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This chapter describes physiographic characteristics and geomorphological processes of the southernmost portion of the Andean Cordillera. This sector of the Andean Ranges includes the only two mountain ice fields of South America which represent the largest freshwater reserve of southern Patagonia. Discharge glaciers flow out of the ice fields on both sides, modeling the landscape in the past and present times. As a product of intense glacial action, the mountain ranges show steep slopes and rugged summits with cirque glaciers. The valleys are partially occupied by lakes, some of them of large size (over 1,000 km 2). These basins are surrounded by basaltic tablelands, complex moraine systems, and glaciofluvial plains. The dominant geomorphological processes are glacial and fluvial, besides mass movements and cryogenic activity in the highest zone. The landscape is covered by several vegetation formations, adapted to the very important W-E rainfall gradient. This orographic system offers a landscape of great beauty and high biodiversity, protected within large national parks both in Argentina and Chile.
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111
Abstract This chapter describes physiographic
characteristics and geomorphological processes of the
southernmost portion of the Andean Cordillera. This
sector of the Andean Ranges includes the only two
mountain ice fields of South America which represent
the largest freshwater reserve of southern Patagonia.
Discharge glaciers flow out of the ice fields on both
sides, modeling the landscape in the past and pres-
ent times. As a product of intense glacial action, the
mountain ranges show steep slopes and rugged sum-
mits with cirque glaciers. The valleys are partially
occupied by lakes, some of them of large size (over
1,000 km2). These basins are surrounded by basaltic
tablelands, complex moraine systems, and glacioflu-
vial plains. The dominant geomorphological processes
are glacial and fluvial, besides mass movements and
cryogenic activity in the highest zone. The landscape
is covered by several vegetation formations, adapted
to the very important W–E rainfall gradient. This oro-
graphic system offers a landscape of great beauty and
high biodiversity, protected within large national parks
both in Argentina and Chile.
Keywords Andean Cordillera • Patagonia • glaciers
• climatic gradient
12.1 Introduction
The Patagonian region occupies the southern end of
the South American continent, extending between lati-
tudes 37° and 56°S. Along its western portion the
Andean Cordillera is located, being the result of
Cenozoic orogenic processes and intense plutonic and
volcanic activity. This section of the Cordillera is
known as the Cordillera Patagónica or Patagonian
Andes. The Cordillera Principal, where Mount
Aconcagua (6,900 m a.s.l; the highest peak in the
Southern Hemisphere) is located, is found northwards,
in central Argentina and northernmost Patagonia. This
mountain range is the backbone of South America,
being the most important positive relief element at the
continental scale.
The Southern Patagonian Andes (Ramos 1999)
extend from the latitude of Lago Fontana (44º58´S)
until the Seno Otway (53º55´S) in the Magellan Straits
region. At latitude 46º30´S it is divided in two seg-
ments whose structure, geological composition, topog-
raphy, and geological history are significantly different.
This boundary is coincident with the Aysén Triple
Junction, which in the Pacific Ocean sector separates
the Nazca and the Antarctic plates (Ramos 1989). The
northern area, though it exposes a volcanic arc, has
lower relative relief than the southern sector. The latter
is described below in greater detail due to the large
variability of its geomorphological features, typical of
high mountain environments modeled by past and
present glacial processes.
12.2 Geology
The southern portion of the Southern Patagonian
Andes (Fig. 12.1) is composed of a fold-and-thrust
belt, generated by the collision of the Pacific tectonic
plates, which caused shortening and uplifting of the
mountain ranges (Ramos 1989). It includes many
granitic peaks such as San Valentín, San Lorenzo, the
famous Fitz Roy or Chaltén, Murallón, Stockes, and
the spectacular Torres del Paine, whose elevations
range between 2,000 and 3,400 m above present sea
level. All these features have impressive, almost vertical
Chapter 12
The Southern Patagonian Andes: The Largest Mountain Ice Cap
of the Southern Hemisphere
Elizabeth Mazzoni, Andrea Coronato, and Jorge Rabassa
P. Migon´ (ed.), Geomorphological Landscapes of the World,
DOI 10.1007/978-90-481-3055-9_12, © Springer Science+Business Media B.V. 2010
112 E. Mazzoni et al.
sideslopes modeled by glacial erosion, of great interest
to expert climbers and mountaineers.
