Exercise 3

The lake trough

Most of the lakes near Poznań were created by Sven. Many of them are in troughs cut by the Continental Glacier. To shape these troughs, Sven used subglacial rivers which flowed under huge pressure. They cut many-kilometres-long tunnels in the ground. They were winding and even 100 metres deep! Today these troughs house lakes.

Try to cut a lake trough! Prepare something you can make an imprint in the mat with, like an exercise wheel.

1. Kneel down.
2. Place the wheel on the floor in front of you.
3. Hold on to the handles – keep your arms straight.
4. Straighten your back and roll the wheel away as far as you can.
5. Go back to the starting position.

Notice that after rolling, the wheel leaves a hollow in the mat. If you were Sven, one repetition of the exercise would leave a 1-metre-deep hollow. Repeat the exercise until your lake gets deeper!

Here you can see the depth of some of the lakes:

Jezioro Niepruszewskie – 5 metres

Jezioro Bnińskie – 8 metres

Jezioro Strykowskie – 10 metres

Jezioro Góreckie – 17 metres

Jezioro Kierskie – 37 metres