# How destructive would a small black hole be on the surface of the Earth?

Say a black hole with the diameter of around 200 meters or so was formed on the Earth's surface, how much damage would it cause?

• That would be a black hole with the mass of a small star. Where would the mass come from? Irrespective of that, there wouldn't be an earth after about 5 seconds, or so, and the black hole would have increased in diameter by about 9mm, I believe. – CuriousOne Jan 1 '16 at 8:25
• On second thought, the actual accretion may be much smaller than the total mass of the planet and most of the matter might actually escape in form of jets... one would have to look at actual simulations of the accretion process near the Schwarzschild radius. – CuriousOne Jan 1 '16 at 8:53
• A black hole the mass of the Earth is about the size of a ping pong ball, so your black hole would be over 10,000 Earth masses. That much mass, even on the far side of the Earth, we'd experience over 2,500 G forces, enough to crumble every building and kill every living thing except, perhaps, bacteria & viruses and that's on the farthest part of the earth from the hole. The nearest parts of the Earth, the effects would be almost like pure energy, hotter than the inside of the sun as the earth was quickly torn into an accretion disk shooting radiation out of the poles of the disk. – userLTK Jan 1 '16 at 8:54
• So, on a destructiveness scale 1-10, I'd rate that one about a 15. – userLTK Jan 1 '16 at 8:55

$$r_s = \frac{2GM}{c^2}$$
$$M = \frac{r_s c^2}{2G} \approx 6.75 \times 10^{28}\,\text{kg}$$