This portion of the Cordillera has a few small volcanic
cones, which are found south of 48°S along the Andean
Volcanic Zone (AVZ) (Stern 2007), coinciding with the
segment of the Antarctic oceanic plate which is sub-
ducting underneath the South American continental
platform. In the AVZ only six small stratovolcanoes are
Fig. 12.1 Location map (Modified from Coronato et al. 2008), indicating the position of the Southern Patagonian Andes
11312 The Southern Patagonian Andes: The Largest Mountain Ice Cap of the Southern Hemisphere
found, largely separated from each other, located in the
westernmost portion of the Cordillera. Some of them,
as the Lautaro and Viedma volcanoes, occur amidst the
Patagonian Ice Cap. Volcán Lautaro is the most active,
with many historical records of activity (Martinic
1988). Other volcanoes, such as Aguilera, Reclus, and
Mount Burney have had eruptions during Late Glacial
and Holocene times (Stern 2007).
12.3 Climate and Vegetation
The regional climatic conditions show strong gradients
both from W–E and N–S and also in altitude, allowing
one to distinguish different climate types. The W–E
gradient is determined by the action of the South Pacific
Anticyclone, which sends winds that discharge most of
their moisture on the western side of the Patagonian
Andes. Thus, total rainfall reaches 4,000 mm per year
along the Pacific Ocean coast (hyperoceanic and oceanic
climates) and then diminishes to values between 1,200
and 730 mm per year at the western side of the Andes, at
the meteorological stations of Coyhaique (45.6ºS, 72.1ºW;
310 m a.s.l.) and Cochrane (47.23ºS, 72.55ºW; 182 m
a.s.l.), respectively (Servicio Meteorológico de Chile,
http://www.meteochile.cl/climas/climas_undecima_
region.html). Along the eastern slope and piedmont area
precipitation varies between approximately 400 and 200
mm per year, defining sub-humid to semiarid climate
types. At the El Calafate meteorological station (50.4ºS,
72ºW; 204 m a.s.l.; Estación Meteorológica El Calafate,
Servicio Meteorológico Argentino) only 123 mm of
annual rainfall was recorded in the 1981–1990 decade.
The N–S gradient is related to latitudinal position
and generates progressive temperature lowering south-
wards. The topographic effect is also shown in the
thermal gradient. Starting from 800 m a.s.l., tempera-
tures are low enough to maintain ice fields. There are
no reliable meteorological records in this sector, but it
may be estimated that the mean annual temperature
may be slightly below 0°C. The mean maximum tem-
peratures rise above 0°C only in summer time, whereas
the mean minimum temperatures are likely to be below
0°C all year around and are extremely low in winter,
thus generating almost exclusively snowfall (www.
meteochile.cl). Under these conditions, there are no
permanent human settlements in this area.
This climatic gradient has a great influence on the
geomorphological and ecological processes, which
produce contrasting landscapes as the observer moves
from west to east. In this sense, and over a distance of
approximately 50 km, the environment changes from
very humid to semiarid climates and from rugged
mountain landscapes to horizontal or sub-horizontal
surfaces, accompanied by ecosystems ranging from
evergreen forests composed mainly of Nothofagus
betuloides (‘guindo’) in the western portion, to meso-
phyllic forests, formed basically by deciduous trees
such as Nothofagus pumilio (‘lenga’) and Nothofagus
antarctica (‘ñire’). Forests occupy mainly the moun-
tain slopes whereas natural pastures occur in the valley
floors. Toward the eastern margin of the Southern
Patagonian Andes, grassy and xeric steppes are found
in contact with the forest (Roig 1998).
Above the upper tree limit, approximately located
at 1,500 m a.s.l., high altitude tundra is developed,
with different types such as Magellanic tundra, Andean
tundra, high altitude prairies with cushion plants and
stony surfaces, showing sparse vegetation (Roig 1998,
Fig. 12.2).
12.4 Glaciers and Lakes
Snow precipitation feeds the accumulation zones of
the mountain ice sheet and other glaciers, known as a
whole as the Northern and Southern Patagonian
Icefield (Hielo Patagónico Norte and Hielo Patagónico
Sur, NPI and SPI, respectively). These ice fields, which
together cover up to 17,200 km2 (Skvarca 2002), are
the most important ones in South America and form a
very significant freshwater reserve for Southern
Patagonia. Discharge outlet glaciers descend from the
ice fields along both eastern and western slopes (see
Table 12.1; Figs. 12.3 and 12.4).
