Geo-engineers from Harvard University believe that spraying sun-dimming chemicals into the stratosphere high above the Earth could slow down global warming.
When you see the top of a storm cloud flattening out into the classic anvil shape, you are looking at the boundary between the troposphere and stratosphere.
In its case the models try to mimic the effects of things like putting veils of reflective particles into the stratosphere, or brightening the clouds over the oceans.
If those rocks contained significant amounts of organic matter-such as the remains of marine organisms-it would have burned up on impact, sending soot shooting up into the stratosphere.