Which statements describe oceanic crust? select the two correct answers. a. it is between 25 and 70 km thick. b. its age ranges from very young to more than 4 billion years old. c. it is formed at zones of volcanic activity on the ocean floor. d. it contains silicate minerals high in iron and magnesium. e. it is made of all types of rocks.

C & D APEX

Options (C) and (D)

Explanation:

The oceanic crust is usually about 5-10 km thick and is comprised of rocks that are basaltic in nature. These rocks are primarily made of minerals such as iron (Mg) and magnesium (Mg) and a comparatively lesser amount of silicate materials. Much of the oceanic rocks are destroyed due to the constant plate tectonic movement. It has been found that the oldest oceanic rocks found on the earth's crust is about 180 million years old only. The new oceanic crust often forms along the mid-oceanic ridge in a divergent type of plate motion, where new materials are added to the crust. Those rocks that are present along the mid-oceanic ridge are the younger rocks and those that are away are the oldest rocks. These oceanic crust are comprised of the volcanoes that form adjacent to the convergent plate boundary.

Thus, the correct answer is options (C) and (D).

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