Science Olympiad Dynamic Planet Practice Test

What type of rock is typically light colored and found in continental crust?

1. Basalt

2. Granite

3. Marble

4. Obsidian

The correct answer is: Granite

Granite is typically the correct answer as it is a light-colored, coarse-grained igneous rock predominantly found in continental crust. It is primarily composed of quartz, feldspar, and usually mica, which gives it a range of light hues including white, pink, and gray. The formation of granite occurs from the slow crystallization of magma beneath the Earth’s surface, allowing large crystals to develop. In contrast, basalt is a dark-colored volcanic rock that forms from the rapid cooling of lava at the Earth's surface and is typically associated with oceanic crust rather than continental. Marble is a metamorphic rock that originates from limestone and, while it can be light-colored, it does not form in the same manner or location as granite. Obsidian is a natural glass formed from rapidly cooling lava and is generally dark in color, often black or dark brown, making it unsuitable in this context.