Master’s thesisPhysical Geography and Quaternary Geology, 60 Credits
Department of Physical Geography
Periglacial and glacial landform mapping in the Las Veguitas catchment,
Cordillera Frontal of the Andes (Argentina)
Eirini Makopoulou
NKA 2112018
Preface
This Master’s thesis is Eirini Makopoulou’s degree project in Physical Geography and
Quaternary Geology at the Department of Physical Geography, Stockholm University. The
Master’s thesis comprises 60 credits (two terms of full-time studies).
Supervisors have been Peter Kuhry at the Department of Physical Geography, Stockholm
University and Dario Trombotto at the Geocryology, CONICET, Mendoza (Argentina).
Examiner has been Johan Kleman at the Department of Physical Geography, Stockholm
University.
The author is responsible for the contents of this thesis.
Stockholm, 12 June 2018
Lars-Ove Westerberg
Vice Director of studies
Abstract
The semi-arid and arid Andes of South America are characterized by large areas with glacial
and periglacial environments. This study focusses on the distribution of glacial and periglacial
landforms in the Las Veguitas catchment, Cordillera Frontal, Argentina. A detailed
geomorphological map of the Las Veguitas catchment is presented, based on high-resolution
elevation data (ALOSPALSAR), satellite imagery (Landsat 8, World View 2, Google Earth),
and field studies. First, a general topographical analysis is performed for the entire Las
Veguitas catchment, including elevation, slope and aspect characteristics. Second, the
altitudinal range of glacial features (glaciers, debris covered glaciers and thermokarst ponds
on glaciers) and the altitudinal range and predominant aspect of periglacial features (active,
inactive and fossil rock glaciers) are analyzed. Currently, glaciers are restricted to ≥ 4300m,
but moraines are identified to elevations of c. 3200m. Active rock glaciers extend down to c.
3450m and have a more southern aspect then both inactive and fossil rock glaciers. Third, a
temporal analysis has been performed of glacier and rock glacier flow using a time series of
remote sensing images. Glacier flow traced by the displacement of thermokarst lake features
(2006-2016) had a mean velocity of 6.66m/yr. The mean velocity of rock glaciers (1963-2017)
was much lower at 0.63m/yr. Finally, the thesis discusses limitations and uncertainties in study
methods and suggestions for further research activities.
Keywords: geomorphological map, glaciers, thermokarst lakes, mountain permafrost, rock
glaciers, Argentinean Andes, remote sensing images, ArcGIS, spatial and temporal analyses
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Contents
1 Introduction ............................................................................................................................ 5
2 Background ............................................................................................................................ 7
2.1 The Cordillera de los Andes ........................................................................................... 7
2.2. Glacial history in the Central Andes ............................................................................. 8
2.3 Glacial Processes and landforms .................................................................................... 9
2.4 Periglacial Processes and landforms ............................................................................ 11
3 Study area............................................................................................................................. 15
3.1 Geology ........................................................................................................................ 15
3.2 Climate ......................................................................................................................... 16
3.3 Vegetation cover .......................................................................................................... 17
3.4 Permafrost distribution ................................................................................................. 17
4 Material and Methods .......................................................................................................... 17
4.1 Pre-field preparatory steps .................................................................................................... 19
4.2 Fieldwork ................................................................................................................................ 20
4.3 Final processing ..................................................................................................................... 21
4.4 Temporal analysis .................................................................................................................. 22
5 Results .................................................................................................................................. 23
5.1 Topography Maps ........................................................................................................ 23
5.2 Land cover and SAVI maps ......................................................................................... 25
5.3 The geomorphological map .......................................................................................... 25
6 Spatial and temporal analyses .............................................................................................. 27
6.1 Topographic analysis ................................................................................................... 27
6.1.1 Elevation, slope and aspect........................................................................................... 27
6.1.2 Landform coverage ........................................................................................................ 29
6.1.3 Altitudinal distribution of current glacial features .................................................... 29
6.1.4 Altitudinal distribution and aspect of rock glaciers .................................................. 31
6.2 Temporal Analysis ....................................................................................................... 33
6.2.1 Thermokarst lake displacement in debris covered glacier (2006-2016)................. 33
6.2.2 Stepanek and Franke rock glacier flow (1963-2017) ................................................ 35
7 Discussion ............................................................................................................................ 37
8 Conclusions .......................................................................................................................... 39
4
9 Limitations and further research .......................................................................................... 40
Acknowledgments................................................................................................................... 41
References ............................................................................................................................... 42
Appendix ................................................................................................................................. 45
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1 Introduction
The Central Andes of South America between Santiago, Chile and Mendoza, Argentina,
consists of three major parts: the Cordillera Principal, the Cordillera Frontal, and the
Precordillera. The Argentinean Andes have abundant mineral resources that attract mining
(Angillieri, 2016). Many deposits are located at higher elevations in periglacial environments.
High altitudes in combination with low mean annual air temperature are the main factors for
Andean permafrost (Trombotto, 2000). Table 1 includes variable information about the
climate, the types of landforms, and the geographic region for every mountain permafrost zone
along the Cordillera de los Andes (Garleff and Stingl, 1986). In Argentina, the presence of
continuous permafrost depends on topography and a mean annual temperature of -2o C to -4oC.
At 33o S, it is found at > 4200m. The discontinuous permafrost zone can be identified by the
presence of rock glaciers (Barsch, 1977). Currently, the lower permafrost limit in the Central
Andes is generally found at an elevation of 3700-3800m (Trombotto, 2000). The term island
permafrost was introduced for landform features found as isolated patches at c. 4000m and
relict permafrost is represented by frozen ground at elevations as low as 3400m, predominantly
in rock glaciers (Trombotto, 2000). Knowledge about the spatial distribution of rock glaciers
and permafrost is important for studies that include the environment and water management,
because rock glaciers are stores of frozen water (Brenning, 2008).
In the high Andes of Argentina and Chile, glacial and periglacial processes have been
studied since the 1970s (Corte, 1976; Wayne, 1984; Lothar, 1996; Trombotto 2000; Trombotto
et al., 1999, 2004; Trombotto and Borzotta, 2009; Azocar, 2010; Angillieri, 2016). Knowledge
of landforms, surface processes, and material distribution supplies critical information for land
practices, especially in dynamic and complex mountainous areas (Barsch et al., 1987). A
geomorphological map should contain information about lithology, morphography, structure,
hydrography, age, and process or genesis (Gustavsson et al., 2006).
