You can investigate a soft rock cliff by using a tank and some sand.

Place the tank on a book, so that it slopes gently. Now make some sand moist and pack it against the upper side of the tank, as though you were making a sandcastle.

Put some water in the tank, making sure you keep it clear of the sand. When you finish adding water it must be just below the bottom of the sand.

You can make waves in the water by moving a 30cm ruler up and down in the water.

Watch what happens as the water waves break against the bottom of the soft sand-rock cliff.