[githulhu]

Huh. Why did the explosion produce two distinct, different-colored smoke clouds?

Also, what's the environmental impact of this kind of accident?

[lutorm]

The rocket has two tanks, one with kerosene, one with liquid oxygen. I bet the black fireball is the kerosene burning, the white cloud is the liquid oxygen vaporizing.

Environmental impact is likely small, the kerosene would have burned anyway and there are little other hazardous chemicals on board. (Unlike for example the Proton failure linked by kryptisk above which is fueled with really nasty hypergolic fuels.)

[AustinDev]

To add to that. I'm sure Space X attempts to collect all the debris that falls to the ground.