This thesis aims to visualize and understand the landscape and its dynamics in the area
of Las Veguitas, Central Andes, by mapping glacial and periglacial landforms. The general
description of the geomorphology in this region has been presented by Wayne (1984), and
hydrological, geomorphological, and global warming observations have been published by
Trombotto and Borzotta (2009). The present study uses high resolution elevation
(ALOSPALSAR) and spectral data (World View 2) to map landforms and a detailed
geomorphological map has been produced. Temporal dynamics of the main glacial and
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periglacial features are assessed using a time series of remote sensing images (1963/2006 to
2016/2017), using statistical techniques with a combination of terrain attributes and remote
sensing variables.
Maps can be easily digitized, analyzed and reproduced in GIS (Geographic Information
Systems), but fieldwork remains the basis of a detailed geomorphological map. With the
technical approaches offered by digital remote sensing and GPS-localized field observations,
the geomorphological mapping can be more accurate. The detailed geomorphological map of
the Las Veguitas catchment is the first of its kind for the Central Andes near Mendoza.
Furthermore, the spatial distribution of mountain permafrost features will be used to assess the
soil organic carbon storage in Andean periglacial environments, for which a field inventory
was conducted in parallel to this study.
Table 1: Permafrost zones in the Andes, adapted from Trombotto (2000) and Garleff and Stingl (1986).
Permafrost
zones
Tropical Andes Dry Andes
(17o-31oS)
Central Andes
(31O-35OS)
Southern
Andes
Continuous
Chimborazo,
Ecuador,
(6275m)
NW Argentina,
-1/-2 oC,
<300mm/yr
-2/-4 oC, 500-
900mm/yr
Discontinuous Active rock
glaciers
Rock glaciers,
>175mm/yr
Active rock
glaciers
(Barsch, 1977)
Active rock
glaciers
Sporadic Rock glaciers Rock glaciers
Island
(Isolated
patches)
Chimborazo,
Ecuador,
<5000m
Cryobasin,
with
cryosediments
Degraded Rock glacier, ice
temp. -1.6 oC
Relict
Salt lakes in the
Atacama and
Altipano
Rock glaciers
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The specific objectives and aims of this thesis are to:
Create a comprehensive geomorphological map for the study area by mapping the
glacial and periglacial landforms by using satellite images, a digital elevation model
(DEM) and field observations
Perform a topographic analysis of the study area by processing the DEM and create
new datasets on slope and aspect
Characterize the altitudinal distribution and aspect of the main glacial and
periglacial landforms
Conduct a temporal analysis of landform dynamics using an aerial photograph from
1963 and compare it with current remote sensing data
2 Background
2.1 The Cordillera de los Andes
The Andes extend along the western side of South America and were created by plate tectonic
processes caused by the compression of the western rim of the South American Plate due to
the subduction of the Nazca Plate and the Antarctic Plate (Ollier and Pain, 2000). The range is
roughly 9000 km long and up to 750 km wide, elevation is in excess of 6000m, and the range
can be divided into three parts (Fig. 1):
1. The Southern Patagonian Andes, from Tierra del Fuego to Gulf of Penas
2. The Central Chilean-Peruvian Andes, from the Gulf of Penas to Amotape
3. The Northern Colombian-Venezuelan Andes, from Amotape to the Caribbean Arc
The evolution of the central Andes as described by Summerfield (1991), has been
continuous subduction since the Mesozoic. During an episode of mountain building that
happened in the Late Cretaceous – Early Cenozoic to the east of the earlier orogeny a period
of emplacement of granite intrusions occurred resulting in the development of the Western
Cordillera. Another consequence of this, was the transmission of compressive stresses to the
East where the Eastern Cordillera was folded and uplifted. In the Pliocene-Miocene,
emplacement of magma caused intense folding and the formation of thrust sheets in the Eastern
Cordillera. High narrow ranges were formed when the Eastern Cordillera was pressed against
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the Brazilian Shield, with the possible result of a change in the orientation of the Andes at
Amotape.
Figure 1: Major structural and morphological divisions of the Andes (modified from A. Gansser,
1973).
" Because of copyright protection, this figure is missing in its electronic format.
See: Summerfield, M. A., 1991. Global Geomorphology, John Wiley and Sons, pg. 64, or the
paper copy. "
2.2 Glacial history in the Central Andes
Clapperton (1983) summarized the glacial history of the Andes by the identification of moraine
groups or drift units from glaciers, which have been assigned to the following periods:
Holocene (10000 BP- present), the late glacial (ca. 16000-10000 BP), the last glaciation ‘late’
(ca. 30000-16000 BP), the last glaciation ‘middle and early’ (ca. 80000-30000 BP), the
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penultimate glaciation (ca. 140000-170000 BP), and the pre-penultimate Pleistocene
glaciations (<1.8-5 Ma BP).
During the last 600 years glaciers have receded dramatically in almost all the Andes
(Clapperton, 1983). Between the limits of the Little Ice Age glaciers and the moraines of the
last glaciation a number of distinct groups of lateral and terminal moraines have been
identified. In the Last Glaciation (ca. 30000-10000 BP), massive lateral-terminal moraine arcs
are located at various distances down valley from the Holocene moraines. Morphologically,
the moraines are fresh with sharp crests. The extent of Andean glacier expansion can be
distinguished at two scales, the events dating to the Holocene and those developed in the Late
Pleistocene (Clapperton, 1983), each glaciation inheriting a more eroded bed (deeper valleys
and basins) than the previous one.
2.3 Glacial Processes and landforms
During the Pleistocene epoch, large sections of the earth’s surface in temperate latitudes were
covered with huge continental ice sheets, and mountain ranges were sites of intense alpine
glaciations at altitudes 1000m below present snowlines, but these glaciers melted away some
10.000 years ago and their impressions remain upon today’s landscape (Easterbrook, 1999).
Glaciers are masses of ice and granular snow formed by compaction and
recrystallization of snow, lying largely or wholly on land and showing evidence of past or
present movement. Important parameters in this definition include the transformation of snow
into ice to thicknesses great enough to promote motion (Easterbrook, 1999). Summerfield
(1991) classified glaciers into six subtypes: ice dome, outlet glacier, ice field, cirque glacier,
valley glacier and other small glaciers. In this study, cirque glaciers are most common (Fig.
2A).
The movement of glaciers can be distinguished in two types of ice movement, internal
deformation and basal sliding, the importance of these two mechanisms varies significantly
with basal sliding accounting for up to 90% of the movement of warm-based glaciers, but being
largely inoperative in cold-based glaciers Summerfield (1991).
Two principal processes, abrasion and plucking (quarrying), are responsible for nearly
all glacial erosion (Easterbrook, 1999). It is difficult to make an estimation of the rate of the
glacial erosion processes. In the majority of glacial areas, traces of the pre-glacial surfaces are
easily recognized and thus, post-Pliocene erosion can be easily recognized, however, in
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continental glacial districts, traces of the pre-glacial surfaces appear to have been subjected to
little alteration, while at the same time there is a complete absence of soil (Pavlopoulos et al.
