The discovery of the periglacial realm

The term periglacial was introduced by the Polish geologist Walery von Lozinsk in 1910 and 1911 to describe the particular mechanical weathering he had observed in sandstones of the Gorgany Range in the southern Carpathian Mountains - today the reactions of the permafrost to changing temperatures is one of the major fields of research. Read more about the periglacial realm on the American Scientific Blog.

The Permafrost Menace

The term permafrost is primarily associated with regions such as Alaska and Siberia, with a vegetation-free tundra, rock-hard frozen ground, and with the famous finds of well preserved carcasses of ice age mammals. But permafrost occurs in much wider geographic range, at least 23% of the Earth surface is influenced by permafrost.

Permanently frozen ground or permafrost is by definition material (bedrock or loose material), which remains at least for one year or two winters frozen, with temperatures below 0 ° C. Water, and so ice, is not necessary "needed" in permafrost, therefore called dry permafrost, but this kind of frozen ground plays geomorphological a minor role.

Climatic change has important effects on the distribution and the energy balance of permafrost , so influencing the amount of ice conservated in it. Permafrost occurence depends of various climatic (like temperature, insolation, precipitation and snowcover) and also from geomorphological (like exposition) and biological (like vegetation cover) factors - the role and interplaying between this factors is still poorly understand.
Permafrost in the middle latutudes lays only some degress under the melting point of water of 0°C, even a sligthly warming of the mean air temperature - and surface temperature, can heavily affect permafrost. The distribution diminuishes, and the depth of the active layer - the layer of permafrost that defrost´s during summer, increases.

How exactly permafrost reacts to the observed warming of 0,5°C during the last century in the Alps is still poorly known, and the exact mechanisms not understand. The strong retreat of glaciers is obvious, but permafrost was though to react much slower, because of the insolation effect of the covering debris layer. But observations of temperature profiles in drillholes showed that percoliating water, resulting from melting of more superficial ice, can "tranport" heat much faster in the underground.

Studying permafrost is a hard job, especially if it hides inside compact rock. PermaNet drill site in the valley of Schnals.

Morains and talus cones not only are habitats for specific, sometimes endemic animals and plants, but consists of loose debris hold together most time only by ice in the cavities between the boulders. Loosing permafrost can destabilise rock walls and debris, causing rockfalls and debris flows, and so putting infrastructures and humans life in danger. In the last 10 years the greatest rockfalls in the Swiss Alps occured in permafrost affected areas, one of the most spectacular in summer 2006 felt from the east-wall of the Eiger.

The rockfall of the Thurwieser mountain (3.652m, 46° 29` 45`` N, 10° 31` 28`` E) occurred on 19.09.2004 (first image befor, second after). 4,5 million cubic meters material felt on the underlying glacier and boulders up to 50 cubic meters slipped on it until 2000m a.s.l. The rockfall was caused probable by ice degradation.

The melting permafrost can influence the percolation and the paths that groundwater can take, so influencing springs. Observations in the european Alps and the Colorado Front Range showed also a change in the water chemistry in lakes and springs where permafrost features, like rock glaciers, occur in the catchement area. The change in water balance and presence can also effect the distribution of vegetation and the species richness of a habitat.

The active rockglacier at Hohe Gaisl - implications on genesis

Active rockglaciers are less common in the mountain ranges composed of carbonatic rocks, such as the Northern Cretaceous Alps ort he Dolomites, even if here more than lithology probably the minor mean elevation plays a role.
Although few active rockglaciers are present in the Dolomites, they have never been studied in detail.
One studied rockglacier is located in the “Gletscherkar (glacier cirque)” on the north-eastern side of the Hohe Gaisl (3146m). The rockglacier lies in a deeply incised cirque, surrounded by steep walls composed of upper Triassic dolomite and limestone.

Fig.1. Air photos and digital terrain modell of the Hohe Gaisl mountain group with two active rockglaciers in the north-eastern cirques (Autonomous Province of Bozen/Bolzano - South Tyrol)

Fig.2. View to west on the Hohe Gaisl mountain group with two active rockglaciers in the north-eastern exposed, deeply incised cirques. The visited rockglacier can be found in the right cirque (north).

Debris of the rockglacier is mainly derived from a prominent, NW-SE-trending fault, along which the bedrock is intensively deformed. The rockglacier is 850m long, 300-550m wide and covers an area of 0,3 square kilometres. The rockglacier extends from an altitude of 2340m at the front to about 2500m. The eastern lobe shows well developed surface topography of transverse ridges and furrows. The surface is coarse grained and varies from place to place, manly constituted of poorly sorted gravel and sand, huge boulders are missing, great blocks exceeding 1m are rare.

