthquake Zone fault right by your house 2022-04-01T04:00:00Z The ice age of which this glaciation period was a part ended approximately twelve thousand years ago. World History: to 1500 2023-04-19T00:00:00Z This is especially true where glaciation has taken place because glaciers in mountainous terrain create steep- sided valleys. Physical Geology 2015-01-01T00:00:00Z Chronology of latest Pleistocene mountain glaciation in the western Wasatch Mountains, Utah, U.S.A. An Introduction to Geology 2017-01-01T00:00:00Z The average temperatures varied during the Pleistocene as glaciation periods were followed by warm intervals. Biology for AP Courses 2022-06-09T00:00:00Z House concedes that the scenario requires an incredible coincidence of events, and there’s no evidence of glaciation at Gale crater. Mars rover detects carbon signature that hints at past life source 2022-01-16T05:00:00Z It is probably not a coincidence that at approximately the same time Earth entered its last glaciation period, humans began their global expansion. World History: to 1500 2023-04-19T00:00:00Z Because rocks of that age are rare, we don’t know much about the intensity or global extent of this glaciation. Physical Geology 2015-01-01T00:00:00Z The calderas are difficult to see today due to the amount of time since their eruptions and subsequent erosion and glaciation. An Introduction to Geology 2017-01-01T00:00:00Z From their efforts emerged visions of distant future glaciations, climate changes, earthquakes, floods, human and animal population changes, and more. The Art of Pondering Earth's Distant Future 2021-08-13T04:00:00Z The cloud might have blocked sunlight and plunged Mars into a deep freeze, causing widespread glaciation and preventing the light carbon in the rain of cosmic dust from being diluted by other carbon sources. Mars rover detects carbon signature that hints at past life source 2022-01-16T05:00:00Z And not long after Earth reached peak glaciation, the first human migrants entered North America from Siberia, by way of a strip of land exposed by low sea levels. World History: to 1500 2023-04-19T00:00:00Z Late in the Proterozoic, for reasons that are not fully understood, the climate cooled dramatically and Earth was seized by what appears to be its most intense glaciation. Physical Geology 2015-01-01T00:00:00Z Tarns are common in areas of alpine glaciation because the thick ice that carves out a cirque also typically hollows out a depression in bedrock that after the glacier is gone, fills with precipitated water. An Introduction to Geology 2017-01-01T00:00:00Z After the last glaciation, different tree species migrated north at different rates and by different routes. The Idea That Trees Talk to Cooperate Is Misleading 2021-07-19T04:00:00Z There is clear evidence that cicadas were pushed south during the last glaciation event, he said, then expanded their ranges northward again as the Earth warmed. WIDER IMAGE Getting up close with cicadas to find climate change clues 2021-05-26T04:00:00Z On one side of the debate was University of Cincinnati plant ecologist Emma Lucy Braun, who thought that the effects of the glaciation on plant communities were relatively mild. The enduring mystery of Critchfield’s spruce 2021-02-14T05:00:00Z Over the past million years, the glaciation cycles have been approximately 100,000 years; this variability is visible in Figure 16.5. Physical Geology 2015-01-01T00:00:00Z In areas of continental glaciation, the crust is depressed isostatically by crustal loading from the weight of thick glacial ice. An Introduction to Geology 2017-01-01T00:00:00Z Geological evidence shows that both pulses of the extinction were quite abrupt, but glaciation often waxes and wanes over millions of years. Familiar Culprit May Have Caused Mysterious Mass Extinction 2020-06-10T04:00:00Z “Given that there is geological evidence of some glaciation 40 million years ago, it is interesting that the climate still was suitable for coldblooded land-living vertebrates,” Mörs said. Before becoming frozen wasteland, Antarctica was home to frogs 2020-05-01T04:00:00Z He thought the glaciation had sweeping effects on North America's plants. The enduring mystery of Critchfield’s spruce 2021-02-14T05:00:00Z The results of glacial erosion are different in areas with continental glaciation versus alpine glaciation. Physical Geology 2015-01-01T00:00:00Z During the last glaciation, the level of the lake fluctuated many times leaving several pronounced old shorelines in the western portion of Utah including Salt Lake Valley identified by wave-cut terraces. An Introduction to Geology 2017-01-01T00:00:00Z These findings allowed the team to paint a new picture — one that doesn’t discount the glaciation at the time, but suggests that the cooler climate was punctuated by global warming events triggered by volcanic eruptions. Familiar Culprit May Have Caused Mysterious Mass Extinction 2020-06-10T04:00:00Z “Given that there is geological evidence of some glaciation 40 million years ago, it is interesting that the climate still was suitable for cold-blooded land-living vertebrates,” Mörs said. Before becoming frozen wasteland, Antarctica was home to frogs 2020-04-24T04:00:00Z Clark has long advanced a hypothesis that repeated glaciations gradually scoured away soil and other loose grit that would have prevented ice from “sticking” to bedrock. World’s oldest ice core could solve mystery of ‘flipped’ ice age cycles 2019-10-30T04:00:00Z Continental glaciation tends to produce relatively flat bedrock surfaces, especially where the rock beneath is uniform in strength. Physical Geology 2015-01-01T00:00:00Z Chronology of latest Pleistocene mountain glaciation in the western Wasatch Mountains, Utah, U.S.A. An Introduction to Geology 2017-01-01T00:00:00Z The museum’s glaciation of its displays came later, in the 1960s and 70s, he said. Budge up, great white males! MoMA goes global with an explosive $450m rehang 2019-10-16T04:00:00Z Jamie begins in a cave in the West Highlands of Scotland, contemplating glaciations and climate change. Climate and crisis: what survives 2019-09-15T04:00:00Z Some 2.6 million years ago, Earth entered a time known as the Pleistocene, which saw the planet swing in and out of deep periods of glaciation at regular 40,000-year intervals. World’s oldest ice core could solve mystery of ‘flipped’ ice age cycles 2019-10-30T04:00:00Z This valley was filled with ice during the last glaciation, and there has been a net rise in sea level here since that time. Physical Geology 2015-01-01T00:00:00Z A minor glaciation that occurred around 440 million years ago in modern-day Africa is also mentioned by some authors. An Introduction to Geology 2017-01-01T00:00:00Z The extent and rate of human impacts on climate could be deciphered only once natural climate change — glaciations and warmer periods — was fully understood. Making the planetary personal: the roots of climate science 2019-09-16T04:00:00Z Ancient glaciations are easy enough to trace, as are hothouse periods when palms grew near the poles. A 500-million-year survey of Earth's climate reveals dire warning for humanity 2019-05-22T04:00:00Z For example, there were no people in the Americas before the last glaciation. Where Glaciers Melt Away, Switzerland Sees Opportunity 2019-02-14T05:00:00Z If the major currents in the oceans were to slow down or stop, how would that affect the distribution of heat on Earth, and what effect might that have on glaciation? Physical Geology 2015-01-01T00:00:00Z Short-term factors are more recognizable for the most recent Pliocene-Quaternary Glaciation and are most relevant to today’s anthropogenic climate change, but may have taken place in the earlier glaciations. An Introduction to Geology 2017-01-01T00:00:00Z Tyndall’s research built on earlier theories, including those of geologist Louis Agassiz on prehistoric glaciations, and physicist Joseph Fourier on how Earth’s atmosphere traps heat. Making the planetary personal: the roots of climate science 2019-09-16T04:00:00Z The team compared the results to records of past glaciations and found a strong correlation. Rise of carbon dioxide–absorbing mountains in tropics may set thermostat for global climate 2018-12-28T05:00:00Z But repeated glaciations gradually scoured this grit away, and meltwater swept it into the ocean. Seafloor cores suggest sticky, thick glaciers caused mysterious shift in ice age rhythms 2018-08-22T04:00:00Z Deposition in this area was taking place during the late Proterozoic Snowball Earth glaciations, as can be seen in Windermere Group rocks of the Toby Formation from the area south of Cranbrook, B.C. Physical Geology 