2009).
Summerfield, (1991) proposed that subglacial debris is transported along the base of a
glacier, but glaciers also acquire supraglacial debris through material falling on to the ice
surface from rock walls or other ice-free areas. Naturally, supraglacial debris is likely to be
most abundant in valley and cirque glaciers and absent over large areas of ice sheets. Once it
is buried, it becomes englacial debris and it can travel as such to the glacier snout (Easterbrook,
1999).
Cirques (Fig. 2A) are characterized by steep headwalls that may vary from less than
100m to many hundreds of meter high (Easterbrook, 1999). Cirque development starts with
the formation of a firn bank in a suitable depression, involving active frost weathering and
mass movement processes promoted by the presence of meltwater around the firn bank.
According to Summerfield (1991), the regular concave long profile form induces rotational
sliding, and the flow lines are inclined away from the glacier surface near the headwall and
towards the surface near the terminus. In order to maintain the ratio between height and length,
deepening of the cirque floor must be accompanied by a retreat of the headwall. It has long
been observed that the top layer of actively moving ice on a cirque glacier is usually separated
from the headwall by a deep chasm known as a bergschrund (Summerfield, 1991).
The physical characteristics of glacial sediments vary widely. Those deposited directly
from glacial ice called till, are poorly sorted and not stratified, whereas those deposited from
meltwater streams (outwash) or lakes (glaciolacustrine sediments) are sorted and stratified
(Summerfield, 1991).
Lateral Moraines (Fig. 2J & K), according to Summerfield (1991), are linear ridges
of till formed by the accumulation of rock debris along the sides of a glacier. Most of the
material is delivered to the moraine by ice movement, much of the rock debris in the lateral
moraine is derived from rock falls and tributary streams from the valley sides above the glacier
and is carried along the glacial margin until released by melting ice.
Medial Moraines are formed when two tributary glaciers come together, the inside
lateral moraines on each glacier no longer have a valley side against which to bank their lateral
moraines, and they unite to form medial moraines that form ribbon like bands down-glacier
(Easterbrook, 1999).
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End Moraines are formed by the accumulation of rock debris at the terminus of a
glacier. They are generally curvilinear in form, reflecting the shape of the glacier terminus and
they are typically composed mostly of till, although bulldozed material and lenses of sand and
gravel are not unusual (Easterbrook, 1999).
Outwash Plains (Fig. 2J) are depositions of sand and gravel by meltwater streams
beyond the margin of glaciers to produce flat, sloping plains. The plains slope away from the
glacier because of the gradient of the meltwater streams that deposit the sediments
(Easterbrook, 1999).
2.4 Periglacial Processes and landforms
The term ‘periglacial’ was introduced in 1909 by the Polish scientist Walery von Lozinski to
describe the landforms and the processes occurring around the margins of the great Pleistocene
ice sheets. Subsequently it was applied more broadly to encompass those processes and
landforms associated with very cold climates in areas not permanently covered with snow or
ice and in many cases located far from glaciers or ice sheets (Summerfield, 1991). Periglacial
refers to non-glacial processes and landforms associated with cold climates, particularly with
various aspects of frozen ground (Easterbrook, 1999). Washburn (1979) presented the
classification of periglacial climates into four distinct categories:
1. Polar lowlands with mean temperature of the coldest month <-3 oC, ice caps,
bare rock surfaces and tundra vegetation
2. Subpolar lowlands with mean temperature of the coldest month <-3 oC and the
warmest month >10 oC which roughly coincides with tree-line in the northern
hemisphere
3. Mid-latitude lowlands with mean temperature of the coldest month <-3 oC and
mean temperature >10 oC for at least four months per year, which corresponds to taiga
type of vegetation
4. Highlands where climate is influenced by altitude and latitude, and diurnal
temperature ranges tend to be large
Periglacial processes, primarily freezing and thawing, are similar to those in temperate
climates, but differ in their frequency and intensity. The effects of periglacial processes on the
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landscape are not restricted to Polar Regions, also freeze-thaw occurs in areas beyond the
permafrost regions and especially during the Pleistocene intense action of periglacial processes
in mid-latitude regions accelerated hillslope development (Easterbrook, 1999).
Solifluction (solum = soil, fluere = to flow) was described by Andersson (1906), who
recognized its importance as a gradational agent in cold climatic regions where the soil is
periodically saturated by the thawing of ice ground. Andersson (1906) defined the process as
the flowing from higher to lower ground of masses of waste saturated with water (this may
come from snow-melting or rain).
Rock glaciers (Fig. 2D, E, F), according to Summerfield (1991), are tongue-shaped
masses of angular boulders resembling in form a small glacier, they have a steep front,
exceptionally exceeding 100m in height, which stands at the angle of repose of the constituent
material. Rock glaciers are usually coming down from cirques or cliff-faces and may reach a
length of 1km or more (Summerfield, 1991).
According to Trombotto et al. (2004), an active rock glacier can be characterized as a
mass of rock fragments and finer material, generally on a slope that contains either an ice core
or interstitial ice and shows evidence of on-going movement. An example is the Stepanek rock
glacier as shown in Fig 2D. On the other hand, an inactive rock glacier is a mass of rock
fragments and finer material, on a slope that contains either an ice core or interstitial ice and
shows evidence of past but not present movement (vegetated part of the Franke rock glacier,
Fig. 2E). A fossil rock glacier can be defined as a former rock glacier area that has lost its ice
content (lower part of the Infiernillo rock glacier, Fig. 2F).
Thermokarst is a term used to describe topographic depressions formed by the thawing
of ground ice (Summerfield, 1991). When these depressions are filled with water they form
thaw lakes, also known as Thermokarst lakes (Black, 1969). In the Las Veguitas catchment,
thermokarst lakes are found on the debris covered glaciers (Fig. 2B & C).
Patterned ground is land in a periglacial region characterized by the surface material
having distinct, symmetrical and geometric shapes (Easterbrook, 1999). Washburn (1956)
developed a descriptive classification of patterned ground which emphasizes both the shape
and degree of sorting of the materials. Five basic patterns are recognized: circles (Fig. 2G &
I), nets, polygons, steps and stripes (Fig. 2H).
13
Figure 2: Glacial and periglacial landforms, illustrated by examples from the Las Veguitas catchment
(Central Andes, Argentina).
