Volcano Journal Entry
Mount Oyama Shoots Ash (March 20, 2001)
Aerial view of collapsed suummit of Japan's Oyama volcano after July 2000 eruption. Photo by S. Nakada. Courtesy Volcanic Research Center.
Japan's Mount Oyama volcano shot a cloud of ash nearly a half-mile (800 meters) into the air on Monday. The volcano, located on the island of Miyakejima about 120 miles (200 kilometers) south of Tokyo, shook with numerous volcanic tremors this week. It had been quiet since eruptions last summer forced the island's residents to evacuate.
The volcano was dormant for seventeen years until it erupted last June. Volcanologists say shifts in huge underground pools of magma may be responsible for recent volcanic and earthquake activity on the island.
Many volcanoes, including those of the Ring of Fire surrounding the Pacific Ocean, form near plate boundaries where oceanic crust returns to Earth's mantle. As one plate slides beneath another in a process called subduction, slabs of crust sink along deep trenches into the mantle. The crust melts and forms magma, which rises up to the surface through a volcano.
Japan, which has many active volcanoes and frequent earthquakes, is found on the Eurasian plate near where the Philippine and Pacific plates subduct it.
