Alba Mons

Alba Mons
Viking image of Alba Mons. The volcano's relief is barely visible in orbital photographs. The broad system of fractures on the volcano's eastern side (right) is called Tantalus Fossae. The narrower fracture system on the western flank is Alba Fossae. (Viking color MDIM 2.1)
LocationNorthern Tharsis Rise, Mars
Coordinates40°30′N 250°24′E / 40.5°N 250.4°E / 40.5; 250.4[1]
DiscovererMariner 9
EponymLatin – White Mountain

Alba Mons (formerly and still occasionally known as Alba Patera, a term that has since been restricted to the volcano's summit caldera;[2] also initially known as the Arcadia ring[3]) is a volcano located in the northern Tharsis region of the planet Mars. It is the biggest volcano on Mars in terms of surface area, with volcanic flow fields that extend for at least 1,350 km (840 mi) from its summit.[4][5] Although the volcano has a span comparable to that of the United States, it reaches an elevation of only 6.8 km (22,000 ft) at its highest point.[6] This is about one-third the height of Olympus Mons, the tallest volcano on the planet.[7] The flanks of Alba Mons have very gentle slopes. The average slope along the volcano's northern (and steepest) flank is 0.5°, which is over five times lower than the slopes on the other large Tharsis volcanoes.[6][8] In broad profile, Alba Mons resembles a vast but barely raised welt on the planet's surface.[9] It is a unique volcanic structure with no counterpart on Earth or elsewhere on Mars.[6]

In addition to its great size and low relief, Alba Mons has a number of other distinguishing features. The central portion of the volcano is surrounded by an incomplete ring of faults (graben) and fractures, called Alba Fossae on the volcano's western flank and Tantalus Fossae on the eastern flank. The volcano also has very long, well preserved lava flows that form a radiating pattern from the volcano's central region. The enormous lengths of some individual flows (>300 km (190 mi)) implies that the lavas were very fluid (low viscosity) and of high volume.[10] Many of the flows have distinctive morphologies, consisting of long, sinuous ridges with discontinuous central lava channels. The low areas between the ridges (particularly along the volcano's northern flank) show a branching pattern of shallow gullies and channels (valley networks) that likely formed by water runoff.[11]

Alba Mons has some of the oldest extensively exposed volcanic deposits in the Tharsis region. Geologic evidence indicates that significant volcanic activity ended much earlier at Alba Mons than at Olympus Mons and the Tharsis Montes volcanoes. Volcanic deposits from Alba Mons range in age from Hesperian to early Amazonian[12] (approximately 3.6[13] to 3.2 billion years old[14]).

  1. ^ "Alba Mons". Gazetteer of Planetary Nomenclature. USGS Astrogeology Science Center. Retrieved 2013-09-08.
  2. ^ "Alba Patera". Gazetteer of Planetary Nomenclature. USGS Astrogeology Science Center. Retrieved 2013-09-08.
  3. ^ Watters, TR; Janes, DM (1995). "Coronae on Venus and Mars: Implications for similar structures on Earth". Geology. 23 (3): 200–204. Bibcode:1995Geo....23..200W. doi:10.1130/0091-7613(1995)023<0200:COVAMI>2.3.CO;2.
  4. ^ Cattermole, 2001, p. 85.
  5. ^ "Mars upside down".
  6. ^ a b c Carr, 2006, p. 54.
  7. ^ Plescia, J. B. (2004). "Morphometric Properties of Martian Volcanoes". J. Geophys. Res. 109 (E3): E03003. Bibcode:2004JGRE..109.3003P. doi:10.1029/2002JE002031.
  8. ^ Boyce, 2008, p. 104.
  9. ^ See Carr, 2006, p. 54, Fig. 3.10 for MOLA profile of Alba Mons compared to Olympus Mons. The difference in relief is striking.
  10. ^ Greeley, R.; Spudis, P. (1981). "Volcanism on Mars". Rev. Geophys. Space Phys. 19 (1): 13–41. Bibcode:1981RvGSP..19...13G. doi:10.1029/rg019i001p00013.
  11. ^ Gulick, V.C.; Baker, V.R. (1990). "Origin and Evolution of Valleys on Martian Volcanoes". J. Geophys. Res. 95 (B9): 14325–14344. Bibcode:1990JGR....9514325G. doi:10.1029/jb095ib09p14325.
  12. ^ Ivanov, M. A.; Head, J.W. (2006). "Alba Patera, Mars: Topography, Structure, and Evolution of a Unique Late Hesperian–Early Amazonian Shield Volcano". J. Geophys. Res. 111 (E9): E09003. Bibcode:2006JGRE..111.9003I. doi:10.1029/2005JE002469.
  13. ^ Werner, S.C.; Tanaka, K.L.; Skinner, J.A. (2011). "Mars: The Evolutionary History of the Northern Lowlands Based on Crater Counting and Geologic Mapping". Planet. Space Sci. 59 (11–12): 1143–1165. Bibcode:2011P&SS...59.1143W. doi:10.1016/j.pss.2011.03.022.
  14. ^ Hartmann, W.K. (2005). "Martian Cratering 8: Isochron Refinement and the Chronology of Mars". Icarus. 174 (2): 317 Tbl. 3. Bibcode:2005Icar..174..294H. doi:10.1016/j.icarus.2004.11.023.