14
15
3 Study area
The study area (Fig. 3) is located between 69o 22’ and 69o26’ W and 32o 57’ and 33o 00 S in
the Cordon del Plata mountains, Cordillera Frontal, Argentina. The study area covers
approximately 30 km2 and reaches heights of approximately 5500 meters above sea level. The
highest peaks which are included in the study area are Cerro Rincon with 5420m, and Cerro
Vallecitos with 5426m. The lower limit for the study area is 3000m, where the drainage of Las
Veguitas catchment joins with the Rio Blanco river.
Figure 3: Location of the study area in South America (ArcMap Basemap) and satellite image of the
Las Veguitas catchment (World View 2).
Sources: Esri, DigitalGlobe, GeoEye, i-cubed, USDA FSA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and
the GIS User Community.
3.1 Geology
The Cordillera Frontal contains a Paleozoic basement constituted by sedimentary,
metamorphic and igneous rocks, which was strongly deformed during the Famatinian and
Gondwanan orogenic cycles (Ramos, 1988) and is intruded by Upper Paleozoic granitoids. An
16
Andean cover lies over the Paleozoic basement and is constituted by Permo-Triassic and
Cenozoic sedimentary, volcanic and volcanoclastic rocks, intruded by Mesozoic and Cenozoic
granitoids (Rabassa and Clapperton, 1990). In the Las Veguitas study area there are quartzites
and related metasediment rocks of volcanic origin, rhyolites and andesites and a few plutonic
rocks. The southern part is composed of dark colorized quartzites, whereas the northern part is
dominated by reddish-brown rhyolites (Wayne, 1984).
3.2 Climate
The study area belongs to Semi-Arid and Arid morphoclimatic zone with mean annual
temperatures of -2 to 15oC and mean annual precipitation of 300-600mm and 0-300mm,
respectively (Summerfield, 1991). According to Lliboutry (1998), conditions for areas with
this type of climate are short lived summers and rigorous winters with low temperatures, scarce
precipitation and strong winds.
The closest meteorological station to the study area is “Vallecitos” at 2550m (32o 56’ S and
69o 23’ W). The mean annual air temperature was 6.3 oC between 1979-1994 and the mean
annual precipitation 442mm between 1979-1983 (Trombotto et al. 2009). At the
meteorological station Cristo Redentor, located at 3800m (32o 54’S and 70o 12’ W), scarse data
are available for the period 1941 to 1984, with a mean annual temperature of -1.3o C, and mean
monthly temperatures ranging from c. +4 to -7o C (Fig. 4).
Figure 4: Mean monthly temperatures at Cristo Redentor, based on 13 years of complete data for the
period 1941 to 1984 (http://climexp.knmi.nl).
-8,0
-6,0
-4,0
-2,0
0,0
2,0
4,0
6,0
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Mean monthly temperatures (1941-1984)
17
3.3 Vegetation cover
The study area is located at high altitude where the vegetation cover becomes limited. With
the semi-arid and arid climate, the vegetation is represented almost exclusively by shrubs,
grasses and cushion plants. Denser vegetation is only present in small wetland areas on
outwash plains, slope fens and stable surfaces of Pleistocene moraines up to 3600m, above
which vegetation becomes very scarse.
3.4 Permafrost distribution
The South American periglacial geomorphology is determined by cryogenic processes
associated to Andean permafrost (Trombotto et al., 1997). Figure 5 shows the distribution of
permafrost along the Cordillera de los Andes, based on modelling in combination with field
evidence (Saito et al., 2016). In the Central Andes (31-35 oS), permafrost extends from the
mountain tops down to elevations of c. 3500m. Periglacial processes that occur in the Las
Veguitas study area are frost-related mass movement, solifluction, nivation, permafrost creep,
and vertical and horizontal sorting. From these processes, the landforms that have been created
are rock glaciers, solifluction lobes, and patterned ground (circles, stripes).
4 Material and Methods
Geomorphological mapping is a powerful scientific tool used to understand landscape
configuration and development (Gustavsson et al., 2006). In order to map the
geomorphological processes in the Las Veguitas catchment, an integrated analysis was carried
out based on a digital elevation model (DEM), interpretation of satellite images and aerial
photographs (Table 2), and field investigations (November 26-December 18, 2017).
Observations were made on landforms, periglacial features and vegetation cover. Despite of
the huge amount of high-resolution data on the Earth’s surface, the visual impression gained
from the direct observations in the field remains invaluable. Though field mapping by its nature
is subjective and affected by the skills (experience) of the mapper, it allows the mapper to
become familiar with the landscape.
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Figure 5: Latitude-altitude cross-section of current permafrost distribution in the Andes (adapted from
Saito et al., 2016). Dark blue: continuous permafrost; light blue. Discontinuous permafrost;
quadrangles: terminus of rock glaciers.
" Because of copyright protection, this picture is missing in its electronic format.
See: https://onlinelibrary.wiley.com/doi/epdf/10.1002/ppp.1863
Saito, K., Trombotto, D.L., Yoshikawa, K., Mori, J., Sone, T., Marchenko, S., Romanovsky,
V., Walsh, J., Hendricks, A. and Bottegal, E., 2015. Late Quaternary Permafrost Distributions
Downscaled for South America: Examinations of GCM-based Maps with Observations.
Permafrost and Periglacial Processes, pg. 51. "
Table 2: Remotely sensed information and data used in this study.
Type
Date
Resolution
Source
WorldView 2 18-03-2017 0.5 cm Digital Globe
Landsat 8 26-01-2017 30 m U.S. Geological
Survey (USGS)
Aerial Photograph ?-?-1963 1:50000 Military Geographic
Institute of Argentina
DEM
(ALOS PALSAR)
?-?-2011 12.5 m
Earth data Nasa
Satellite Imagery 03-06-2006,
04-09-2010,
20-03-2016
2.5 m Google Earth
According to Otto and Smith (2013), the production of good and purposeful maps in
the field requires a clear definition of the aims and objectives. The mapping procedure included
(1) pre-field preparatory steps, (2) the fieldwork and (3) final processing to produce the
geomorphological map. Finally, (4) a temporal analysis of glacier and rock glacier flow could
be performed based a time series of remote sensing images.
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4.1 Pre-field preparatory steps
The first step before the field study was to obtain high resolution data for the Las Veguitas
catchment. The Digital Elevation Model (DEM) was provided by Earth Data, NASA and
downloaded from https://vertex.daac.asf.alaska.edu/. The DEM has a spatial resolution of 12.5
meters and it is constructed from Radar data which were geometrically and radiometrically
corrected. The products created from the DEM are:
a topographic map
a slope map
an aspect map
a preliminary landform map
All the maps and visualizations were produced in ArcMap 10.5, ArcGIS software and
they are referenced to WGS-84 (World Geodetic System-84), using the UTM zone 19S
(Universal Transverse Mercator), as a projected coordinate system. The study area was mapped
in ArcMap 10.5 and with Google Earth Pro software (satellite imagery). All the landforms
were digitized from Google Earth Pro imagery and then converted through ArcMap 10.5 into
shape files for further analysis. The preliminary geomorphological map for the study area
(glaciers, debris covered glaciers, rock glaciers, outwash plains, moraines, cirques, thermokarst
lakes, colluvium and exposed bedrock) was prepared for a better understanding of the study
area before the field trip. The criteria for the landform classification and identification are
presented in Table 3, and are compatible with other geomorphological descriptions and
previous studies (Barsch, 1977; Summerfield, 1991; Easterbrook, 1999; Trombotto et. al.,
2004).
