Ключевые слова: abstract, aged, background, cave, creation, crust, danger, debris, dissolving, earth, effect, element, environment, eroded, erosion, excavation, exploration, exposed, extraction, formation, fossil, geological, geology, ground, historic, iron, layered, layers, mass, material, mine, mineral, mineralization, mountain, natural, old, process, risk, rock, rocks, rough, science, search, sedimentary, sediments, site, slope, slow, stone, structure, surface, texture, textured, time, travel,