why the Lobate Moraine lookes like a toung??
Answers
Answer:
1) A variety of features on Mars are very similar to fea-
tures on Earth that form in glacial and periglacial
environments.
2) Confusing nomenclature, genetic classifications,
possible form convergence or equifinality, and un-
certain origins of many of the terrestrial examples
all make direct application of general Earth morpho-
logical comparisons to Mars difficult.
3) We therefore have developed a descriptive and non-
genetic nomenclature for these features.
4) Careful comparison of the Mars features to well-
studied Earth analogs in the Mars-like environment
of the Antarctic Dry Valleys can lead to insights into
the origin of these features on Mars.
5) The morphology and characteristics of the Mars fea-
tures examined in this study have been carefully
compared to three types of features in the Antarctic
Dry Valleys: 1) gelifluciton lobes, 2) rock glaciers,
and 3) alpine glaciers.
6) The tongue-like lobate, concave nature of these fea-
tures is very similar to alpine glaciers and debris-
covered glacier deposits. In these cases, the percent-
age of ice in the original deposit was very high, and
sublimation and melting led to retreat, and subsi-
dence and downwasting of any debris cover, leaving
marginal morainal ridges as a main feature.
7) The presence of fainter, broad lobe-like features
with scalloped margins of similar orientation sug-
gest the former wider extent of such activity.
8) The lack of cross-sectional convexity in these
tongue-shaped lobes and related deposits suggests
that the ice involved in their formation is now
largely gone. This suggests that conditions in the
past favored the formation of active glaciers and
glacial landforms, and that the present time is more
equivalent to an interglacial period.
9) The presence of these features on pole-facing inte-
rior crater walls suggests that this micro-
environment is very favorable for the accumulation
of snow and the initiation of local glaciation.
10) This type of glaciation appears to be a significant
process in the modification of crater walls and
floors.
References: [1] Whalley, W. B. and Azizi F. (2003) JGR, 104
(E4),8032, doi: 10.1029/2002JE001864. [2] Head J. W. and Mar-
chant, D.R. (2003) Geology, (accepted; in press). [3] Lucchitta, B. K.
(1981) Icarus, 45 (2), 264-303. [4] Benn, D.I. and Evans, D.J.A.
(1998) Glaciers and Glaciation, Arnold Publishers, London.
[5] Johnson, P.G. (1984), Annals of the Association of American
Geographers, 74, 408-419. [6] Martin and Whalley (1987), Progress
in Physical Geography, 11, 260-282. [7] Humlum, O. (1982), Norsk
Geografisk Tidsskrift, 82, 59-66. [8] Potter et al. (1998), Geograf-
iska Annaler, 80, 251-265.
Figure 1. Skin flow model of periglacial rock glacier forma-
tion. (From [5])
Figure 2. Model for ice accumulation in rock glaciers.
(From [6])
Sixth International Conference on Mars (2003) 3091.pdfFigure 3. Morphological features associated with each type of rock glacier. (From [7])
Figure 4. MOC image M04/02881 of a crater wall at
248°W/36°S, Mars. North is at the top of the image, and
illumination is from the northwest.
Figure 5. MOC image M18/00898 of a crater wall at 247°W/38.6°S,
Mars. North is at the top of the image, and illumination is from the
northwest.
Sixth International Conference on Mars (2003) 3091.pdfFigure 6. Protalus lobes near Pearse Valley, Antarctica
Figure 7. Beacon Valley, Antarctica.
Figure 8. Rock glacier extending to the floor of Beacon Valley, Antarctica.
Sixth International Conference on Mars (2003) 3091.pdf