A satellite image from Landsat 8 with resolution 30 meters spatial resolution was
downloaded from https://earthexplorer.usgs.gov/. Based on this satellite image, the following
preliminary products were developed:
A land cover map
A Soil Adjusted Vegetation (SAVI) map
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The satellite image was processed with ENVI 5.4 software and the product is a
supervised land cover classification which includes Spectral Angle Mapper (SAM). The
SAM method is a spectral classification technique that uses an n-D angle to match pixels to
training data. This method determines the spectral similarity between two spectra by
calculating the angle between the spectra and treating them as vectors in a space with
dimensionality equal to the number of bands. Smaller angles represent closer matches to the
reference spectrum. The pixels are assigned to the class with the smallest angle (Exelis, 2015).
The selection of training data for the study area was based on Google Earth observation and
the satellite image, which resulted in the identification of four different land cover types: snow-
ice, barren ground, sparse vegetation, dense vegetation.
The Soil adjusted vegetation index (SAVI) is similar to NDVI but is used in areas
where the vegetation cover is low and it uses the red and near infrared (NIR) spectral
wavelengths to nearly eliminate the soil influences in vegetation indices (Huete, 1988). The
equation is:
SAVI = 𝑵𝑰𝑹−𝑹𝑬𝑫
𝑵𝑰𝑹+𝑹𝑬𝑫+𝑳∗ (𝟏 + 𝑳)
where “L” is a correction factor that ranges from 0 to 1. The value 0 is used when the area has
very high vegetation cover and then it becomes the same equation as NDVI. The value is 1 for
areas with very low vegetation. In this study, the value is 0.5 which is typically used for
intermediate vegetation cover (Huete, 1988).
4.2 Fieldwork
The field trip took place from the 27th of November to the 17th of December 2017. During the
field campaign the use of a hand-held GPS was helpful to localize ground truth observations.
The main purpose was to check the preliminary maps that had been created. Tracks and
waypoints from the study area show exactly the area that was covered in this field trip (Fig. 6).
The sample points are located along transects selected for the soil organic carbon inventory in
21
the study area. At these sample points, detailed descriptions of land cover and landform types
were made. Written notes and photos were also taken for better analysis.
Figure 6: GPS tracks and ground truth points from the fieldwork in the study area.
Sources: [Worldview 2] © [2018] DigitalGlobe, Inc.
4.3 Final processing
After fieldwork, a 1963 aerial photo (scale 1:50000) from the study area was obtained from
Argentinean colleagues. Furthermore, a high resolution satellite image from WorldView-2 was
acquired (spatial resolution of 50cm).
The WorldView 2 image was georeferenced through ArcGIS with 7 Ground Control
Points (GCPs), (Appendix, Fig. A1), a 1st Polynomial Order and a total Route Mean Square
(RMS) error of about 2.92m, without the distortions in or warping of the image as caused by
2nd or 3rd Polynomial Orders. The interpretation of the landforms was performed with manual
delineation, to create the final geomorphological map for the study area. An important step
was the integration and comparison from GPS field data with the already existing data and
products through ArcGIS software in order to validate remotely sensed observations.
22
The same procedure was followed for the georeferencing of the aerial photo from 1963.
For the temporal analysis described below, it was necessary to georeference the photo two
times, in different parts of the study area, because it had too many distortions and warps when
the georeferencing was done for the whole area. These two separate procedures have been done
for the two big rock glaciers in the study area (Stepanek and Franke). The algorithm that has
been used is a 1st Polynomial Order, and the RMS errors are 1.6m and 7.8m for the Stepanek
and Franke rock glaciers, respectively (Appendix, Fig. A2 & 3).
4.1.4 Temporal analysis
Glacier flow was traced through the displacement of thermokarst lakes in the debris covered
parts of glaciers. The resolution of the aerial photo was not good enough to unambiguously
recognize these features in 1963, instead this analysis has been done only through Google Earth
imagery. The dates that the study area was without clouds and snow are (Appendix, Fig. A4):
20/3/2016
9/4/2010
6/3/2006
By manual digitization from Google Earth and by exporting the data into ArcGIS, it
has been possible to calculate the size from each thermokarst lake for these years. For the
movement, the centroid has been calculated and then the distance between them between year
of observation could be used to calculate the mean velocity of the glacier flow for each interval
in meters per year.
A similar procedure has been followed for the rock glaciers. However, in this case the
1963 aerial photograph and the 2017 satellite image could be used. For the two rock glaciers
(Stepanek and Franke), the displacement of prominent ridges or lobes could be followed and
again expressed as mean velocity of rock glacier flow in meters per year.
23
5 Results
5.1 Topography Maps
The topographic map (Fig. 7) reveals the relief of the area by contour lines that represent 100m
elevation intervals. The slope map (Fig. 8) is based on the DEM (ALOSPALSAR), and
includes seven classes: 0o-2o, 2o-5o, 5o-15o, 15o-20o, 20o-25o, 25o-35o and 35o-90o, which
according to the IGU (International Geographical Union) is an acceptable way to visualize the
slope characteristics of an area but always depends on the opinion of the interpreter. The slope
algorithm from ArcMap was run on the elevation dataset. The steeper slopes are shaded red,
whereas green represent the gentler slopes. The aspect map (Fig. 9) identifies the downslope
direction of an area. It displays 45 o intervals, measured clockwise in degrees from 337.5o to
337,5o (the first interval being 337.5 o to 22.5 o, or North).
Figure 7: Topographic map of the study area
24
Figure 8: Slope map for the study area, created from the high resolution digital elevation model.
Figure 9: Aspect map of the study area, created from the high resolution digital elevation model.
25
5.2 Land cover and SAVI maps
The software ENVI 5.4 was used to develop the land cover classification (Fig. 10) and the Soil
Adjusted Vegetation Index (Fig. 11) maps. The four main classes that were recognized in the
study area are: Snow/Ice, Barren Land, Sparse Vegetation and Dense Vegetation. The Soil
Adjusted Vegetation index (SAVI) minimizes the soil brightness.
Figure 10: Land cover classification map based on the Worldview 2 image.
