Oceanic Crust

Oceanic crust is the part of Earth's lithosphere that underlies the ocean basins. It is thinner and denser than continental crust and is primarily composed of basaltic rock.

Composition and Characteristics

Oceanic crust is primarily composed of basalt, a type of igneous rock that forms from the rapid cooling of lava. It is relatively young compared to continental crust, with most oceanic crust being less than 200 million years old. The thickness of oceanic crust ranges from 5 to 10 kilometers.

Formation

Oceanic crust forms at mid-ocean ridges through the process of seafloor spreading. Magma wells up from the mantle at these ridges, solidifies, and creates new oceanic crust. As new crust forms, older crust is pushed away from the ridge, leading to the spreading of the seafloor.

Subduction

One of the defining features of oceanic crust is its interaction with continental crust at convergent plate boundaries. Oceanic crust is denser than continental crust, which causes it to be forced beneath the less dense continental crust in a process known as subduction. This process leads to the formation of deep ocean trenches and volcanic arcs.

Study Guide

1. What is the primary rock type that makes up oceanic crust?
2. How does oceanic crust form?
3. What is the process by which oceanic crust interacts with continental crust at convergent plate boundaries?
4. How does the age of oceanic crust compare to that of continental crust?
5. Describe the thickness of oceanic crust.