Topography generally affects climate and soils and plays a considerable role in the differentiation and distribution of climates and vegetation zones. For example, the Caspian zone is humid, due to the high Alborz mountain range. In the Sefid-Rud valley as a result of the low altitude, dry winds from the interior move towards Guilan, creating an area of low rainfall which extends up to some 40 kilometres from Rasht (Capital of Guilan Province). The great chain of Albors and Zagros forms a “V shaped” natural barrier which inhibits the humid winds of the southwest and prevents the majority of clouds from reaching the centre of the country, so steppes and deserts are created.