The Gigantic Volcano-Glacial Edifice (Tuya) Olympus Mons as an Indicator of Ancient Large Glaciation on Mars

Olympus Mons (basement dimension is 550 x 600 km, absolute height is 21.1 km, relative elevation is 21.9 km, volume is 2.4 x 10(9) km(3)) is the largest volcanic edifice on Mars as well as on Earth. The Mars images of the regular combinations of features of volcanic and glacial forms on Olympus Mons have been interpreted and analyzed. The cardinal external similarity of these forms to the forms of large terrestrial tuyas of young volcanic regions was revealed. This, probably, testifies to their similar origin. The Olympus Escarpment, 3-6 km in height, bounds Olympus Mons at low latitudes (center is at 18 degrees N, 113 degrees E), which indicates that, during the formation of Olympus Mons, vast glaciers existed not only in the polar regions of Mars but far away from them. The distribution of extensive glacial moraines allowed us to evaluate the area of glaciation, equal to 1.5-2 x 10(6) km(2), as well as the ice sheet thickness (about 3-6 km), comparable to the recent height of the Olympus Escarpment. Some distinct fragments of the glacial relief point to several phases of glaciations; the directions of the moraine lobe propagation record a clearly manifested asymmetry in the glacier distribution. In the SW, W, NW, N, and NE sectors of the Olympus Mons piedmont, the edge of the glacier was at a distance of 700-750 km from a crater; in the other zones, the glacier edge was at a distance of 500-600 km. Glacial and water-glacial formations, enriched in volcanic debris, are removed from the center of the volcano by colossal lahar-type mud-and-stone flows to the maximum (1100 km, Acheron Fossae) distance. These flows were formed as a result of the dramatical destruction of the walls of the glacial basin in which the Olympus tuya-volcano grew. A terrestrial analogue of a similar process is the catastrophic Jokulhlaup feature in Iceland, which is attributed to ice-filled calderas with volcanoes growing within them.