We have had a lot of volcanic activity in Alaska this year. We currently have six volcanos at an elevated alert level of either Code Yellow or Code Orange.
None are more intriguing to me than the newest member of Code Yellow: Trident Volcano in Katmai National Park. Trident is a member of what is known as The Katmai Cluster. In addition to Trident, the cluster includes Mount Katmai, Mount Mageik, Mount Martin and Novarupta.
Trident has seen an increase in activity the past year, but since May, the earthquake frequency underneath the volcano has gone up considerably. Add that to the ground uptick at Trident, and you have the signs of moving magma. Katmai, Mageik and Martin have all seen an increase in seismic activity recently, as well.
Trident was last active between 1953-1974, when it went quiet. The eruptions of ’53 and ’74 formed new vents, which means it could be difficult to pinpoint exactly where an eruption could come from.
On June 6, 1912, the largest volcanic eruption of the 20th Century exploded out of the Katmai Cluster. For years, it was assumed that Mount Katmai was the culprit. It wasn’t until 1953 that Novarupta was determined to be the source. The majority of the magma was lying beneath Mount Katmai, but when the cluster erupted, the explosion came out of Novarupta, which is 6.5 miles away. Mount Katmai then collapsed into itself. Trident Volcano stands just 3 miles from Novarupta.
The amount of magma expelled from Novarupta was 30 times that of Mount St Helens. The devastation of the eruption formed the valley we now know as The Valley of Ten Thousand Smokes.
Mount Shishaldin on Unimak Island has been restless for a while. A USCG plane flying by noticed molten lava at the crater last week. Finally, on Friday the volcano erupted with a plume of ash that reached 15,000 feet. By Saturday evening, the eruption had earned a Level Red Warning, which had returned to Orange by Sunday night.
I have not heard of a major disruption to air traffic yet.
Great Sitkin, further out on the Aleutian Chain is also at Warning Level Orange.
Late on Saturday night, a 7.2 magnitude earthquake was recorded 55 miles southwest of Sand Point, Alaska. That triggered a Tsunami Warning from NOAA and the NWS for early Sunday morning. Luckily, waves of only 6″ high were reported, and the warning was cancelled long before I even woke up in the Interior of Alaska.
By Sunday evening, the Alaska Earthquake Center had recorded roughly two dozen aftershocks from the M7.2 quake, the largest at M5.7.
Not to be left out, the city of Anchorage had a gang of emus on the loose. No word on where the emus escaped from. At one point, they were reportedly spotted near the Campbell Airstrip, which I can say from experience, is a great place to start a hike. I also read through the comments on the post, and I must say that not one was remotely helpful on catching a runaway emu.
Yesterday was the 59th anniversary of Alaska’s Good Friday Earthquake. The above photo from the Alaska Digital Archives show the rail line north of Seward after the 9.2 magnitude quake struck South-central Alaska.
Last April, a series of earthquakes around and under Mount Edgecumbe brought greater attention to what was considered a dormant volcano. Measurements show that magma is moving deep underneath Edgecumbe. Other signs have also brought new scrutiny: Hikers have discovered vents with bubbling gas near the volcano, and satellite images show a bulging of the ground around Edgecumbe.
None of this means that Edgecumbe will blow anytime soon, but the State of Alaska has reclassified Mount Edgecumbe as a “high risk volcano”. With 73,000 people living in the region, the reclassification was probably wise. Currently, the east side of Edgecumbe is bulging faster than any volcano in Alaska.
The Alaska Volcano Observatory has plans to install seismic sensors and other instruments on Mount Edgecumbe over the coming months. Core samples show that the volcano erupted between 4000 -4300 years ago, and Tlingit oral history tells of an eruption approximately 800 years ago.
Currently, Alaska has one volcano at Code Orange, and four others at Code Yellow.
The Nenana Basin lies southwest of Fairbanks. The Parks Highway runs along its eastern boundary, and the Tanana River runs right through the middle of it. The basin is 56 miles long and 7.5 miles wide. Over the course of millions of years, the basin has been filled in with river sediment. Considering that the basin is 4 miles deep (7km), that is a lot of fill.
