from lake to marsh
Changing nature
Nature often changes so slowly that we are hardly able to perceive the process. The formation of a marsh from a lake provides a good example.
Ancient lakes
The lakes of Sweden were formed after the most recent ice age which ended about 17,000 years ago. Rainwater accumulated in low areas of the bare ground which the retreating ice left behind. Rain water running into a lake carries tiny particles of earth along the way. These particles sink to the lake bottom and form layers of clay.
Life
Before long, the lake is alive with plants and animals – plankton, algae, fish, worms, crustaceans and so on. The remains of dead organisms sink gradually to the bottom and add to the layers of sediment.
Rising sediments
In a lake rich in nutrients and with abundant plants and animals, sediments accumulate rapidly – up to one millimetre every year.
