lena river source：Lena River Sedimentation

Winding 4,400 kilometers (2,800 miles) across northeastern Siberia from its headwaters in the Baikal Mountains, the Lena River is one of the longest rivers in the world. Along the way, the river and its 500 tributaries gather sediment from a drainage basin covering 2.5 million square kilometers and carry it toward the river’s massive delta.

The Lena River Delta is 400 kilometers (250 miles) wide and fans out 100 kilometers (60 miles) into the Laptev Sea. It was formed as river sediments slowly filled in small bays that were created by Arctic Ocean sea-level rise over the past 7,000 years. Each year, the river discharges nearly 550 cubic kilometers (130 cubic miles) of freshwater and more than 20 million metric tons of suspended sediment into the Laptev Sea.

Some of that suspended sediment is visible flowing from beneath a...