Considering all the recent fun involving asteroids and meteors, I thought it would apropos to show a visual history of major impact structures around the world to answer the question: Are we “due”?
In fact, we’re never due, in the same way a die is never due to roll a three. So in the same sense, we’re always due. And we have been as long as the Earth has existed. This interactive chart I made shows 51 impact structures that have been identified over the past 750 million years, each of which left a crater at least 20 kilometers across. The size of the circle represents the size of the crater. For reference, the largest included in this dataset is the Shiva impact structure in Asia, 500 kilometers across, from an impact event 500 million years ago.
I cut it off at 750 million years because the data gets really sketchy at that age. Impact structures are harder to find the older they are, and the more erosion has taken place. Even after 250 million years, you can see that it thins out.
Since this dataset is limited only to 20+ km craters, it represents only a tiny fraction of impacts that would produce global climactic catastrophe. Even craters as small as 1 km represented impacts that almost certainly would have resulted in years of cold, enough to dramatically affect species populations.
It’s worthwhile to note that I found it difficult to correlate crater size (which I’m reporting here) with the object’s size, known extinction events, estimated megatons of the impact, and popular object fragments. A list of known strikes from the geological record may not match up very well to this list, nor would a list of meteorite fragments. We don’t know where a lot of big ones hit as their craters are underground. There’s a lot we don’t know, and crater size is dependent upon speed, angle, mass, and type of object (rocky, metallic, or a comet). So take this as an incomplete history, but a history that is — nevertheless — of strikes that all had potential to be planet killers.
a WordPress rating system