re: A cool little video of arch formation: - Thank you, pdrock.
Interesting that on Earth the Pleistocene period began about 1,600.000 years ago and ended 10,000 years ago (preceded by the Pliocene Epoch of the Tertiary Period, followed by the Holocene Epoch.) Whatever and nonetheless...
Needless to say that the volcanoes on Tharsis could have been active at the time. Just one element in whatever Mars was like at the time.
Yes, those arches are formed primarily from running water and finally wind and erosion.
Still, when we find such arches, it would be a grand finding.
I know, it's Mars and not Earth.