The SPI is the more extended icefield, being the
largest mass of ice in the Southern Hemisphere outside
of Antarctica (Aniya et al. 1996). It has mean width of 35
km and minimum width of 9 km, and is composed of 48
major outlet glaciers and over 100 small cirque and valley
glaciers (Casassa et al. 2002). Glaciers on the western
slopes end in deep fjords, whereas those in the eastern
slope do so into relict glacial lakes located in ecotone
areas. The largest glacier is the Pio XI Glacier on the
western slope, followed by the Viedma and Uppsala
glaciers, which flow toward the eastern Andean slope.
In the Glaciares National Park of Argentina, close
to the town of El Calafate, the Perito Moreno Glacier
114 E. Mazzoni et al.
is noteworthy as one of the most accessible glacier
tongues in temperate regions of the world, very well
known for its peculiar glaciological dynamics, charac-
terized by repeated advance of its front and subsequent
damming of the southernmost branch of Lago
Argentino, known as Brazo Rico. This glacier has a
length of 30 km and an ice surface of 258 km2, distrib-
uted from an elevation of 2,950 m a.s.l. to its terminal
front into the aforementioned lake at an elevation of
only 175 m a.s.l.
The glacier has not shown significant thickness
changes in recent decades (Rignot et al. 2003) suggesting
that its mass balance is in equilibrium (Rott et al. 1998)
due to, among other factors, the fact that its hypsomet-
ric distribution presents a strong slope in the zone
around its equilibrium line altitude (ELA). Thus the
temperature increase that took place in Patagonia
between 1960 and 1990 (Rosenblüth et al. 1997) has
not forced any significant reduction of its accumula-
tion zone (Naruse et al. 1995). This glacier has one of
the highest net annual accumulation rates on the planet
(5,250 ± 474 kg m−2) and a very high rate of ice loss
due to calving (that is, iceberg formation), which also
explains the ice front stability of recent decades
(Stuefer 1999). Table 12.1 shows the main characteris-
tics of the outlet glaciers of the Patagonian Ice Cap.
The lakes of this region are amongst the largest
freshwater bodies in the South American continent,
among which the Buenos Aires, Viedma, and Argentino
lakes are the largest, each of them with surface areas
above 1,000 km2. Table 12.2 provides the basic charac-
teristics of the major Southern Patagonian lakes.
The drainage system is well-integrated and includes
the upper reaches of allochtonous streams that drain
Fig. 12.2 Typical landscape of the Southern Patagonian Andes,
where the amplitude of its relative relief may be observed, as
well as the presence of forest ecosystems occupying the slopes
almost up to the permanent snowline. In the foreground, a detail
of several Nothofagus individuals. In the center of the picture is
the Río de las Vueltas (49º07’S; 72º55’W) (Photo E. Mazzoni)
115
12 The Southern Patagonian Andes: The Largest Mountain Ice Cap of the Southern Hemisphere
toward the Atlantic Ocean and smaller basins which
cross the Andean ranges toward the Pacific Ocean.
12.5 Landforms and Geomorphological
Processes
The mountain ranges that form the Southern Patagonian
Andes have, in general, very abrupt slopes and sum-
mits, with cirque glaciers and glacial troughs occupied
by many lake basins (Fig. 12.4). The relative local relief
is very significant, sometimes over 2,000–2,500 m. The
bottoms of the larger glacial valleys are located around
200 m a.s.l. These valleys are bounded by basaltic
tablelands, complex moraine systems, and glaciofluvial
plains that originated either during the Last Glacial
Maximum (LGM), which took place around 25,000
years ago (Singer et al. 2004; Kaplan et al. 2004;
Rabassa 2008) or during Early and Middle Pleistocene
glaciations (Rabassa et al. 2005; Rabassa 2008).
This orographic system, modeled by past and
present glacial action, covered by dense, pristine for-
ests and drained by mountains creeks and lacustrine
basins, offers a magnificent landscape of noted beauty
and rich biodiversity which is protected by the Los
Glaciares and Perito Moreno national parks in
Argentina and the Bernardo O’Higgins and Torres del
Paine national parks in Chile, several of them having
been inscribed as UNESCO World Heritage monuments
(see Fig. 12.1 for location).
