Which rock type forms the seabed crust and has a density of about 2.9 g/cm^3?

Which rock type forms the seabed crust and has a density of about 2.9 g/cm^3?

• A. Granite
• B. Diorite
• C. Basalt
• D. Rhyolite

Answer: (C)

Oceanic crust on the seabed is formed primarily from basalt, a dense mafic igneous rock. Basalt forms when mantle-derived magma erupts at mid-ocean ridges and cools quickly underwater, producing a rock with a dense mineral makeup. Its density is about 2.9 g/cm^3, which matches the value given in the question, so it fits the setting and the density criteria. Granite and rhyolite are felsic continental rocks with lower densities and are not typical of the ocean floor. Diorite is an intermediate rock that is more common in continental settings and, while denser, does not represent the primary composition of seabed crust. Basalt best accounts for both the environment (oceanic crust) and the reported density.

Oceanic crust on the seabed is formed primarily from basalt, a dense mafic igneous rock. Basalt forms when mantle-derived magma erupts at mid-ocean ridges and cools quickly underwater, producing a rock with a dense mineral makeup. Its density is about 2.9 g/cm^3, which matches the value given in the question, so it fits the setting and the density criteria.

Granite and rhyolite are felsic continental rocks with lower densities and are not typical of the ocean floor. Diorite is an intermediate rock that is more common in continental settings and, while denser, does not represent the primary composition of seabed crust. Basalt best accounts for both the environment (oceanic crust) and the reported density.