Science Olympiad Dynamic Planet Practice Test

What does the term "graben" refer to in geology?

1. A valley with distinct escarpments on both sides

2. A raised fault block in the Earth’s crust

3. A series of parallel normal faults

4. A flat area between mountain ranges

The correct answer is: A valley with distinct escarpments on both sides

The term "graben" specifically refers to a geological feature that forms when sections of the Earth's crust are pulled apart, leading to subsidence. In this process, the land sinks between two normal faults, creating a valley that has distinct escarpments or steep slopes on both sides. This characteristic makes grabens distinct from other geological structures, as they are valleys that are basins formed by tectonic activity, often resulting in a floor that is lower than the surrounding terrain. While the other choices describe various geological features, they do not accurately define a graben. For instance, a raised fault block is known as a 'horst,' which is the opposite of a graben. A series of parallel normal faults refers to a fault system or structural style, and a flat area between mountain ranges is typically referred to as a basin or plateau, but it does not capture the specific characteristics of a graben. Understanding the formation and structure of grabens is essential in the context of tectonic processes and landscape evolution.