Precarious boulder
From Wikipedia, the free encyclopedia
Precarious boulder refers to a large rock or boulder resting either on the ground or on another rock in an apparently unstable position. This can arise by a few mechanisms:
- Erosion may have removed the basal rock or sediment, leaving the boulder exposed
- The rock may have been transported from an ice sheet and was left exposed when the ice retreated—this is more accurately called a glacial erratic
- The rock may have been transported and placed at the location from a catastrophic geologic process, such as:
- Through a rockfall
- From a volcanic eruption, which results in lava bombs
- From a cataclysmic flood, such as a glacial lake outburst flood
 Yeager Rock, a 400 ton erratic on the Waterville Plateau, Washington, USA. |
 A precarious boulder, which was first transported from a rockfall, then exposed on a column of sediment from erosion. |
 A lava bomb from the Capelinhos Volcano, Faial Island, Azores. |
