Earth as Inspiration: Mt. Shasta for Earth Science Week, October 14-20

Mt. Shasta and Shastina from the north

I usually don't need an inspiration to write about Mt. Shasta, but I realized (two days in) that October 14-20 is national Earth Science week, and the theme of the celebration this year is "Earth as Inspiration". In case you have not yet realized this yet, but I am in fact inspired by the Earth. It started early on in my life with family vacations to some stunning places in California and the American Southwest, continued with scouting experiences nearly every weekend in my teens that included extensive work with topographic maps, and right into my college major and subsequent career as a geology professor. And then I found the form of story-telling called blogging in 2008.

Panther Meadows at the 8,000 foot level on Mt. Shasta

Mt. Shasta is an earthly inspiration. We visited two weeks ago as part of our field course on California's volcanoes. The stops included a drive to the end of the highway at Panther Meadows at 8,000 feet on the side of the 14,179 foot high volcano, and another stop on the north flank where we could see the glaciers and one other astounding feature of the volcano (mentioned below). Shasta is the second tallest volcano (behind Mt. Rainier) but is the most voluminous composite cone (stratovolcano) in the range (I'm parsing words here; there is a larger volcano, but it is of a different kind and will be discussed in a future blog). As a classic composite cone, it is composed of the remains of at least four previous incarnations, capped by the current active vent, Hotlum Cone. The oldest lava and ash dates back to around 600,000 years ago, but the youngest is a mere couple of hundred years. It likely erupted in 1786.

As the highest mountain in Northern California, it supports seven glaciers. Whitney Glacier, with a length of two miles, is the longest in the state (below). The glaciers are responsible for one of Shasta's unique hazards: jokulhlaups! These are floods caused when meltwater is sealed underneath the glacial ice which then breaks out in a catastrophic manner. Although caused by eruptions under the glacial ice in places like Iceland, those that occur on Shasta can happen almost any time. They are generally more of a nuisance, messing up roads and bridges, rather than a killer.

The biggest dangers of a volcano like Shasta are volcanic mudflows (lahars), and hot ash flow eruptions. Lava flows, unless they interact with the ice, are of a lesser concern. Andesite lava has a pasty consistency and is not likely to flow overly far from vents on the mountain. Lahars are of the greater concern, as they are capable of producing massive casualties and structural damage. The towns of Mt. Shasta, Weed, and McCloud are constructed on old lahar deposits. Major events could cause the closure of Interstate 5. Hot Pompeii-style ash eruptions are somewhat less likely, based on the previous history of the volcano.

Whitney Glacier, the largest in California

One of the most outrageous landscapes to be found anywhere on the planet lies to the north of Mt. Shasta. When compiling geologic maps of the region in the 1970s, geologists weren't sure how to interpret the vast region extending north from the mountain reaching 28 miles to the edge of the village of Yreka. It was a hummocky landscape, made of hundreds of small hills and cones of lava fragments with intervening hollows, some containing lakes and ponds. Was it some kind of odd field of cinder cones? It didn't make a lot of sense until the eruption of Mt. St. Helens in 1980.

The St. Helens eruption was initiated when an earthquake caused the entire north flank of the volcano to collapse in a gigantic debris avalanche that traveled for twelve miles down the Toutle River valley. Humans had never witnessed a landslide so large. It uncapped the volcano, leading to the very explosive ash eruption that followed.

To the geologists studying the region around Shasta, it was a revelation. The avalanche at St. Helens formed hundreds of hummocks similar to those found at Shasta. It quickly became clear that the deposit on the north flank of Shasta was the remains of a gigantic debris avalanche. The St. Helens avalanche involved less than a cubic mile of material (0.67 cubic miles), but the now-apparent debris avalanche at Shasta was ten times larger (about 6.5 cubic miles), and it traveled twice as far. It seems to have happened between 360,000 and 300,000 years ago. It's stunning just to image seeing something like this happen.

What aspects of the Earth do you find inspiring?

