T86 The G. K. Gilbert Award Session: Flowing and Blowing: Volcanic and Aeolian Deposits Around the Solar System II

Tuesday, 27 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

BUILDING ASCRAEUS MONS: SUMMIT CALDERAS AND THEIR BIG ERUPTIONS

Paper number: T86-12
Program: Technical Sessions
Time: 4:10 PM – 4:25 PM

Authors

Abstract

Ascraeus Mons (18 km in height and ~350 km in diameter) is the northeastern-most of the large shield volcanoes located in the Tharsis province on Mars. We mapped the large summit caldera complex at a 1:100,000 scale using THEMIS, CTX, HiRISE, and HRSC imagery, and MOLA topography, and made estimates of caldera, magma chamber, and erupted volumes for each of the 9 calderas. The order of caldera formation from oldest to youngest is: the western-most crater (I), consistent with the crater-counts of Neukum et al., (2004, Nature Vol 432 971-979) and Werner (2009, Icarus 201 44–68); the northwestern caldera (II); the eastern-most caldera (III), which was modified by the collapse events of calderas IV, V, and VI, where V and VI have lower floor elevations; the two southeastern calderas (VII and VIII), such that the larger diameter crater predates the smaller crater; and finally the large central caldera (IX) with highly disrupted crater walls, that suggest multiple collapse events during caldera formation.

We then calculated the magma chamber volume (VT) and the minimum volume erupted (Vemin) required to generate caldera collapse using the model of Geshi et al., (2014, Earth and Planetary Science Letters 396, 107–115). Estimates of VT range from 102 - 104 km3 and corresponding values of Vemin are 10 - 102 km3, consistent with volumes of individual lava flows in Tharsis. Input parameters include magma density, assumed to be 2800 kg/m3; bulk modulus of the magma assumed to be 2.11x1011 Pa; caldera radius and wall slope, measured from the MOLA DEM; and depth to magma chamber, varied from 10 to 20 km. Displaced caldera volumes estimated using the Polygon Volume Tool in ESRI ArcGISTM range from 102 – 103 km3, and place an upper-bound on the erupted volumes. Further sensitivity analysis will be conducted to better constrain depth to chamber and erupted volumes and later compared with other Martian volcanoes.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-356433

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.