For nearly a decade, geologist Dallas Abbott and her colleagues have been trying to prove that an enormous space rock, possibly an asteroid, smashed into the Indian Ocean about 10,000 years ago and created a megatsunami, a set of giant waves that washed over the east coast of Africa. Such a tsunami could have created waves as high as 300 feet (91 meters)—three times larger than the Indian Ocean tsunami in 2004 that left 230,000 dead.

The proof, Abbott contends, lies in sandy wedge-shaped features called chevrons in Madagascar, as well as what might be a deep ocean crater between Madagascar and Australia. The idea is that either a huge impact, or a large landslide from a volcano on the island