Medical Definition of amnesia. 1: loss of memory sometimes including the memory of personal identity due to brain injury, shock, fatigue, repression, or illness or sometimes induced by anesthesia a period of amnesia after the wreck.
Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call mud. This composition places shale in a category of sedimentary rocks known as mudstones.
Igneous rocks can be subjected to heat, pressure, and the action of fluids to form metamorphic rocks. Igneous rocks can be re-melted, forming a new generation of igneous rocks. Sedimentary rocks can be weathered and eroded to form a new generation of sedimentary rocks.