Fig.3. View to west on front of the "Gletscherkar" rockglacier.

In the upper part massive ice is exposed during the summer months at several places below a less than 1m thick debris layer. The ice is coarse-grained, banded, and contains thin, fine-grained debris layers parallel to the banding. Rarely larger clasts occur within the ice.
During the melting season small thermokarst lakes may be developed on the upper part of the rockglacier.

Fig.4a. Ice-exposure on the rockglacier (15.09.2007).
Fig.4b. Fine-grained debris layers parallel to the banding in the ice (15.09.2007).

Georadar measurements provided information on the internal structure and thickness of the rockglacier. The data indicate that the rockglacier has a total thickness of approximately 25m. In the lower and middle part the debris layer is 3-5m thick. Below the debris layer numerous, well developed reflectors are visible indicating the presence of shear planes in the frozen body of the rockglacier, which according to ice exposure in the upper part is composed of coarse (glacier) ice with numerous thin debris layers parallel to the banding. A thin sediment layer (?lodgement till) may be present at the base of the rockglacier.

Internal structure and ice exposure clearly indicate that the rockglacier in the Gletscherkar developed from a debris-covered cirque glacier. It is suggested that the glacier has developed from a small cirque glacier during retreat trough inefficiency of sediment transfer from the glacier ice to the meltwater. The presence of a cirque glacier at Gletscherkar is documented in the older literature and on older maps, for example on a topographic map published in 1902 (FREYTAG 1902).

References:

KRAINER, K. & LANG, K. (2007): Active rock glaciers at Hohe Gaisl (eastern Dolomites). Geo.Alp 4, 127-131
LANG, K. (2006): Geologie des Hohe Gaisl Massivs (Pragser- und Ampezzaner Dolomiten) unter besonderer Berücksichtigung der aktiven Blockgletscher. Unveröff. Diplomarbeit, Institut für Geologie und Paläontologie Leopold-Franzens-Universität Innsbruck, 170S.
SHRODER, J.F.; BISHOP, M.P.; COPLAND, L. & SLOAN, V.F. (2000): Debris-covered glaciers
and rock glaciers in the Nanga Parbat Himalya, Pakistan. Geografiska Annaler 82(A):
17 - 31

Rockglaciers from Mars !!!

"No one would have believed in the last years of the 20th century that this world was being watched keenly and closely by intelligences other than martians's and yet as mortal as his own. Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this mars with envious eyes, and slowly and surely drew their plans against us. "

From all planets and minor objects of the solar system, most similarities to features of periglacial regions on Earth can be found on the red neighbour - Mars.
The term periglacial refers here to immediate results of frost as climatic factor acting on soil substrat/detritus (geologic component).

Even if the terminus is mostly debated and in part imprecise, he can be summarized as “conditions, processes and landforms associated with cold, nonglacial environment”.

Permafrost – perennially frozen soil- is one diagnostic criteria for a periglacial environment, that can, but mustn’t contain ground ice. In the last case it can be called “dry permafrost”, but it plays a minor role in the development of characteristics or spectacular landforms of the periglacial realm.
The most spectacular forms of permafrost imply the presence of water and ice. Pingos (or hydrolaccolith), literally small mountains, contain a core of pure ice, and can reach up to 50m high. Other features that imply frozen water are ice-wedges or ice-lens and bodies.
Important macroscale features of permafrost are rockglaciers. Rockglaciers can best be defined by their morphology, saying that a rockglacier is “an accumulation of angular rock debris that contains either interstitial ice or an ice core and shows evidence of movement through creep and deformation of the ice-part”.

The presence of ice on Mars was never questioned. Even the first modern geographical maps by american astronomer Richard Antony Proctor from 1867 located two huge icecaps on both the poles. Today we know that the polar ice caps of Mars contain at least a part of water-ice, but it seemed not so extraordinary much, in ever case lesser, then some author speculated needed for a civilisation on Mars.

The question still remaining –even today- is, how much ice, and so water exist on Mars, and where else it can be found, in an atmosphere with so less pressure that it is prohibiting that water can exist in liquid form (at least for a longer period)? Models showed that a cover of detritus could prevent the ice to sublimate, so allowing in theory in some regions great amounts of subsurface ice, and maybe even liquid water. But how to prove the existence of this modelled ice?

Landforms indicative of ground ice on Mars have known since the first flyby missions of the 1960s. Images from Viking orbiters provided an overwhelming list of permafrost and ground ice indicators.
Mars resembles an astounding variety of landforms that on Earth can found in recent glacier covered, and/or in past glaciated areas, like patterned ground, thermokarst, mass movement phenomena, cirques and horns, grooves and valley troughs filled with morain-like material. On earth they are declared to prove glacial to periglacial conditions and glacier ice. On the other side, on Mars there exist a lot of forms that have no counterpart on Earth.

The most recent space probes measured the emission of neutrons from the surface of Mars. Water ice adsorbs more neutrons that dry detritus, so mapping the amount can be used to map and estimate the presumed water ice content of the first meters of the surface detritus, the so called regolith.

Fig.1. Watercontent in percent of weigth of the martian regolith, ranging from 3% (light blu) to 11% (dark blue). The presence of water ice is correlated with latitude, radiation and elevation/temperature. Red zones are areas with dense numbers of "debris aprons" (after KERR 2003).

The Phoenix Mission finally discovered subsurface ice covered only by centimeters of some dust and detritus on the high latitude (ca. 70°N) of the northern hemisphere. But still they prove only an ice content up to 6-11% in the first 1 to 2 meters of the regolith.

On Mars there are different types of features whose morphology certainly indicate the presence of deep buried ground ice - rampart craters, debris flows, lobate debris aprons, terrain softening and collapsing and patterned or polygonal terrain.

Many martian craters have a unique morphology - they are surrounded by lobes or tongues with layered ejecta, terminating in a low ridge or escarpment. This “rampart craters” are unique for Mars in our solar system, and probably represents refrozen ejecta from an impact that melted the subsurface ice-rocks mixture.

Most curious and debated are very large features, up to hundreds of kilometres long, that shows ridges and furrows on their surface, and seem to flow along rock walls and follow valleys.

Three main forms can be distinguished

- linear valley fills – long features, that resembles lava flows that fill the valleys

- pancake-like crater fills (like found in the hourglass crater)

- and lobate to tonguelike shorter mass movements, that initiate from a rock wall, shows a pronounced ridge and furrow morphology, and end with a gently slope on flat terrain.

Fig.2. Infrared MOC-image, east of the Hellas-basin, Mars. A typical association of debris aprons, debris tongues and crater fills. Note the superimposed features in the center of image. Scale in 100 kilometers.

Interpretations range from lavaflows, that some features resemble, to vast mass-movements and rockfalls deposits.
The huge aureole deposits, that form a ring extending up to 1.000km around the basal escarpment of Olympus Mouns, were also interpreted to represent immense submarine landslides.

Studies on (primarily mentioned) terrestrial rockglaciers and debris-covered glaciers in recent years offered a new explanation – the rockglacier like features on Mars are - according to the duck test … rockglaciers.

Fig.3. Terrestrial rockglaciers, Alps. Scale in 100 of meters. Showing a tongue like rockglaciers, and two "lobate debris aprons".

A rockglacier can be active - containing enough ice to show creep and deformation, inactive – still containing ice, but to less to show movement, and relictic – containing no more ice, but still displaying the morphology of past movement

Under modern climatic conditions on Mars, and assuming a behaviour comparable with terrestrial rockglaciers in Antarctica, the rockglaciers on Mars can possibly be active containig both water as CO2-ice in a belt stretching approximately on the 30° latitude (Fig.4).

Fig.4. Martian rockglaciers. Mean elevation data map (blu - deep, red - high) showing areas with high density of lobate debris aprons, like east of the Hellas basin, the chaotic terrain from Deuteronilus and Protonilus Mensae, the west escarpment of Olympus Mons and the Argyre basin.

MOC (Mars Global Surveyor Camera) Orbiter images of lineated valley fills and lobate debris aprons show that the surface of this features are practically uncratered, indicating likely emplacement and formation within the past several million years. With this method, the lobes of Olympus Mons were dated to be polygenetic with ages ranging between 280-130, 60-20, and -surprisingly- 4 million years and younger.

Fig.5. The west escarpment of Olympus Mons, with pronounced lobes (note the ridges)expanding for more then 200 km (scale) - some authors interpreted the morphology as deposits from glaciers, or remanents of debris covered glaciers. It is unclear however if they still contain ice.

However at current Mars surface temperatures, and very low accumulation rates of material, flow rates large ice masses would be so slow, that they could not be younger then 1 to 10 millions of years, but still much older then the crater counting let conclude. But assuming higher past temperatures in geologically speaking recent times, a young age became more convincing.
Overlapping tongues seen on some lobes even let assume that they were periodically active, implying possibly glacial and interglacial periods on Mars, driven by the steep tilted axis of Mars (15-35°).

