Gradual subsidence of terrain along the western coast of Siberia since the end of the last ice age has thwarted the formation of river deltas there, a new study suggests.
When large rivers reach the sea, they slow and drop much of their sediment. As the material accumulates on the seabed, it diverts the river along other paths where it then deposits more sediment, and a classic river delta forms. Many of today's deltas began growing about 8,500 years ago, when global sea level stabilized after the last ice age ended, says Glenn A. Milne, a geophysicist at the University of Durham in England.
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