Millions of people were safely evacuated due to tsunami warnings rapidly issued after a powerful earthquake rumbled off the coast of Russia’s Kamchatka peninsula on 29 July. Though the quake didn’t end up generating waves as large as expected, the speed and scale of the warnings shows the progress tsunami science has made since major tsunamis in 2004 and 2011 killed tens of thousands of people.

“I think it’s a great achievement based on the lessons learned from the past,” says at the University of East London, UK.

The improved warnings are largely thanks to an expanded network of sensors monitoring for tsunami hazards. These include seismometers that measure shaking generated by earthquakes, as well as a network of buoys operated by the US National Oceanic and Atmospheric Administration that measure wave height and quickly relay information to satellites. Advances in modelling now enable researchers in tsunami warning offices to use this information to rapidly project where and when the waves will reach shore, and issue alerts.

On 29 July, this system allowed tsunami offices around the Pacific to issue warnings almost immediately after the magnitude-8.8 quake was detected in Russia, one of the strongest on record. In nearby Japan, almost two million people were evacuated from coastal areas. Others were evacuated in Hawai’i, states on the US West Coast and as far south as Chile.

“The reaction was immediate and it was good,” says at the British Geological Survey. However, he points out despite the magnitude of the earthquake, it didn’t ultimately generate very large waves or flooding. This suggests there is still room for improvement to more precisely forecast flooding based on early detections of shaking and wave height, he says.

Jayaratne adds some parts of the world vulnerable to tsunamis, such as Bangladesh and Sri Lanka, still lack both adequate warning systems and sufficient public awareness of the dangers. “The past shows that high-tech detection tools are effective only when paired with strong public communication and evacuation planning,” he says. “Coastal areas must run mock drills, maintain public awareness, and ensure alerts reach the most vulnerable via multiple channels.”

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About 3.4 billion years ago, an enormous megatsunami swept over the face of Mars after an asteroid slammed into one of the planet’s oceans. Now, researchers think they have found the crater where the megatsunami began. The size of the crater hints that the impact was similar to that of the Chicxulub asteroid on Earth, which is thought to have killed off the dinosaurs.

In fact, the first images we have of the Martian landscape – taken by the Viking 1 lander in the 1970s – may have contained evidence of this megatsunami. We just didn’t know it yet. Observations of the surface of Mars have previously suggested that a megatsunami happened on the planet, but scientists had not yet found the impact site of the asteroid that caused it. at the Planetary Science Institute in Arizona and his colleagues combined data from several Mars orbiters to undertake a search.

They found a crater 110 kilometres wide called Pohl in the northern lowlands of Mars that seems just right. It sits atop channels that likely formed as the area first flooded, creating a huge ocean, but there are deposits thought to have come from a later tsunami on top of it. That means that it almost definitely formed in the right time period, before Mars dried out.

Based on the dimensions of the crater and a series of simulations, the researchers found that the asteroid which caused it was either about 9 kilometres across or 3 kilometres across, depending on the properties of the ground it hit. Either way, it probably generated a megatsunami with 250-metre-tall waves reaching as far as 1500 kilometres from the impact site.

“When we think of a tsunami, we think of a wave, a wall of water approaching the shoreline and overrunning it. This would have been very different,” says Rodriguez. “You would have seen this massive wall of turbulent, reddish water, with some of it flying upwards and falling back into the wave along with rocks and soil.” Because Mars has lower gravity than Earth, the water and debris would fall more slowly than it does on Earth.

The impact would have also generated a seismic wave propagating hundreds of kilometres around the crater, throwing dirt and rocks into the air and creating a catastrophic flow of debris along with the wave. “Very terrifying, definitely nothing to surf on,” says Rodriguez. “But if you have a debris flow, you have a lot of soil spread around. So if you actually landed there, you have a chance to sample the ancient marine sediments.”

We actually have landed in the area. The Viking 1 lander, the first craft to ever land on Mars, touched down in the northern lowlands in 1976, within the area the tsunami would have probably reached. The strange boulders in the first pictures we ever saw from the surface of Mars were probably tossed there by a megatsunami, and strange channels on that landscape may have been caused by the water sloshing back into the ocean afterwards.

We may be able to predict deadly tsunamis using their magnetic fields. Because seawater is electrically conductive, when significant amounts of it move at once, it generates a small magnetic field. That magnetic field can be used to predict tsunamis before the sea level starts to change at the shore.

żěè¶ĚĘÓƵs have thought that this should be possible for years, but we lacked the data to prove it. at Kyoto University in Japan and his colleagues have now used data from two tsunamis – one that hit Samoa in 2009 and another in Chile in 2010 – to demonstrate that it is possible. Furthermore, the magnetic field changes can be used to accurately estimate the sea level change from a tsunami.

Usually, we use pressure gauges on the sea floor to tell us when a tsunami is moving over the sensors. But these pressure changes only tell us there is a tsunami after it has passed the sensors. Lin and his team instead used a set of sensors in the south Pacific Ocean to measure magnetic field and sea level change simultaneously for the two tsunamis in that area in 2009 and 2010. They found that the tsunamis were indeed preceded by changes in the magnetic field in the water.

“Pressure sensors respond to the tsunami right after the tsunami sea level change,” says Lin. “But the tsunami magnetic field arrives earlier than the tsunami sea level change.”

How much earlier it arrives is expected to depend on the water’s depth in the area, says Lin, but in these cases the magnetic field change arrived about 1 minute before the sea level change.

This is important because pressure sensors are often too close to coastlines to give practically useful prior warning of tsunamis.

“There are networks of buoys that measure water pressure around the Pacific, typically nearer coast lines rather than out in the [open ocean], but magnetometers would be ideally used in the middle of the [open ocean’s] abyssal plain,” says at the University of Colorado, Boulder. “They could give data on tsunamis before the tsunami reaches the pressure buoys.”

This, combined with the fact that the changes in the magnetic field predicted the height of tsunami waves, could help coastal communities prepare for incoming tsunamis.