2015-01-01T00:00:00Z The steady drop in carbon dioxide levels over the past 40 million years, which contributed to the Pleistocene glaciations, is partly attributable to the formation of the Himalayan Range. An Introduction to Geology 2017-01-01T00:00:00Z The episode known as the Last Glacial Maximum extended from 26,500 to 19,000 years ago, and is often thought of as a prolonged time during which glaciation was continuously at its greatest extent1. Ancient ice sheet had a growth spurt 2018-07-24T04:00:00Z There is abundant evidence that fleets of icebergs episodically surged into the North Atlantic during the last glaciation. A fresh take on ancient climate change in the North Pacific 2018-07-10T04:00:00Z Although Earth is considered stable, it has still suffered global glaciations and meteorite impacts — and yet life has survived. Thursday’s Summer Solstice and the Search for Life in the Galaxy 2018-06-20T04:00:00Z Over the past two million years this area — like most of the rest of Canada — has been repeatedly glaciated, and the erosional effects of those glaciations are obvious. Physical Geology 2015-01-01T00:00:00Z The most intense part of the current glaciation is the last 1 million years of the Pleistocene Epoch. An Introduction to Geology 2017-01-01T00:00:00Z It also supports the only other known find to date of the Sturtian glaciation—rocks from northwest Canada that put the onset at about 717 million years ago. Ancient Earth froze over in a geologic instant 2018-06-07T04:00:00Z The onset of a new glaciation could cause the sea level to stop rising. The Sea Is Rising, but Not Because of Climate Change 2018-05-15T04:00:00Z Evidence for Hesperian glaciation along the Martian dichotomy boundary. Timing of oceans on Mars from shoreline deformation 2018-03-18T04:00:00Z Tarns are common in areas of alpine glaciation because the ice that forms a cirque typically carves out a depression in bedrock that then fills with water. Physical Geology 2015-01-01T00:00:00Z Antarctic temperature changes during the last few glaciations compared to global ice volume. An Introduction to Geology 2017-01-01T00:00:00Z Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacific Ocean. Initiation and long-term instability of the East Antarctic Ice Sheet 2017-12-12T05:00:00Z It could even fall 400 feet, to the level at the last glaciation maximum 18,000 years ago. The Sea Is Rising, but Not Because of Climate Change 2018-05-15T04:00:00Z The modern world is already recovering from its own miniature glaciation, the “Little Ice Age”, which lasted from about 1500 to 1850. Why shrinking glaciers could mean more volcanic eruptions 2017-11-30T05:00:00Z Sediments transported and deposited during the Pleistocene glaciations are abundant throughout Canada. Physical Geology 2015-01-01T00:00:00Z For example, in the Pacific Northwest east of the Cascades, a region close to the border of grasslands and forest, a study tracked pollen over the last 125,000 years covering the last two glaciations. An Introduction to Geology 2017-01-01T00:00:00Z The oldest is the Ordovician-Silurian extinction which is linked to mass glaciation leading to rapid cooling and then falling sea levels. Past extinctions point to a current and future biodiversity crisis 2017-07-19T04:00:00Z All this, because it is much warmer now than 12,000 years ago, at the end of the most recent glaciation. The Sea Is Rising, but Not Because of Climate Change 2018-05-15T04:00:00Z That leaves “a gap for the oldest part, which is really the last glaciation before the warming that brought us into the present interglacial,” Sharp says. Unique Canadian ice core collection suffers catastrophic meltdown 2017-04-10T04:00:00Z Figure 16.30 A depiction of the various types of sediments associated with glaciation. Physical Geology 2015-01-01T00:00:00Z They analysed the trigger conditions for a glaciation, like the one that gripped Earth over 12,000 years ago. Carbon emissions 'postpone ice age' - BBC News 2016-01-13T05:00:00Z In particular, the 1.55 meters of bedrock at the core’s base revealed much about the island’s history of glaciation, Schaefer says, in atoms that chronicle exposure to the elements. Greenland was once ice free 2015-12-15T05:00:00Z Dark-eyed and quick-witted, Tyndall was a dazzling figure who drew huge audiences to his public lectures on lively new subjects like glaciation, radiation and sound. The Great Victorian Weather Wars 2015-08-07T04:00:00Z If no GPS stations were present, they used computer models to estimate known changes, such as how some regions continue to rebound from the last glaciation, when heavy ice sheets caused land to sink. Sea level rise accelerating faster than thought 2015-05-11T04:00:00Z Eskers are most common in areas of continental glaciation. Physical Geology 2015-01-01T00:00:00Z At its maximum extent, the last glaciation witnessed a big freeze spread over much of North America, northern Europe, Russia and Asia. Carbon emissions 'postpone ice age' - BBC News 2016-01-13T05:00:00Z Gold-bearing quartz veins—quijo, in Quechua—were first exposed by Pleistocene glaciation, and signs of ancient hard-rock gold mining have been revealed by the retreat of the glaciers. A Fortune at the Top of the World 2015-04-13T04:00:00Z It is also the longest period of globally stable climate and sea level in at least the last 400,000 most recent years of seesaw between glaciation and warmer times. Nuclear Blasts May Prove Best Marker of Humanity's Geologic Record [In Photos] 2015-02-10T05:00:00Z The rate of temperature change is pretty fast this time and we’re heading to be warmer than at any point in this long period of glaciations. The Great Climate Model 2014-10-13T04:00:00Z The periodicity of the Pleistocene glaciations is related to subtle changes in Earth’s orbital characteristics, which are exaggerated by a variety of positive feedback processes. Physical Geology 2015-01-01T00:00:00Z Over the next three years, he studied the obsidian deposits and evidence of past glaciation in the area with geologist Gordon Bromley of the University of Maine. The first South Americans: Extreme living 2014-09-30T04:00:00Z Unwilling to admit they did not grasp the basics of say, glaciation, the self-deceiving candidate glides on the meltwater of injustice to seek a reason for their failure. Best and worst excuses for GCSE pain 2014-08-20T04:00:00Z Molecular studies reveal that nematodes, mites, midges and freshwater crustaceans survived past glaciations. Polar research: Six priorities for Antarctic science Global cooling and glaciations occur for various reasons, the primary one being Earth’s continuously changing position with respect to the Sun, both its distance and tilted orientation during orbit. The Great Climate Model 2014-10-13T04:00:00Z Cool summers — as opposed to cold winters — are the key factor in the accumulation of glacial ice, so the upper scenario in Figure 19.4 is the one that promotes glaciation. Physical Geology 2015-01-01T00:00:00Z “This previously overlooked positive feedback was initiated in the run up to the onset of extensive Northern Hemisphere glaciation,” said the authors. What Started The Ice Ages? Panama 2014-06-30T04:00:00Z A corrie is a basin-shaped feature created by glaciations in the mountains. Scotland 'had a glacier up to 1700s' 2014-01-21T13:00:17Z Greenland isn’t that big for a canyon of that size, and for it to survive in its pre-glacial form after successive glaciations is quite something.” Huge canyon under Greenland ice 2013-08-29T18:00:06Z These orbital properties oscillate on various time scales and periodically the orbital geometries converge to reduce or increase global temperatures sufficiently to initiate glaciation at the poles. The Great Climate Model 2014-10-13T04:00:00Z Since the last glaciation, sea-level rise has been about 125 m; a huge area that used to be land is now flooded by heat-absorbent seawater. Physical Geology 2015-01-01T00:00:00Z These were, at their maxima, among the most extensive glaciations in the Earth’s history. The Cambrian explosion: Kingdom come 2013-03-21T16:02:17Z After this time, significant glaciations occurred in just the high latitudes, and life took off. Alien Life May Not Survive on Planets With Uranus-Like Tilts 2012-02-12T15:15:00.267Z As a result, global temperatures dropped, initiating a cycle of widespread glaciation and melting that, over millions more years, would significantly grind Earth’s surface. Thanks to Plants, We Will Never Find A Planet Like Earth 2012-02-01T11:45:00.243Z The localization of glaciation is assignable to the two great areas of permanent atmospheric depression that have their present centres near Greenland and the Aleutian Islands respectively. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 1 "Gichtel, Johann" to "Glory" 2012-01-11T03:00:20.463Z All three of these volcanoes were active during the last glaciation. Physical Geology 2015-01-01T00:00:00Z These warm winds probably counteracted the cooling effect of glaciation in the lowlands and thereby maintained tropical conditions near the seas. A Distributional Study of the Amphibians of the Isthmus of Tehuantepec, Mexico 2011-12-31T03:00:17.400Z Williams' hypothesis has its own big gap: a mechanism that could have clipped the planet's tilt by about 30 degrees in 100 million years prior to the Earth's oldest confirmed circumpolar glaciation. Alien Life May Not Survive on Planets With Uranus-Like Tilts 2012-02-12T15:15:00.267Z More information is available about the Wisconsinan, or last, glacial age, than about the earlier ones, because the last glaciation in many montane areas destroyed evidence of earlier glaciations. Speciation of the Wandering Shrew 2011-12-22T03:00:30.143Z It is of interest to note that Alaska seems to be free from excessive glaciation, and that a remarkable “driftless” area lies in Wisconsin. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 1 "Gichtel, Johann" to "Glory" 2012-01-11T03:00:20.463Z The characteristics of these various environments, and the processes that take place within them, are also discussed in later chapters on glaciation, mass wasting, streams, coasts, and the sea floor. Physical Geology 2015-01-01T00:00:00Z In the hypsithermal period following Pleistocene glaciation, cottonmouths gradually moved northward occupying areas beyond their present range. Natural History of Cottonmouth Moccasin, Agkistrodon piscovorus (Reptilia) 2011-12-17T03:00:17.963Z Effect of topography on movement.—The effect of glaciation on topography has been sketched, but the topography in turn exerted an important influence on the direction of ice movement. The Geography of the Region about Devils Lake and the Dalles of the Wisconsin 2011-11-29T03:00:17.347Z Wisconsinan glaciation again rendered Canada uninhabitable, and it is quite possible that extensive areas in the Rocky Mountains, the Cascades and the Sierra Nevada were heavily glaciated. Speciation of the Wandering Shrew 2011-12-22T03:00:30.143Z In a similar manner Professor Chamberlin and other American geologists have recognized the following stages in the glaciation of North America: The Champlain, marine substage. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 1 "Gichtel, Johann" to "Glory" 2012-01-11T03:00:20.463Z The most recent of the Pleistocene glaciations ended around 11,700 years ago. Physical Geology 2015-01-01T00:00:00Z Around 34 million years ago, there was an abrupt decline in levels of carbon dioxide in the atmosphere which prompted the glaciation of Antarctica. "Alps under the ice" gives clues to global warming 2011-11-16T18:09:56Z Because of their greater accessibility, the latter offer the better facilities for determining the effects of glaciation. The Geography of the Region about Devils Lake and the Dalles of the Wisconsin 2011-11-29T03:00:17.347Z If this had happened often enough to cause all the glaciations known to geologists, the planetary orbits would be strongly elliptical instead of almost circular. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In Asia the evidences of a former extension of glaciation are traceable in the Himalayas, and northward in the high ranges of China and Eastern Siberia. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 1 "Gichtel, Johann" to "Glory" 2012-01-11T03:00:20.463Z The longest such records can take us back over 25 ka, to the height of the last glaciation. Physical Geology 2015-01-01T00:00:00Z The good news is that students did not do all that poorly: Fifty-six percent of high school seniors knew, for instance, that glaciation formed the Great Lakes. | Arnold Goldstein and David P. Driscoll : A Progress Report on Geography 2011-08-01T00:24:15Z The great depressions, together with the intervening highland, are therefore believed to be responsible for the absence of glaciation in the driftless area. The Geography of the Region about Devils Lake and the Dalles of the Wisconsin 2011-11-29T03:00:17.347Z During the Archeozoic, no evidence of glaciation has yet been discovered. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The maximum glaciation of the Glacial period was clearly centred around the North Atlantic. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 1 "Gichtel, Johann" to "Glory" 2012-01-11T03:00:20.463Z The crust and mantle respond in a similar way to glaciation. Physical Geology 2015-01-01T00:00:00Z Thus it may well be that oxygenation of seawater and other changes in ocean chemistry spurred by the massive global glaciation pulled the trigger on the development of "big life". When Cells Discovered Architecture 2011-06-13T16:15:00.343Z Shape of an erosion hill before glaciation 81 29. The Geography of the Region about Devils Lake and the Dalles of the Wisconsin 2011-11-29T03:00:17.347Z Thus, whenever the sun is near groups of stars we should expect that the earth would show many minor climatic pulsations and stages which might or might not be connected with glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z But since destruction by glaciation no way has been opened for their return. The Chain of Life in Geological Time A Sketch of the Origin and Succession of Animals and Plants 2011-06-01T02:00:24.880Z During glaciation, mantle rock flowed away from the areas beneath the main ice sheets, and this material is now slowly flowing back, as illustrated in Figure 9.18b. Physical Geology 2015-01-01T00:00:00Z During certain periods of this time of intense glaciation great additions of ice-borne d�bris must have been made to the continental shelf. North America 2011-05-05T02:00:20.027Z The streams outside the area of glaciation were less seriously disturbed. The Geography of the Region about Devils Lake and the Dalles of the Wisconsin 2011-11-29T03:00:17.347Z For example, the profound crustal changes at the end of the Mesozoic were not accompanied by widespread glaciation so far as is yet known, although the temperature appears to have been lowered. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z On the Atlantic border, proper glaciation was felt only in the northern part, down to about latitude 40°. The Chain of Life in Geological Time A Sketch of the Origin and Succession of Animals and Plants 2011-06-01T02:00:24.880Z There is also evidence of some shorter glaciations both before and after these. Physical Geology 2015-01-01T00:00:00Z The detached areas of glaciation in the western portion of the United States are here assigned to the Wisconsin stage, but in the Rocky Mountains and Sierra Nevada there are records of two ice advances. North America 2011-05-05T02:00:20.027Z Or perhaps the relief was sculpted by glaciation, and it didn’t matter what the rock landscape looked like before.” Novel Technique Reveals How Glaciers Sculpted Their Valleys 2011-04-04T16:38:00Z Or there might be glaciation in high latitudes, such as that of southern Alaska in the Middle Silurian, and none elsewhere. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z We shall name, for convenience, the parts of this Pleistocene revolution which include the great subsidence and glaciation, the Glacial Age, that extending from the re-elevation to the modern the Post-glacial. The Chain of Life in Geological Time A Sketch of the Origin and Succession of Animals and Plants 2011-06-01T02:00:24.880Z The end of the Cryogenian glaciations coincides with the evolution of relatively large and complex life forms on Earth. Physical Geology 2015-01-01T00:00:00Z Professor Renevier, of Lausanne, has proposed a somewhat different scheme, founded upon the epochs of Swiss glaciation. A Manual of the Antiquity of Man 2011-02-21T03:00:07.080Z Mitochondrial DNA offers strong support for the separation of northern and southern clades, which molecular dating suggests split before the onset of the last glaciation. Editors' Choice 2011-02-03T19:25:02.600Z Yet glaciation is now far less extensive than in the Pleistocene. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z "It shows the extent of the glaciation, which has been very controversial." How to Read a Prehistoric Thermometer 2011-01-27T21:05:13Z Although there may have been some alpine glaciation at this time, there is no longer any record of it. Physical Geology 2015-01-01T00:00:00Z Here he made valuable researches relative to the glaciation of the country. Comrade Kropotkin 2010-12-26T03:00:20.093Z "The fossil record suggests that all of the major eukaryotic groups, with the possible exception of animals, existed before the Sturtian glaciation," Macdonald says. Scientists Find Signs of "Snowball Earth" 2010-03-08T17:03:00Z On the other hand, if the axis were tilted more than now, the winter nights would be longer and the winters more severe than at present, and there would be a tendency toward glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z A scientific discussion of the effect of glaciation upon the character of the people of different portions of Illinois. The Settlement of Illinois, 1778-1830 This further restricted the transfer of heat from the tropics to the poles, leading to a rejuvenation of the Antarctic glaciation. Physical Geology 2015-01-01T00:00:00Z Moreover, the duration of each glaciation during this Ice Age is usually considered to have been much longer than the 10,000 years or so given by the Astronomical Theory. The Geological Story of the Isle of Wight "Our data also suggest that the Sturtian glaciation lasted a minimum of five million years." Scientists Find Signs of "Snowball Earth" 2010-03-08T17:03:00Z The testimony of ancient glaciation as to the slight difference in the climate and therefore in the atmosphere of early and late geological times is almost as clear as that of life. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z We know the height at which snow must have lain permanently during the Glacial period, or during the maximum phase of glaciation. The History of the European Fauna The steady drop in carbon dioxide levels over the past 40 million years, which led to the Pleistocene glaciations, is partly attributable to the formation of the Himalayan Range. Physical Geology 2015-01-01T00:00:00Z Glacial deposits certainly do exist in the Permo-carboniferous formations, which are described under that head, but in the true Carboniferous system glaciation may be taken as not proven. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" Evidences of one of the oldest known glaciations have been found near the summit in the district of Hay. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 2 "Camorra" to "Cape Colony" Under such conditions the theoretical chance of an approach that would cause glaciation is one in 130 million years. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z A few words on the phenomena of glaciation are added before bringing the chapter to a close. The History of the European Fauna Alfred Wegener died in Greenland in 1930 while carrying out studies related to glaciation and climate. Physical Geology 2015-01-01T00:00:00Z It may be regarded as a type area, for the history of its streams and the effects of glaciation are representative of those of the entire State. Drainage Modifications and Glaciation in the Danbury Region Connecticut State of Connecticut State Geological and Natural History Survey Bulletin No. 30 These afford the clearest evidences of glaciation on a great scale in early Carboniferous times. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 2 "Camorra" to "Cape Colony" During the last few decades there has been great interest in ancient glaciation and geologists have carefully examined rocks of all ages for signs of glacial deposits. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The time of maximum glaciation had then passed away; the great glacier which was believed to have invaded the lowlands of Northern Europe had again retreated, before the Siberian mammals made their appearance in Germany. The History of the European Fauna Almost all of Canada and parts of the northern United States were covered in thick ice sheets at the peak of the last glaciation. Physical Geology 2015-01-01T00:00:00Z The present profile of Rocky River and the singular manner in which the lower course of the river is doubled back on the upper course are believed to represent changes wrought by glaciation. Drainage Modifications and Glaciation in the Danbury Region Connecticut State of Connecticut State Geological and Natural History Survey Bulletin No. 30 He has a minute description with map of the Upper Arkansas valley and its glaciation, and of the old lake system of the West. The Galaxy, June 1877 Vol. XXIII.—June, 1877.—No. 6. Late in the Triassic and early in the Jurassic, the climate appears to have been rigorous, although no tillites have been found to demonstrate glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This passage is evidently written by a person familiar with the phenomena of glaciation, and as Captain Aylward's preface is dated from Edinburgh, he has probably seen similar markings in Scotland. Island Life Or the Phenomena and Causes of Insular Faunas and Floras The current hypothesis is that glaciation is favoured at low seasonal differences as summers would be cooler and snow would be less likely to melt and more likely to accumulate from year to year. Physical Geology 2015-01-01T00:00:00Z The evidence shows, therefore, that if Still River has suffered reversal, glaciation is not responsible for the change, and thus the first two hypotheses for explaining the history of the valley are eliminated. Drainage Modifications and Glaciation in the Danbury Region Connecticut State of Connecticut State Geological and Natural History Survey Bulletin No. 30 Much of the grandest scenery is due to glaciation. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 6 "Cockaigne" to "Columbus, Christopher" Since the Indian and the African glaciations of Proterozoic times are as yet undated, we cannot be sure that they are not of the same date as the others. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z North America the marks of glaciation are even more extensive and striking than in Europe, stretching over the whole of Canada and to the south of the great lakes as far as latitude 39�. Island Life Or the Phenomena and Causes of Insular Faunas and Floras Now the marks of recent glaciation showed plainly. Alaska Days with John Muir This divide owes its position to the effects of glaciation. Drainage Modifications and Glaciation in the Danbury Region Connecticut State of Connecticut State Geological and Natural History Survey Bulletin No. 30 One condition of glaciation in the coincidence of winter with the maximum of remoteness from the sun, is present; the other—a high eccentricity—is deficient. A Popular History of Astronomy During the Nineteenth Century Fourth Edition In the other glaciations the evidence is not yet clear. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Perhaps the most striking of all the evidences of glaciation are the grooved, scratched, or striated rocks. Island Life Or the Phenomena and Causes of Insular Faunas and Floras As there is no permanent glaciation on a planet which has lost its water, the snow-cap would melt to a very large extent, and the resultant water must go somewhere. To Mars via The Moon An Astronomical Story A south-flowing Still River, and much less an ancient Housatonic, could not have had its course through this ravine just previous to glaciation. Drainage Modifications and Glaciation in the Danbury Region Connecticut State of Connecticut State Geological and Natural History Survey Bulletin No. 30 The near-by peaks and ridges stood out with dazzling distinction, the glaciation, the drainage, the relation of each part to the others all revealed. The Ascent of Denali (Mount McKinley) A Narrative of the First Complete Ascent of the Highest Peak in North America In Asia numerous ranges also contained large glaciers, but practically all the glaciation was of the alpine type and very little of the vast northern lowland was covered with ice. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z We may be quite sure that glaciation would then be far more severe, and that an ice-sheet corresponding to that of Greenland might extend to beyond the parallel of 50� S. Lat. Island Life Or the Phenomena and Causes of Insular Faunas and Floras As successive terminal moraines result from successive glaciations, so each frontier leaves its traces behind it, and when it becomes a settled area the region still partakes of the frontier characteristics. The Frontier in American History The planet's in the middle of a glaciation, the land surface down to the fiftieth parallel is iced over solid. Space Viking With regard to the Glacial theory propounded by Agassiz, no one welcomed it with greater ardour than Buckland, and he zealously sought to trace out evidences of former glaciation in Britain. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" Then it would be able to cause glaciation at a correspondingly great distance. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This, however, did not prevent the occurrence of local glaciation wherever other conditions led to its initiation, and the most powerful of such conditions is a great extent of high land. Island Life Or the Phenomena and Causes of Insular Faunas and Floras The glaciation hadn't started in the time of the Third Empire. The Keeper Then there had been Imhotep; in twenty or thirty thousand years, it would be a fine planet, but at present it was undergoing an extensive glaciation. Naudsonce As before remarked, all the regions which have been subjected to glaciation are still each year brought temporarily into the glacial state. Outlines of the Earth's History A Popular Study in Physiography The height of the snow line and of glaciation furnishes another means of testing glacial hypotheses. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z No less remarkable is the coincidence of the districts of greatest glaciation with those of greatest rainfall at the present time. Island Life Or the Phenomena and Causes of Insular Faunas and Floras The ship had reached another planet, with vast ice-caps and what appeared to be no more than a twenty-degree-wide equatorial belt where there was less than complete glaciation. Operation: Outer Space Study of ice structure and glaciation was undertaken by Mr. C.S. South with Scott Natural as it may seem to look for exceeding cold as the cause of glaciation, the facts show us that we can not hold this view. Outlines of the Earth's History A Popular Study in Physiography It is well established that in times of glaciation the snow line was depressed everywhere, but least near the equator. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z So in Europe, the Alps and the Scandinavian mountains have excessive rainfall, and have been areas of excessive glaciation, while the Ural and Caucasian mountains, with less rain, never seem to have been proportionally glaciated. Island Life Or the Phenomena and Causes of Insular Faunas and Floras Traces of the subsequent partial glaciation it has been subjected to are also manifested in glacial valleys of considerable depth as compared with the size of the island. Scientific American Supplement, No. 312, December 24, 1881 The backbone of our present system of determining the series of pre-historic epochs is the geological theory of an ice-age comprising a succession of periods of extreme glaciation punctuated by milder intervals. Anthropology Within the field of glaciation, so far as the ice rested bodily on the surface, the rocks were rapidly worn away. Outlines of the Earth's History A Popular Study in Physiography In the Alps and in many other mountains the glaciation of the Pleistocene period appears to have had its upper limit no higher than today. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It seems probable, then, that in all northern lands glaciation would commence when autumn occurred in aphelion. Island Life Or the Phenomena and Causes of Insular Faunas and Floras Now, since these great glaciations have occurred at various intervals in the world's past history, they must depend upon some frequently recurring cause. Falling in Love With Other Essays on More Exact Branches of Science There are abundant evidences of glaciation, and much boulder clay and drift sand covers the older rocks. Encyclopaedia Britannica, 11th Edition, Volume 2, Part 1, Slice 1 Thus the most evident cause of glaciation must be sought in those alterations of the land which affect the movement of the oceanic currents. Outlines of the Earth's History A Popular Study in Physiography Part of the loess overlies the non-glacial materials of the great central plain, but the northern portions overlie the drift deposits of the first three glaciations. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It may be that existing geographical and physical conditions are there such potent agents in producing a state of glaciation that no change in the phases of precession would materially affect it. Island Life Or the Phenomena and Causes of Insular Faunas and Floras On ascending the canyon the glaciation is very conspicuous, and becomes more and more beautiful at every step. The Lake of the Sky Lake Tahoe in the High Sierras of California and Nevada, its History, Indians, Discovery by Frémont, Legendary Lore, Various Namings, Physical Characteristics, Glacial Phenomena, Geology, Single Outlet, Automobile Routes, Historic Towns, Early Mining Excitements, Steamer Ride, Mineral Springs, Mountain and Lake Resorts, Trail and Camping Out Trips, Summer Residences, Fishing, Hunting, Flowers, Birds, Animals, Trees, and Chaparral, with a Full Account of the Tahoe National Forest, the Public Use of the Water of Lake Tahoe and Much Other Interesting Matter Tolima, they could never have got down again, with the assistance of forty glaciations. Life: Its True Genesis Mac was saying a great deal about the Ice Age and the first and second periods of glaciation, but nobody could hear what. The Magnetic North According to the assumptions employed in Table 5 an average single star would influence the sun enough to cause glaciation if it came within approximately 200 billion miles. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Statement modified as to supposed glaciation of South Africa. Island Life Or the Phenomena and Causes of Insular Faunas and Floras The glaciation is distinct also up the sides of the canyon 1000 feet above its floor. The Lake of the Sky Lake Tahoe in the High Sierras of California and Nevada, its History, Indians, Discovery by Frémont, Legendary Lore, Various Namings, Physical Characteristics, Glacial Phenomena, Geology, Single Outlet, Automobile Routes, Historic Towns, Early Mining Excitements, Steamer Ride, Mineral Springs, Mountain and Lake Resorts, Trail and Camping Out Trips, Summer Residences, Fishing, Hunting, Flowers, Birds, Animals, Trees, and Chaparral, with a Full Account of the Tahoe National Forest, the Public Use of the Water of Lake Tahoe and Much Other Interesting Matter The monumental researches of Penck and Bruckner in the Alps have there established four glaciations with mild interglacial periods, but all of these cannot be clearly traced in Britain. The Antiquity of Man Vague and visionary as these speculations must seem to many, to others who are acquainted with the enormous glaciation to which America has been subjected they will appear to be based on substantial truths. The Naturalist in Nicaragua If glaciation is indirectly due to stellar influences, the epochs might fall close together, or might be far apart. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Gregory, F.G.S., of the former extension of glaciers on Mount Kenya 5,000 feet below their present limits, renders probable the former glaciation of the South African Highlands. Island Life Or the Phenomena and Causes of Insular Faunas and Floras Over the lip of this cliff, and in the bed of the canyon above, and up the sides of the cliff-like walls, 1000 feet or more, the most perfect glaciation is found. The Lake of the Sky Lake Tahoe in the High Sierras of California and Nevada, its History, Indians, Discovery by Frémont, Legendary Lore, Various Namings, Physical Characteristics, Glacial Phenomena, Geology, Single Outlet, Automobile Routes, Historic Towns, Early Mining Excitements, Steamer Ride, Mineral Springs, Mountain and Lake Resorts, Trail and Camping Out Trips, Summer Residences, Fishing, Hunting, Flowers, Birds, Animals, Trees, and Chaparral, with a Full Account of the Tahoe National Forest, the Public Use of the Water of Lake Tahoe and Much Other Interesting Matter This last stage of glaciation may have coincided with that of the parallel roads of Glen Roy, spoken of in the last chapter. The Antiquity of Man There were signs of previous glaciation in the form of erratics and many examples of polishing and grooving. The Home of the Blizzard Being the Story of the Australasian Antarctic Expedition, 1911-1914 If the sun were especially active when the terrestrial conditions prohibited glaciation, changes of climate would still occur, but they would be milder than under other circumstances, and would leave little record in the rocks. