December 2, 2013

Hundreds of earthquake tremors recorded by scientists in Antarctica have rocked the geological world by producing evidence of the first active volcano found so far inland on that frozen continent. Numerous volcanoes, both active and extinct, have been found along the Antarctic coastline and on nearby islands.

The earthquake swarms originated about 15 to 25 miles (25 to 40 kilometers) below the surface, near the Executive Committee Range in the Marie Byrd Land region of West Antarctica. The ice in that region is about 0.5-mile (0.8 kilometer) thick. The scientists, led by researchers from Washington University in St. Louis, stressed that they did not detect an actual eruption. Instead, the tremors likely resulted from the fracturing of rock as flowing magma and fluids opened new channels within the volcano. The tremors occurred beneath a 3,200-foot- (1,000-meter-) tall bulge under the ice that may be the cone (peak) of a volcano that formed sometime in the past as lava erupted from the volcano’s vent (opening).

The scientists detected the tremors while towing seismic equipment across the icy surface in 2010 and 2011 to map the structure of Earth’s mantle, the layer between inner core and outer crust. The seismic vibrations the scientists detected in Antarctica were nearly identical to so-called deep, long-period earthquakes (DLP’s) that have been detected beneath volcanoes in Alaska and Washington state. Although DLP’s sometime precede eruptions, scientists do not know if the tremors in Antarctica are signs that an eruption will occur there in the near future.

Volcanoes are common in Antarctica. Some are active, and others are hidden beneath the ice. But most of the known volcanoes are along the coastlines of the continent. © Rod Planck, Photo Researchers

If the volcano was to erupt, some of the ice above the vent would certainly melt, producing millions of gallons (liters) of water. Such a massive infusion of meltwater would speed of flow of nearby ice streams (slowly flowing “rivers” of ice within ice sheets). But unless the eruption was historically massive, it almost certainly would not melt all of the ice above. Scientists stressed that the greatest threat to Antarctica is still climate change. The Pine Island Glacier in West Antarctica, for example, is shrinking faster than any other glacier on Earth. It also ranks number one among glaciers whose melting is contributing to the rise of global sea levels.

Additional World Book articles:

• Science in Antarctica
• The Great Meldown

April 16, 2013

Iran was hit by a 7.8-magnitude earthquake this morning, its most powerful quake in nearly 40 years. According to the U.S. Geological Survey, the epicenter was  near the city of Khash, in southeast Iran close to the Pakistani border. It occurred at a depth of 60 miles (96 kilometers). The earthquake was felt throughout the Middle East. The tremors were strong enough in Karachi, Pakistan, and New Delhi, India, for offices to be evacuated.

An earthquake occurs when Earth's rock suddenly breaks and shifts, releasing energy in vibrations called seismic waves. The point on Earth where the rock first breaks is called the focus. The point on the surface above is known as the epicenter. (World Book illustration)

There are conflicting reports on casualties. The Iranian Crisis Center in Tehran, the capital, claims there were no fatalities. However, an unnamed Iranian government official told Reuters news agency that there are 1,700 villages in the area with most of the buildings made of mud: “We are expecting hundreds of dead.” In Pakistan, local government officials report that the quake left at least five people dead in the town of Mashkel, which is near the border with Iran. In 2003, 30,000 people were killed when a 6.6-magnitude quake destroyed much of the city of Bam, in the same southeastern region of Iran.

Additional World Book articles:

• When the Earth Moves (a special report)
• Iran 2003 (a Back in Time article)