describe the leading theory for what causedthe repeatedadvancingand retreatingof glaciers duringthelast iceage
397056
didyoueverhearofaspacebar
762290
Water...\n\n* Liquid water, eg in rivers and coasts (in the sea this is largely caused by the gravitational effect of the moon);\n* Liquid water is a major cause of landslides - soil becomes over-saturated and therefore loses its adhesion to the soil or rock beneath;\n* The action of freeze-thaw where liquid water seeps into cracks, expands when it freezes thereby widening the crack and ultimately splitting rocks apart;\n* Frozen water in the form of glaciers grinding away at mountains;\n\nOther causes of erosion include:-\n* the wind, especially when it blows sand particles with it which erode rocks;\n* the Sun which alternatively heats and cools rocks so that they split in much they same way as freeze-thaw (especially in desert areas);\n* humans - we contribute to many of the above processes by our own actions, eg deforestation prevents the soil from holding as much water so landslides become more likely; over-farming creates deserts which are subject to wind and sun; coastal "management" often results in more rapid erosion of some areas of coastline
1000629
I think it's gonna be real cold.  Like Michigan (where i live).  But no, If it is in fact a ice age, that means that  huge amounts of water  are frozen into glaciers (and because we only have so much water on earth) sea levels will actually go down because water is locked in the glaciers.  Global warming causes glaciers to melt and hence rises sea level.  And by the way, we are still technically in an ice age (we still have huge ice sheets) we are in what's known as an inter-glacial period.  The last glacial maximum was about 22,000 years ago.  Sea levels were so low that humans could walk across dry land from Ireland to Britain then to the mainland of Europe! Check out a map!
734739
Glaciers flow because of gravity.\n\nView this page:\nhttp://www.answers.com/topic/last-glacial-maximum\nFor info and a pic of what the world probably looked like during the last ice age. The grey denotes glaciers. The land (brown) has been adjusted for the drop in sea level and the ocean temperature difference is shown.\n\nThe ocean levels dropped. Much of the continental shelf which is now under water was exposed, dry land. The water that now covers them was locked up in the the glaciers.\n\nAlso look:\nhttp://uk.encarta.msn.com/encnet/RefPages/RefMedia.aspx?refid=461527006&artrefid=761570002&pn=3&sec=-1
1128536
Our current understanding of the long-term climate cycles shows that for the past 800,000 years, periods of approximately 100,000 years’ duration, called Ice Ages, have been interrupted by periods of approximately 10,000 years, known as Interglacials. (We are now about 10,500 years into the present Interglacial.)
674251
An ice age is a period of long-term downturn in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers ("glaciation"). Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this definition we are still in an ice age (because the Greenland and Antarctic ice sheets still exist). More colloquially, when speaking of the last few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and Eurasian continents: in this sense, the last ice age ended about 10,000 years ago. This article will use the term ice age in the former, glaciological, sense; and use the term glacial periods for colder periods during ice ages and interglacial for the warmer periods.\n\nMany glacial periods have occurred during the last few million years, initially at 40,000-year frequency but more recently at 100,000-year frequencies. These are the best studied. There have been four major ice ages in the further past.
879280
Where the glaciers have deposited their till, it will be full of soil and rocks. Plants still can grow, but the rocks get in the way, so raising grazing animals such as cattle is the preferred method of farming. In glacial eroded areas, the soil may have been totally scraped out, leaving rocks and minerals available for open mining. In some cases, there will be some soil deposited that is rich in nutrients, which is good for growing crops.
