The Bering Land Bridge was a land bridge connecting present-day eastern Siberia and the United States' state of Alaska during Earth's historic ice ages. For reference, Beringia is another name used to describe the Bering Land Bridge and it was coined in the mid-20th century by Eric Hulten, a Swedish botanist, who was studying plants in Alaska and northeastern Siberia. At the time of his study, he began using the word Beringia as a geographic description for the area.
Beringia was about 1,000 miles (1,600 km) north to south at its widest point and was present at different times during the Pleistocene Epoch's ice ages from 2.5 million to 12,000 years before the present (BP). It is significant to the study of geography because it is believed that humans migrated from the Asian continent to North America via the Bering Land Bridge during the last glaciation about 13,000-10,000 years BP.
Much of what is known about the Bering Land Bridge today aside from its physical presence comes from biogeographical data showing connections between species on the Asian and North American continents. For example, there is evidence that saber tooth cats, woolly mammoths, various ungulates and plants were on both continents around the last ice age and there would have been little way for them to appear on both without the presence of a land bridge.
In addition, modern technology has been able to use this biogeographical evidence, as well as modeling of climate, sea levels and mapping of the sea floor between present-day Siberia and Alaska to visually depict the Bering Land Bridge.
Formation and Climate of the Bering Land Bridge
During the ice ages of the Pleistocene Epoch, global sea levels fell significantly in many areas around the world as the Earth's water and precipitation became frozen in large continental ice sheets and glaciers. As these ice sheets and glaciers grew, global sea levels fell and in several places across the planet different land bridges became exposed. The Bering Land Bridge between eastern Siberia and Alaska was one of these (animation).
The Bering Land Bridge is believed to have existed through numerous ice ages- from earlier ones around 35,000 years ago to more recent ice ages around 22,000-7,000 years ago. Most recently it is believed that the strait between Siberia and Alaska became dry land (map) about 15,500 years before the present but by 6,000 years before the present, the strait was again closed due to a warming climate and rising sea levels. During the latter period, the coastlines of eastern Siberia and Alaska developed roughly the same shapes they have today (map).
During the time of the Bering Land Bridge, it should be noted that the area between Siberia and Alaska was not glaciated like the surrounding continents because snowfall was very light in the region. This is because the wind blowing into the area from the Pacific Ocean lost its moisture before reaching Beringia as it was forced to rise over the Alaska Range in central Alaska. However, because of its very high latitude, the region would have had a similar, cold and harsh climate as is present in northwestern Alaska and eastern Siberia today.
Flora and Fauna of the Bering Land Bridge
Because the Bering Land Bridge was not glaciated and precipitation was light, grasslands were most common on the Bering Land Bridge itself and for hundreds of miles into the Asian and North American continents. It is believed that there were very few trees and all vegetation consisted of grasses and low lying plants and shrubs. Today, the region surrounding what remains of Beringia (map) in northwestern Alaska and eastern Siberia still features grasslands with very few trees.
The fauna of the Bering Land Bridge consisted mainly of large and small ungulates adapted to grassland environments. In addition, fossils indicate that species such as saber toothed cats, woolly mammoths and other large and small mammals were present on the Bering Land Bridge as well. It is also believed that when the Bering Land Bridge began to flood with rising sea levels during the end of the last ice age, these animals moved south into what is today the main North American continent.
Humans and the Bering Land Bridge
One of the most important things about the Bering Land Bridge is that it enabled humans to cross the Bering Sea and enter North America during the last ice age about 12,000 years ago. It is believed that these early settlers were following migrating mammals across the Bering Land Bridge and for a time may have settled on the bridge itself. As the Bering Land Bridge began to flood once again with the end of the ice age however, humans and the animals they were following moved south along coastal North America.
To learn more about the Bering Land Bridge and its status as a national preserve park today, visit the National Park Service's website.
National Park Service. (2010, February 1). Bering Land Bridge National Preserve (U.S. National Park Service. Retrieved from: http://www.nps.gov/bela/index.htm
Wikipedia. (2010, March 24). Beringia - Wikipedia, the Free Encyclopedia. Retrieved from: http://en.wikipedia.org/wiki/Beringia