Not all adversities are immediately lethal, but many will kill you eventually if you don't adapt.
Anyway It's not necessarily the surviving the immediate disaster that's evolutionarily selected for. No adaptation is going to make a human volcano or tsunami proof. It's the survivors piecing a viable way of life back together in the aftermath that matters.
No, we aren't. Adversity from other humans, but not adversity from nature.
Natural disasters routinely kill huge numbers of people, because we don't know how to deal with them.