The Many Sides of California's Incredible Composite Cone Mt. Shasta

Hotlum Cone and Shastina, the two youngest cones of Shasta are seen here from the north on Highway 97

California has a lot of incredible volcanoes, but looming above them all is Mt. Shasta, the huge composite cone that rises above the mountains of Northern California. At 14,179 feet, it towers over all but a few of the highest peaks of the Sierra Nevada, but none of them are close by. It is more than a mile higher than any other nearby peaks. I and my students have been traveling around it the last two days, and we've seen it from every side.

From the south it was largely hidden by the smoke from the recent wildfires, but we drove up the Everritt Memorial Highway to the 8,000 foot level at Panther Meadows. The barren valley once hosted a ski resort until folks realized the lack of trees in the area was because of the constant avalanches. The ski area was moved, but the road remains, and serves as a high trailhead for summit attempts.

The Sargent's Ridge and Misery Hill cones of Mt. Shasta. These cones are older and more deeply eroded.

A careful study of the ridges and valleys reveals that there have been more than one "Shasta". At least five volcanoes have developed over the Shasta magma chamber, but most of them have been removed by erosion, explosion and avalanche. Only the highest cone, Hotlum, and the satellite summit of Shastina seem untouched by serious erosion. They are both less than 10,000 years old, and Hotlum has continued to erupt at intervals of several hundred years.

From the northeast, Shasta is highly symmetrical. That large snowfields remain in the fall season is evidence of the presence of glaciers. Shasta has at least five of the them, and Whitney Glacier is the longest glacier in all of California, at two miles.

The peak shined bright and clear in the morning light, but by this evening, it was shrouded in clouds and lightning was flashing in the skies above. The mountain, a so-called composite cone is a mountain of many moods.

I'm pretty sure I don't want to see the mountain angry...

Running Circles Around California's Greatest Volcano

From the northwest, Shasta and Shastina are two prominent peaks.

I'm going to get into rhetorical trouble for this. "Greatest" is a hugely subjective term, and there are going to be some disagreements. But Mt. Shasta is California's greatest volcano. Not necessarily my favorite (though it might be), but the greatest. How does one judge such thing? My standard of the day is topographic prominence and topographic isolation.

A gigantic debris avalanche covers the countryside for 28 miles north of Shasta.

Topographic prominence is the elevation difference between the summit and the highest or key col to a higher summit. Topographic isolation is the minimum great circle distance to a point of higher elevation. By those metrics, Mt. Whitney, the highest point in the state has the greatest prominence and isolation. It's 1,646 mi (2,649 km) to another mountain that is higher than Whitney, and it has a prominence of 10,080 ft (3072 m). But Whitney is surrounded by dozens of mountain peaks that are nearly as tall. It doesn't exactly stand out. But Mt. Shasta stands alone, with a prominence of 9,832 ft (2997 m), and it is 335 mi (539 km) to another peak that is higher (in the Sierra Nevada). In short, Shasta is a huge mountain that provides an awesome sight from all compass directions. And that's what today's pictures are about.

Last week we took four days to completely circle Shasta, first traveling north on Interstate 5 to pass by the western flank of the mountain, then following Route 97 to swing around the north side. We took Route 161 along the Oregon border to get to Tulelake and Lava Beds National Monument for a view form the northeast. We then drove over Medicine Lake Highland for a look at the south flank.

Whitney Glacier is the longest glacier in California, and the only valley glacier.

Shasta has a few other distinctions. It has the largest and longest glaciers in California (above). Whitney glacier is 2 miles (3.2 km) long, while adjacent Hotlum glacier covers 0.7 square miles (1.8 km²). Both glaciers have grown in size over the last fifty years, seemingly at odds with global warming. The growth is explained by increased precipitation over the years (from higher evaporation rates over the warmer oceans), even though temperatures in the region have increased 2-3 degrees. As warming continues, the growth spurt will end, and so probably will the glaciers themselves.

