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If a mountain fell in the wilderness...

Camped on an island in Southeast Alaska a few mornings ago, Sasha Calvey heard a commotion outside her tent.

“(On Aug. 10) at 5:45 a.m., I woke to a loud roar of rushing water,” the 25-year-old kayaker and outdoor educator said. “Then there was this massive tidal surge just inches away from our tent.”

Calvey and her two friends — on a summer-long paddling trip from Washington state to Glacier Bay in Alaska — watched in disbelief as the ocean crept up the shoreline more than 15 feet, carrying away many of their possessions. 

“I saw my kayak spinning in a whirlpool,” Calvey said over the phone from Juneau, one day after her experience. 

She then watched her boat disappear with a receding wave. 

Calvey’s kayak was the most vital piece of gear the ocean grabbed during a tsunami caused by a massive avalanche of rock into the ocean more than 30 miles away. Experts at the 51�������� Geophysical Institute say the landslide-caused tsunami may be the largest one detected in Alaska during the last decade.

Calvey and her companions Billy White and Nick Heilgeist took stock of their situation after the waves subsided offshore of Harbor Island, where they were camped. 

They were thankful they decided to pitch their three-person tent in the forest well above the high-tide line. And though they had lost Calvey’s boat — along with a dry suit, boat paddles, a bear fence, a stove and prescription sunglasses (among other things) — they had plenty of fresh water, warm clothes for all, four days of food and a radio.

The three decided no “mayday” call was merited but knew they were quite stuck without Calvey’s boat. 

They radioed their situation to anyone who might be monitoring a certain frequency. Within minutes, a boat captain answered the call. He transported them and their remaining gear to Alaska’s capital city of Juneau.

As well as a ride to Juneau, the crew of the private charter yacht Blackwood provided the three with warm blankets, “a lovely breakfast and a wonderful lunch,” Calvey said.

51�������� the same time the kayakers’ campsite was flooded, Christine Smith was cooking food for guests 30 miles away on a 65-foot ship upon which she and her husband Jeffrey provide eight-day adventures in Southeast Alaska.

The ship was in Endicott Arm, a finger of ocean reaching toward British Columbia.

“We have been anchoring there for 20 years,” Smith said by phone from the MV David B one day after the tsunami. “I had never seen water rushing over this sandbar while the tide was going out.”

Smith texted her neighbor and friend Jackie Caplan-Auerbach, who is a professor of geology at Western Washington University in Bellingham, Washington.

Caplan-Auerbach searched online for a possible seismic signal, one that might indicate a large mass had avalanched into the ocean nearby.

“What I love about Christine is that despite her not being a scientist, she totally told me to look for a landslide,” Caplan-Auerbach said over the phone from Bellingham.

Caplan-Auerbach, once a postdoctoral researcher at 51�������� who studies landslide seismicity, soon found the dramatic squiggles of the landslide. She then looked for — and found — “little stuttering events” that preceded the much-larger shaking. Those precursors sometimes happen before a giant landslide, but not always. 

Caplan-Auerbach relayed the information to Smith, who mentioned that heavy rains had pelted them for days, possibly lubricating a steep slope into catastrophic failure.

Seismic stations more than 600 miles away picked up the rumbling as a mountainside collapsed upon South Sawyer Glacier and into the ocean at the head of Tracy Arm, said Geophysical Institute researcher Ezgi Karasözen.

Karasözen applied a “landslide characterization algorithm” on the available data from Southeast Alaska seismic stations. She found it was potentially the largest landslide and tsunami in Alaska since Taan Fjord in 2015.

So far, the kayakers’ gear is the largest human loss associated with part of a mountain falling into the ocean (“with a very large possible volume of 30-290 million cubic meters,” according to Karasözen). 

Also perhaps lost was the feeling of accomplishment one might get from paddling your kayak for a whole summer from Washington to Glacier Bay. Instead of achieving their entire goal, Calvey said, she and her partners would end their trip in Juneau.

Calvey was happy to raise more than $10,000 along the way to start a youth kayaking group back home in Washington. She also values the notion of a few news stories upping awareness of rogue tsunamis.

Members of the Juneau ocean kayaking community have offered loans of gear to replace what the three kayakers lost. In deciding her near future, however, Calvey remembered some advice.

“A mentor of mine told me once, ‘When nature tells you it’s time to stop, it’s time to stop.’”

Since the late 1970s, the 51�������� Geophysical Institute has provided this column free in cooperation with the 51�������� research community. Ned Rozell ned.rozell@alaska.edu is a science writer for the Geophysical Institute.