Mount Edgecumbe



Just over 100 miles south of Alaska’s Glacier Bay National Park resides a stratovolcano known to the Tlingit as L’ux.

The name means “to flash” or “blinking,” a fascinating moniker for a volcano, ostensibly because the Tlingit first encountered the mountain while it produced smoke or erupted. In an interesting etymological confluence, lux is the Latin word for “light;” lux is the unit for illuminance in the International System of Units (SI). One lux is one lumen per square meter.

How many lux would L’ux produce while erupting?

In English, we call this crag Mount Edgecumbe, the name Captain James Cook gave as he passed it during his third voyage around the world. Cook either honored a hill of the same name overseeing Plymouth Harbor in England or George, Earl of Edgcumbe.

While Edgecumbe is a decent designation, we vote for the far more sublime L’ux.

Mount Edgecumbe - photo by Duncan Mariott

Edgecumbe sits on the southern end of Kruzof Island, about 15 miles west of the town of Sitka (trivia: under Russian control in the 1700s, Sitka was known as New Archangel). Rising 3,201 feet above sea level, the mountain is the highest point on the volcanic field named for Mount Edgecumbe. L’ux doesn’t possess world-shattering verticality, but being on an island in the Gulf of Alaska means all the elevation is also prominence. In other words, Edgecumbe rises sharply from the water.

Kruzof Island and its volcanic field are members of the Ring of Fire, the horseshoe-shaped region that lines the Pacific Ocean. The Ring of Fire packs an unprecedented number of volcanoes and earthquake activity into its confines, the result of tectonic plates that smash into each other.  Mount Edgecumbe is about as close to the strict boundaries of the Ring of Fire as a volcano can be: it lies just 9.9 miles from the Queen Charlotte Fault, the line where the North American Plate and the Pacific Plate meet. 

An overview of the Queen Charlotte Fault - United States Geological Service

Despite this proximity to the world’s fiery epicenter, Mount Edgecumbe has been classified as a dormant volcano. Its last major eruption occurred approximately 4,000 years ago circa 2220 BCE. Beyond the big blows, Edgecumbe has not produced any minor activity in about 800 years, which just goes to show how old the Tlingit name must be.

In 1974, locals wondered if that eight-century dormancy might have ended. From Sitka, residents started to view smoke rising from the cone:

Smoldering Edgecumbe in 1974 - photo from Sitka.com

Fortunately for those living nearby, the date was 1 April 1974.

A man named Oliver Bickar hired a helicopter to lug 70 old tires to the crater. He and the pilot ignited the tires, causing a plume of black smoke to rise. Below the summit, Bickar spray-painted 50-foot letters that spelled “APRIL FOOL.” 

He had alerted the FAA and the police in Sitka but forgot to notify the Coast Guard. Spying the possible eruption, they scrambled a plane to check the situation. They were perhaps not as amused to see the giant message scrawled on the mountain, but this stunt is often cited as one of the greatest April Fool pranks of all time. Looking at the photograph above, the scale of a giant volcano really comes into perspective; the conflagration from 70 tires would be no small blaze, yet it barely covers a speck of the mountain’s crater.

Mount Edgecumbe from the air - USGS

The 1974 caper did not signal a centuries-old switch from dormancy to active for Edgecumbe.

However, this mountain has recently, to mix metaphors, rumbled onto the radar of seismologists and volcanologists. In April 2022, a swarm of earthquakes under Mount Edgecumbe began to shake the region. And, this time, the activity was no joke. The swarm began not on 1 April but 11 April, totaling hundreds of temblors.

The Alaska Volcano Observatory started to monitor the area and noticed deformation across an 11-mile diameter area around the volcano. The activity is likely caused by a magmatic intrusion three miles below the surface. This magma movement caused the area to the east of the mountain to rise 11 inches since April. That figure might not sound like a lot, but, in geological terms, it’s quite significant. For perspective, Mount Everest continues to gain height because two continental plates are still in the process of creating the Himalayas. The world’s tallest mountain gains 0.16 inches per year.

Gorgeous Mount Edgecumbe - photo from Sitka.com

Scientists worked quickly to allay the fears of residents. Magmatic intrusions and earthquake swarms do not necessarily mean an eruption is imminent or even likely. It does, however, signal that the “dormant” status attached to the mountain for the past centuries is no longer really appropriate. The Alaska Volcano Observatory installed seismometers and sensitive GPS equipment on Kruzof island in an attempt to watch the volcano intensely. Volcanologists believe that, if Edgecumbe were to erupt in the future, it would be proceeded by activity even more severe than that of 2022. So, plenty of warning will probably arrive if she ever blows.

This volcano is actually climbable. The first recorded ascent happened in 1805 by a Russian named Urey Lisianski. In the 1930s, the Civilian Conservation Corps created a trail to the summit. The 6.8-mile trail starts in taiga and ends in volcanic ash and snowfields.

An ascent on this exquisite peak might now pose a bit more threat than it did in the past, but the journey would certainly be enlightening. You could see the lux on L’ux! Where else could you make that claim?

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