A Proposed Origin of the Olympus Mons Escarpment
Abstract
Olympus Mons (Nix Olympica) is delimited by a step nearly circular scarp that is unique to this largest of Martian volcanic constructs. The origin of the scarp is most probably by erosion; such an origin is difficult to explain if the volcanic pile is assumed to be made up exclusively of basalt flows. Although interpretive evidence is accepted for basalt flows underlying the central slope areas, additional criteria are presented here to support the hypothesis that the outer reaches of the slopes comprise dominantly ash-flow tuffs which presumambly were deposited by nuées ardentes. Because of cooling during emplacement, the average degree of compaction of each ash sheet would normally decrease with radial distance from its source vent. It is suggested that the tuffs originally extended greater distances from the central caldera complex and merged the slopes with the surrounding substrate. At the distal edges eolian erosion worked on the relatively noncompacted tuffs and was a major factor in the development of the scarp. The height of the scarp increased as it retreated toward the central caldera complex and eolian undercutting caused slump which in turn furthered the migration of the scarp. The rate of scarp migration would have decreased as the scarp increased in height and as more densely compacted ash nearer to the center of the construct was encountered. By this model, then, the circularity of the scarp in plan reflects an approximately concentric distribution of the zones of average degree of compaction about the center of Olympus Mons.
- Publication:
-
Icarus
- Pub Date:
- October 1974
- DOI:
- 10.1016/0019-1035(74)90008-6
- Bibcode:
- 1974Icar...23..300K
- Keywords:
-
- Escarpments;
- Mars Surface;
- Spaceborne Photography;
- Volcanology;
- Astronomical Models;
- Basalt;
- Erosion;
- Lava;
- Mariner 9 Space Probe