Blowing up Iraq

I just heard journalist Seymour Hersh on National Public Radio, saying that in one 15-month period, the air support wing of the Marines dropped the equivalent of 2 million 500-pound bombs in Iraq. He had no figures for the Army or Air Force.

Either there are a whole lot of unreported Iraqi deaths and casualities; or there are hundreds of thousands of non-Iraqi combatants, or the fatalities per bomb are very very low. One wonders - what are they blowing up in Iraq?