for National Geographic News
About 500 homes were destroyed, and the death toll is expected to rise.
Reports put the waves' size between 10 and 16 feet (3 and 5 meters).
The tsunami was triggered by a large earthquake, magnitude 8.1, centered 215 miles (345 kilometers) northwest of the islands' capital of Honiara. (See map of the Solomon Islands).
The earthquake struck at 7:39 a.m. local time Monday morning, and the waves hit soon afterward, washing as far as half a mile (0.8 kilometer) inland.
The quake occurred at the boundary where three tectonic plates collide with the large Pacific Plate at an average velocity of about 4 inches (10 centimeters) a year.
The tectonics of the region are extremely complex, said Emile Okal, a geophysics professor at Northwestern University.
"It is a very active area," Okal said. "There are earthquakes there all the time."
However, he added, "to my knowledge this is the biggest [earthquake] in that particular section in probably 100 years."
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The quake's epicenter was extremely close to the surface, centered only 6 miles (10 kilometers) below the seafloor, the U.S. Geological Survey reported on its Web site.
This may have contributed to the formation of the tsunami, Okal said.
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