What is the continental crust made of?Geology
Asked by: Susan Brown
Continental Crust Continental crust is mostly composed of different types of granites. Geologists often refer to the rocks of the continental crust as “sial.” Sial stands for silicate and aluminum, the most abundant minerals in continental crust.
What is a continental crust?
continental crust, the outermost layer of Earth’s lithosphere that makes up the planet’s continents and continental shelves and is formed near subduction zones at plate boundaries between continental and oceanic tectonic plates. The continental crust forms nearly all of Earth’s land surface.
What is the oceanic crust made of?
Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates.
Is continental crust made of basalt?
Oceanic crust is generally composed of dark-colored rocks called basalt and gabbro. It is thinner and denser than continental crust, which is made of light-colored rocks called andesite and granite.
Is continental crust made of granite?
Continental crust is indeed “granitic”, and has the general composition typical of granitic rocks, made up of mostly aluminium silicates (the SiAl).
Why is continental crust made of granite?
As long as subduction occurs, water is released and is delivered to the base of the crust, melting pre-existing basaltic rock to form granite magma. As it rises and cools, the granite magma crystallises to continental crust.
What type of rock are continental plates made on?
Continental crust is composed of granitic rocks which are made up of relatively lightweight minerals such as quartz and feldspar. By contrast, oceanic crust is composed of basaltic rocks, which are much denser and heavier.
How do continental crust and oceanic crust differ?
Oceanic crust differs from continental crust in several ways: it is thinner, denser, younger, and of different chemical composition. Like continental crust, however, oceanic crust is destroyed in subduction zones. The lavas are generally of two types: pillow lavas and sheet flows.
What is difference between continental crust and oceanic crust?
It is either continental or oceanic. Continental crust is typically 30-50 km thick, whilst oceanic crust is only 5-10 km thick. Oceanic crust is denser, can be subducted and is constantly being destroyed and replaced at plate boundaries.
Is basalt continental or oceanic?
Basalt is the dark, heavy volcanic rock that makes up most of the world’s oceanic crust. Some of it erupts on land, too, but to a first approximation, basalt is an oceanic rock. Compared to the familiar granite of the continents, basalt (“ba-SALT”) is darker, denser and finer grained.
What type of rock is oceanic crust?
The oceanic crust forms the ocean floor, and is thinner than the continental crust. It is made up of only a few types of rocks such as basalt and gabbro, dark rocks with white mineral flecks. These are called igneous rocks.
Why is oceanic crust predominantly basalt?
The oceanic crust, which, on average, is only about six kilometers thick, is primarily made up of the igneous rock basalt. Basalt tends to come from lava that flows smoothly and quietly from a volcanic vent, unlike the viscous lava typical of the violent eruptions of many continental volcanoes.
What makes continental crust different from oceanic crust?
The oceanic crust is mainly made out of dark basalt rocks that are rich in minerals and substances like silicon and magnesium. By contrast, the continental crust is made up of light-colored granite rocks full of substances like oxygen and silicon.
Why continental crust is thicker?
The crust is thickened by the compressive forces related to subduction or continental collision. The buoyancy of the crust forces it upwards, the forces of the collisional stress balanced by gravity and erosion. This forms a keel or mountain root beneath the mountain range, which is where the thickest crust is found.
How thick is the continental crust?
While the continental crust is 30–70 km thick, the oceanic crustal thickness is 6–12 km. The oceanic crust is also denser (2.8–3.0 g/cm3) than the continental crust (2.6–2.7 g/cm3). The average Archean crust is ~35 km thick, whereas the Proterozoic crust is significantly thicker (~45 km).
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