5.3 The geomorphological map
The geomorphological map (Fig. 12) has been completed by combining the preliminary map,
field work observations and the post mapping methods already described, using the following
criteria for identifying and mapping glacial and periglacial features (Table 3).
26
Figure 11: Soil Adjusted Index (SAVI) map.
Figure 12: Geomorphological map of the study area (for larger printout, see Appendix Fig. A5).
27
Table 3: Identification criteria for the main landforms in the study area.
Feature Identification criteria
Glacier Perennial flowing ice masses, free of debris cover
Debris covered
glacier
Debris covered flowing ice masses, often found at the terminus
of a glacier
Thermokarst lake,
glacier
Melt ponds developed in the debris covered glacier
Active rock glacier Lobate or tongue-shaped body, perennially frozen ice, inclined
front part
Inactive rock glacier There is no movement, contains some perennial ice
Fossil rock glacier There is no movement, contains no perennial ice
Lateral moraine Linear ridges of till along the sides of a glacier
Medial moraine Formed when two tributary glaciers come together by the inside
lateral moraines
Terminal moraine Ridges, generally curvilinear in form
Outwash plain Depositions of sand and gravel by meltwater streams
Colluvium with
talus
Angular shaped rock material on the slopes and foothills of
mountains, sometimes organized in distinct cones
6 Spatial and temporal analyses
6.1 Topographic analysis
6.1.1 Elevation, slope and aspect
The topographic analyses for this project are based on the DEM and the products that are
derived from it (slope, aspect). Figure 13 shows the distribution of elevation as a cumulative
proportion of the total study area (29.7 km2). Figure 14 shows the same graph, but for slope.
Both lowest and highest elevations and gentlest and steepest slopes are under-represented in
the study area. Figure 15 shows the predominant orientation of the study area, which is mostly
northeast, east and southeast on account of its location on the eastern flank of the Cordillera
Frontal.
28
Figure 13: Cumulative elevation distribution in the study area.
Figure 14: Cumulative slope distribution in the study area.
3000
3500
4000
4500
5000
5500
0% 20% 40% 60% 80% 100%
Elev
atio
n
Cumulative area
Elevation distribution
0
10
20
30
40
50
60
70
80
90
0 20 40 60 80 100
Slo
pes
in d
egre
es
Cumulative area %
Slope distribution
29
Figure 15: Orientation of the study area.
6.1.2 Landform coverage
Figure 16 shows the percent of the surface area in the Las Veguitas catchment (29.7 km2)
occupied by the various recognized landform classes. Most of the study area (c. 71%) is
characterized by exposed bedrock, located at high altitude, and colluvium on steeper slopes
(often with talus features). Landforms of glacial origin, including perennial snow patch,
glacier, debris covered glacier (with thermokarst lakes) and moraines, together occupy c. 18%
of the area. The periglacial landform rock glaciers cover c. 9% of the Las Veguitas catchment,
with the remaining c. 2% represented by outwash plains.
6.1.3 Altitudinal distribution of current glacial features
Figure 17 shows the altitudinal distribution of four types of current glacial landforms (perennial
snow patch, glacier with exposed surface ice, debris covered glacier and thermokarst lake)
within the study area. Glaciers and snow patches are found above c. 4180m, the debris covered
glacier extends down to c. 4200m, with the thermokarst lakes on the debris covered glaciers
confined to a narrow altitudinal range between c. 4350 and 4500m.
N
NE
E
SE
S
SW
W
NW
Orientation of the study area
30
Figure 16: Landform percentage cover in the Las Veguitas catchment.
Figure 17: Altitudinal distribution of the four types of current glacial features in the Las Veguitas
catchment, showing mean, median, 1st and 3rd quartiles and min/max altitude for each landform class.
0,04
0,06
0,84
0,94
1,36
2,03
2,56
3,01
4,02
6,87
7,17
34,17
36,93
0 5 10 15 20 25 30 35 40
Thermokarst lakes
Terminal Moraine
Medial Moraine
Fossil rock glacier
Inactive rock glacier
Outwash Plain
Perennial snowpatch
Glacier
Lateral Moraine
Debris covered glacier
Active rock glacier
Exposed Bedrock
Colluvium
Landform cover percentage for the study area
31
6.1.4 Altitudinal distribution and aspect of rock glaciers
A detailed analysis has been performed for the elevation and aspect of individual rock glaciers,
where the larger rock glaciers have been subdivided into their active, inactive and fossil parts
(Fig. 18). There are six larger rock glaciers with active, inactive and/or fossil parts (Stepanek,
Franke, Infiernillo, A, B and C), The seven smaller rock glaciers are all considered active.
Figures 19 and 20 show the distribution with elevation and the orientation of these rock glaciers
(and their subdivisions).
Figure 18: Location of rock glaciers in the Las Veguitas catchment.
Sources: [Worldview 2] © [2018] DigitalGlobe, Inc.
Most of the smaller active rock glaciers that exist in the study area are located at
altitudes above 3900m, the only exceptions being the small rock glacier #7 (Figs. 18 and 19).
32
All the smaller rock glaciers have in common that they have a predominantly South to East
aspect (Fig. 20) and that they are flanked on their northern side by steep mountain bedrock.
Figure 19: Altitudinal distribution of smaller active rock glaciers and larger rock glaciers (subdivided
into active, inactive and fossil parts) in the Las Veguitas catchment. For coding see Figure 18.
Among the larger rock glaciers, the active part of Stepanek reaches the lowest elevation
(terminus located at c. 3350m). This rock glacier is flanked on its northern and northeastern
side by steep mountain bedrock (Fig. 18). As in the case with the smaller active rock glaciers,
the active parts of the larger rock glaciers have often a southeastern component in their aspect
(Fig. 20). The exception is the active part of Franke rock glacier (Fig. 18) with a northeastern
aspect, but this is restricted to elevations of >4000m (Fig. 19) and for Infiernillo rock glacier
between 3900 and 4100 meters. The fossil parts from the larger rock glaciers are located
33
between 3400 and 3900 meters (Fig. 19), except for the fossil part of rock glacier A (Fig. 18),
which is located above 4000m (Fig. 19) and is oriented east to southeast. (Fig. 20).
Figure 20: Orientation of rock glaciers, grouped into active, inactive and fossil parts of the larger rock
glaciers, and the smaller active rock glaciers.
