The Difference Between Oceanic Crust and Continental Crust

How is oceanic crust different from continental crust

The Earth has three different layers to it. The crust is the part of the Earth right on top where people live. The crust is subdivided into two types, oceanic and continental.

Oceanic crust

Oceanic crust is found under oceans, and it is about four miles thick in most places. A feature unique to oceanic crust is that there are areas known as mid-ocean ridges where oceanic crust is still being created. Magma shoots up through gaps in the ocean’s floor here. As it cools, it hardens into new rock, which forms brand new segments of oceanic crust. Since oceanic crust is heavier than continental crust, it is constantly sinking and moving under continental crust.

Composition: Mainly composed of basalt, which is a mafic rock rich in iron (Fe) and magnesium (Mg). These rocks are denser than the rocks of continental crust.

Thickness: Much thinner than continental crust, typically only around 6-10 kilometers thick.

Formation: Continuously formed at mid-ocean ridges by the upwelling of molten rock from the Earth's mantle.

Features: Characterized by oceanic trenches, volcanic islands, and seamounts.

Age: Relatively young, with the oldest parts only about 200 million years old.

Continental crust

Continental crust varies between six and 47 miles in thickness depending on where it is found. Continental crust tends to be much older than the oceanic kind, and rocks found on this kind of crust are often the oldest in the world. Examples of such rocks are those in Quebec, Canada which are estimated to be about 4 billion years old.

Composition: Mainly composed of granite, gneiss, and other felsic rocks, which are rich in silica (SiO₂) and aluminum (Al). These rocks are lighter and less dense than the rocks of oceanic crust.

Thickness: Much thicker than oceanic crust, ranging from 20 to 40 kilometers in thickness.

Formation: Primarily formed through mountain-building processes over millions of years, involving collisions of tectonic plates and the subsequent melting and cooling of rock.

Features: Characterized by mountain ranges, plateaus, and cratons (ancient, stable regions of continental crust).

Age: Generally much older than oceanic crust, with some parts dating back to billions of years ago.


The Difference Between Oceanic Crust and Continental Crust?
Comparing the two different kinds of crust.

Oceanic and Continental Crust Comparison


Oceanic crust is dominated by mafic and ultramafic intrusive igneous rocks whereas continental rocks are dominated by granitic (felsic) intrusive igneous rocks. The mantle, oceanic crust, and continental crust all have different compositions due to a process called partial melting.


The differences between oceanic crust and continental crust are due to the different ways in which they are formed. Oceanic crust is formed from magma that rises from the mantle and cools at the ocean floor. Continental crust, on the other hand, is formed from the accumulation of sediments and the melting of rocks.

Oceanic Crust and Continental Crust
What Is the Difference Between Oceanic Crust and Continental Crust?


The difference in density has an impact on isostacy of crust floating on the semi-fluid upper mantle (asthenosphere), with continental crust (about 2.7g/cm3) rising or floating above oceanic crust (about 3.5 g/cm3). 


The continental crust is older than the oceanic crust. This fact can be easily explained by the recycling process of the oceanic crust. The recycling process does not happen to the continental layer. Consequently, this ensures that the oceanic layer is always younger geologically.


Because continental crust is less dense than oceanic crust it floats higher on the mantle, just like a piece of Styrofoam floats higher on water than a piece of wood does.


Oceanic crust is much thinner than continental crust.
Oceanic crust
is typically about 5-10 kilometers thick, while continental crust can be up to 40 kilometers thick.


Oceanic crust is much younger than continental crust, so it does not contain as many fossils. Continental crust, on the other hand, is much older and contains a wealth of fossils. These fossils provide scientists with a valuable record of the evolution of life on Earth.


Oceanic crust is rich in iron and magnesium, which are important for the formation of minerals such as magnetite and olivine. These minerals are important for the formation of rocks such as basalt and gabbro. Continental crust is rich in silicon and oxygen, which are important for the formation of minerals such as quartz and feldspar. These minerals are important for the formation of rocks such as granite and sandstone.

What Type of Crust is Found Under the Continents

The type of crust found under the continents is continental crust, also known as sial (rich in silicates (SiO₂ ) and aluminum (Al)) due to its composition of silicates and aluminum. This type of crust differs significantly from the oceanic crust that lies beneath the oceans. Continental crust is buoyant and floats on the denser mantle, allowing continents to rise above the ocean floor.


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