[2] Together with the Quaternary glaciations in the Southern Andes, the diagonal has controlled the distribution of vegetation throughout Chile and Argentina.
[4] The northern portion of the Arid Diagonal is a result of the blocking of the trade winds by the barrier formed by the Central Andes and the South Pacific High.
[5] To the south in the westerlies, the rain shadow that the Southern Andes cast over eastern Patagonia similarly blocks moisture.
[3] The origin of the aridity of the northern part of the diagonal is linked to two geologic events: a) the rise of the Andes — an event that led to the permanent block of both the westward flow of moisture along the tropics, and the eastward flow of moisture in Patagonia[6] and b) the permanent intrusion of cold Antarctic waters (the Humboldt Current) along South America's west coast.
[5] Together with the Quaternary glaciations in the Southern Andes, the diagonal controls the distribution of the vegetation types over Chile and Argentina.