6.2 Temporal Analysis
6.2.1 Thermokarst lake displacement in debris covered glacier
(2006-2016)
For the temporal analysis of glacier flow, the main focus has been the thermokarst lakes in the
debris covered glacier of the upper, central valley (Figs. 12 and 21). In this study, thermokarst
lakes were studied through a time series of Google Earth Worldview 2 images Digital Globe
(Fig. A4). From 2006 to 2016, the number of thermokarst lakes have changed, but no trend is
34
apparent (Table 4). For the analysis of glacier flow, only five of these lakes were selected
because they were persistent and could easily be recognized despite varying snow cover over
the years of observation. Table 5 shows that the size of these thermokarst lakes, calculated by
ArcGIS in hectares, has consistently increased over time.
Table 4: Number of thermokarst lakes on the debris covered glacier through the years 2006-2010-2016.
Years 2006 2010 2016
Number of lakes 8 14 12
Table 5: Size of selected thermokarst lakes on the debris covered glacier through the years 2006-2010-
2016.
No. lakes/Year 2006 (ha) 2010 (ha) 2016 (ha)
1 0,024 0,027 0,038
2 0,028 0,041 0,100
3 0,003 0,029 0,039
4 0,009 0,014 0,039
5 0,018 0,040 0,048
Figure 21 shows the change of location of the five selected thermokarst lakes over time.
The centroid of each thermokarst lake was used to calculate the distance of displacement from
2006 to 2010 to 2016. From this, the velocity of glacier flow could be calculated (Table 6).
There is no apparent trend over the (short) periods of observation. The average velocity of
glacier flow over the period 2006-2016 is 6.66 m/yr.
Table 6: The velocity of glacier flow in m/yr deducted from the displacement of five thermokarst lakes
for the years 2006, 2010 and 2016.
No. lake/Year 2006-2010 2010-2016 2006-2016
1 4.28 5.80 5.19
2 8.52 4.63 6.19
3 9.49 6.35 7.60
4 11.15 5.14 7.54
5 6.56 6.89 6.76
35
Figure 21: Displacement of five thermokarst lakes on the debris covered glacier between 2006-2016.
Numbering refers to Tables 5 and 6.
Source: “Las Veguitas, Andes.” 32o 58´44.87´´ S and 69o 25´08.85´´ W. Google Earth Pro. March 20,
2016. Acquisition date: April 8, 2018.
6.2.2 Stepanek and Franke rock glacier flow (1963-2017)
The downward movement of the Stepanek and Franke rock glaciers was assessed by measuring
the displacement of prominent ridges and lobes that could be recognized both in the 1963 aerial
photograph and the 2017 satellite image. In order to increase accuracy, separate georeferencing
was carried out based on fixed points within the vicinity of both rock glaciers. For the
Infiernillo rock glacier, the georeferencing was not satisfactory enough.
In the case of the rock glacier Stepanek, the RMS error from the georeferencing is 1,6m.
Figure 22 shows the displacement of four distinct features between 1963 and 2017. The mean
velocity of the Stepanek rock glacier over these 54 years has been 0.98 m/yr (Table 7).
36
Figure 22: Stepanek rock glacier flow between 1963 and 2017. Numbering refers to Table 7.
Sources: [Worldview 2] © [2018] DigitalGlobe, Inc.
Table 7: Velocity calculations for Stepanek rock glacier.
No. of points Distance (meters) Velocity (m/yr.)
1 25.97 0.48
2 64.07 1.18
3 81.7 1.51
4 40.93 0.75
For the Franke rock glacier, the RMS error from the georeferencing is quite large, 7,8m. For
the displacement and velocity calculations, three points have been taken into account (Figure
23 and Table 8). In this case, the mean velocity has been calculated to 0,28 m/yr. Due to the
relative large RMS (compared to the actual calculated displacement) for the Franke rock
glacier, velocities should only be considered approximate.
37
Figure 23: Franke rock glacier flow between 1963 and 2017. Numbering refers to Table 8.
Sources: [Worldview 2] © [2018] DigitalGlobe, Inc.
Table 8: Velocity calculations for Franke rock glacier.
No. of points Distance (meters) Velocity (m/yr.)
1 14.10 0.26
2 17.94 0.33
3 13.95 0.25
7 Discussion
The studies that had been done so far for this part of the Andes mostly included larger areas in
other catchments and they studied the glacial and periglacial environments in much less detail
(Corte, 1976; Wayne, 1984; Lothar, 1996; Trombotto, 2000; Trombotto et al., 1999, 2004;
Trombotto and Borzotta, 2009; Azocar, 2010; Angillieri, 2016).
38
The purpose of this study was the creation of a detailed geomorphological map for the
Las Veguitas catchment in the Central Andes of Argentina. All landforms have been
considered as separate, discrete forms. Statistical information has been extracted from these
landforms. The produced map is one of a very few or even the first one with such a focus on
the glacial and periglacial landforms in the Central Andes of Argentina. The study area can be
seen as a representative case study for other catchments in this part of the Andes, characterized
by the presence of cirque glaciers and frost weathered debris on top of the glaciers, rock
glaciers and moraines.
The glaciers in the Las Veguitas catchment are located at elevations above 4200m, the
largest of them showing two well-developed cirques (Fig. 12). The lower part of this and other
glaciers are debris covered glaciers (with some thermokarst lakes). These debris covered
glaciers then grade into active rock glaciers that can be considered of glacigenic origin
(Trombotto and Borzotta, 2009). The smaller active rock glaciers seem to have developed
directly into slope materials.
Considering the results from this and other studies carried out in this region of
Argentina, it can be stated that rock glaciers have developed in areas with low mean annual
temperature and low precipitation, steep slopes, intensive weathering, and extensive debris
cover (Schrott et al., 2012). Most of the active rock glaciers in the study area are located well
above 3400m. They are flanked by steep bedrock to the North and have a South to East
orientation, which reduces incoming solar radiation.
The lower part of the Las Veguitas central valley is characterized by the presence of
lateral, medial and terminal moraines, which formed during former glacial advances.
According to Mercer (1976), the Cordon del Plata had large glaciers extending as far down
valley as 2600m during the last glaciation, which terminated c. 12.000 BP.
In other parts of the study area such as La Cancha (4150m; see Fig. 12), solifluction
lobes and patterned ground phenomena in the form of circles and stripes were recognized,
which can be considered representative of active periglacial processes. At an altitude of c.
3500m relict sorted circles were observed. Although dating is lacking, these relict features can
be assumed to have formed during the Little Ice Age (Clapperton, 1983).
Remote sensing techniques, including Orthorectification, and image feature tracking
were used in order to depict and measure the displacements of two larger rock glaciers in the
study area by comparison of the aerial photo from 1963 with the Worldview 2 image. The
calculated average speed in the Stepanek and Franke rock glaciers (0.98 and 0.28 m/yr,
39
respectively) are similar to those of rock glaciers in the Alps. For the latter, Barsch (1977)
reported average speeds between 0.05-1.00 m/yr.
