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Dassen Island

Dassen Island is situated about 10km west of Yzerfontein and 55km north of Cape Town half way between Table Bay and Saldanha Bay). The island is a proclaimed nature reserve and is the biggest island off South Africa's west coast.


It is about 4.5km long & 2km wide.  The island is flat and low-lying with its highest point about 18m high (most of the island lies well below this).

Except for the eastern side, which is clear of dangers, Dassen Island is fringed with dangerous reefs & many ships have run aground here.  It is composed of a fine-grained tourmaline-granite (with a few areas of biotite granite) outcrop covered with sand.  Some of the granites along the shore, to just above the high-water mark, consists of large, rounded boulders - which sticks out above the sand.  

Though in the winter temporary pans forms in the interior, there is generally little fresh water on the island.

The island is surrounded by the cold Atlantic Ocean, which has a tempering effect on its temperatures.


In summer the prevailing winds come from the south and south-west, and in winter they prevail from the north and north-west.  The spring months are the calmest (from September till Novemeber).

Dassen Island experiences sunny, dry summers & relatively wet winters  (a temperate, Mediterranean-type climate). The hottest months are normally January to March, and the coldest July. 
The largest chunk of rain occurs from May until September, with July usually being the wettest month. The average annual rainfall for the period 1990-1999 was about 330 mm.

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