What is a land bridge?
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Bering land bridge

map showing ocean between russia and alaska
Bering Strait - today there's ocean,
but long ago there was a land bridge

September 2016 - During an Ice Age, when the world is colder, more of the world's water freezes into ice. So less water is in the oceans than before. This makes the level of the oceans lower, like the water in your bath is lower if you let some out. Because the ocean level is lower, more of the land sticks out, like your knees in the bath.

cold ocean and ice
The Bering Strait today, with the land bridge underwater

In some places, this makes islands where before the land had been underwater. In other places, this makes a long bridge of land that connects two different continents. During the last Ice Age, about 12000 BC, there was a land bridge between East Asia and North America, leading from Siberia to Alaska, and most archaeologists think that some people and dogs crossed over this land bridge and began to live in North America at that time.These probably weren't the first people to come from Central Asia to North and South America - the first people may have come in an earlier Ice Age, or they may have come by boat.

The people who crossed on the land bridge probably got stuck in Alaska for quite a while, because giant glaciers were blocking the way south. They could only walk south after the Ice Age ended, when the glaciers melted.

Learn by doing: On a globe, trace the path people followed from Africa to South America
More about the Paleo-Indians

Bibliography and further reading about ice ages and land bridges:

Archaeology : Uncovering the Mysteries of Our Past, by Richard Panchyk (2001). With twenty-five projects, like counting tree rings, and serializing cars from photographs. Includes a project on soil types.

More about the Paleo-Indians
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Professor Carr

Karen Eva Carr, PhD.
Assoc. Professor Emerita, History
Portland State University

Professor Carr holds a B.A. with high honors from Cornell University in classics and archaeology, and her M.A. and PhD. from the University of Michigan in Classical Art and Archaeology. She has excavated in Scotland, Cyprus, Greece, Israel, and Tunisia, and she has been teaching history to university students for a very long time.

Professor Carr's PSU page

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Quatr.us celebrates the victory of the Sioux people and their allies at Standing Rock. Here's more about the history of the Sioux and some of their neighbors: the Mandan, the Crow, the Cree, the Shoshone, and the Paiute. And about global warming.