Comment: 08:12 - 09:20 (01:08)
Source: Annenberg/CPB Resources - Earth Revealed - 3. Earth's Interior
Keywords: "Thomas Henyey", "continental crust", "igneous rock", metamorphism, "sedimentary rock", "igneous rock", "metamorphic rock", "sedimentary rock", silicate
Our transcription: Also, the continents are somewhat thicker than in the oceans.
The continents are between about 25 and 40 kilometers thick.
The oceanic crust is something between 5 and 10 kilometers thick.
The continental crust is made up of materials, which have been swept together during dynamic processes on the Earth.
They include: igneous rocks from volcanic and magmatic events, sedimentary rocks that have been pushed in from the oceans, and metamorphic rocks which have been modified by heat and pressures.
They've been taken to depths on the continents into the Earth's interior and then regurgitated again.
The chemistry of continents as a result is very complex; but by and large, much of the crust is composed of silicates: primarily of aluminum, potassium, calcium, with some iron and magnesium.
Geology School Keywords