Sandhill Cranes pause in their migration at the Tulelake National Wildlife Refuge on the northeast side of Shasta

Another strange aspect of Shasta is the unusual hummocky surface that extends north from the mountain for 28 miles (43 kms), almost to the town of Yreka. The lumpy surface is the remains of a gigantic debris avalanche that destroyed a previous incarnation of Mt. Shasta around 300,000 years ago. The avalanche was not recognized for what it was until a similar event traveled 12 miles from Mt. St. Helens in the eruption of 1980. The landslide is one of the largest ever documented in the world.

Shasta from the Tulelake National Wildlife Refuge

Volcanism has been taking place at Mt. Shasta for around 600,000 years, but most of the cone-building has happened within the last 200,000 years. Shasta is actually an edifice of four different cones that formed at different times. The Sargents Ridge and Misery Hill cones are the oldest, and the least obvious. Whitney Glacier follows the edge of the Misery Hill crater.

The southeast flank of Shasta from near Bartle.

Shastina erupted around 9,700-9,500 years ago, and the main peak, Hotlum Cone, has been erupting during the last 9,000 years. The most recent volcanic episode may have been only 200 years ago. Several villages have been constructed on the flanks of the volcano, including McCloud, Weed, and Mt. Shasta City. Around 20,000 people call the volcano home.

Unless you count the Lemurians. And the Atlanteans. Such a prominent mountain could not be without legends and myths, and Shasta has plenty. Tired half-conscious climbers have reported seeing survivors of the Atlantic disaster wandering the upper slopes, and an entire cottage industry swirls around the mysticism of the mountain, and all the beings who live in gigantic underground cities within the volcano. I suppose it all makes sense...

The biggest volcano in the Cascades, the biggest volcano in California, visible for a hundred miles or more in many directions, it's a great volcano. Maybe the greatest.

The Other California: A Land of Fire and Ice (but mostly ice today)

I'm breaking my own rules here. My latest series is exploring the places in California that aren't on the postcards, but are worth a visit. The thing is, Mt. Shasta is one of the most familiar sights in the state of California. The gigantic stratovolcano, the largest of its kind in the Cascades Province (and one of the largest in the world) reaches an altitude of 14,162 feet, and can be seen from over a hundred miles away in some directions. It's on a lot of postcards. But most people see the volcano on their way from California to Oregon along Interstate 5, and in doing so have a hard time seeing one of the most remarkable things about the volcano that isn't volcanic.

California, the sunny, mostly arid, almost semi-tropical state is not known for its glaciers, but it most certainly has them. The Sierra Nevada has between a dozen and several dozen glaciers, depending how one defines them. The largest Sierra glacier lies beneath the peaks of the Palisades, and is a mile wide and half a mile long. But farther north, Mt. Shasta has at least seven, including both the longest, and the largest glaciers in the state. They are most easily seen from viewpoints along State Highway 97 between Weed and Klamath Falls, Oregon.

Whitney glacier is the longest glacier in the state, with a length of about two miles. It is also the only valley glacier in the state. It zigs, then zags down the center of the photo above. Most all the other glaciers occupy the cirques at the head of glacial valleys. Whitney displays many classic glacial features, including bergshrunds, ice falls, crevasses, and moraines.

Whitney is the longest glacier in the state, but it is fairly narrow in its valley. The honor of the largest glacier in the state is nearby Hotlum Glacier, which coats a slope on the northeast flank of the volcano. It is about 1.3 miles long and 0.7 miles wide. In the picture above, Hotlum can be identified from the rounded cracks (the bergshrund) on the left flank of the volcano. Bolam Glacier is in the center of the photo, and bits of Whitney are on the right.

The glaciers of Shasta have a unique distinction: they are one of the few glaciers in the world that are actually growing in size. Before any global warming deniers get excited, the growth is actually a consequence of the rise of world temperatures. Warming of the northern Pacific is causing an increase in evaporation, and is increasing the amount of precipitation on the mountain. The increase of snow is able to offset the loss of ice due to melting during the 1.8 degree Fahrenheit rise of average temperature in the region over the last century. Continuing increases in global temperatures will eventually overwhelm the glaciers, and they will most likely be gone in a century or so.

See them while you can!