The geomorphic processes that have modeled these
landscapes are diverse and complex, including endog-
enous and exogenous agents, whose relative participa-
tion varies according to the analyzed geographical
areas. The orogenic and volcanic processes had their
maximum expression during earlier periods of the
Cenozoic, but are still very active, being associated
with the subduction of the Pacific oceanic plates such
as the Nazca and the Antarctic plates underneath the
South American continent. The intense eruption of
Volcán Hudson (45º55’S, 72º58’W) in 1991 covered
thousands of square kilometers in the Province of
Santa Cruz (Argentina) with volcanic ashes that
reached as far as Tierra del Fuego. As a noted testi-
mony of the present volcanic activity, while a first draft
of this chapter was being completed, Volcán Chaitén
(43º30’S) was erupting in Chile, throwing its ashes on
to the Argentinean city of Esquel, located 100 km east-
wards, to the entire piedmont area of the Northern
Patagonian Andes in Argentina and even to the Atlantic
coast of Buenos Aires province (38°S).
Table 12.1 Physical characteristics of several outlet glaciers from the Southern Patagonian Icefield (From Casassa et al. 2002).
Information is only partially available for most glaciers
Glacier name Location
Length
(km)
Total area
(km2)
Maximum
elevation (m)
Minimum
elevation (m)
Equilibrium
Line Altitude (m) Orientation
Jorge Montt 48º 04´ S, 42 464 2,640 0 950 N
73º 30´ W
Greve 48º 58´ S, 51 438 3,607 1,000 NW-W
73º 55´ W
HPS8 49º 02´ S 11 38 SE
73º 47´W
Pío XI 49º 13´ S 64 1,265 3,607 0 W
74º W
Amalia 50º 57´ S 21 158 0 900 W
73º 45´ W
Tyndall 51º 15´ S 32 331 50 900 E
71º 15´W
Perito Moreno 50º 30´ S 30 258 2,950 175 1,150 NE
73º W
Uppsala 49º 59´ S 60 902 3,180 175 1,150 SE
73º 17´ W
Viedma 49º 31´ S 71 945 250 1,250 E-S
73º 01´ W
O’Higgins 48º 55´ S 46 810 3,607 285 1,300 N-S-E
73º 08´W
116 E. Mazzoni et al.
Cryogenic and glacial processes are still active
above the tree limit, at the summits and within upper
slopes (Fig. 12.5). Glacier action is evident in the low-
lands, where the large lakes of the eastern piedmont
area are located, but also down to present sea level at
the western margin, where an intricate network of gla-
cial troughs, fjords, and channels was excavated by the
Pleistocene glaciers during the LGM, when sea level
was at least 120 m lower than today. Mass movement
processes shaped the slopes, leading to the origin of
stony surfaces in the higher zones of bare rocks, whereas
landslides affected the forested slopes during periods of
exceptionally high precipitation. Debris flows are con-
centrated in channels and ephemeral stream beds, trans-
porting big glacial boulders and tree trunks, which
usually generate drainage obstruction or diversion, and
block roads in the piedmont or lowland areas.
Fluvial action appears to be dominant at present,
basically due to the high erosive power of mountain
streams. The high availability of water in the system,
provided by ice and snow melt and abundant oro-
graphic precipitation, is shown by a very high drainage
Fig. 12.3 Satellite mosaic in which the Southern Patagonian
Ice Cap and its discharge glaciers are shown (the images are
Landsat 7, Band 8). In whitish, shiny tones the fresh snow is
distinguished from the icefields, where the highest peaks of the
mountain ranges are found. The glaciers appear in greyish tones,
draining toward large Patagonian lakes of the eastern slopes or
to the Pacific coastal fjords
117
12 The Southern Patagonian Andes: The Largest Mountain Ice Cap of the Southern Hemisphere
density of fluvial networks composed of permanent
and ephemeral streams. The trunk streams reach the
lower portions of the landscape where they flow in the
main, flat-bottomed, ancient glacial valleys with
braided channel patterns. In these conditions, streams
lose energy and increase alluvial deposition.
Fig. 12.4 A view of the Southern Patagonian Ice Cap, between
49º07’ and 50º34’S. The Landsat image (a) shows the main dis-
charge glaciers coming from this icefield, which reach different
fjord-like branches of the Viedma (upper) and Argentino (lower)
lakes along the eastern slopes. The southernmost glacier that
appears in the image is the Perito Moreno Glacier, whose details
are shown in the lower picture (d-picture 3). Photograph b-pic-
ture 1 exposes the granitic arête in which the famous peaks
Cerro Fitz Roy and Cerro Torre are found, as well as the cirque
and valley glaciers of the area. In the central photography
(c-picture 2) the transitional tablelands/Cordillera landscape
and the immense amplitude of the Patagonian landscape may be
observed. There, the main housing facilities of the “estancias”
