Subsea Volcanoes Found near Hawaii
Mnastersky, Richard, Science News
Subsea volcanoes found near Hawaii
Using a high-resolution sonar to shoot pictures of the ocean bottom, geologists have discovered extensive young lava flows several hundred kilometers from the Hawaiian islands. The find may force scientists to revise their ideas about the volcanic system that formed this island chain in the mid-Pacific.
"These were totally unknown until last April," says Mark Holmes of the U.S. Geological Survey (USGS) in Seattle, Wash. "The surface area of the flows that we've mapped is twice the size of the subaerial [above sea level] portions of the major Hawaiian islands, so it's really a phenomenal amount of material that's erupted."
These findings emerged from a continuing USGS project to map the Exclusive Economic Zone, the 200-mile-wide border extending from all U.S. coast-lines. At its heart, the project relies on the GLORIA sidescan sonar, which uses sound waves to create detailed pictures of the seafloor. Holmes and his colleagues reported their discoveries last week in Denver at the meeting of the Geological Society of America.
The lava flows appear on the sonar images because they are young and covered only by a thin veneer of sediment. The relatively rough lava surface reflects more sound energy than the surrounding seafloor, which is topped by a thick sediment layer. …