The crust below the oceans is . mostly granite
made of sand and salt sediment
basalt and a layer of salt sediment
made of metamorphic rock and granite

Basalt and a layer of sand sediment

Explanation:

Oceanic crust, extending 5-10 km (3-6 km) beneath the ocean floor, is mostly composed of different types of basalt. Geologists often refer to the rocks of the oceanic crust as “sima.” Sima stands for silicate and magnesium, the most abundant minerals in oceanic crust.

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