are the only expressions of human activity, detected by implanted
European trees (mostly poplars), which provide some shelter
from the roaring westerlies. In the central section of the photo-
graph the Viedma Glacier and Lago Viedma are found (Photos
E. Mazzoni)
118 E. Mazzoni et al.
Table 12.2 Physical characteristics of the most important lakes located along the Southern Patagonian Andes. In italics, the Chilean
name of the lakes if they extend both in Argentina and Chile. Location was measured in the central point of the lake; the absolute
maximum depth of many of these lakes is still unknown
Lake name Location m a.s.l. Surface (km2)
Maximum
depth (m) Mean depth (m)
Length of the
shoreline (km) Slope
Buenos Aires 46º 29´S 217 1,850 590 No data 422.1 Pacific
General Carreras 71º 26’ W
Pueyrredón 47º 20´S 320 No data No data 171.5 Pacific
Cochrane 71º 56´W
Posadas 47º 30´S 112 45.3 No data 31.2 26.6 Endorreic
71º 50´W
Belgrano 47º 47´S 919 42.8 No data No data 1.4 Atlantic
72º 14´W
Burminster 47º 51´S 931 14 No data No data 68 Atlantic
72º 08´W
San Martín 49º 08´S 285 1,013 836 No data 571 Pacific
O’Higgins 72º40´W
Del Desierto 49º 02´S 12 No data 70 22.7 Atlantic
72º 52´W
Viedma 49º37´S 250 1,100 No data No data 234 Atlantic
72º30´W
Argentino 50º 13´S 187 1,466 500 150 558.2 Atlantic
72º 30´O
Fig. 12.5 At elevations above 1,500 m a.s.l. tundra and stony surfaces with sparse vegetation are found. In these high portions of
the landscape, glacial and cryogenic processes are particularly active (Photo A. Coronato)
11912 The Southern Patagonian Andes : The Largest Mountain Ice Cap of the Southern Hemisphere
At the eastern piedmont of the Andes, where the
large relict glacial lakes are found, coastal processes
have modeled their shores by intense wave action,
forced by the permanent action of the westerlies. In
these open spaces, parabolic and longitudinal dunes
are found, as well as aeolian pavements. These mostly
occur along ancient shorelines lacking vegetation or in
deforested areas or those with vegetation degraded by
desertification processes (Fig. 12.6).
12.6 Final Remarks
The Southern Patagonian Andes is one of the regions
with the highest landscape diversity of the austral end
of the South American continent. This geomorpholog-
ical diversity, due to the regional geological and climate
characteristics, offers a variety of natural resources,
particularly those of a scenic nature which have
determined that a large portion of these territories is
protected as national parks and natural reserves,
including the declaration of the Los Glaciares National
Park, among others, as a UNESCO World Heritage site
in 1981.
This mountain environment has a wet, cold climate
that allows for the development of dense forest cover
on its slopes and the survival of one of the most impor-
tant icefields of the temperate regions on Earth. The
availability of water resources is also shown in a very
dense drainage network composed of many streams
and large lakes of glacial origin. The rugged relief and
the abundance of ice and water have favored the devel-
opment of active geomorphological processes that are
accompanied by very strong wind action, particularly
in the eastern piedmont.
Fig. 12.6 A view of dune fields, partially covered by vegetation, extending along the eastern margins of large lakes (Photo E. Mazzoni)
120 E. Mazzoni et al.
Some of the most beautiful and spectacular land-
scapes in the Southern Hemisphere are found in the
Southern Patagonian Andes. The combination of lively
Cenozoic tectonics, powerful volcanic activity, vigor-
ous glacial action, abundant meltwater runoff, a harsh
climate, and pristine ecosystems has created the geo-
morphological conditions for the development of such
a magnificent landscape.
The Authors
Elizabeth Mazzoni is Professor of Geomorphology
and Remote Sensing at the Universidad Nacional de la
Patagonia Austral (UNPA), Río Gallegos, Argentina.
She is a member of the Laboratorio de Teledetección
and GIS, Unidad Académica Río Gallegos, UNPA,
working on projects in physical geography and remote
sensing. In recent years she has worked on geomor-
phology and hydrology of Patagonian volcanic land-
scapes, desertification, and continental wetlands in arid
environments.
