Here's why:
* Composition: Felsic rocks are rich in silica (SiO2) and have high levels of aluminum, potassium, and sodium. This gives them a lighter color compared to mafic rocks, which are rich in magnesium and iron.
* Examples: Common felsic rocks found in continental crust include:
* Granite: A coarse-grained rock with visible crystals of quartz, feldspar, and mica.
* Rhyolite: A fine-grained, volcanic equivalent of granite.
* Gneiss: A metamorphic rock with distinct bands of light and dark minerals.
* Formation: Felsic rocks are typically formed from the slow cooling and crystallization of magma deep within the Earth.
Other details:
* Density: Continental crust is generally less dense than oceanic crust, which is composed primarily of mafic rocks like basalt. This difference in density is why continents "float" higher on the mantle than oceanic crust.
* Thickness: Continental crust is much thicker than oceanic crust, ranging from 30 to 70 kilometers (19 to 43 miles) thick.
So, when you see a light-colored rock in a mountain range or on the surface of the Earth, it's likely a felsic rock, a key component of the continental crust.
