SOVIET SCIENTIFIC TEAM
DEEP CORE DRILLING
Your leader is Dr. Mohorovicic of the University of Moscow.
In 1958, the ship Soviet Glory sailed from its port in Minsk. Soviet Glory is a ship operated by the Soviet Academy of Science. The scientists on the ship drilled holes deep into the ocean floor in many pieces of the Pacific Ocean. The purpose of the study is to learn more about oceanic crust.
Before they were able to drill so deep, Soviet scientists got clues about the structure of ocean crust from ophiolites - bits of ocean crust that have been pushed up onto continents. These rocks suggested that the ocean crust is made of three layers. The top layer is "pillow basalt," formed from cooled lava. The next layer is a mass of minerals that pushed the lava to the surface. The bottom layer consists of gabbro, or crystallized basalt. Scientists thought that ophiolites probably had been changed during their journey to land, so they wanted to get samples directly from the ocean crust.
Soviet Glory drilled a hole about 1500 meters into the crust off the west coast of South America. The samples that were brought up confimed the three-layered structure that the ophiolites had suggested.
The sediments also contained evidence of changes in climate along the coast. The different types of plant and animalfossils in the sediment indicate that the climate has changed repeatedly over the years.
Other drilling sites provided information about heat flow and water exchange on the ocean floor. Scientists learned that in areas with high heat, water carrying chemicals from the crust flows up through the sediment. In areas of low heat, seawater filters downward, replacing the water that flows up from the crust.
The diagram on the reverse page represents the thickenss of the crust under the ocean compared with the thickness of the crust under the continents.
1. What did sediments dug up by Soviet Glory reveal about the structure of ocean crust?
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2. Compare and contrast ocean crust with continental crust.
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Go to the websites listed below and read what is there.
Continental and Oceanic Crust - Ignore the section labeled "Continental Tectonic Provinces"