Black sand beaches can be formed by the Earth's weather patterns causing lava to erode into the sandy beaches. The tides help break up the lava that rests on the shallow ocean floor -- turning it into a fine sandy material -- and then will redeposit the sand on the beach.hough black sand beaches are a rare occurrence throughout the world, there are several regions where they are common. Islands that have black sand beaches include Iceland, Hawaii, Indonesia and Polynesia.