Anne Helmenstine
Why is the sand so soft and light at Waikoloa? As you can see, Ryan isn't exactly breaking a sweat, even though he is hefting a large chunk of coral. It's much lighter than stone.
When living, many corals are vibrantly colorful. Dead coral bleaches to pink and white. Bleaching is primarily due to exposure to the sun. Ultraviolet light breaks chemical bonds, causing pigment molecules to become uncolored.