What is a horst in geological terms?

A horst is defined as an uplifted block of the Earth's crust that is bordered by normal faults. The critical aspect of a horst is its relationship to these faults; it arises when the land between two normal faults drops down, effectively pushing the horst upward in comparison to the surrounding terrain. This uplifting process results in a structure that typically stands out in the landscape, often characterized by steep sides and a relatively flat top.

Understanding the geological significance of a horst involves recognizing its role in the broader context of tectonic processes. It can influence local geology, hydrology, and even ecosystems due to its elevation and the elevation gradient it creates in the surrounding area.

In contrast, a down-dropped block, known as a graben, occurs when the land between two normal faults sinks rather than rises. The options referring to sedimentary structures or lateral movement in fault zones do not accurately capture the definition of a horst, further reinforcing the distinction between these geological terms.