Consider the following differences between the Oceanic Crust and Continental Crust:
1.The Continental crust is denser in comparison to the Oceanic Crust
2.The Continental crust has more of quartz , while the Oceanic Crust has more of Feldspar
3.The Continental Crust is otherwise called SIMA, while the Oceanic Crust is otherwise called SIAL
4.The rocks that make the continental crust are little denser than those making Oceanic crust.
Which among the above statements is / are correct?
The oceanic crust is thinner than the Continental Crust. Oceanic Crust measures from 5 to 10 kilometers, averaging about 7 kilometers in thickness; the continental crust measures between 25 to 100 kilometers, averaging about 30 kilometers thick. Obviously, the thickest continental crust regions are under large mountain ranges.
Apart from the thickness, the oceanic and continental crusts also differ in composition and density. The oceanic crust is composed of dark, iron-rich rock similar to basalt. It is high in silica and magnesium, that is why called SIMA. It is often distinguished from the mantle by having more silica. This implies that Oceanic crust is more basaltic. Since Magnesium is denoted by Mg and Iron is denoted by Fe, these rocks have also been named Mafic Rocks. Most common rock-forming Mafic minerals in the oceanic crust are olivine, pyroxene, amphibole, and biotite.
The continental crust’s composition is more complex. In general, continental rocks are light-colored, with an average composition between diorite (generally hornblende and plagioclase feldspar with a little quartz) and granodiorite (the same composition as diorite, but with more quartz present). These are rocks high in silica and aluminium and are often referred to as SIAL. This implies that Continental crust is more
Then, there is a difference in density also. The oceanic crust has a density of 3,000 kilograms/m³ while the continental crust has a lower density of 2,500 kilograms/m³. This also implies that the rocks which make continental crust are slightly less dense than those making the Oceanic Crust. The less dense rocks such as granite is more common in continental crust than in oceanic crust. Density of Sial is lower than Sima primarily because of the increased amount of aluminium.
Please note that at a certain depth, the SIAL of the Continental Crest becomes close in its physical properties to SIMA. The temperature of the crust increases with depth, reaching values typically in th range from about 200-400°C at the boundary with the
This question is a part of GKToday's Integrated IAS General Studies Module