Question

shown above is great rock, cape cod national seashore, with some of dr. alley's relatives for scale. the rock is metamorphic. the picture includes most but not all of the above-ground portion; the rock goes about as far below ground as above. what is the rock doing here in the middle of cape cod?

Answer 1

Often, landowners along eroding beaches will build groins, which are walls or dams sticking out into the ocean or lake from the beach. Why are these built, and what happens?

1. The landowners are trying to catch sediment from the longshore drift to add to the beach; this can work, but often erosion on the "downstream" side of the groin makes the neighbors