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Earth Sense: Pacific not so peaceful under the surface
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When Ferdinand Magellan’s ships emerged from the wild waters of Cape Horn in 1520, the newly discovered ocean seemed so peaceful that he named it Pacific Ocean. In modern times, we know that the Pacific is far from being a quiet place. Under its waters, the solid layer that separates us from the molten interior is so thin that if the globe were the size of a basketball, its hard crust would be no thicker than a sheet of paper.

In addition, it is divided into several pieces called plates that move and grind against each other. Where the plate containing Australia is driving into a bigger, earthquakes are frequent. Between Feb. 5 and Feb. 9, the Solomon Islands were hit by no fewer than 40 serious quakes. Of those, the ones of Feb. 6, 7, and 8 showed magnitudes in the 7 and 8 range, which puts them on the list of the world’s most powerful earthquakes.

The Solomon Islands are a chain located about 1,100 miles northeast of the Australian coastline. News reports are still sketchy, but it is confirmed that the magnitude 8 quake triggered a tsunami which killed five people on the island of Santa Cruz with its destructive waves. This isn’t in the category of the Indonesia tsunami of 2004 which killed 150,000 or the one in Japan (2011, nearly 16,000 victims), but the nation of Solomon Islands has close to 600,000 people living in harm’s way.

At the time of writing last week, the series of earthquakes was continuing with shocks in the magnitude 5 range. On the scale of magnitudes, a one-step increase means 10 times more power. This makes a magnitude 8 quake 1,000 times as powerful as a 5. For comparison, the 1989 quake causing death and destruction in Oakland and Santa Cruz, Calif., was a 7.

Tsunamis are tall waves generated by the shaking of the ocean floor. They travel across deep water at the speed of a jet plane. It gets dangerous when the waves reach land and break, destroying the buildings within their reach.

It appears that the factor which saved the Solomon Islands was the deep-seated nature of the quakes, which produced shallower waves than tremors occurring closer to the ocean bottom. Exact information about the latest quakes anywhere in the world is found at earthquake.usgs.gov/earthquakes/map.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His email is rkiefer@brenau.edu.

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