They are Plot Devices. As such, there are no mechanics that can adequately describe them. Players who try to throw around such magic should be mocked.
Eh. What about some of the spells that Harry has pulled off, then? The wall of fire in White Night is the same kind of vulcanology on a smaller scale, as is
the giant gravity effect in Changes, powered by the leyline.
In both cases, he mentions that Earth Magic is hard to get going and difficult to stop once started.
The effects here -- other than the Ward, which I agree is NUTS -- aren't really as crazy as they seem.
Volcano eruption? Note that in the case of Krakatoa there was already a mountain there and it was a former volcano. All he really had to do was provide some fissures to allow the pressure to begin escaping -- nature will handle the rest. I think we would all agree that a little earth magic can crack a few rocks, right? It takes frighteningly small shifts in a mountain for a 'dormant' volcano to become active again if the magma hotspot is still there...
Earthquake? Same deal as the Volcano. The pressure is already there. The potential builds up over centuries or millenia and it only takes the tiniest nudge to let them slip. Nature provides all the destruction. There was a show on Discovery a while back about a scientist who had some preliminary data showing that a minor detonation -- on the order of single sticks of dynamite -- in the right spot could trigger a massive earthquake in a faultline.(NOTE: If you're in an area with no faultline, then this one falls back into the 'idiotically powerful' range).
Satellite colony drop? Orbits are incredibly fragile. I got the sense -- which could be wrong -- that Ebenezzer didn't directly pull it down, just nudged it out of orbit on a specific course. The media treated it as a natural occurrence, after all -- and a satellite suddenly falling DIRECTLY from orbit would be noticed... and could theoretically be explained without magic. If your character has good Scholarship (and does the math), then puts enough distance shifts in to *nudge* an object most likely weighing less than ~1,000lbs (old Soviet probe, after all), gravity does all the real work for you.
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The REAL problem, in all of these cases, is the MASSIVE number of Lawbreaker feats you're going to rack up unless you're the Blackstaff. We're talking instant-NPC for all of them, IMO. None of these is precision work, after all -- part of the point in each case was to show the Council's policy of disproportionate retribution and ENSURE the other supernatural factions know who is to blame.