This sediment stays in suspension in the water for a while settling out slowly. If the sedimentation rate is high enough, it can cause the lake to dry up by forcing the water to find a new outlet channel. Lakes varves are a depositional feature found in many glacial lakes. These varves show cycles of the sediment settling out of the lake water. It is possible to tell how long the lake was in existence by counting the varves, usually 1 year per depositional unit.
Rivers often carry glacial sediment from melting glaciers and glacial lakes.
These sediment deposits have a different look to them than those of the lake environment. The river sediments usually have a noticable direction of flow in their bedding as compared to the horizontal lake sediments. They are mostly caused by ice-dammed and subglacial lakes. This is because the increase in temperature helps to erode holes and channels in the ice. This weakens the ice and causes it to break releasing the lake water and glacier ice, forming icebergs.