The Earth’s crust, the outermost layer of the planet, is made up of a layer of solid rock. There are two types of shell, the oceanic crust that covers the ocean floor, and the continental crust that forms the continents.
The main difference between the two is density and composition. The oceanic crust is denser and composed of basalt. The continental crust is less dense and consists mainly of granite.
Three layers can be clearly distinguished in the Earth’s internal structure: crust, mantle and core. The crust is the outermost, it’s actually the earth we live on.
Each of these layers has a different composition and density. Density is mass per unit volume. The higher the density, the heavier the material, which determines the position of each layer in relation to the others.
The least dense layers, such as the crust, sit on top of the densest mantle, and the mantle sits on top of the core, which is the densest of the three layers.
Without melting, the upper command rocks have enough ductility to allow tectonic plates to slide as if the crust were floating on top of the mantle.
As we will see later, density is also one of the most important differences between oceanic and continental crust.
oceanic crustOceanic crust is formed by the partial melting of upper mantle rocks and is continually recycled.
The oceanic crust is the earth’s crust that covers the seabed. It is mainly composed of basaltous rock type composed of silicon, oxygen and magnesium.
The density of oceanic crust is about 3.0 g/cm3, greater than the density of continental crust, which explains in part why continental crust is higher in altitude than oceanic crust.
Oceanic crust is formed by partial melting of mantle rocks. In areas where oceanic plates diverge, at mid-ocean ridges, magma flows from the mantle.
When magma solidifies, it turns into basaltic rocks that form the oceanic crust. As oceanic crust plates age, older rocks move away from mid-ocean ridges.
As the oceanic crust is denser, when it meets the continental crust it sinks until it reaches the mantle and melts again. This occurs in subduction zones.
Continuous eastern recycling makes oceanic crust much thinner and also much younger than continental crust. The oldest oceanic crust is only 200 million years old, while there are areas of continental crust that are up to 4 billion years old.
The average density of the continental crust is 2.6 g/cm3. It is mainly composed of granite rock with abundant aluminum, oxygen and silicon.
Being less dense than oceanic crust, continental crust floats more freely in the mantle than oceanic crust, which allows continents to remain immersed for longer. The rate of creation and destruction of continental crust is much slower.
Continental crust is also much thicker than oceanic crust, varying between 30 and 70 km compared to 8-10 km for oceanic crust.
Differences between oceanic and continental crust
As explained, composition and density are the most striking differences between the two types of bark. From these differences derive the other characteristics.
The most important differences are:The oceanic crust is mainly composed of basalt rock rich in minerals such as silicon and magnesium. The continental crust is mainly composed of granite rocks rich in minerals such as aluminum and silicon. Oceanic crust is denser than continental crust. The density of the crust is 3.0 g/cm3 and that of the continental crust is 2.6 g/cm3. Continental crust is much thicker than oceanic crust. The continental crust varies between 35 and 70 km, while the average thickness of the oceanic crust is 8 to 10 km. Continental crust is older than oceanic crust. The oceanic crust is subjected to a continuous recycling process that makes it always younger than the continental crust.