Andrea Coronato is Professor of Physical Geography
at the Universidad Nacional de la Patagonia-San Juan
Bosco in Ushuaia, Tierra del Fuego, Argentina, and
researcher of the Laboratorio de Cuaternario, Centro
Austral de Investigaciones Científicas (CADIC),
Consejo Nacional de Investigaciones Científicas y
Tecnológicas (CONICET) at Ushuaia, with emphasis
on the physical geography, geomorphology, and
paleoenvironments of Southern Patagonia and Tierra
del Fuego. In the last years she has worked on the
study of glacial, fluvial, and aeolian geomorphology,
Quaternary glaciations and environmental impact of
Canadian beavers on fluvial systems of Tierra del
Fuego.
Jorge Rabassa is Professor of Geography at the
Universidad Nacional de la Patagonia-San Juan Bosco,
Ushuaia, Tierra del Fuego, Argentina, and researcher
of the Laboratorio de Cuaternario, Centro Austral de
Investigaciones Científicas (CADIC), Consejo
Nacional de Investigaciones Científicas y Tecnológicas
(CONICET) at Ushuaia, working on Late Cenozoic
geology, geomorphology, and paleoenvironments.
During the past years he has studied glacial geology
and geomorphology of Southern Patagonia and Tierra
del Fuego, Late Cenozoic glaciations, and the impact
of global climate change on Patagonian glaciers. His
recent publications include the book The Late Cenozoic
of Patagonia and Tierra del Fuego (2008).
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Innsbruck
... Patagonia is a continental landmass that emerges at mid-latitudes in the Southern Hemisphere, encompassing Pacific and Atlantic lowlands and coasts, valleys, archipelagos, tablelands and high plains (Coronato et al. 2008). It is a nearly pristine environment that extends from 37°S to Cape Horn, made up of unique aquatic and terrestrial ecosystems (Mazzoni et al. 2010); it contains the third most important reserve of freshwater in the world (Vince 2010) and includes a high diversity of lakes, rivers and fjords . The fjord region provides essential ecosystem services, which are often ignored in the assessment of development projects; it is now considered a highly vulnerable region (Iriarte et al. 2010). ...
... The geographical location of the Baker River gives us the opportunity to quantify LRD (if detected) in a Southern Hemisphere river and also to test specific hypotheses about its possible origin. We expect a high level of LRD in the Baker River runoff time series, because it drains freshwater from two large reservoirs: the Northern Patagonia Icefield which includes 28 glaciers with an ice surface area of about 4200 km 2 (Aniya 1988) and General Carrera Lake (1850 km 2 , Mazzoni et al. 2010) (Figure 1). The continuous freshwater contribution of both reservoirs through time makes it likely that monthly runoff values are strongly correlated well beyond the seasonal time scale. ...
Article
The Baker River is the largest free-flowing river in Chilean Patagonia. Long-range dependence (LRD), a recognised hydrological property of river runoff worldwide, was detected for the Baker River runoff time series. Analyses were conducted on a monthly scale between 1961 and 2015 using the fractal and multifractal detrended fluctuation analysis methodology. A long-range-dependent Hurst coefficient (H) equal to 0.94 was obtained. A scaling range, which is the signature of LRD, was detected for the Baker River runoff time series between 1 and 5.25 years. Baker River runoff showed a strong correlation (r = 0.96) with the Antarctic Oscillation (AAO) Index during the 2007–2015 period. The high storage capacity of Lake General Carrera, the size of the Baker River basin area and the dynamics of AAO are proposed as main factors that contribute to the emergence of LRD in the Baker River runoff time series.
... Southern Patagonia in Argentina and Chile hosts some of the most spectacular glaciated landscapes on Earth, including both glaciers themselves and a variety of glacial and paraglacial landforms inherited from the Pleistocene and earlier intervals of the Holocene (Mazzoni et al. 2010). ...
Article
Geodiversity and geoheritage play an increasingly important role in the tourism industry, although visitors’ interest in natural phenomena is much older than these two, relatively modern concepts. This chapter reviews several key issues emerging at the interface of geoheritage and the needs and expectations of the tourism industry, both tourists and service providers. Specific themes discussed include evaluation of geodiversity and geoheritage resources for tourism purposes, problems of interpreting Earth heritage for the general public, accessibility issues related to conservation, and the role of geoparks and allied initiatives in fostering local development. More general overviews are supplemented by case studies, illustrating each theme. These are taken from various localities globally, from Europe, South America and Oceania. It is concluded that the coverage of thematic studies at the interface between geoheritage resources and tourism science is uneven. Inventories and assessments of geoheritage and geodiversity sites for geotourism are widely reported and new resources for geotourism development are commonly explored, whereas much less is known about the actual perception of geoheritage values among visitors and the quality and effectiveness of their interpretation. Likewise, the positive impact of geotourism on local economies seems to be more hypothesized or anticipated than actually demonstrated.