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The south-westerly anti-trades would also be stronger in the same proportion, and would bring with them a greatly increased quantity of moisture, which is the prime necessity to produce a condition of glaciation. Island Life Or the Phenomena and Causes of Insular Faunas and Floras Now after it has been lying for some time, it will form a crust on top which is sometimes the effect of wind pressure and sometimes—under favourable conditions—of superficial glaciation. Over Prairie Trails On the whole, I conclude that the Glen Roy terrace-lines and those of some neighbouring valleys, were formed on the borders of glacier-lakes, in times long subsequent to the principal glaciation of Scotland. The Antiquity of Man There were no signs of recent glaciation or of ice-striae, though the rock was much weathered, and all the cracks and joint-planes were filled with disintegrating material. The Home of the Blizzard Being the Story of the Australasian Antarctic Expedition, 1911-1914 The only way to get winds and hence precipitation would be to invoke some other agency, such as cyclonic storms, but that would be a departure from the supposition that glaciation arose from cloudiness. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z That high land in an area of great precipitation is the necessary condition of glaciation, is well shown by the general state of the two polar areas at the present time. Island Life Or the Phenomena and Causes of Insular Faunas and Floras The valley of the Merced from the mouth of Yosemite downward is an open valley strewn with huge angular granite rocks and shows no signs of glaciation whatever. Time and Change In like manner the glaciation although identical in kind is on so small a scale in the existing Alpine glaciers as at first sight to disappoint a Swedish, Scotch, Welsh, or North American geologist. The Antiquity of Man It evidently belongs to the valley or to a later stage of glaciation. The Home of the Blizzard Being the Story of the Australasian Antarctic Expedition, 1911-1914 If the storminess became extreme when terrestrial conditions were thus universally favorable to glaciation, it would presumably produce glaciation in low latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z But directly we go back a very short period, we find the superficial evidences of glaciation to an enormous extent over three-fourths of the globe. Island Life Or the Phenomena and Causes of Insular Faunas and Floras My speculation was based upon the former glaciation of the northern temperate zone, and the inference of a warmer period preceding and perhaps following. Darwiniana; Essays and Reviews Pertaining to Darwinism But that the larger part of the glaciation of that country has been supramarine, I am willing to concede. The Antiquity of Man In the north, glaciation is not so marked and, as a rule, coastal areas are free from ice, except for valley-glaciers which transport ice from the high interior down to sea-level. The Home of the Blizzard Being the Story of the Australasian Antarctic Expedition, 1911-1914 Any hypothesis of Permian and Proterozoic glaciation must explain not only the glaciation of low latitudes but the lack of glaciation and the accumulation of red desert beds in high latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Two main causes would bring about this glaciation. Island Life Or the Phenomena and Causes of Insular Faunas and Floras On this continent one species, at least, had reached to the vicinity of its present habitat before the glaciation of the region. Darwiniana; Essays and Reviews Pertaining to Darwinism In Ireland we encounter the same difficulty as in Scotland in determining how much of the glaciation of the higher mountains should be referred to land glaciers, and how much to floating ice, during submergence. The Antiquity of Man Hamaker contradicts our current preoccupation with global warming and makes a believable case that a new epoch of planetary glaciation is coming, caused by an increase in greenhouse gas. Gardening Without Irrigation: or without much, anyway The present cold oceans seem to be the expectable result of the Pleistocene glaciation and of the present relatively disturbed condition of the sun. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The mere geographical position of the southern extremity of America does not seem especially favourable to the production of such a state of glaciation. Island Life Or the Phenomena and Causes of Insular Faunas and Floras The glaciation of most of the central plateau of France will not fail to be recognized by the French geologists, when they pay more attention to the glacial deposits altogether. Mutual Aid; a factor of evolution These erratic blocks of foreign origin are often polished and striated, having undergone what is called glaciation, of which more will be said by and by. The Antiquity of Man Similar deposits prove glaciation in Norway succeeding the pre-Cambrian stage of elevation, and Cambrian glacial drift has recently been found in China. The Elements of Geology If a sudden disturbance threw the solar atmosphere into violent commotion within a few thousand years during Permian times, glaciation might occur as described above, while the oceans were still warm. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Even Mr. Walberg felt an extensive area of glaciation setting in. Merton of the Movies In spite of the fact that glaciation causes swamps and lakes, the proportion of land cultivated in the glaciated areas is larger than in the driftless. The Red Man's Continent: a chronicle of aboriginal America The glaciation of the Scotch mountains was traced by him to the height of at least 3000 feet.* The Antiquity of Man On mountains now destitute of glaciers, but whose glaciation shows that they have supported glaciers in the past, there are found similar crescentic hollows with high, precipitous walls and glaciated floors. The Elements of Geology Moreover, others of undoubted Permian age are probably not strictly contemporaneous with the glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z As for glaciation, I will not venture to express any opinion, for when in S. America I knew nothing about glaciers, and perhaps attributed much to icebergs which ought to be attributed to glaciers. More Letters of Charles Darwin — Volume 2 Moreover glaciation diverted countless streams from their old courses and made them flow over falls and rapids from which water-power can easily be developed. The Red Man's Continent: a chronicle of aboriginal America In later times, however, a school of geologists arose who attributed the glaciation of Britain to land-ice of the Continental or Greenland type. The Antiquity of Man Fjords are found only in regions which have suffered glaciation, such as Norway and Alaska. The Elements of Geology Hence arises the hypothesis that the wind obtained the loess from the flood plains of streams at times of maximum glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z To him the two or three labored guesses that Sir Charles suggested or borrowed to explain glaciation were proof of nothing, and were quite unsolid as support for so immense a superstructure as geological uniformity. The Education of Henry Adams We have considered the Laurentian highland and the glaciation which centered there. The Red Man's Continent: a chronicle of aboriginal America Although highly probable, it cannot yet be regarded as conclusively demonstrated that the Pleistocene glaciations of Europe and of North America were exactly contemporaneous. The Antiquity of Man Stranger still, the geologists of India have discovered extensive areas of glaciation, belonging to this period, running down into the actual tropics. The Story of Evolution The conditions might be favorable for glaciation at latitudes as low as those where the Permo-Carboniferous ice sheets appear to have centered. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Let us now inquire how the cyclonic hypothesis accounts for glaciation in low latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z We have already seen how much the soil was improved by glaciation in Wisconsin and Ohio. The Red Man's Continent: a chronicle of aboriginal America In neither period were all parts of high latitudes glaciated; yet in both cases glaciation occurred in large regions in lower latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It is claimed by continental geologists that certain early Tertiary beds in Bavaria actually prove a similar, but smaller, glaciation in Europe, but this is disputed. The Story of Evolution This would not mean glaciation in high latitudes, however, even when the lands were widespread as in the Mesozoic and early Tertiary. