Science Olympiad Dynamic Planet Practice Test

What is the characteristic of the basalt rock found in the Earth's crust?

1. It is light in color.

2. It is dark and dense.

3. It is mostly composed of sediment.

4. It is a type of sedimentary rock.

The correct answer is: It is dark and dense.

Basalt is an igneous rock that forms when lava cools and solidifies quickly after an eruption, typically in a volcanic environment or on the ocean floor. One of its defining characteristics is its dark color, which is due to the high concentration of iron and magnesium-rich minerals it contains, such as pyroxene and olivine. Additionally, basalt is considered dense compared to many other types of rocks, particularly igneous rocks like granite, which is usually lighter in color and less dense because it is rich in quartz and feldspar. The density of basalt is important because it directly influences its behavior in the Earth's crust and its role in tectonic processes. For instance, basalt is commonly found in oceanic crust, contributing to the formation of mid-ocean ridges and playing a significant role in the oceanic-continental tectonic interactions. This dark, dense nature makes basalt a critical component in understanding geological processes such as plate tectonics, volcanic activity, and the composition of the Earth's crust.