The distribution of the presumed activ and relict rockglaciers seem to support this hypothesis, they only occur in a narrow belt of 30 to 50° of latitude on both hemisphere, region that in past “passed trough” the climatic zone that enables the formation of great amounts of ice and activity of rockglaciers (Fig.4.).

Discovery of microbial activity inside of active terrestrial rockglaciers give room for speculation that rockglaciers on Mars can be a habitat for primitive live forms. Pressure of the overlaying rockdetritus, with an average thickness calculated from thermodynamic constrictions of 200 up to 300 meters, maybe melt some waterice, or some water pentrates from deeper zones of the martian crust on the base of the formations and create pockets of liquid water.

And so we are (re) arrived to new frontiers...

P.S.

Until today, rockglaciers are only known from Earth and Mars. Mercury and Venus are much to hot to possess water, or even ice. The gas giants lack a surface, and the minor objects in the solar system seemed to small or to cold to enables creep and deformation of material.
But the Voyager in 1979, and the Cassini-Galileo in 1997 mission have provided some images from one of the moons of Jupiter, Callisto.

The high resolution image from the Galileo space probe shows a crater with a lobate deposit, protruding from the craterrim to the centre for 3 to 3.5 kilometers.

The nature of this morphology is still unknown, possible interpretation includes landslides or creep of ice-detritus mixture. The morphology, tonguelike to lobate with a low surface angle and a steep escarpment at the end resemble a rockglacier. But the very low temperature on the surface of Callisto of -180°C does not support creep of water ice. Alternately a different ice component, like methane or other gases, maybe is still capable to deform and so creep along the inner craterrim.

References:

BAKER, V.R. (2001): Water and the martian landscape. Nature, 412: 228-236
BARSCH, D. (1996). Rockglaciers. Indicators for the Present and Former Geoecology in High Mountain Environments. Berlin, Springer-Verlag: 331
CABROL, N.A. & GRIN, E.A. (2005): 10. Ancient and Recent Lakes on Mars. In (ed.) Tokano, T.: Water on Mars and Life. Adv. Astrobiol. Biogeophys, Springer, Berlin, Heidelberg
CHUANG, F.C. & CROWN, D.A. (2005): Surface characteristics and degradational history of debris aprons in the Tempe Terra/Mareotis fossae region of Mars. Icarus, 179: 24-42
DEGENHARDT Jr., J.J. & GIARDINO, J.R. (2003): Subsurface investigation of a rock glacier using ground-penetrating radar: Implications for locating stored water on Mars. Journal of Geophysical Research, 108: 8036-8053
EISFELD, R. & JESCHKE, W. (2003): Marsfieber-Aufbruch zum Roten Planeten Phantasie und Wirklichkeit. Droemer-Verlag, München: 272
EVIN, M. (1987): Dynamique, repartition et áge des glaciers rocheux des Alpes du Sud. PhD thesis. Université de Grenoble.
FARMER, C. B. & DOMS, P. E. (1979): Global and seasonal variation of water vapor
on Mars and the implications for permafrost. Journal of Geophysical Research, 84: 2881– 2888

