To (very) suddenly catch on fire. 🤗 🌈 Nicky

I am a native english speaker and, like Ffi, I don't recall seeing "flash into flames." But based on the context of Near Earth Objects, the reference is to an asteroid fragment crashing into earth. (This scenario caused the extinction which eliminated dinosaurs, and every other complex life form on earth). In that context, Randy's meaning is correct. I would have avoided this rather awkward usage however and made the point in terms of a nuclear explosion. Objects are simply vaporized. Burning is the mechanism, but the speed with which it occurs makes any reference to "flame" misleading.

'Flashing into flames' is different from 'bursting into flames' in that it happens very fast. So fast that the vegetation would likely be completely burned up in seconds. Something that 'bursts into flames' could still continue burning after it ignites, but something that 'flashes into flames' is completely incinerated in an instant.

To be honest I've never heard "flash into flames" used. "Burst into flames" is an expression often used which means that something catches fire suddenly. So "And all the vegetation all over the world where that happened would burst into flames" meaning all the vegetation would catch fire/begin to burn.