Mega-Landslide Could Shake Hawaii

April 25, 2008 -- Every 100,000 years or so, something gives way on the island of Hawaii, producing the largest landslides on Earth.

Aside from burying everything in their path, the landslides might also launch huge tsunamis that travel across the Pacific. Such mega-slides of the past are obvious to oceanographers mapping the undersea slopes of all the Hawaiian islands.

But with Hawaii's population tipping 1.3 million, not counting tourists, what of the next mega-landslide?

Researchers testing rocks from a core drilled more than 10,000 feet (1.9 miles) into the island of Hawaii think they see just the sort of weak rocks that could serve as a surface for a gigantic landslide. The rocks are loose, ground-up glass still being made today when lava flows from a volcano to the ocean, is quenched there, and then ground and churned by waves.

"Basically, we're looking at a pile of glass," said Donald DePaolo, director of the Center for Isotope Geochemistry at the University of California, Berkeley.

DePaolo worked on the Hawaii Scientific Drilling Project (HSDP), which bored a hole down into the volcano near Hilo to find out more about how the Hawaiian Islands were created.

The weakest layers of ground-up glass were found about two-thirds of a mile (3,520 feet) down, said geologist Nick Thompson of Bournemouth University in the U.K. Thompson is the lead author of a paper about the stability of the Hawaiian volcano's flanks, which appeared in the April issue of the Journal of Volcanology and Geothermal Research.