GeologyRocks

Ultrabasic

A rock which contains mainly ferro-magnesium minerals and feldspars with the virtual exclusion of quartz.

Unconformity

A break in the stratigraphic record which represents a period of no sediment deposition. The interval of geologic time not represented is called a hiatus.

There are three types of unconformities: disconformity, nonconformity, and angular unconformity.

Unloading

Unloading usually results in pressure release formations. A good example is the tilting of the UK due to the removal of ice sheets in the north. Scotland is moving upwards, southern Britain is moving downwards. The evidence can be seen in raised beaches in Scotland, which gives the past sea level.