Enigmas of the Ionian Rock Cycle
Abstract
Io's rock cycle is unlike any other in the Solar System today, driven by the need to extract the prodigious amounts of tidal heating within Io. While the advection of hot magma to the surface and the rapid subsidence of cold lava has attracted the most attention, there is also a second, tectonic, branch to the Ionian rock cycle. This involves the uplift of deep crustal material along faults, producing towering mountains that are eroded by mass wasting. The volcanic cycle transports ~1014 W of heat from the mantle to the surface, equivalent to ~1 cm/year of global average resurfacing by lava. However, distinct lava flows and lava lakes only cover a few percent of Io's surface and volcanic centers appear stable over at least decades, suggesting that resurfacing is not homogeneous. The rate of tectonic resurfacing has not been measured but theoretically should be similar to the volcanic resurfacing rate. Tectonic uplift seems to be focused into discrete massifs that make up only a few percent of Io's surface, again pointing to inhomogeneities in resurfacing rates. The volcanic and tectonic branches of Io's rock cycle are expected to be intimately connected because it is the subsidence of volcanic materials that creates the compressional stresses that uplift mountains, and local relief of the compressional stresses by orogenic faults should play a key role in localizing volcanic vents. To date, determining the relationship between these two processes has been challenged by the inconsistent and incomplete nature of the global imaging of Io. Modelling efforts are hampered by the inherent complexity of the problem and the great uncertainty in the nature of Io's lower crust, which may transition into a magma ocean. Furthermore, the role of volatiles is potentially critical since (a) plume deposits are the only material from within Io that are dispersed widely across the surface, (b) volatiles could lubricate faults and thus reduce the stresses within the lithosphere, (c) the flow of crustal fluids has the potential to alter the iotherm, and (d) volatiles could affect the remelting of rocks at the base of the crust. New global imaging, geophysical constraints on the nature of the lithosphere, detailed topography of individual mountains and their surroundings, and improved understanding of the composition and movement of volatiles are all needed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMP025.0002K
- Keywords:
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- 6218 Jovian satellites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5480 Volcanism;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5499 General or miscellaneous;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS