Asteroids are rocks that revolve around the sun and that occasionally collide with the Earth. An asteroid large enough to cause a global catastrophe hits Earth every 120,000 years, scientists estimate. It’s likely what killed the dinosaurs, and if an asteroid even one-tenth the size of the one that caused their extinction hit Earth today, the results would be devastating. Scientists estimate it could release enough particles to block the sun for months and cause a famine killing hundreds of millions.
NASA announced in 2011 that it had mapped more than 90 percent of objects in space larger than 1 kilometer in diameter, and that none of them are likely to hit Earth. But there’s still a lot we don’t know about smaller objects that, while unlikely to cause a global catastrophe, could have a big enough local impact to disrupt social and economic systems.
Asteroid impact
A supervolcanic explosion 74,000 years ago ejected so much debris into the atmosphere that scientists believe it caused the Earth to cool by several degrees Celsius. Some experts believe this caused the greatest mass plant and animal extinction in human history, bringing the species to the brink of extinction.
How likely is that to happen today? It’s hard to say since we don’t have much to compare it to, but data suggests a supervolcanic eruption occurs on average every 17,000 years. If that’s true, then we’re overdue — the last one we know of was 26,500 years ago in New Zealand.
We don’t have a way to anticipate eruptions more than a few weeks or months in advance, and we don’t really have any way to reduce the likelihood of eruption right now, but scientists are monitoring several areas of risk, including Yellowstone in the US.
Supervolanic eruption
