Introducing Volcano Mount Baker

[BrickFielder]

Introduction
My intention is to produce a series of articles (depending on interest) which introduces ideas about volcanic and earthquake activity. I want to go slightly off the beaten track to explore oddities, volcano hazards, analysis methods, Wonders and Mankind’s impacts. Keep in mind I am not expert (corrections gratefully received), but hopefully these will at least give a flavour of some different places in the world and provide a few minutes escape from people’s troubles.

Introducing Volcano Mount Baker

Reason for Interest
Thought to be the second most active volcano in the continental United states after Mount St Helens then this volcano warrants some attention. Recent activity is thought to be mainly Hydrothermal with little suggestion of any coming eruption however there are potential hazards from earthquake activity or even minor eruptions. Despite being in view of both Vancouver and Seattle the threat to major cities would be mainly around infrastructure and travel.

The Setting
Mount Baker sits just below the Canadian border in the north west of the United States and lies within the beautiful Mount Baker Snoqualmie National Forest spans 1.7 million acres on the western slopes of the Cascade Range in Washington. The forest includes glacier-covered peaks, spectacular mountain meadows and old-growth temperate rainforests. The verdant valleys and forested mountains host an array of amazing wildlife including salmon, northern spotted owls, fishers, elk and more. The Mount Baker Snoqualmie National Forest is one of the most visited National Forests in the country with over 2.5 million people visiting each year. Vegetative cover is typical of the west slopes of the Cascades including western redcedar, coast Douglas-fir, noble fir, Pacific silver fir, subalpine fir, western hemlock and mountain hemlock, and at higher elevations, alpine meadows. Animals include mountain goats and hoary marmots.

On the slopes is the town of concrete named after the Superior Portland Cement Company plant was built there. The Henry Thompson Bridge at the center of the town was the longest single-span reinforced concrete bridge in the world when it was built.

Downstream is the city of Mount Vernon named after George Washington Estate in Virginia. Since this city was founded, the downtown area of Mount Vernon bordering the Skagit River has been plagued by flooding, especially during times of heavy rain. 

The Tectonic environment
The last of the Farallon Plate is now made of three small fragments The Gorda, Juan de Fuca and Explorer plates. The Explorer Plate broke off from the Juan de Fuca plate between 5 and 7 million years ago. As it did, the Cascade Arc resumed and the modern Cascade and Olympic Mountains began to rise. When the Cascade Arc volcanicity resumed 4 to 5 million years ago after reorganization of the Explorer Plate, there were some changes along the northern end. Where the northern end of the arc originally extended due north from the modern-day location of Glacier Peak into the Chilliwack Batholith and the Pemberton Belt in Canada, it now headed northwest into the Mount Baker and the Garibaldi area. This apparently reflects a steepening of the subduction zone on the northern end of the Juan De Fuca Plate. At the same time, the Juan De Fuca Plate assumed a more easterly-directed sense of motion relative to the continent. Mount Baker is the most recent descendent in a long line of volcanoes tracing their ancestry back into the Oligocene Chilliwack Batholith. 

The Volcano
Snow and ice-covered Mount Baker also known as Koma Kulshan (white Steep Mountain) located in northern Washington is the third tallest mountain in the state at 10,781 feet. Located in the Mount Baker Wilderness it is visible from Vancouver in British Columbia and to the south from Seattle. Mount Baker is a stratovolcano constructed above the east flank of an older eroded volcano the remnants of which are the Black Buttes craggy peaks west of Baker and SW of the early Kulshan caldera. The Schreibers Meadow cinder cone on the SE flank erupted about 9800 years ago. All other historic activity within the past 10,000 years seem to have taken place on the summit vent. A major magmatic eruption at Mount Baker occurred about 6500 years ago. The volume of ice on Mount Baker is greater than that of all the other Cascades volcanoes except Mount Rainier combined. At mount Baker continued elevated gas and heat flux from fumaroles in sherman crater indicate the presence of a degassing magma reservoir. The volcano was named for Lt. Joseph Baker, a member of the British expedition led by Captain George Vancouver that explored the waters of what’s now Washington and British Columbia in 1792. 

Ice filled Carmelo Crater is under the summit ice dome and is the source for the last cone-building eruptions. The highest point of Mount Baker, Grant Peak, is on the exposed southeast rim of Carmelo Crater. Carmelo Crater is deeply dissected on its south side by the younger Sherman Crater. This crater is south of the summit, and its ice-covered floor is 1,000 ft (300 m) below the summit ice dome. 

