Global sea level has fluctuated substantially in the past and is presently rising slowly. The present rise may be due to the melting of glacier ice and thermal expansion of the oceans caused by global warming. Wind action is capable of moving dry, fine sediments that are not protected by a vegetation cover and is an effective landforming agent in deserts, semiarid regions and along coasts. The removal of loose particles from the ground surface by wind is called deflation . It can produce blowouts, desert pavements and dust storms.
Sand dunes form where there is an abundant source of sand available for movement by wind.
Variations in wind conditions, vegetation cover and sand abundance produce a wide variety of dune types. Extensive loess deposits in North America were derived from fresh glacial deposits exposed at the end of the last ice age. Human disturbance of the vegetation cover in semiarid regions can expose the soil to wind erosion. Sea caves, sea arches and stacks are landforms often associated with marine cliffs. Ria coasts and fjord coasts are both coastlines of submergence.