What is defined as a "highwall" in surface mining?

In surface mining, a "highwall" is defined as the steep cliff face that remains after the overburden has been removed to extract coal or other minerals. This vertical or near-vertical wall forms as the material above the coal seam is stripped away, revealing the mineral deposit below.

Understanding the highwall is critical for mining operations, as it poses significant safety concerns and potential hazards. The stability of the highwall is essential to prevent collapses that could endanger workers and equipment. Additionally, monitoring the highwall conditions can help in the planning of further mining activities and in implementing necessary protective measures.

In the context of other options, while blasting is an important aspect of surface mining, it does not define a highwall. The lowest point of the excavation site refers to the bottom of the mine pit rather than the vertical face of the highwall. Lastly, a safety barrier for equipment is a different concept focused on operational safety, rather than describing a geological feature.