 

Hazard risks
If a summit magmatic eruption occurred then all drainages around the volcano will be susceptible to non cohesive debris flows  that form as the result of hot volcanic material, melting snow and ice. These debris flows will likely transform downstream into watery debris flows or floods. Of special concern is a debris flow entering Baker Lake and displacing enough water to either overtop Upper Baker Dam or cause failure of the dam. Either scenario would have consequences for the stability of Baker Dam. If Baker Dam should fail, the resulting debris flow or flood would most likely affect the entire Skagit flood plain to Puget Sound. Debris avalanches could occur without an accompanying eruption from the Sherman Crater due to earthquakes or hydrothermal activity.
Because winds are dominantly from the west, it is likely that any tephra that is produced will be carried to the east. Even minor amounts of Ash can affect the performance of aircraft, communications, damage machinery, close transport routes, block car air filters and electricity supplies. An under appreciated risk is the hazard of forest fires which happened during previous eruptions.
Today lake baker is bounded by two hydro electric dams which modelling shows that if they failed would increase flood water levels in the city of Burlington by 12 feet which might be enough to break the protective levees. In the event of an eruption and lahars then Transportation routes like the I5 into Vancouver could be damaged, along with closure of local airports, local power outages and not least rural areas the size of New York could be flooded.

Past Eruptions

The largest eruption in the history of the Mount Baker volcanic field occurred more than 50 km3 of rhyodacite magma exploded from a shallow magma storage region and filled the caldera and surrounding valleys. That amount of material would cover the island of Manhattan to the greater than the height of the empire state building. As the eruption progressed, the rock on top of the magma storage region collapsed forming the depression of the Kulshan caldera.

For 160,000 years after the caldera-forming event, dike-fed eruptions produced lava domes and lava flows inside the Kulshan caldera. Additionally, at least two eruptions occurred about 3 to 4 km (1.9 to 2.5 mi) west of the caldera at Chowder Ridge and Dobbs Cleaver.

Near Lava Divide and Parke Butte, are the signs of the initial shift of volcanic activity to the southwest, away from Kulshan. Located about halfway between present-day Mount Baker's summit and the western Kulshan caldera boundary. Near the southern foot of modern Mount Baker, a basaltic lava flow near Park Butte erupted around 716 ka. Today there is a lookout for hikers atop Park Butte, which is a former fire lookout.

Recent Activity

Mt. Baker erupted in 1843. This eruption resulted in the deaths of many fish in the Baker River, a large forest fire, and the dropping of volcanic ash.Explorers reported a widespread layer of newly fallen rock fragments "like a snowfall" and that the forest was "on fire for miles around". Rivers south of the volcano were reportedly clogged with ash, and Native Americans reported that many salmon perished. A short time later, two collapses of the east side of Sherman Crater produced two lahars, the first and larger of which flowed into the natural Baker Lake, increasing its level by at least 10 feet (3.0 m). 

In Spring 1975, scientists measured a ten-fold increase in thermal activity and detected magmatic gases, increasing concern that an eruption could occur. The steam eruptions in and of themselves were not really a threat but what was a threat was the rock on the east rim of the crater, where there’s an opening and the Boulder Glacier comes out of the crater and goes down the side of the mountain. The fear was that a big chunk of that rim of the crater might slide down the mountain and into Baker Lake. A landslide that big could potentially create a wave that would wipe out anything along the shores of Baker Lake and even damage or possibly destroy the Upper Baker Dam. Such an event would result in a large volume of water rushing into the Lake Shannon reservoir and potentially cause a surge of water over, or failure of, the Lower Baker Dam. Failure of the Lower Baker Dam would result in catastrophic flooding down the Skagit River with little to no warning. This was an especially worrying scenario for the town of Concrete which lies at the foot of the Lower Baker Dam. The data collected suggests that magma may have intruded beneath the volcano in 1975, but it did not have enough energy to erupt. The magma stalled, likely in the form of a dike, and has been cooling since. By the fall of 1975, melting of Sherman Crater glacier resulted in a snow-free area three times larger than typical summer exposure and revealed a shallow lake and previously unknown fumaroles.

Between June 16 and August 22, 2009, a swarm of least 39 low-frequency (LF) seismic events occurred at shallow depths beneath Mount Baker, a Cascade Range composite stratovolcano located in northern Washington. The LF events had several characteristics similar to classic volcanic low-frequency events.

Analysis of Mount Baker  earthquake events found other examples of shallow LF events occurring in 2005, 2006, and 2007, and similar events have been recorded in 2010-2012, all during the months of May-October. Based on several lines of evidence, including their seasonal occurrence, scientists believe that these events are occurring along the base of a glacier at Mount Baker, most likely the Easton or Deming glaciers (where most of the events locate), and are not related to volcanic activity.

In contrast to the virtual absence of shallow earthquakes at Mount Baker, at depth it has the highest concentration of so-called Deep Long-Period events of any volcano in the Washington and Oregon Cascades. A 2011 study cataloged DLP events in the Washington and Oregon Cascades, and found that, since 1980, more DLP events have been located in the vicinity of Mount Baker than at the rest of the Cascade volcanoes combined. These events are thought to be related to movement of fluids or magma.

Discussion
On the face of it this is a remote volcano with very little suggestion of activity yet there are some potential hazards associated with it. I guess my interest is the contrast between the stunning scenery and sleepy towns against the slumbering giant that could throw a curve ball.