Several entities have been drilling test holes throughout the basin looking for oil and gas, so the University of Alaska – Fairbanks has been studying the basin’s makeup. One thing they found is that earthquakes last longer and feel a lot stronger in the basin, than just outside the basin.
The shockwaves from an earthquake travel differently through the sediment, which is mostly gravel, than the solid rock along the ridge lines. Reverberation also plays a roll here: The seismic waves are amplified by the basin walls and floor.
Seismic sensors have verified what local residents have been claiming: The shaking is a lot worse down in The Flats than up in the hills.
Source credit: Alaska Public Media, University of Alaska – Fairbanks
A couple of weeks ago, I posted about the swarm of earthquakes underneath Mount Edgecumbe. The numbers are in, and radar satellite data reveals a ground deformation around the volcano. Data was analyzed for the past 7.5 years, and since 2018, an uplift around Mt Edgecumbe has been constant. The peak activity, around the crater, has shown an average uplift of 3.4″ per year since 2018, and a total uplift of 10.6″.
With the data of the ground deformation, AVO has come to the conclusion that the swarm of earthquakes is due to the movement of magma below Mount Edgecumbe, and not due to tectonic activity.
Mount Edgecumbe, a 3200 foot high stratovolcano, lies 15 miles to the west of the community of Sitka. There is no volcanic monitoring system on Edgecumbe, but there is at Sitka. AVO plans to install instruments closer to the volcano in the near future.
The rising of magma under a volcano does not necessarily mean that an eruption is imminent. The deformation and earthquakes could cease at any time. If an eruption were to occur, warning signs such as increased rate of deformation, and an increase in the earthquake swarms, would give advance warning of an eruption.
Mount Edgecumbe is a 3200′ stratovolcano located on Kruzof Island. The volcano is approximately 15 miles from the town of Sitka, which was Alaska’s capital prior to its purchase from Russia by the United States.
Mount Edgecumbe has been dormant for at least 800 years. Recently, however, there has been a swarm of over 100 earthquakes from near the volcano. The swarm does not mean that an eruption is near, but the number is somewhat unusual. The previous two years saw only twenty quakes each year. Volcanologists are studying the data to see if these recent earthquakes are volcanic or tectonic in nature.
Tlingit oral history has the volcano having small eruptions roughly 800 years ago. The last eruption in the geological record happened 4500 years ago. Mount Edgecumbe had a massive eruption 13,000 – 15,000 years ago. That eruption dropped dropped 3 feet of volcanic ash on what is now Sitka, and 98 feet of ash fell on Kruzof Island.
Alaska has had 90 volcanos that have erupted in the past 10,000 years. Currently, we have three that are at Level Orange and one that is at Level Yellow.
A swarm of earthquakes and aftershocks hit the Aleutian Chain, just past Unalaska, on Tuesday. A couple of foreshocks were detected, then a 6.8 magnitude earthquake – which was the largest of the swarm, followed by a whole series of aftershocks. A dozen of the aftershocks came it at a 4.4 or higher, with one 6.6 magnitude shaker.
According to the Alaska Earthquake Center, the event was a “very unusual, very energetic swarm of earthquakes.”
No major damage was reported, and the earthquakes did not generate any tsunamis.
I found this map fascinating. There is almost a month differential across the Fairbanks Borough on the date of the first freeze this fall. I was in the August 18 Camp, which my zucchini never really recovered from.
Many of the recording areas with “After Sept 14”, will fall today, the 15th, as we are expected to drop into the Blue Zone by morning. My place was at 23F on Tuesday morning.
Officially, the Fairbanks Airport is on a decent streak of 135 days above freezing. Which is the fourth longest since recording began. 144 days is the record, which happened in 1974.
There was a 4.9 magnitude earthquake just east of Fairbanks on Monday night, just before 10pm. The cabin went through a decent shake.