Satellite-based radar data provide new insight on volcanoes

Historically remembered for their role in evolutionary theory, the Galapagos Islands may now provide clues about the workings of volcanoes. Researchers applied radar interferometry - an advanced technique that uses satellite-borne data to produce high-resolution maps of displacements of the Earth's surface - to the Galapagos volcanoes. These volcanoes are very similar to the Kilauea and Mauna Loa volcanoes on the Big Island. Falk Amelung, Young Investigator at the University of Hawai'i at Manoa School of Ocean and Earth Science and Technology, led a team of scientists whose paper - Widespread uplift and 'trapdoor' faulting on Galapagos volcanoes observed with radar interferometry.

Not much was known of the Galapagos volcanoes because it's such a remote area that's mostly known for its unique wildlife, and not very many people live there, Amelung says. There were no previous ground-based measurements.

Radar interferometry is a measurement technique that uses satellite data to map surface displacements, which occur in earthquake and volcanic areas. The technique is similar to that used by NASA's Shuttle Radar Topography Mission in February. Whereas SRTM was an effort to provide more extensive topographic data on the Earth's surface, Amelung is interested in topographic changes caused by displacements of the Earth's surface over time.

The satellite travels at 17,000 miles per hour and, even through clouds, can make accurate measurements, within a quarter inch, Amelung says. It's quite exciting because we can get these surface deformation maps for very remote areas whereas before we only could get measurements at certain points and this after days or weeks of travel.

The team - which also included Stanford University scientists Sigurjon Jonsson, Howard Zebker and Paul Segall - discovered new information on the behavior of six Galapagos volcanoes. The accumulation of magma in subsurface reservoirs causes vertical displacements of the volcano's surface, or volcanic uplift, and often causes the volcano to erupt. Uplift was detected at nearly all the Western Galapagos volcanoes indicating active magma reservoirs beneath. Scientists thought that significant volcanic uplift was a reliable precursor for eruptions. However, radar data taken from the Sierra Negra volcano, one of seven in the Galapagos, showed that uplift does not always lead to eruption because of 'trapdoor' faulting, a fracture system formed over time within the caldera. This system might help to relax stresses above the magma-filled chamber and thus inhibit eruptions.

Amelung says Hawai'i's volcanoes are very similar to those in the Galapagos. Both are fed by so-called hot spots in the Earth's mantle. Isabela, the largest island in the Galapagos, is about 120 kilometers from its northernmost point to its southernmost, or about one-third the size of the Big Island. Averaged over time, the Hawaiian volcanoes produce more magma than the Galapagos volcanoes.

The Galapagos usually has three big eruptions within 10 years, lasting about four to eight weeks, Amelung says. In Hawai'i, the continuously erupting Kilauea is relatively well understood, and many ground measurements have been taken for it at the U.S. Geological Survey's Hawaiian Volcano Observatory. But Mauna Loa is so big that only a fraction is covered by the observatory. Mauna Loa is currently silent, but scientists believe that it may erupt in the next 10 to 20 years.

This research and mapping technique will help to detect any activity at an early stage. Good data about the Galapagos volcanoes will help to understand what Mauna Loa is doing when it resumes activity. For more information, on the latest GPS News see maps gps.

Author Notes:

John Climee contributes and publishes news editorial to http://www.handheld-gps-reviews.com.  A wealth of information about Global Positioning Systems for commercial or personal use.