separation animation have been heavily eroded by the
Quaternary glaciations. from 1990 to 2000
Paleozoic Era The oldest rocks in Chile are
micaceous
schists,
phyllites,
gneisses and
quartzites, many examples of which are found in the
Coast Range of south-central Chile. The schists of
southern Chile were initially formed by sediment in the proto-Pacific Ocean, and later metamorphosed in the
forearc wedge of the Peru–Chile Trench.
Mesozoic Era During the
Triassic Period about 250 million years ago Chile was part of the
supercontinent Pangaea, which concentrated the world's major land masses.
Africa,
Antarctica,
Australia and
India were near Chile. When Pangaea began to split apart during the
Jurassic period, South America and the adjacent land masses formed
Gondwana. Floral affinities among these now-distant landmasses date from the Gondwanaland period. South America separated from Antarctica and Australia 27 million years ago with the development of the
Drake Passage. Across the -wide Drake Passage lie the mountains of the
Antarctic Peninsula, south of the Scotia plate, which appear to be a continuation of the Andes. In the extreme south, the
Magallanes–Fagnano Fault separates
Tierra del Fuego from the small
Scotia plate. The formation of the Andes began during the Jurassic. During the
Cretaceous, the Andes began to assume their present form by the uplifting,
faulting and
folding of
sedimentary and
metamorphic rocks of ancient
cratons. Tectonic forces along the
subduction zone along the west coast of South America continue to their
orogenesis, resulting in earthquakes and volcanic eruptions to this day.
Cenozoic Era The
Altiplano plateau was formed during the
Tertiary, with several mechanisms proposed; all attempt to explain why the topography of the Andes incorporates a large area of low relief at high altitude (high plateau): • Existence of weaknesses in the Earth's crust prior to tectonic shortening. Such weaknesses would cause the partition of tectonic deformation and uplift into eastern and western cordillera, leaving the necessary space for the formation of the Altiplano basin. • Magmatic processes rooted in the asthenosphere might have contributed to uplift the plateau. • Climate controlled the spatial distribution of erosion and sediment deposition, creating the lubrication along the Nazca plate subduction and hence influencing the transmission of tectonic forces into South America. • Climate also determined the formation of internal drainage (endorheism) and sediment trapping within the Andes, potentially blocking tectonic deformation in the area between the two cordilleras.
Quaternary The
Quaternary glaciations left visible marks in most parts of Chile, particularly
Zona Sur and
Zona Austral. These include
ice fields,
fjords,
glacial lakes and u-shaped valleys. During the
Santa María glaciation glaciers extended into the Pacific Ocean at 42° south, dividing the
Chilean Coast Range and creating what is now
Chacao Channel.
Chiloé, part of the Chilean Coast Range, became an island. South of Chacao Channel, Chile's coast is split by fjords, islands and channels; these glaciers created
moraines at the edges of the Patagonian lakes, changing their outlets to the Pacific and shifting the
continental divide. The remnants of the
Patagonian Ice Sheet which covered large parts of Chile and
Argentina are the
Northern and the
Southern Patagonian Ice Fields. It has been suggested that from 1675 to 1850 the
San Rafael Glacier advanced during the
Little Ice Age. The first documented visit to the area was made in 1675 by the Spanish explorer
Antonio de Vea, who entered
San Rafael Lagoon through
Río Témpanos ("Ice Floe River") without mentioning the many
ice floes for which the river is named. De Vea also wrote that the
San Rafael Glacier did not reach far into the lagoon. In 1766 another expedition noticed that the glacier did reach the lagoon and had
calved into
icebergs.
Hans Steffen visited the area in 1898, noting that the glacier now penetrated far into the lagoon. As of 2001, the glacier has retreated behind its 1675 border due to climate change. ==Pacific islands==