Islands of the Pacific Ring of Fire (Island Week 4)
Friday, 2nd October 2009 by Alex Turnbull
It’s Island Week 4 here at GSS, which means we’ll mostly be posting about Islands. For about a week.
On September 29, 2009, just south of the islands that make up the Independent State of Samoa in Polynesia, an earthquake measuring 8.0 on the Moment Magnitude scale occurred, which generated a tsunami that swept across the nearby islands killing at least 149 people.
Most of the victims were on Samoa itself, where reports of a wave between 3 and 10 metres have emerged. Many low-lying areas in the Samoan islands have been completely destroyed, including the Prime Minister’s home village of Lepa.
Several other Polynesian islands were affected including the Unincorporated U.S. Territory of American Samoa to the east, where they lost at least 25 people, and to the south Tonga, where 6 people are so far known to have died.
Just 16 hours after the Samoan tsunami, another large earthquake occurred just off the southern coast of Sumatra, Indonesia. This eruption registered a lower moment magnitude reading of 7.6, but even without a tsunami has still claimed at least 1,100 lives.
Separated by 9,749 km, these two earthquakes were unrelated. They also lie on separate faults; Samoa sits just north of the Tonga Trench, and Sumatra is located on one of the world’s most active fault lines, the Great Sumatran fault.
What the two earthquakes do share however, is that all the affected islands fall within the Pacific Ring of Fire, a 40,000 km long horseshoe-shaped region that is defined by a nearly continuous path of volcanic features, including 452 volcanoes. 75% of the world’s active and dormant volcanoes are located within the region, and together they are responsible for about 90% of the world’s earthquakes.