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In all cases the occurrence of glaciation in low and middle latitudes is probably due to the same general causes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Taking everything into consideration it appears that the ancient glaciation of Wisconsin increases the present agricultural output by from 20 to 40 per cent. The Red Man's Continent: a chronicle of aboriginal America If they are magnified still more the result is apparently glacial epochs like those of the Pleistocene, and if they are magnified to a still greater extent, the result is Permian or Proterozoic glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It is unnecessary to-day to explain at any length the evidences by which geologists trace this enormous glaciation of the northern hemisphere. The Story of Evolution Yet within a hundred million years, according to many estimates of geological time, and almost certainly within a billion, there have been at least half a dozen glaciations. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Hence, uplift alone cannot account for extensive glaciation in subtropical latitudes during the Permian and Proterozoic. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z They owe their surpassing richness largely to glaciation. The Red Man's Continent: a chronicle of aboriginal America It has been assumed by Marsden Manson and others that increased general cloudiness would account for the subtropical glaciation of the Permian and Proterozoic. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In North America the glaciation was even more extensive. The Story of Evolution In that case Alpha Centauri is now so near that it introduces a disturbing effect equal to about one-sixth of the effect needed to cause glaciation on the earth. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Therefore, under the hypothesis of general cloudiness there would be no supply of moisture to cause glaciation in low latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The canyons, waterfalls, and geysers of the cordillera share their youth with the lakes, waterfalls, and rapids due to recent glaciation in the east. The Red Man's Continent: a chronicle of aboriginal America We will first consider the terrestrial conditions in the early Permian, the last period of glaciation in such latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It was at one time customary to look out beyond the earth itself for the ultimate causes of this glaciation. The Story of Evolution Most authorities estimate the culmination of the late Wisconsin glaciation as twenty or thirty thousand years ago. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This would tend to produce low temperature and thus make the conditions favorable for glaciation as soon as an accentuation of solar activity caused unusual storminess. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Whether they reached Bering Sea and the Kamchatkan shore before the next epoch of glaciation we do not know. The Red Man's Continent: a chronicle of aboriginal America It must not be supposed, however, that these conditions would absolutely limit glaciation to subtropical latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z On the other hand, we have already, in discussing the Permian glaciation, discovered two agencies which are very effective in lowering the temperature of the earth. The Story of Evolution The actual duration of the various glaciations probably did not vary in so great a ratio as did the intervals from one glaciation to another. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Nevertheless it is not yet possible to determine how warm the oceans were at the actual time of the Permian glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Yet a difference of 100,000 years would be more than enough to allow the fossils to have lived either before or after the glaciation, or in an inter-glacial epoch. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Taken all and all, the Permian glaciation seems to be accounted for by the cyclonic hypothesis quite as well as does the Pleistocene. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It is pointed out, in the first place, that the glaciation seems to have come long after the elevation. The Story of Evolution The absence of glaciation in large parts of the Arctic regions of North America and of Asia makes it certain that low temperature was not the controlling factor. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Their distribution shows that at the time of maximum glaciation the strong winds along the south coast of Ireland were from the northeast while today they are from the southwest. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Nevertheless, fairly extensive glaciation existed much nearer the equator than is now the case. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In considering the localization of Pleistocene glaciation, three main factors must be taken into account, namely, temperature, topography, and precipitation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Yet even under such conditions no glaciation occurred, although in other places, such as parts of Canada and northwestern Europe, intense glaciation occurred where the mean temperature is much higher. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In similar fashion the windward slopes of the Alps, the Caucasus, the Himalayas, and many other mountain ranges suffered extensive glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The topography of the lands apparently had much more influence upon the localization of glaciation than did temperature. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z If the sun were sufficiently active the belt of maximum storminess would apparently pass through the Keewatin and Labradorean centers of glaciation instead of well to the south of them, as at present. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The assumption of a great general lowering of temperature is also not adequate to explain glaciation in subtropical latitudes. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This, however, was not the primary cause of glaciation, for many of the areas which were soon to be glaciated were little above sea level. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In the Arctic lowlands and on the leeward side of mountains, the slight development of glaciation appears to have been due to scarcity of precipitation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z I. The first problem, the localization of the ice sheets, arises from the fact that in both the Pleistocene and the Permian periods glaciation was remarkably limited. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In the southern hemisphere glaciation at low latitudes was less striking than in the northern hemisphere. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Most of their results are the reverse of those which brought on glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z When the ice sheets expanded from the main centers of glaciation, the belt of storms would be pushed southward and outward. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This condition may have been one reason why widespread glaciation does not appear to have prevailed in high latitudes during the Proterozoic and Permian glaciations, even though it occurred farther south. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z According to the older glacial hypotheses the lower temperature which is postulated as the cause of glaciation would almost certainly mean less evaporation over the oceans and hence less precipitation during glacial periods. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Thus, from almost every point of view a mere lowering of temperature seems to be ruled out as a cause of Permian glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Those which apparently brought on glaciation seem to have acted as follows: In the first place the storminess lowered the temperature of the earth's surface in several ways. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Its effect, however, was always to cause glaciation exactly where it would be expected and not in unexpected places as actually occurred. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This would require that the chief source of warmth be the interior of the earth, a condition which the Proterozoic, Permian, and other widespread glaciations seem to disprove. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z On the windward side of mountains, on the other hand, a notable increase in precipitation seems to have led to abundant glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z It would presumably cross another center in Greenland, and then would traverse the fourth of the great centers of Pleistocene glaciation in Scandinavia. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z He considers that the suddenness of the coming of glaciation is one of the strongest arguments against the carbon dioxide hypothesis of glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Since much more is known about the recent Great Ice Age, or Pleistocene glaciation, than about the more ancient glaciations, the problems of the Pleistocene will receive especial attention. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Students of glaciology are more and more thoroughly convinced that glaciation depends on the availability of moisture even more than upon low temperature. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In the present chapter the oncoming of glaciation and the subsequent disappearance of the ice will be outlined in the light of what would be expected according to the solar-cyclonic hypothesis. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In the Rockies, the Cascades, and the Sierra Nevadas glaciation was common as far south as Colorado and southern California, respectively, and snowfields were doubtless extensive enough to make these ranges ribbons of white. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z From what has been said as to temperature and topography, it is evident that variations in precipitation have had much more to do with glaciation than have variations in temperature. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Again, in mountainous regions, such as the glacial areas of Alaska and Chile, the glaciation ought not to be confined to the windward slope of the mountains so closely as is actually the fact. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Hence the cyclonic hypothesis does not accord with the idea of great deposition of loess at the time of maximum glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The sudden coming of glaciation is another problem which has been a stumbling-block in the way of every glacial hypothesis. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z According to the cyclonic hypothesis, however, the suddenness of the oncoming of glaciation is merely what would be expected on the basis of what happens today. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Farther west lowland glaciation was abundant as far south as western Washington. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z According to the solar-cyclonic hypothesis, the Pleistocene glacial period was inaugurated at a time when certain terrestrial conditions tended to make the earth especially favorable for glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Students of glaciation believe that during the last glacial epoch the mean temperature of the earth as a whole was only 5° or 6°C. lower than at present. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Nevertheless, widespread lands, even if they are not all high, lead to climatic conditions which favor glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The next step in our history of glaciation is to outline the disappearance of the ice sheets. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z A constantly growing collection of facts, however, indicates that glaciation does not occur in the two hemispheres alternately, but at the same time. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The second great condition which enabled increased storminess to bring on glaciation was the location of the storm tracks. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In this connection it may be well to consider briefly the most recent hypothesis as to the growth and hence the localization of glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Another important condition in bringing on glaciation would be the fact that when storms are numerous the total precipitation appears to increase in spite of the slightly lower temperature. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In the Pleistocene, however, terrestrial conditions permitted glaciation, and therefore the supposed increase in storminess caused great ice sheets. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The emission of internal heat, however, had probably ceased to be of much climatic significance near the beginning of the geological record, for in southern Canada glaciation occurred very early in the Proterozoic era. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This, as he carefully states, is a very slow process, and cannot of itself lead to anything so sudden as the oncoming of glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The cyclonic hypothesis supposes that increased storminess accounts for pluvial climates in regions that are now dry just as it accounts for glaciation in the regions of the ice sheets. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z There has not been time to erode them away since the Pleistocene glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Moreover, the distribution of the centers of glaciation both in the Permian and Pleistocene periods does not seem to conform to this hypothesis. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z As glaciation is soon succeeded by a mild climate, some agency would then be needed to raise the sun's temperature. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z As to the climatic potency of changes in the lands there is practical agreement among students of climatology and glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z V. The occurrence of widespread glaciation near the tropics during the Permian, as shown in Fig. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Third, the hypothesis calls for the constant and frequent repetition of glaciation at absolutely regular intervals. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z These considerations lead to the conclusion that the carbon dioxide hypothesis and the reversal of the oceanic circulation should be regarded as a tentative rather than a final explanation of glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Hence it seems impossible to avoid the conclusion that the cause of glaciation is still operating with considerable although diminished efficiency. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Another hypothesis, which has some adherents, especially among geologists, holds that the position of the earth's axis has shifted repeatedly during geological times, thus causing glaciation in regions which are not now polar. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Another phase of the vertical distribution of glaciation has been the subject of considerable discussion. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z At the present time there seems to be no way of determining whether the general tendency is toward aridity or toward glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z During the time of maximum glaciation the British Isles stood twenty or thirty feet higher than now and Scandinavia was "considerably" more elevated. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z This in turn is supposed to have caused further expansion of the ice and to have led to full-fledged glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z In view of the fact that rocks of Paleozoic age cover much smaller areas than do those of later age, the three Paleozoic glaciations seem to indicate a relative frequency of glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z For example, they would explain such puzzling conditions as the localization and periodicity of glaciation, the formation of loess, and the occurrence of glaciation in low latitudes during Permian and Proterozoic times. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z But our knowledge of early geological times is extremely limited, so limited that lack of evidence of glaciation in the Archeozoic may have no significance. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The next step in our study of climate is to review the main hypotheses as to the causes of glaciation. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z Second, Croll's hypothesis demands that glaciation in the northern and southern hemisphere take place alternately. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z After each period of continental uplift and glaciation—for such are preëminently the times of complexity—it is doubtful whether the earth has ever returned to quite its former degree of monotony. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z The recent discovery of glaciation in latitudes as low as 30° in the Proterozoic is correspondingly significant. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z |
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