Sea Level During The Ice Ages

One thing that does not get discussed very much, but must have had a profound effect on the world that we have today, is the effect of the ice ages on sea level. Consider the following facts: The earth's surface is about 72% water. Glacial ice during the ice ages might have been 2-3 kilometers in thickness. The northern ice cap covers about 10% of the earth's surface today, but that increases to about 30% during the ice ages.

This can only mean that there must have been a drastic drop in worldwide sea levels during the ice ages of from maybe two hundred to five hundred meters. Shallow seas and continental shelves all over the world became dry land.

There is one really curious thing about the extent of glaciation during the ice ages. Almost all major glaciation on land during these times occurs in the northern hemisphere. Even though Antarctica is supposedly the coldest place on earth, there seems to be little of the glacial effects on Australia and southern Africa that can be seen all over North America and Europe. There are some glacial effects on the east coast of Australia, for example, but these are from locally-produced mountain glaciers.

I find that this fact reveals a lot about what goes on in the oceans during the ice ages.

My belief is that glaciers moving to lower latitudes from the polar regions during ice ages can only cross land, not deep water, or they would start to melt. Wide stretches of deep ocean is why Antarctic glaciers do not reshape southern lands in the same way as happens in the north. The ocean between Antarctica and other southern continents is simply too deep to be transformed into land by the water redistribution so that glaciers can cross.

This must mean that the shallow water all around northern Europe becomes land during ice ages. On a physical map of the area, it is easy to see the deep underwater trench all around the southern part of Norway, carved by the movement of vast icebergs. This raises the question of what effect this has on living things in these shallow waters in high latitudes. There seems to be little documentation concerning this question that I can find.

I reason that there must have been a mass exodus of fish and other marine life away from these shallow northern seas that cease to be to the deeper water that remains ocean. But deeper water and shallow water are altogether different environments for marine life. The edible plants at the base of the food chain grow on the sea floor and so are much more accessible in shallow seas. There is practically no plant life below about 180 meters depth because the sunlight on which plants depend cannot penetrate any deeper.

This can only mean that large fish populations in shallow water simply do not survive the move to deeper water that does not become land during the ice ages. We do know that the reason there is a wider variety of plants in North America than there is in northern Europe is because when the glaciers moved southward, some species of plant were blocked from retreating southward by the Alps Mountains. My hypothesis is that marine life must have been affected in a similar way but I can find little writing about this.

Another effect that the removing of shallow seas during the ice ages would have had is to increase the salinity of nearby deeper water that remained ocean. This is because the salt would become more concentrated. This must also have had an effect on life in the sea that I cannot find documented.

Another factor that may have contributed to bringing the ice ages to an end is the effect of the much lower sea level on the precipitation that is necessary to maintain glaciers. Some glacial ice is always melting, but is replaced by more falling snow which gets compressed into ice. If the surface area of the world's oceans is vastly reduced by this redistribution of water then that must mean much less water evaporating to eventually fall as snow to replenish the glaciers.

It might also seem that, since the oceans absorb a lot of carbon dioxide which is a greenhouse gas, with less ocean surface there would be more CO2 in the air to warm the planet and end the ice age. While this may be a factor also, this lack of absorption would be at least partially made up for by the growth of land plants, and their absorption of CO2, on dry areas of former sea bed. There must have been trees and plants and animals on vast areas of land that have since returned to the sea.

Have you ever wondered how people in prehistoric times got to all of the places on earth that they did, without sea-worthy ships? If the sea level of the world's oceans underwent this drastic drop, many isolated lands would then become accessible.

Asians could walk from Siberia to Alaska to populate the western hemisphere and become the native Indians, from the Eskimos to the Inca, over time. Other Asians could walk to Japan and settle there before they were once again cut off by the rising waters at the end of the ice age. Britain and Ireland were a part of Europe without the North or Baltic Seas. One could easily walk from India to Sri Lanka, or across the dry seabed of what is now the Persian Gulf. Prehistoric Greeks could walk to any of the Aegean islands. Italy was joined to Europe to the east over a dry Adriatic Sea. Florida and Mexico's Yucutan Peninsula had much more land than they do today.

Other formerly isolated lands were, if not directly connected by dry land, were brought close enough to settled lands to be crossed by people on primitive rafts or floating logs. This is how Aboriginals got to Australia when the Sunda and Arfura shelves became dry land, joining the islands of Indonesia together and bringing an expanded Australia within rafting distance.

This explains why no prehistoric people ever reached Iceland. It has no original inhabitants, but only the descendents of much later European settlers. It is because the waters around Iceland are deep.

There were migrations of animals also, but this is not the same thing as what I will call "Hemisphere Pairing". The eastern and western hemispheres were once together geologically, and we can see this in the similarities in some animal species which developed separately after the tectonic split.

There is a lot of similarities between camels on one side of the world, and llamas in South America. There are lions in Africa, and cougars in North America. Likewise, there are leopards and cheetahs in Africa and related jaguar in South America. There are monkeys in both hemispheres, but only those in the western hemisphere can grasp with their tails. The reason that wolves are found in both hemispheres is that they can withstand the cold enough to journey from Siberia to Alaska.

The last ice age ended in prehistoric times, about 12,000 years ago. But we can see how it has influenced human civilization. Civilization began in the Middle East and to some extent in the Far East. Notice that the Middle East is mostly desert, which is relatively free of disease in comparison with jungle, and also far enough south to be away from most of the glaciation during the ice age. I do not believe this to be coincidence.