A very simple visualization of rock folding.

Stress is being applied to a piece of fabric from two sides. Over panels 1 to 4, “mountains” start forming.

See? When I said “very simple” I meant “very simple”. But it does help explain why sometimes rock layers are not nice and horizontal.

Oceanography teachers investigating rock formations on one of the field trips of the “teaching oceanography” workshop in San Francisco in 2013.

This demo works really well with a piece of paper towel, too, especially if that is grabbed from a dispenser in the lecture theatre during the lecture and hence the impression is conveyed that it is a spontaneous visualization rather than one that was carefully planned…