Map Project Uncovers Lava Flow, Landslides Off Hawaiian Islands : Cartography: Scientists say charting of sea floor will improve understanding of U.S. ocean resources.
Large undersea landslides and a huge sea-floor lava flow off the Hawaiian Islands are the most significant discoveries of a seven-year mapping project scientists say will lead to a greater understanding of America’s ocean resources.
The $35-million project completed the first mapping of the entire 200-mile exclusive economic zone of the United States--the area extending around the nation’s perimeter where only American interests can make use of ocean resources for economic benefit.
Scientists made several significant discoveries, mostly around the Hawaiian chain, but also along the East and West coasts and Alaska. The maps will be used in studies scientists hope will lead to more efficient and environmentally compatible uses of the ocean.
An underwater sonar system transmitted electronic pulses that were converted into mosaic images resembling satellite photographs. The photos are being used to make maps for inclusion in atlases that government, science and industry can use for assessing the ocean’s resource potential.
“Before we can make intelligent decisions on how to use the ocean from an economic and environmental standpoint, we need to understand what’s there,” said Dave Cacchione, chief of the marine science branch of the U.S. Geological Survey.
The maps provide that, said Colin Jacobs, a geologist with the Institute of Oceanographic Sciences, Deacon Laboratory, part of the Natural Environment Research Council in Britain.
“If you want to do some detailed work, you need to have a road map to see where you’re going,” Jacobs said. “That’s what we’re doing, building a road map.”
The USGS, with the help of the British scientists, began work in 1984, after President Ronald Reagan ordered the mapping. The mapping was done with the GLORIA side-scan sonar system, developed in the 1960s. GLORIA stands for Geological Long Range Inclined ASDIC. ASDIC is a British term for sonar used in World War II.
The mapping, completed in late October after 50 cruises, discovered previously unknown features and looked at already known topography, particularly around the Hawaii.
A sea-floor lava flow hundreds of miles long was found 100 miles north of Oahu Island, where Honolulu is located. The flow is not near the “hot spot” that spews the magma that created the volcanoes that formed--and continue to form--the island chain. Scientists next will try to learn how and when the flow originated.
One theory, Jacobs said, is that the weight of the islands is bending the Earth’s crust, causing cracks that allow lava to escape from undersea volcanoes. The flow was discovered in 1987.
Scientists said the most significant work was the detailed mapping of huge undersea landslides, land that once was part of Oahu. The landslides were discovered previously but never had been mapped in detail, said Dave Clague, who supervised the mapping and now is scientist in chief at Hawaii Volcano Observatory.
“We would like to understand better when the landslides happened and how they happened so we can tell whether we have to worry about them,” said Clague. “If one were to happen today, it would be a major disaster, a catastrophe.”
Future projects will seek answers to those questions, said Cacchione, who thinks most of the landslides occurred when volcanoes were active on Oahu millions of years ago. Parts of the island continue to fall off, but in very small amounts.
Smaller lava flows buried beneath 100 feet of sediment were found near Kauai Island and the northwestern Hawaiian Islands. Scientists also discovered the Molokai Fracture Zone, a rift that stretches from California beneath the island chain and at least as far as Johnston Atoll, 830 miles south of Hawaii, Jacobs said.
