Can a rock help to prevent soil erosion?
Yes. A rock large enough breaks up the wind. Large numbers of small rocks can be used to retain soil by simply covering it. On Easter Island this was done to help cultivate in high wind areas, it also helps to keep in moisture. Plants grow up between the rocks, sometimes the rocks had to be moved by hand to help the plants. You can also see it in “cap rock” areas. A common type seen in parts of the mid west is shale beds covered by limestones. The limestone protects the shale underneath and you find pillars being held up by the cap rock. Where the limestone fails the erosion of the weak shales beneath is sudden. The final result is a broken up table land with isolated columns and mesas separated by gullies.
