By Ella Nilsen, Sam Hart, CNN
(CNN) — The world’s second-tallest tsunami wave on record tore through the remote Tracy Arm fjord in Alaska last August, leaving immense destruction in its wake.
Luckily, there were no people nearby. But in its aftermath, scientists immediately went to work, piecing together what happens when a mountainside collapse kicks off a mega-tsunami and no one is around to see it.
This is how it happened: On August 10, at 5:30 in the morning, an entire mountainside at the mouth of the receding South Sawyer glacier detached, falling into the ocean and producing a monster wave. At its peak, the wave raced up over 1,500 feet on the opposing wall of the fjord — a height taller than Kuala Lumpur’s twin Petronas towers.
The mega-tsunami wreaked havoc across the landscape, stripping forests down to bare rock, ripping trees out by their roots and hurling boulders.
It also produced a seismic vibration so strong it shook the entire planet for days. Only the second time that an effect like this has been recorded anywhere, it was caused by trapped energy from the wave sloshing around in the fjord for days following the initial event.
In the months following the tsunami, a dozen scientists from the US, Canada and Europe have been doing “detective” work, attempting to “re-create this hazards cascade,” said Daniel Shugar, a geomorphologist and professor at the University of Calgary.
Scientists see the fingerprints of climate change all over this event and several others like it that have occurred in recent years. Many of them have been linked to retreating glaciers, as melting ice destabilizes the mountains and land that had been covered for centuries.
“As the climate is changing, as glaciers are retreating, we are likely going to see more of these kinds of events in high latitude environments in the Arctic and the sub-Arctic,” Shugar said.
“I can barely believe it”
Even for scientists who study these kinds of disasters, the awe-inducing destruction and power of the Tracy Arm mega-tsunami is hard for the human brain to comprehend.
The mountainside that slid off to produce the skyscraper-size wave was, itself, more than 3,200 feet tall — higher than the world’s tallest building. Today, the mountainside looks bare, as though the 370 million metric tons of rock were scooped out as they slid into the ocean below, leaving a concave scar.
When tsunami modeler and researcher Patrick Lynett traveled with a team to the site of the landslide months later for field work, he was left in awe by the disaster’s magnitude.
“I saw it in real life, and I can barely believe it,” said Lynett, a professor at the University of Southern California.
It may seem odd that such a disaster left no injuries or deaths. But the sheer height of tsunami waves doesn’t always correspond with the number of fatalities. Counterintuitive as it might be, the deadliest tsunamis in the world happened with much smaller waves than either Tracy Arm or the 1958 Lituya Bay tsunami — the current record-holder for biggest wave. (Lituya Bay killed between 2 and 5 people, sources differ.)
Landslide-induced tsunamis can best be thought of as a big splash set off by many tons of rock falling into deep water, often in narrow channels like mountain fjords. Just like when you throw a big rock into a river, the splash happens quickly. Colossal as it was, the Tracy Arm wave happened in just 45 seconds to a minute.
Earthquake-caused tsunamis