Simulations find that most meteorites striking the sea shouldn’t be sufficient to start a tsunami
On February 6th, 2016, a larger-than-average asteroid hit the Earth. The resulting explosion was thought to be around the same size as 13,000 tons of exploding TNT, but no harm was done thanks to the rock entering our atmosphere over the Southern Atlantic Ocean. Most people didn’t even notice the asteroid’s arrival, which makes a lot of sense since even an asteroid surviving the trip to the ocean wouldn’t make a huge impact. In fact, according to recent simulations, big asteroids hitting the sea aren’t likely to be felt on our shores much at all.
With famous impacts in the Earth’s history creating mass extinctions and craters over 100 miles across, it’s not a huge stretch of the imagination to also picture massive amounts of water being displaced in the form of tsunamis on every shore. To check these assumptions, Galen Gisler from the Los Alamos National Laboratory created detailed, computer simulations to see just how dangerous an impact at sea would actually be. Beyond idle curiosity, understanding potential tsunamis is relevant to designing safety protocols around the world in the somewhat likely event of a large-ish asteroid hitting an ocean somewhere on Earth. Fortunately for anyone living near a beach, it doesn’t look like a marine-landing would be all that bad, as long as it’s not too close to the beach.
Splash, steam, but no tsunami
The point of impact would still be rough. Large amounts of water would be vaporized in the impact, with some water being sprayed over a 1000 feet into the air. Shock waves and wind would disrupt the local environment, but all these effects would also decrease the amount of energy left to push a big wave towards shore. Waves would be created, but they’d be dispersed in all directions, and without the magnitude to really flood the shore.
Overall, the simulation found that an asteroid under 1000 feet in diameter would behave a lot like a rock dropping into a bucket of water. There would be a splash, but the overall contents wouldn’t move too much. To really make a beach-threatening wave, you’d need to shake the whole bucket at once, which in nature occurs when an earthquake moves the sea floor all at once, pushing water with the force necessary to create a massive wave like a tsunami. So while explosions and vaporizing water is nothing to sneeze at, at the very least it looks like the huge amount of water around the globe should help protect us medium-sized meteorites.
Source: If an Asteroid Hits the Ocean, Does It Make a Tsunami? (Probably Not) by Ian O'Neill, Live Science