Where Earth's insides ooze out.Earth Sciences Where Earth's insides ooze out Drilling into a recently discovered form of underwater seamount seamount Large submarine volcanic mountain rising at least 3,000 ft (1,000 m) above the surrounding seafloor; smaller submarine volcanoes are called sea knolls, and flat-topped seamounts are called guyots. Seamounts are abundant and occur in all major ocean basins. , oceanographers have found a spot where material from Earth's mantle oozes onto the seafloor in cold eruptions. Most seamounts that dot the ocean floor arise when hot, molten basaltic ba·salt n. 1. A hard, dense, dark volcanic rock composed chiefly of plagioclase, pyroxene, and olivine, and often having a glassy appearance. 2. A kind of hard unglazed pottery. rock spews out of volcanoes and builds layer upon layer. But scientists several years ago identified a new type of submerged mountain. Dredged rock samples and dives in the submersible submersible, small, mobile undersea research vessel capable of functioning in the ocean depths. Development of a great variety of submersibles during the later 1950s and 1960s came about as a result of improved technology and in response to a demonstrated need for Alvin have revealed that these seamounts consist of serpentinite serpentinite A metamorphic rock consisting almost entirely of minerals in the serpentine group. Serpentinite forms from the alteration of ferromagnesian silicate materials, such as olivine and pyroxene, during metamorphism. , a nonvolcanic rock formed when water reacts with minerals in the mantle (SN: 11/19/88, p.333). Now, to get a better look, researchers have drilled into underwater mountains near the Izu-Bonin and Mariana trenches south of Japan. Reaching more than a mile above the seafloor, these seamounts sit above a subduction zone in which the Pacific plate slides under the Philippine plate, creating the famous trench system that includes the lowest point on Earth's surface. The drilling cores, taking during a recent leg of the Ocean Drilling Program The Ocean Drilling Program (ODP) was an "international" "cooperative" "effort" to explore and study the composition and structure of the earth's ocean basins. ODP, which began in 1985, was the direct successor to the "highly successful" Deep Sea Drilling Project initiated in , show that serpentinite not only covers the tops of the seamounts but also fills their interiors. While the Izu-Bonin seamount is extinct, the Mariana seamount remains active, and the researchers pulled up soft, plastic serpentinite there. In fact, the drill could penetrate only 150 meters into the center of the seamount before sticking, says, Patricia Fryer of the University of Hawaii (body, education) University of Hawaii - A University spread over 10 campuses on 4 islands throughout the state. http://hawaii.edu/uhinfo.html. See also Aloha, Aloha Net. at Manoa in Honolulu, a co-chief scientist on Leg 125. On the basis of holes drilled into the seamounts' centers and flanks, the researchers believe they can now explain the processes that create these structures. Fryer says the origin relates directly to the subduction sub·duc·tion n. A geologic process in which one edge of one crustal plate is forced below the edge of another. [French, from Latin subductus, past participle of going on underneath. The serpentinite forms when water escapes out of rocks on the sinking Pacific plate. Because serpentinite is lighter than the surrounding mantle rock, it rises toward the surface. Reaching the crust, the serpentinite "mud" oozes upward along fractures that lead to the seamount summit. As it erupts, the cool mud flows down the flanks like lava from a volcano. Flow textures in some of the drill cores support this idea, Fryer says. |
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