Geoscience Reference
In-Depth Information
21
South American deserts
We here [in Peru] have unequivocal evidence that a ridge had been
uplifted right across the old bed of a stream . . . and a new channel
formed. From that moment, also, the neighbouring plain must
have lost its fertilising stream, and become a desert.
Charles Darwin (1809-1882)
The Voyage of H.M.S. Beagle
(3rd ed., 1845)
21.1 Introduction
South America is the only continent that extends from equatorial to high southern
latitudes and thus provides a record of continental climatic fluctuations spanning
68 degrees of latitude, from 12
30
Nto56
S. The Atacama Desert is the driest desert
on earth. It may also be the oldest (Houston and Hartley,
2003
; Hartley et al.,
2005
).
Its history is intimately associated with that of the Andes, which run parallel to the
western coastline for 7,000 km and have always exerted a major influence on regional
climate. This chapter gives an overviewof present-day environments in SouthAmerica
and of the Cenozoic evolution and Quaternary climatic fluctuations of this unique and
fascinating continent. The historic floods and droughts linked to El Ni no-Southern
Oscillation events (for which there is a 500-year annual record form Peru) are covered
in
Chapter 23
and are therefore not discussed here.
°
°
21.2 South American landscapes
Because the climates of South America, including those of the drier regions of the
continent, are so strongly influenced by its topography, we beginwith a brief account of
the major topographic elements of South America. The three dominant elements
of the South American landscape are the Andes Cordillera to the west, the plateaux
of the Precambrian Shield areas to the east and the lowlands between the Andes
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