Blowout (geology)

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Blowouts are sandy depressions in a sand dune ecosystem (psammosere) caused by removal of material by wind.

Sand dunes are found just inland from a beach, and are formed as the wind blows dry sand inland beyond the beach. It follows that this can only happen when there is an area of reasonably flat land inland from the beach. In time, this rather inhospitable surface will be colonised by pioneer species. These species (e.g. marram grass) will stabilise the dunes and prevent them moving any more. The process of plant succession will eventually see these dunes converted to woodland (in the UK anyway - it depends on the climate) and a mature soil will have formed.

A blowout can occur when something destroys an area of this vegetation, allowing the wind once again to start to move the sand in that area.

Causes of destruction include fire (natural or caused by humans) or in, extreme cases, trampling by feet, horses, cars, bicycles etc. Fire is the most common cause, however.

In time, succession will begin again as suitable seeds are blown in and pioneers will become re-established.

Although they generally remain small, they can expand up to kilometers in size and up to around 70m in depth. They are an important habitat for flora and fauna.