A "Graben" is a geological term that refers to a block of the Earth's crust that has dropped between two fault lines, creating a valley. This process occurs due to tectonic forces that pull the crust apart, leading to the formation of a low-lying area surrounded by higher land. Graben structures are often found in regions with significant tectonic activity, such as rift zones. One of the most famous examples of a graben is the East African Rift, which stretches from Ethiopia to Mozambique. This rift system is characterized by a series of grabens and horsts, showcasing the dynamic nature of the Earth's surface and the ongoing processes of plate tectonics.