... The Nunatak Viedma located in the Southern Patagonian Icefield ( Fig. 1; 49°22′S, 73°19′W), has been considered as an active volcano because of its geomorphologic features, which resemble a group of volcanoes (Lliboutry, 1956;Mazzoni et al., 2010). The early descriptions were based on the first aerial survey that covered the Patagonian icefields (Lliboutry, 1956). ...
Article
The Nunatak Viedma within the Southern Patagonian Icefield has been considered as a volcanic center based on its geomorphologic features, despite the fact that field explorations by Eric Shipton determined its metamorphic nature 70 years ago. We carried out fieldwork to characterize this isolated outcrop and performed the first U-Pb dating in detrital zircons from the basement rocks located inside the Southern Patagonian Icefield. We recognized very-low grade metamorphic rocks, corresponding principally to metapelites and metapsammites, and scarce metabasites. Detrital zircons in three metapsammitic samples (composite group of 240 grains) yielded prominent age population peaks at ∼1090, ∼960, ∼630, ∼520, ∼480–460, ∼380, ∼290–260, ∼235-225 Ma that are typical of Gondwanide affinity, and youngest grains at ∼208 Ma. Maximum depositional ages of 225, 223 and 212 Ma were calculated for each sample from the youngest cluster of ages. This distinctive and novelty Late Triassic age justifies differentiate the Nunatak Viedma Unit from the Devonian-early Carboniferous and Permian-Early Triassic (?) belts of the Eastern Andean Metamorphic Complex. Possible primary source areas for the detrital zircons are outcropping in southern Patagonia, the Antarctic Peninsula, and the Malvinas Islands. Additionally, secondary sources could be part of the erosion and recycling of metasediments from the Eastern Andean Metamorphic Complex. We propose that the cluster of Triassic ages is related to the volcanic arc emplaced along the Antarctic Peninsula and active at that time when was still attached to southern Patagonia during the Triassic. The dynamics of the early Mesozoic orogen is also discussed.
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Rime mushrooms, commonly called ice mushrooms, are large bulbous or mushroom-shaped accretions of hard rime that build up on the upwind side of mountain summits and ridges and on windward rock faces. This paper reviews the characteristics of rime mushrooms; the topographical, geographical, and meteorological conditions under which they form; and the significant challenge they pose to climbers. Photographs and descriptions from Southern Patagonia, where rime mushrooms are well known, illustrate the phenomenon.
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The foothills of the northern segment of the Magallanes basin between 47° and 49°S latitudes record the development of a complex fold-and-thrust belt in the Patagonian Cordillera during the late Miocene. Upper Paleozoic sedimentary and metasedimentary rocks and thick sequences of Lower Cretaceous deposits with well-defined source and reservoir rocks are deformed by the Andean events. The structure is characterized by a triangle zone and a series of related underthrusts, which define a nonemergent backthrust system at the mountain front. The stratigraphy of the molasse deposits constrains the beginning of the deformation at least to the early Tertiary. Analysis of the evolving subduction zone located west of and beneath the study area shows that the formation of a subsequent volcanic gap in the magmatic arc and the development of extensive retro-arc basalts are related to the collision of a segment of the Chile Ridge during the late Miocene. -from Author
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A Landsat TM mosaic of the Southern Patagonia Icefield (SPI), South America, was utilized as an image base map to inventory its outlet glaciers. The spI is South America's larg-est ice mass with an area of approximately 13,000 km2. The icefield does not have complete topographic map coverage. With the aid of stereoscopic interpretation of aerial photo-graphs and digital enhancement of the Landsat TM image, glacier divides were located and glacier drainage basins were delineated, giving a total of 48 outlet glaciers. Employing a supervised classification using Landsat TM bands 1, 4, and 5, glacier drainage basins were further divided into accumula-tion and ablation areas, thereby determining the position of the transient snow line (TSL). After comparing with existing data, it was found that the TSL could be taken, for practical purposes, as the equilibrium line (EL). The position of the TSL was then compared with topographic maps, where available, to determine the equilibrium line altitude (ELA). Altogether, 11 parameters relating primarily to glacier morphology were inventoried. Pio XI Glacier (1265 kmz) is found to be the largest outlet glacier in South America, a i d m a y also be its longest. The average accumulation area ratio of 0.75 is larger than those of the Northern Patagonia Icefield and European glaciers. All but two outlet glaciers calve into fjords or pro-glacial lakes.
