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.
It can also explode violently, dispersing magma into the air that falls back to the surface as ash and tuffs. Compared to intrusive rock, this type of igneous rock cools and crystallizes at a much faster rate due to it being exposed to air or water, which results in it being fine-grained. 1  How igneous rocks are formed. Credit: Wikipedia Commons/Jasmin Ros. 2  Basalt rock, a common form of igneous rock.