The oceanic crust is composed mainly of diabase, gabbro, and
a. basalt.
b. quartz.
c. obsidian.
d. aquamarine.

The oceanic crust has three layers; layer 1, layer 2 and layer 3. Layer 1 consists f unconsolidated or semiconsolidated sediments. It contains of land sediments. Layer 2 is divided into two parts; uppermost volcanic layer and finely crystalline basalt. It s thin in the mid ocean but thickens away from the ridge. The third layer consists of coarse grained gabbros and igneous rocks that have a low content of silica rocks. It also consists of diabase dikes. So the answer is letter A.

Iam pretty sure it is c. 2000 bce

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