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Geology Talk, Geology













A map of Siberia and Alaska showing Beringia as the tan areas. Image courtesy of the US National Park Service.
A map of Siberia and Alaska showing Beringia as the tan areas. Image courtesy of the US National Park Service.

Beringia: The Siberia to Alaska 'bridge'

An inquiry from a secondary school student about the impact of geology on humans has prompted Bill Langer to revisit the theory behind ‘Beringia’, the supposed ‘land bridge’ between Siberia and Alaska …

A little while ago I received an email from Caty, a Year 7 student at a STEM (science, technology, engineering and mathematics) academy in Wisconsin. Caty was studying geology and how it had changed over the course of time. She asked a number of questions, one of which was: “How does geology influence humans?”

Now, I don’t provide answers to questions from students; I provide ideas for them to consider. I told Caty that during the ice age massive ice sheets locked up water from the oceans, thus making sea level about 120 metres (nearly 400 feet) lower than it is today.

I suggested that Caty look at the Bering Strait between Siberia and Alaska. The average water depth of the Bering Strait is 40m to 50m (130’ to 160’). Therefore, when sea level dropped during the ice age, a land bridge, referred to as “Beringia”, formed as the receding water exposed the sea floor. I suggested Caty look at how Beringia influenced humankind.

Hopefully Caty discovered that the land bridge allowed the forebears of Native Americans to migrate from Asia to North America.

It is believed North Americans’ forebears migrated from Asia via the land bridge.
It is believed North Americans’ forebears migrated from Asia via the land bridge.

When the ice age ended, the vast ice sheets melted and liberated billions of litres of water. Global sea levels rose and Beringia slowly grew smaller and smaller. At the same time, the entire Beringian region grew warmer and moister. When this happened, the shrub tundra vegetation replaced the steppe-tundra plants that had dominated the interior lowlands of Beringia.

As the glaciers receded, new routes opened into North America. Woolly mammoths and other large grazing animals followed the steppe-tundra as it moved off Beringia, and the humans in the region (who were hunter-gatherers) followed the migrating herds into the Alaskan interior and the Yukon. Keep in mind that this took place over centuries, and both the game and the humans slowly spread into new territories.

But time marched on, the glaciers continued to melt, and eventually Beringia disappeared under the sea.

As early as the 1500s, European intellectuals were interested in discovering how humans had populated North and South America. One theory suggested that Norsemen migrated across Greenland into North America. Another theory proposed that human life in the New World generated out of mud.

A more realistic answer came in 1590, when the Spanish missionary Fray Jose de Acosta proposed a land bridge between Asia and North America. De Acosta believed the land bridge was still in existence during his lifetime.

In the 18th century, Danish explorer Vitus Bering proved otherwise. Peter the Great, the Russian tsar from 1682 to 1725, recruited Bering to lead an exploration of the eastern borders of the Russian Empire. Before the expedition, maps of Siberia sometimes contained a large landmass across the water from Siberia to Alaska, in line with what de Acosta wrote. However, Bering’s expeditions in 1724 and 1741 established that there was no land bridge connecting Siberia and Alaska.

On his 1778 expedition, Englishman Captain James Cook confirmed the presence of Alaska and produced detailed maps of the Alaskan coast. The results of his exploration helped enlighten the outside world about the Bering Strait region and lent credence to theories of human migration between Asia and North America.

But it was not until the mid-1920s that scientists would begin to understand how people came to populate North America and ultimately move south out of theArctic region, all the way to Central and South America.

So, Caty, all of this took place thanks to geology.


Author’s note
1. Actually, the story of how the Americas were populated is still open to debate but this article pretty much summarises one prevailing theory.











ABOUT THE AUTHOR
Bill Langer
Independent Research Geologist

Bill Langer is a freelance writer and retired Senior Research Geologist for the U.S. Geological Survey. Bill is now an independent researcher specialising in aggregate resources. Click here to email Bill or visit his website.
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Thursday, 24 October, 2019 2:37am
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