Here's a breakdown of the key aspects of this definition:
* Natural: Caves are formed by natural processes, such as weathering, erosion, and geological activity. They are not man-made.
* Underground: Caves are located beneath the surface of the Earth.
* Opening or void: They are spaces within the Earth that are not filled with solid rock.
* Large enough for a human to enter: This distinguishes caves from smaller openings like fissures or cracks.
Cave formation processes include:
* Dissolution: The most common process, especially for limestone caves, where acidic water dissolves the rock over time.
* Erosion: Water, wind, or ice can wear away rock, creating cavities that eventually become caves.
* Lava tubes: When volcanic lava flows leave hollow channels, these can later become caves.
* Faulting and fracturing: Movement of the Earth's crust can create cracks and fissures that evolve into caves.
Understanding these formation processes helps us appreciate the diversity of cave types, sizes, and shapes found across the globe.