Researchers think they've spotted hug...

Researchers think they've spotted huge volcanic calderas on Mars

There are 1 comment on the Ars Technica story from Oct 7, 2013, titled Researchers think they've spotted huge volcanic calderas on Mars. In it, Ars Technica reports that:

Martian volcanoes are not known for being hard to spot. The behemoth Olympus Mons, for example, claims the mantle of the largest known volcano in the Solar System.

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“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#1 Oct 9, 2013
Nice pic.

This one shows the main centre with what appears to be a large oval caldera & an embayment.

It probably formed both features in the same event as a result of the problems with caldera infilling by ejecta in multiple nested caldera events. The preservation of an older caldera as a side feature would however be possible if the younger caldera was deeper then the floor of the former.@ that point the intracaldera fill largely ponds in the new caldera during the closing stages of the eruption infilling the older to much the same level, and compacting both into a welded ash flow tuff filled depression.

Problems come from modelling of the atmosphere. The pressure may have been so low that the bulk of the ejecta was lofted out of the caldera on ballistic trajectories during the main eruptive phase leaving an infill in the late stage.

Fun bit for recognising old supervolcanoes should be a resurgent dome. The pic shows the main source caldera to have an offcentre resurgent dome (should show uplifted ash flow tuff with fractures in the dome top. Another old caldera & resurgent dome may show up to the right of the grey main crater.

Being a planet with a thick crust & a lower than terrestrial internal heat budget, the martian supervolcanoes may be trachye, Phonolite, Benmoreite or alkali rhyolite rather then classical rhyolite of the terrestrial standard, but differentiation would eventually produce rhyolite in old nested calderas even on Mars.

Have a nice day: Ag

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