418848
You are misunderstanding a few different concepts here.  That is a pretty good definition of uniformitarianism...but it's important to understand that mountains are also building as they are eroding. An example of this is the Himalaya; they are sill rising about 3 inches every decade.  Hardly any erosion takes place on the higher peaks - too cold/covered in snow and ice.\n\nAlso, mountains build up in some areas, some areas erode, and many areas (of land) remain little changed (that's where you get your (relatively) young bones.  Many areas of land are also deposition areas that add material on top of old material (that's why you dig up bones and fossils).\n\nCatastrophism is now viewed as a very legitimate factor. Think of asteroid impacts, volcanoes, or the massive flooding caused by the end of the ice ages (do you think that little Colorado River carved the Grand Canyon?).\n\nSo we rectify both by seeing the proper blending of the two - a largely uniform Earth that is infrequently influenced by catastrophes.
603130
Read the article below and you start to understand how variable earth's climate has been and more than likely will continue being.\n\n\n\n\n\n\nClimatologists have used various techniques and evidence to reconstruct a history of the Earth's past climate. From this data they have found that during most of the Earth's history global temperatures were probably 8 to 15° Celsius warmer than today. In the last billion years of climatic history, warmer conditions were broken by glacial periods starting at 925, 800, 680, 450, 330, and 2 million years before present.\n\nThe period from 2,000,000 - 14,000 B.P. (before present) is known as the Pleistocene or Ice Age. During this period, large glacial ice sheets covered much of North America, Europe, and Asia for extended periods of time. The extent of the glacier ice during the Pleistocene was not static. The Pleistocene had periods when the glacier retreated (interglacial) because of warmer temperatures and advanced because of colder temperatures (glacial). During the coldest periods of the Ice Age, average global temperatures were probably 4 - 5° Celsius colder than they are today.\n\nThe most recent glacial retreat is still going on. We call the temporal period of this retreat the Holocene epoch. This warming of the Earth and subsequent glacial retreat began about 14,000 years ago (12,000 BC). The warming was shortly interrupted by a sudden cooling, known as the Younger-Dryas, at about 10,000 - 8500 BC. Scientists speculate that this cooling may have been caused by the release of fresh water trapped behind ice on North America into the North Atlantic Ocean. The release altered vertical currents in the ocean which exchange heat energy with the atmosphere. The warming resumed by 8500 BC. By 5000 to 3000 BC average global temperatures reached their maximum level during the Holocene and were 1 to 2° Celsius warmer than they are today. Climatologists call this period the Climatic Optimum. During the climatic optimum many of the Earth's great ancient civilizations began and flourished. In Africa, the Nile River had three times its present volume, indicating a much larger tropical region.\n\nFrom 3000 to 2000 BC a cooling trend occurred. This cooling caused large drops in sea-level and the emergence of many islands (Bahamas) and coastal areas that are still above sea-level today. A short warming trend took place from 2000 to 1500 BC, followed once again by colder conditions. Colder temperatures from 1500 - 750 BC caused renewed ice growth in continental glaciers and alpine glaciers, and a sea-level drop of between 2 to 3 meters below present day levels.\n\nThe period from 750 BC - 900 AD saw warming up to 150 BC. Temperatures, however, did not get as warm as the Climatic Optimum. During the time of Roman Empire (150 BC - 300 AD) a cooling began that lasted until about 900 AD. At its height, the cooling caused the Nile River (829 AD) and the Black Sea (800-801 AD) to freeze.\n\nThe period 900 - 1200 AD has been called the Little Climatic Optimum. It represents the warmest climate since the Climatic Optimum. During this period, the Vikings established settlements on Greenland and Iceland. The snow line in the Rocky Mountains was about 370 meters above current levels. A period of cool and more extreme weather followed the Little Climatic Optimum. A great drought in the American southwest occurred between 1276 and 1299. There are records of floods, great droughts and extreme seasonal climate fluctuations up to the 1400s.\n\nFrom 1550 to 1850 AD global temperatures were at their coldest since the beginning of the Holocene. Scientists call this period the Little Ice Age. During the Little Ice Age, the average annual temperature of the Northern Hemisphere was about 1.0 degree Celsius lower than today. During the period 1580 to 1600, the western United States experienced one of its longest and most severe droughts in the last 500 years. Cold weather in Iceland from 1753 and 1759 c
402321
I was told that it was becuase of the mountains.The ice or snow of mountains would melt into water,forming small rivers that turn into more and more bigger rivers{or something like that} that turn into oceans."Where does the snow of a mountain or ice of a mountain come from?",you might ask.That I dont know.
193598
well, there is the theory of plate tectonics which tells us that the earth's crust is comprised of plates that converge, spread, subduct,  and slide with one another.  This is the main culprit of orogeny, which is mountain building.  Then you have to consider weathering which is performed mainly by wind and water, ie..rivers, lakes, streams, ocean currents and tides.  Once that has taken place erosion takes effect and carries the weathered material away and deposits it somewhere else.
46345
During the ice age a large glasher cut tho the landscape\nand then the glashers melted and wind and water did the rest !
1093172
Due to the weight of the glacier the ice at the bottom melts.The water is under great pressure and is forced through cracks in the ice eventually forming tunnels.Bacteria,spores and pollen have been found in glacial ice.
806684
Glacier movement.  The links go into more detail.
211211
You need to think about this in terms of the question, that is what one of these processes involves movement of sediment.\n\nWeathering does involve movement of sediment, since weathering includes lots of processes that break down rocks into smaller particles or even dissolve rocks. Dissolution of limestone by carbonic acid in water is weathering that 'moves' rock. Freeze-thaw weathering of sandstone breaks the sandstone into smaller particles that are carried away by water, gravity, and wind. \n\nDeposition is the end result of the process of moving sediment, and may be the only one that does not answer your question, but because it is part of the process of 'moving' sediment it probably counts. \n\nErosion definitely moves sediment. Soil, sand, and rock are eroded by moving water and transported to new locations. \n\nAbrasion results in 'moving' sediment. Glaciers abrade underlying rock and grind it into small particles. Wind blows sand grains against rock and abrades it and reduces it to smaller particles. \n\nI think the only correct answer here is "all of the above.”
566098
i think it might of been the start of the extinction and possibly other factors as well.   through out time animals adapt so it is possible that the meteor hit along with the rapid climate change caused this all the happen or appear to happen at once.   how do we know that the extinction was not already in progress before the meteor hit.   i don't think we will ever know.   Science is fact and a little bit of art when they come up with these ideas.
536734
Alfred Wegener, German meteorologist, was gathering climate information with a partner when he started noticing glacial deposits that matched on different continents.\n\nThis led to more study of course. Why were similar deposits found in such far removed places?\n\nWhile looking into this, he also noticed that rocks & fossils on different continents were also identical.\n\nThis, along w/ the "continent puzzle" led to his hypothesis of continental drift. Notice, it is referred to as a hypothesis. This is because Wegener could never provide a driving mechanism for continental drift.\n\nWegener tried explaining how continents could move but to no avail. His explanation that the continental crust literally plowed through oceanic crust did not "cut" it. PUN intended. This was not possible w/o leaving torn crustal plates behind & there was no evidence of that.\n\nMost scientists rejected his hypothesis. Some, however, kept searching for the "driving mechanism" behind continental drift.\n\nIn 1968, scientists could finally provide this force behind the movement of the crust. It was named the theory of plate tectonics.\n\nThis theory stated that the earth's crust was broken down into many major & minor lithospheric plates. These plates moved due to uneven heating of the molten magma in the earth's mantle.\n\nConvection currents w/in the mantle are created by cooler magma sinking & hotter magma rising. As the hotter magma rises towards the asthenosphere, it will cool & then sink. This principle works in the same manner as it does in the atmosphere.\n\nPlates were either pulled apart at divergent boundaries or subducted at convergent boundaries unless it is at two continental convergent boundaries. In this case the two crusts are less dense than the magma below & will deform rather than be subducted.\n\nSo yes, Alfred Wegener did suggest the theory of continental drift. But it was not actually taken seriously until the theory of plate tectonics came along.