Article
We present here a review of the current glaciological knowledge of the Southern Patagonia Icefield (SPI). With an area of 13,000 km2 and 48 major glaciers, the SPI is the largest ice mass in the Southern Hemisphere outside of Antarctica. The glacier inventory and recent glacier variations are presented, as well as ice thickness data and its variations, ice velocity, ablation, accumulation, hydrological characteristics, climate changes and implications for sea level rise. Most of the glaciers have been retreating, with a few in a state of equilibrium and advance. Glacier retreat is interpreted primarily as a response to regional atmospheric warming and to a lesser extent, to precipitation decrease observed during the last century in this region. The general retreat of SPI has resulted in an estimated contribution of 6% to the global rise in sea level due to melting of small glaciers and ice caps. Many glaciological characteristics of the SPI, in particular its mass balance, need to be determined more precisely.
Article
During the Pleistocene, east of Lago Buenos Aires, Argentina, at 46.5degreesS, at least 19 terminal moraines were deposited as piedmont glaciers from the Patagonian ice cap advanced onto the semi-arid high plains adjacent to the southern Andes. Exceptional preservation of these deposits offers a rare opportunity to document ice-cap fluctuations during the last 1.2 m.y. Ar-40/ Ar-39 incremental-heating and unspiked K-Ar experiments on four basaltic lava flows interbedded with the moraines provide a chronologic framework for the entire glacial sequence. The Ar-40/Ar-39 isochron ages of three lavas that overlie till 90 km east of the Cordillera at Lago Buenos Aires, and another 120 km from the Andes along Rio Gallegos at 51.8degreesS that underlies till, strongly suggest that the ice cap reached its greatest eastward extent ca. 1100 ka. At least six moraines were deposited within the 256 k.y. period bracketed by basaltic eruptions at 1016 +/- 10 ka and 760 +/- 14 ka. Similarly, six younger, more proximal moraines were deposited during an similar to651 k.y. period bracketed by an underlying 760 14 ka basalt and the 109 +/- 3 ka Cerro Volcan basalt flow that buried all six moraines. Coupled with in situ cosmogenic surface exposure ages of moraine boulders, the 109 ka age of Cerro Volcan implies that moraines deposited during the penultimate local glaciation correspond to marine oxygen isotope stage 6. Further westward toward Lago Buenos Aires, six additional moraines younger than the Cerro Volcan basalt flow occur. Surface exposure dating of boulders on these moraines, combined with the C-14 age of overlying varved lacustrine sediment, indicates deposition during the Last Glacial Maximum (LGM, 23-16 ka). Although Antarctic dust records signal an important Patagonian glaciation at 60-40 ka, moraines corresponding to marine oxygen isotope stage 4 are not preserved at Lago Buenos Aires; apparently, these were overrun and obliterated by the younger ice advance at 23 ka. Notwithstanding, the overall pattern of glaciation in Patagonia is one of diminishing eastward extent of ice during successive glacial advances over the past 1 m.y. We hypothesize that tectonically driven uplift of the Patagonian Andes, which began in the Pliocene, yet continued into the Quaternary, in part due to subduction of the Chile rise spreading center during the past 2 m.y., maximized the ice accumulation area and ice extent by 1.1 Ma. Subsequent deep glacial erosion has reduced the accumulation area, resulting in less extensive glaciers over time.
Article
Accumulation, ablation, calving, and flow dynamics of Moreno Glacier, one of the main outlet glaciers of the Southern Patagonia Icefield, were studied based on field campaigns and on spaceborne radar imagery acquired by SIR-C/X-SAR. Ice velocities and ablation were measured through two summers and one winter. The ice depth was sounded seismically at a transect 8 km above the calving front, showing a maximum depth of 720 m. The velocity field of the terminus was derived from SIR-C/X-SAR data by means of interferometry and amplitude correlation. The average specific annual net accumulation is 5540+/-500mm water equivalent. The bottom topography of the lake and the high ratio of calving flux to net accumulation explain the remarkable stability of Moreno Glacier throughout this century which is in contrast to the retreat of other glaciers in this region.