[jacquesm]

trees flattened in a radial pattern might show up in the geological record somehow.

[gota]

Unlikely after several years, let alone several thousands, right?

[bell-cot]

It would require coordinated excavation over how many square miles, to spot the radial pattern? (Assuming, as gota points out, that the fallen trees were somehow preserved.)

Then there's bolides over desert, savanna, tundra, ice sheets, etc.