Exploring Ponds and Lake Ponds and Lakes form when water collects in hollows and low-lying areas of land.

Ponds Smaller than lakes Shallow enough for sunlight to reach bottom. Plants/Algae grow throughout. Bottom is covered in mud, weeds, and algae.

Lakes Bigger and Deeper than ponds. Sunlight doesn’t reach bottom. Plants only near shoreline. Few organisms live near bottom. Bottom is made of sand, pebbles, and rock.

5 Ways Lakes Are Formed When river channel loops around. (Oxbow Lake) Depressions created by ice sheets that melted in last “Ice Age” Created by movements in Earth’s crust. When water collects inside the crater of an inactive volcano. Created by PEOPLE when we build a dam across a river. (Lake Lure)

Why do we build lakes? Irrigation for farming Recreation Drinking Water Reservoir: a lake that stores water for drinking.

How do lakes change? In addition to seasonal changes, a lake can undergo long-term changes that may eventually lead to its death.

Seasonal Changes (Lake Turnover) In summer, sun warms the water. This warm water floats on top of the less dense cooler water. In fall as the water cools, it sinks and mixes with the water below. “Turnover.” Lake “turnover” refreshes the supply of nutrients throughout the lake.

Long Term Changes Over time, nutrients build up in a process called EUTROPHICATION. During this process, a lake or pond will eventually become a grassy meadow. To determine the rate of Eutrophication, you measure the amount of dissolved oxygen in the water.

Eutrophication