Different stages of development can be observed in the Franke rock glacier. An active
rock glacier grades into an inactive form (at c. 4000m), with at its foot a fossil part (at c.
3600m). These three types of a rock glacier can be differentiated relatively easy. The active
part has multiple active ridges. In the inactive part, the surface has mainly stabilized and is
already partially covered with vegetation. The fossil part is mainly characterized by a collapsed
surface.
Trends in the number and size of thermokarst lakes on debris covered glaciers were
studied in the study area over the periods 2006-2010 and 2010-2016. No obvious trend was
visible in the number of thermokarst lakes, which changed from 8 to 14 and then back to 12.
However, the size of the lakes has increased over the years. This increase in size could be
related to an increase in mean annual temperature observed for the region (Trombotto and
Borzotta, 2009).
8 Conclusions
This study presents a detailed geomorphological map of the glacial and periglacial
landforms in the high altitude study area of the Las Veguitas catchment, Cordillera Frontal,
Andes, Argentina. The mapping is based on interpretation of satellite images (Worldview 2,
Landsat 8, and Google Earth) and observations in the field. The high resolution Worldview 2
image provided a solid base for an accurate identification of landforms. Geographic
Information Systems (GIS) and remote sensing are useful tools that allow the processing of a
huge amount of data and the creation of new products for any particular study. However, the
use of these two tools needs careful examination and some adjustments to the observations
from the field.
The main glacial and periglacial landforms that exist in the Las Veguitas catchment are
cirques, glaciers, debris covered glaciers (with thermokarst lakes), rock glaciers (active,
inactive and fossil), moraines and outwash plains.
The glaciers are located between 4200 and 5100m, below well-developed cirques and
they are facing mostly to the southeast, south and southwest. The debris covered glaciers are
located mostly between 4200 and 4900m, with some thermokarst lakes at 4300 with 4500m,
and a main orientation to north, northeast and east.
40
By measuring the change in location of five selected thermokarst lakes on debris
covered glaciers over the years 2006, 2010 and 2016, the average velocity of glacier flow could
be calculated to 6.66m/yr.
Almost all active parts of rock glaciers that exist in the Las Veguitas catchment are
located at altitudes above 3900m, with the exceptions being one small active rock glacier and
the lower part of the large Stepanek rock glacier. This can be explained on account of their
Southeast to South orientation. The active parts of rock glaciers with a more northern aspect,
like the Franke rock glacier; are located at higher elevations.
The rock glacier flow in the Las Veguitas catchment was calculated for the active parts
of the Stepanek and Franke rock glaciers, with a mean velocity of 0.98 and 0.28 m/yr,
respectively.
The inactive parts of the large rock glaciers are generally located at elevations below
4000m, whereas the fossil parts from the larger rock glaciers are found between 3400 and
3900m.
9 Limitations and further research
The temporal analysis of glacier and rock glacier flow could have been more accurate, by
having better-defined GCPs for the georeferencing of the aerial photo from 1963. The size of
the thermokarst lakes has also been a major limitation for a better interpretation of satellite
images or the aerial photograph, because in this area all the lakes were quite small without big
amounts of water.
Because the mapping system is still developing and Geographic Information Systems
(GIS) are still improving, it is relevant to check the accuracy of the scale in the digital
environment. An important factor about scale is when data from different sources are combined
in the analysis (Gustavsson, 2006). Aerial photographs have lower radiometric quality and
spatial resolution than the high-resolution satellite data (Worldview 2), and it is difficult to
have accurate measurements from historical aerial photographs (Sannel and Brown, 2010). In
this study, the aerial photograph from 1963 is a representative of medium data quality. The
georeferencing of the photo could not be done at one and the same time for the whole study
area because the RMS error and the distortion were too big. According to Gianinetto and
Scaioni (2008) an acceptable RMS error for an aerial photograph should be ¼ of the scale.
That means in this case that 1:50000 is 12.5m. In this study, for the three times that the aerial
41
photograph has been georeferenced, the RMS error was between 1 and 7m. It should also be
mentioned that the study area is located in a high altitude and dynamic environment, with
variable seasonal snow cover from year to year. Additionally, there are differences between
each interpreter and how they decide to process the data.
Future work in this type of mountain environment could have a similar approach but in
other catchments of the Central Andes with a different predominant orientation. As it has been
shown for rock glaciers, their distribution depends on elevation in combination with aspect.
Also, a more detailed assessment in the study area with a focus on the periglacial processes
and cryogenic structures would be very interesting. The use of radar or Lidar data for a detailed
analysis of thermokarst on glaciers would be very interesting as there are not many studies of
thermokarst lakes in the Central Andes. The analysis of rheological properties will aid in the
understanding of the movement in landforms such as rock glaciers, talus slopes and solifluction
lobes. Last, a search for techniques which can permit reliable, automated mapping of
permafrost distribution would be great value for assessing the impacts of a changing climate
on permafrost regions.
Acknowledgments
I wish to express my deepest gratitude towards my two supervisors Professor Peter Kuhry
(Department of Physical Geography, Stockholm University) and Professor Dario Trombotto
(Department of Geocryology, Instituto Argentino de Nivologia, Glaciologia y Ciencias
Ambientales, CONICET, Mendoza, Argentina) for their input and guidance. They gave me the
opportunity to perform this field work in the Argentinean Andes and helped me with the
analysis. I would also like to thank Mrs. Ivanna Pecker Marcosig and Mr. Didac Pascual, who
accompanied me on this field trip, Dr. Karin Helmens who contributed with the design of the
final geomorphological map, and last but not least, Dr. Ian Brown and Dr. Norris Lam for their
support with remote sensing and GIS throughout this report. The field work and acquisition of
aerial imagery was supported by the EU-JPI project on Constraining Uncertainties in the
Permafrost Carbon Feedback (COUP).
42
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Appendix
Fig. A1a/b: Georeferencing of the Worldview 2 image: (a) selected points, (b) table with the points
and the RMS error.
Sources: [Worldview 2] © [2018] DigitalGlobe, Inc.
46
Fig. A2a/b: Georeferencing of the aerial photo for Stepanek rock glacier: (a) selected points, (b) the
table with the points and the RMS error.
47
Fig. A3a/b: Georeferencing of the aerial photo for Franke rock glacier: (a) selected points, (b) the table
with the points and the RMS error.
48
Fig. A4: Google Earth images for the temporal analysis of thermokarst lake displacement.
Source: “Las Veguitas, Andes.” 32o 58´44.87´´ S and 69o 25´08.85´´ W. Google Earth Pro. March 20,
2016. April 9, 2010. March 6, 2006. Acquisition date: April 8, 2018.
Fig. A5 (next page): Geomorphological map of the study area (larger printout)