Gamma rays would not penetrate Earth’s atmosphere well to burn the ground, but they would chemically damage the stratosphere. Melott estimates that if WR 104 were to hit us with a burst 10 seconds or so long, its gamma rays could deplete about 25 percent of the world’s ozone layer, which protects us from damaging ultraviolet rays. In comparison, the recent human-caused thinning of the ozone layer, creating “holes” over the polar regions, have only been depletions of about 3 to 4 percent, he explained.
“So that would be very bad,” Melott told SPACE.com. “You’d see extinctions. You might see food chain collapses in the oceans, might see agricultural crises with starvation.”
Gamma ray bursts would also trigger smog formation that could blot out sunlight and rain down acid.
http://www.space.com/scienceastronomy/080310-mm-grb-us.html
“The flash of heat and light might flash-burn anything not in the shade,” he said. “Heating the atmosphere would cause big winds. The air would be much hotter for weeks, as hot as an oven depending on the distance. This would affect the other side of the Earth eventually.”
http://www.space.com/scienceastronomy/astronomy/gammaray_bursts_010522-1.html
The chastisement, of course, doesn’t have to obey the laws of physics as it is, after all, sent by God. But maybe it will anyway because, as you point out, there are natural mechanisms that could result in quite effective catastrophe.
Bump to read later.