Shouldn't the Probes have observed a siesmic disturbance if there had been an explosion on the surface or in the atmosphere? There was no report that I can recall indicating anything amiss like that.
On the other hand, Andrew's account of how the Ipsos were looking out to space and were apparently agitated/excited about what they saw could be a sign that something bad is here or on the way. Could they be viewing a possible Amphibian Invasion of the Earth?!? (Why am I suddenly reminded of the NBC TV movie come series "V" all of a sudden? The main characters were lizard-like creatures with a human appearing outer skin.)
The image could be a smoke column. It could be the result of the opening and closing of the Groove. We still don't know where all that Carbon in the caves came from. Perhaps the smoke we see is an exhaust of Carbon and the filters in the caves are there to keep that material from reentering the complex.
Koala, Captain, Team Andrew -- Holding out hope for Gail's safe return.