Dry Andes Explained

Dry Andes
Country:	Chile, Northwest Argentina, Bolivia
Parent:	Andes
Length Km:	1200
Highest:	Aconcagua
Elevation M:	6961

thumb|200px|Map of the climatic regions of the Andes. The Dry Andes are shown in yellow. The Tropical Andes are shown in green and the Wet Andes in dark blue.The Dry Andes (Spanish; Castilian: Andes áridos) is a climatic and glaciological subregion of the Andes. Together with the Wet Andes it is one of the two subregions of the Argentine and Chilean Andes. The Dry Andes runs from the Atacama Desert in northern Chile and Northwest Argentina south to a latitude of 35°S in Chile. In Argentina the Dry Andes reaches 40°S due to the leeward effect of the Andes. According to Luis Lliboutrythe Dry Andes can be defined by the distribution of penitentes.^[1] The southernmost well-developed penitentes are found on Lanín Volcano.

Rock glaciers occur in parts of the Dry Andes, but are lacking in the more southern Wet Andes.^[2] In the Dry Andes, ordinary glaciers develop usually at higher altitudes than rock glaciers.^[2] Around Aconcagua rock glaciers reach altitudes as a low as 900 m a.s.l.^[2]

The Principal Cordillera near Santiago may have been subject to significant glaciation as early as 1 million years ago, as indicated by the development of glacial valleys.^[3]

Paleogeography, paleoclimatology and paleoglaciology

Though precipitation increases with the height, there are semiarid conditions in the nearly 7000m (23,000feet) towering mountains of the Andes. This dry steppe climate is considered to be of the subtropic type at 32-34° S. In the valley bottoms only dwarf shrubs grow. The largest glaciers, e.g. the Plomo glacier and the Horcones glacier, do not reach 10km (10miles) in length; the ice thickness is not very significant. During glacial times however, c. 20,000 years ago, the glaciers were over ten times longer. On the east-side of this section of the Mendoza Andes they flowed down to 2060m (6,760feet) and on the west-side to c. 1220m (4,000feet).^{[4] [5]} The massifs of Cerro Aconcagua 6962m (22,841feet), Cerro Tupungato 6550m (21,490feet) and Nevado Juncal 6110m (20,050feet) are situated deca-kilometres away from each other and were connected by a joint ice stream network. Its dendritic glacier arms, i.e. components of valley glaciers, were up to 112.5km (69.9miles) long, over 1250m (4,100feet) thick and spanned a vertical distance of 5150m (16,900feet). The climatic glacier snowline (ELA) was lowered from the current 4600m (15,100feet) to 3200m (10,500feet) during glacial times.^{[6] [7] [8] [9] [10] [11] [12] [13] [14]}

Notes and References

1. Web site: Glaciers of the Dry Andes. Louis Lliboutry, USGS. 2008-12-21.
2. Rock glaciers. Biuletyn Peryglacjalny. Corte. Arturo E.. 26. 175–197. 1976.
3. Charrier . Reynaldo . Iturrizaga . Lafasam. Charretier . Sebastién . Regard . Vincent . 2019 . Geomorphologic and Glacial Evolution of the Cachapoal and southern Maipo catchments in the Andean Principal Cordillera, Central Chile (34°-35º S) . . Reynaldo Charrier . 46 . 2 . 240–278 . 10.5027/andgeoV46n2-3108 . June 9, 2019. free .
4. Kuhle, M. (2011): The High-Glacial (Last Glacial Maximum) Glacier Cover of the Aconcagua Group and Adjacent Massifs in the Mendoza Andes (South America) with a Closer Look at Further Empirical Evidence. Development in Quaternary Science, Vol. 15 (Quaternary Glaciation - Extent and Chronology, A Closer Look, Eds: Ehlers, J.; Gibbard, P.L.; Hughes, P.D.), 735-738. (Elsevier B.V., Amsterdam).
5. Brüggen, J. (1929): Zur Glazialgeologie der chilenischen Anden. Geol. Rundsch. 20, 1–35, Berlin.
6. Kuhle, M. (1984): Spuren hocheiszeitlicher Gletscherbedeckung in der Aconcagua-Gruppe (32-33° S). In: Zentralblatt für Geologie und Paläontologie Teil 1 11/12, Verhandlungsblatt des Südamerika-Symposiums 1984 in Bamberg: 1635-1646.
7. Kuhle, M. (1986): Die Vergletscherung Tibets und die Entstehung von Eiszeiten. In: Spektrum der Wissenschaft 9/86: 42-54.
8. Kuhle, M. (1987): Subtropical Mountain- and Highland-Glaciation as Ice Age Triggers and the Waning of the Glacial Periods in the Pleistocene. In: GeoJournal 14 (4); Kluwer, Dordrecht/ Boston/ London: 393-421.
9. Kuhle, M. (1988): Subtropical Mountain- and Highland-Glaciation as Ice Age Triggers and the Waning of the Glacial Periods in the Pleistocene. In: Chinese Translation Bulletin of Glaciology and Geocryology 5 (4): 1-17 (in Chinese language).
10. Kuhle, M. (1989): Ice-Marginal Ramps: An Indicator of Semiarid Piedmont Glaciations. In: GeoJournal 18; Kluwer, Dordrecht/ Boston/ London: 223-238.
11. Kuhle, M. (1990): Ice Marginal Ramps and Alluvial Fans in Semi-Arid Mountains: Convergence and Difference. In: Rachocki, A.H., Church, M. (eds.): Alluvial fans - A field approach. John Wiley & Sons Ltd, Chester-New York-Brisbane-Toronto-Singapore: 55-68.
12. Kuhle, M. (1990): The Probability of Proof in Geomorphology - an Example of the Application of Information Theory to a New Kind of Glacigenic Morphological Type, the Ice-marginal Ramp (Bortensander). In: GeoJournal 21 (3); Kluwer, Dordrecht/ Boston/ London: 195-222.
13. Kuhle, M. (2004): The Last Glacial Maximum (LGM) glacier cover of the Aconcagua group and adjacent massifs in the Mendoza Andes (South America). In: Ehlers, J., Gibbard, P.L. (Eds.), Quaternary Glaciation— Extent and Chronology. Part III: South America, Asia, Africa, Australia, Antarctica. Development in Quaternary Science, vol. 2c. Elsevier B.V., Amsterdam, pp. 75–81.
14. Kuhle, M. (2011): The High-Glacial (Last Glacial Maximum) Glacier Cover of the Aconcagua Group and Adjacent Massifs in the Mendoza Andes (South America) with a Closer Look at Further Empirical Evidence. Development in Quaternary Science, Vol. 15 (Quaternary Glaciation - Extent and Chronology, A Closer Look, Eds: Ehlers, J.; Gibbard, P.L.; Hughes, P.D.), 735-738. (Elsevier B.V., Amsterdam).