Luanne Kubake, aged 10, of Milwaukee, for her question:

How are lakes made?

We are told that rain and melted snow always flow down t o loin the sea. But there is no rule that says they must get there in a hurry. Same of the water dashes down steep, stony mountains in a great rush to loin the sea. Some dawdles along in slow rivers. Some gets frozen solid for a while in glaciers. Some sinks underground.

A lot of fresh water gets trapped in lakes ‑. but only for a while. A lake is rather like a big bathtub, It has an inlet and an outlet. The bed of a lake is like a basin. The basins of the Great Lakes were hollowed out by the glaciers of the Ice Ages. Crater lake is the hollow crater of an ancient volcano. Sometimes a lake basin is below the level of the sea. Sometimes it is miles above sea level.

Water flows into these basins and makes the lakes. Sometimes it seeps in from underground water. Sometimes it flows in from wells and underground springs. Sometimes It comes in from creeks and rivers. But there is always an outlet to the lake. You may have to walk around looking for it, But there is always a little stream to run off the water when the lake gets too full. Lake water stays fresh because a new supply is always flowing in as the old water runs out.