I don’t consider 50 ft cataclysmic. I’m talking about those mile wide asteroids that do hit the earth every billion years.
Odds of a 1 in a billion years event happening in the next 50: 1 out of 20 million.
And within 50 to 100 years, we’ll probably have the tech to do something.
Assuming we dont’ destroy ourselves with technology of course.
A mile wide happens more often than that; the 10-mile-plus bolides which produced the major paleontological boundaries are only tens of millions of years apart (and not on any exact schedule) and the Ries impact (and a probably simultaneous, smaller impact) was less than 15 million years ago, and the impactor is estimated at less than a mile in diameter.
The key to preventing large impacts is early detection; with that, even large impactors can be deflected just a little, enough to avoid collision with Earth.