Studies of Volcanos on Other Planets Yield Understanding of Earthquakes
December 14, 2006
NASA’s missions to Mars and Venus have contributed greatly to our ability to better understand Earth-based phenomena.
— Patrick McGovern
LPI Planetary Scientist
HOUSTON, TX — Who would have expected that traveling 35 million miles to Mars could help us better understand the planet on which we live? Dr. Patrick McGovern, staff scientist at the Lunar and Planetary Institute, has been studying the growth and evolution of large volcanos throughout the inner solar system (the planets Earth, Venus, and Mars). He analyzes image, topography, and gravity data from NASA’s missions to Venus (Magellan) and Mars (Mars Global Surveyor, Mars Odyssey, Mars Express) to better understand the history and formation of the surface and subsurface of these planets. Using these observations, McGovern has generated a computer model that uses mechanical analyses to predict how stresses resulting from volcanic eruptions may impact a planet’s surface.
Two months ago, on October 15, two successive earthquakes shook the Hawaiian Islands, causing hundreds of minor injuries, knocking out electrical service to over 45,000 customers, and inflicting damages estimated at $40 million. As the dust settled and scientists looked more closely at these earthshaking events, an interesting situation emerged. Existing models for earthquake analysis could not accurately explain the occurrence and location of two earthquakes.
Olympus Mons, the solar system’s tallest volcano, measures 600 kilometers wide and 23 kilometers high, three times as tall as Mount Everest (the Earth’s tallest feature).
Image courtesy of NASA.
The October quakes were caused by stress built up over many years of volcanic activity, and were notable in that they occurred deep within the Earth’s upper mantle. The first earthquake occurred 39 kilometers below sea level, with a magnitude of 6.7. Seven minutes later and about 30 kilometers to the north, a second earthquake (magnitude 6.0) struck at 19 kilometers below sea level. Existing earthquake models could explain the first quake, but models fell short when trying to explain why the second earthquake was so deep. Most earthquake models treat the lithosphere, or strong outer layer of the planet, as one uniform plate, while McGovern’s model recognizes the importance of modeling the lithosphere in discrete layers. It was this insight that made successful modeling of the October earthquakes possible. According to McGovern’s model, the second earthquake occurred in the deeper, stiffer mantle, rather than the shallower, less-stiff crust.
McGovern’s studies of volcanos on Venus and Mars are complementary to studies of Earth’s large volcanos in several ways. Volcanos on Venus and Mars are not subject to obscuration and erosion by an ocean; thus pristine examples of volcanic structures are available for examination on such planets. Furthermore, volcanos on Venus and Mars are not subject to the destructive processes of plate tectonics, thereby preserving more numerous (Venus) and larger (Mars) volcanos than on Earth. On the other hand, volcanos like the Hawaiian Islands have been subject to extensive seismic, geodetic, and geochemical analyses that reveal volcanic structure in ways not yet possible for Venus and Mars. In particular, the deep structural insights yielded by seismic studies of the Hawaiian Islands have greatly inspired the development of models for large martian volcanos such as the immense Olympus Mons edifice.
McGovern will be presenting his results at the 2006 American Geophysical Union Fall Meeting being held this week in San Francisco, California. McGovern is a Staff Scientist at the Lunar and Planetary Institute (LPI), a research institute that provides support services to NASA and the planetary science community and conducts planetary science research and space science education programs.
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Last updated January 30, 2008
