Continental Crust vs Oceanic Crust
The surface of the earth and a small portion beneath the surface of the earth is called earth’s crust. This is a very thin layer of rocks that makes up nearly 1% of the total volume of the planet earth. If anything, you can assume earth’s crust to be akin to the skin of potato or apple. Despite its small size, earth’s crust is considered very important. Of course, it is important because we live over it, and our entire world is confined on this earth crust. This crust is divided into two parts; the oceanic crust and the continental crust. This article attempts to highlight the differences between these two parts of the crust.
As we go down beneath the surface of the earth, nearly 50 km down the surface starts an altogether different structure of rocks that is referred to as mantle. Above this mantle lies the earth’s crust. This artificial boundary has been made after the discovery made by a seismologist in 1909 that seismic waves get refracted and also reflected back once they hit the rocks below the crust. This is similar to the manner in which light behaves at the discontinuity that is seen between air and water. Thus, above the mantle, which starts at about 50 km below the surface of the earth, the rocky structure is referred to as earth’s crust.
The surface of the earth that is found on the continents is called the continental crust, which has a thickness of around 25 to 70 km. This crust is made up of igneous, sedimentary and metamorphic rocks, and that together make up the structure of our continents.
Billions of years ago, earth was a hot ball of molten rocks. Slowly, with the passage of time, the heavy parts of the rocks that contained iron and nickel sank down and formed the core of the earth. The outer surface cooled down and became hard. This formed the crust of the earth. Continental crust is mainly made up of granite.
As the name implies, oceanic crust is the floor of the oceans. Obviously, this crust is thinner than the continental crust. The major type of rocks making up oceanic crust is basalt. In general, the thickness of oceanic crust is around 7 to 10 km.
What is the difference between Continental Crust and Oceanic Crust?
• Oceanic crust is heavier and denser (2.9 g/cubic cm) than continental crust (2.7 g/cubic cm).
• Oceanic crust is mainly basalt whereas continental crust is mainly granite.
• Oceanic crust is relatively younger than continental crust.
• Continental crust is made up of landmasses, whereas oceanic crust is the floor of the oceans.
• Continental crust is thicker (25-70 km) than oceanic crust (7-10 km) and is nearly 35-40km deep.