GASSELT, S. (2007): Cold-Climate Landforms on Mars. PhD University of Berlin
HUMLUM, O. (1982): Rock glacier types on Disko, central West Greenland. Norsk Geografisk Tidsskrift, 82: 59-66
HUMLUM, O. (1998): The Climatic Signifcance of Rock Glaciers. Permafrost and Periglacial Processes, 9 (4):375-395
HUMLUM, O. (2000): The geomorphic significance of rock glaciers: estimates of rock glacier debris volumes and headwall recession rates in West Greenland. Geomorphology, 35 (1-2): 41-67
HUMLUM, O.; CHRISTIANSEN, H.H. & JULIUSSEN, H. (2007): Avalanche-derived Rock Glaciers in Svalbard. Permafrost and Periglacial Processes,18: 75-88
HVIDBERG, C.S. (2005): 6. Polar Caps. In (ed.) Tokano, T.: Water on Mars and Life. Adv. Astrobiol. Biogeophys, Springer, Berlin, Heidelberg
KERR, R.A. (2003): Iceball Mars? Science, 300: 233-236
KRAINER, K. & MOSTLER, W. (2006): Flow velocities of active rock glaciers in the Austrian Alps. Geografiska Annaler, 88 A (4): 267-280
KUZMIN, R.O. (2005): 7. Ground Ice in the Martian Regolith. In (ed.) Tokano, T.: Water on Mars and Life. Adv. Astrobiol. Biogeophys, Springer, Berlin, Heidelberg
LANG, K. (2006): Geologie des Hohe Gaisl Massives (Pragser - und Ampezzaner Dolomiten) unter besonderer Berücksichtigung der aktiven Blockgletscher. Diplomarbeit, Naturwiss. Fak. Univ. Innsbruck : 172
MAHANEY, W.C.; MIYAMOTO, H.; DOHM, J.M.; BAKER, V.R. & CABROL, N.A. (2007): Rock glaciers on Mars: Earth-based clues to Mar’ recent paleoclimatic history. Planetary and Space Science 55: 181-192
MASSON, P.: CARR, M.H.; COSTARD, F.; GREELEY, R.; HAUBER, E. & JAUMANN, R. (2001): Geomorphological evidence for liquid water. Space Science Reviews 96: 333-364,
Neukum,G.; Jaumann, R..; Hoffmann, H.; Hauber,H.; Head, J. W.; Basilevsky, A. T. ; Ivanov, B. A.; Werner, S. C.; van Gasselt, S.; Murray, J. B.; McCord T. & The HRSC Co-Investigator Team (2004): Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera. Nature , 432: 971-979
NICOLUSSI, K. (1986): Höhengrenzen im Nord-Süd-Profil über die Stubaier und Ötztaler Alpen: Waldgrenze - Blockgletscher - Permafrostuntergrenze – Schneegrenze. Diplomarbeit, Naturwiss. Fak. Univ. Innsbruck: 89
PIERCE, T.L. & CROWN, D.A. (2003): Morphologic and topographic analysis of debris aprons in the eastern Hellas region. Mars. Icarus, 163: 46-65
ROSSI, A.P.; CHICARRO, A.; PACIFI, A.; PONDRELLI, M.; HELBERT, J.; BENKHOFF, J.; ZEGERS, T. FOING, B.; NEUKUM, G. & HRSC Co-Investigator Team (2006): Widespread periglacial landforms in Thaumasia Highland, Mars. Lunar and Planetary Science XXXVII
SCHMINCKE, H.U. (2004): Volcanism. Springer-Verlag, Berlin-Heidelber-New York: 324
SERRANO, E. & LOPEZ-MARTINEZ, J. (2000): Rock glaciers in the South Shetland Islands, Western Antarctica. Geomorphology 35:145-162
SQUYRES, S.W. (1979): The distribution of lobate debris aprons and similar flows on Mars. Journal of Geophysical Research 84: 8087-8096
WHALLEY, W.B. & PALMER, C.F. (1998): A glacial interpretation for the origin and formation of the Marinet Rock Glacier, Alpes Maritimes, France. Geografiska Annaler 80A (3-4): 221-236
WHALLEY, W.B. & AZIZI, A. (2003): Rock glaciers and protalus landforms: Analogous forms and ice sources on Earth and Mars. Journal of Geophysical Research 108: 8032 – 8045
WILLIAMS, M. (2004): CU-BOULDER research team discovers first evidence of life in Rock Glaciers. Marsbugs: The Electronic Astrobiology Newsletter, 11, (47)

Warm winter show unexpected influence on permafrost

The lack of precipitation (snow) and the high temperatures measured in the winter 2006/2007, showed in part unexpected influence on the permafrost in the european alps. On steep mountainwalls, with no snowcover, the swiss team leaded by Dr. Hölzle measured rising temperatures caused maybe by the increased insolation. In the Eiger nord-wall (2.800m s.l.) the temperatures rised well above 0°C during April, with temperatures +4°C above the mean of the last years. On flat landscape, the missing snowcover in contrast provides no isolation against the cold winterair, the temparure drops in the first meters of the ground. The mean temperature was -1°C under the mean temperature from 2003.

Source: mbe/AP

Homepage Dr. Hölzle

Pingos and lakes

Dzhangyskol is a small lake of glacial origin in the central part of the Altai Mountains in southern Siberia. Pollen stratigraphies and chronologies of two cores record the vegetational development of the area from the Late Glacial treeless landscape to the forest and steppe of today. The modern lake is a remnant of a much larger ice-dammed lake, which was reduced in size and then temporarily drained after diversion of the inflowing mountain meltwater stream, which had low d18O values. The dry lake floor allowed development of permafrost and small pingos (frozen mounds of lake sediments). With the onset of greater climatic humidity in the mid-Holocene, the input of local water with higher d18O caused a rise in lake level, drowning the earlier pingos. Growth of a broad fen on the margin of the lake led to formation of a modern pingo complex.

BLYAKHARCHUK et al. (2007): The role of pingos in the development of the Dzhangyskol lake–pingo complex, central Altai Mountains, southern Siberia. Palaeogeography, Palaeoclimatology, Palaeoecology Vol. 257, 4

Rockglacier