Anniversary of the Donnell Fire: Nothing in this World is Permanent, Except for Change

The Dardanelles Crest in 2006

On August 1, 2018, a fire started in the Stanislaus National Forest near Donnell Vista on Highway 108. It's not known how the fire started, but lightning was not the cause. It was clear that day. There wasn't much concern, it was confined at first to a few acres, but it blew out of control and started spreading. The so-called Donnell Fire ultimately burned 36,450 acres (57 sq. miles; 147.5 sq. km.) and destroyed 135 structures including the historic Dardanelles Resort. There were nine injuries, but thankfully nobody was killed.

The Dardanelles Crest, August 1, 2019

It was a coincidence, but exactly one year later to the day, we headed up Highway 108 to view the damage for the first time. It was sobering. The fire can't be compared to the devastating fires that ravaged Paradise and Redding last year or Sonoma County in 2017 when dozens of lives were lost and tens of thousands of homes burned. But still this fire was a tragedy. It burned memories and experiences. Like so many fires both in Southern California and in the Sierra Nevada, it took away landscapes that have shaped my life.

The Dardanelles in 2008

Fires have always been a player in the environment of California. A Mediterranean climate, with mild wet winters and long dry hot summers is an absolute guarantee that fires will burn. But we have entered into a new climate regime due to global warming that is deeply altering the patterns of fire in California and across the American West. Warmer average temperatures intensify the effects of droughts, causing greater evaporation and drier soils, so trees and shrubs are less able to deal with fires. The fires have increased in size to massive conflagrations, and burn more intensely, "crowning" more easily, and at times altering the soils so they are less able to absorb moisture when precipitation does come.

The Dardanelles on August 1, 2019

It was a relief to see that in many areas the fire took on a checkerboard aspect, missing some of the forest groves, which means that the forest can re-seed more readily. In other areas, the destruction was more complete, as in the slopes above the former Dardanelle Resort, seen in one of the pictures below. The recovery of that forest will take much, much longer.

Columns of the Giants, 2016

We stopped at a number of our favorite localities. Donnell Vista was not directly affected by the fire, but the viewpoint offered views of a major portion of the burned areas, including the slopes below the Dardanelles Crest, as seen in the first four pictures above. We also checked out Columns of the Giants, one of most awesome geological features along all of Highway 108. The trails and the bridge over the river were intact, but much of the forest and brush around the site were destroyed (see the pictures above and below for a comparison).

Columns of the Giants, August 1, 2019

The Dardanelle Resort was an especially sad sight. The historic old resort was obliterated, as were the slopes above. The resort had fallen into some disrepair over the years, but it had been purchased by new and ambitious owners only three months before the fire. They intend to rebuild, and a temporary trailer is already in place, serving as a temporary store.

The Dardanelle Resort 

Highway 108 near the Middle Fork of the Stanislaus River at the Old Dardanelle Bridge (which burned in the fire)

The historic 1933 Dardanelle Bridge was destroyed in the fire (photo below). It was apparently the last scissor truss-style bridge in the United States. It had been replaced by a more modern bridge around 1990 but was still maintained for walking. Ironically it was almost destroyed during the construction of the new bridge when some boulders from nearby blasting landed on the bridge, but it is unlikely to be replaced now.

The old abutments for the 1933 Dardanelle Bridge are left of the highway in the center of the photo

For all that was lost, much still remains. Highway 108 and other roads provided access for firefighters to battle the fire, so many sections of forest adjacent to the highway survived relatively unscathed. The firefighters were able in particular instances to set backfires just uphill from the highway that moved upslope, removing fuel for the oncoming main fire. In this way many of the cabins and developments were saved.

One of endangered developments was the High Sierra Institute at Baker Station. Originally a road maintenance facility, the cabins operate today as a research and educational center for the Yosemite Community College District which includes Columbia College, and my own institution, Modesto Junior College. Some trees on the property were lost, but the backfires preserved all of the buildings on the property.

Fires destroy, and fires renew. We live in a new climate regime, and we need to learn how to deal with this new world. Forests will regrow, but they will not be the forests that were lost. The ranges of the animals and plants are shifting northwards and upwards as the climate in California grows warmer and drier. Some organisms will be driven to extinction (the pika is in particular danger, as it lives at very high altitudes, and therefore has nowhere to retreat).

But there is also an emotional toll. We can't maintain the world as a museum where our favorite places remain, unaltered and unchanged by time. Change comes no matter what efforts we expend to preserve the past. Sometimes we can plan for the changes, such as developing master plans for parks and monuments, but wildfires are the bull in the china shop, causing destruction and change without pity or mercy. I grew up in Southern California and watched some of my favorite haunts in the San Gabriel Mountains disappear in wildfires. I moved to central California 30 years ago, and in that time have witnessed apocalyptic events like the Rim and Ferguson fires destroy large portions of the forests along and in the margins of Yosemite National Park.

As those of us who study geology know from our studies, there is nothing permanent about the world except for change. And sometimes the changes are tragic.

The Sierra Beyond Yosemite: Donnell Vista and Sonora Pass

It's gloomy and foggy, and I haven't seen the sun for days. It's a few more weeks before field season (Death Valley!), but I can't help exploring the sunnier places from warmer times. I'm looking back at the pics from our fall semester where we explored a lot of places in the Sierra Nevada that aren't Yosemite.

That's the thing. Say "Sierra Nevada", and a lot of people will immediately think of the beautiful valley of the Ah-wah-nee, John Muir's favorite place on the planet, and in many ways mine as well. But the floor of Yosemite Valley is about 7 square miles. The national park covers 1,190 square miles (3,081 square kilometers). But the Sierra Nevada? It covers 39,612 sq miles (102,594 km²).  You could hide more than 30 Yosemite parks in the rest of the range. It is in fact the largest single range in the lower 48 states (large mountain systems like the Rockies and Appalachians are made up of numerous smaller sub-ranges).

So we are off onto a short exploration of some of the wonderful corners of the Sierra Nevada that aren't Yosemite Valley. We are following a week's worth of our trips last fall that took us over the range at Sonora Pass and down the east side of the range as far as Lone Pine and Mt. Whitney. We'll also explore the other national parks of the range, Sequoia and Kings Canyon, which we visited on a second trip.

We began our journey in some serious smoke from a series of fires burning through the western slopes of the Sierra Nevada. The drought and the fires have been catastrophic. We made a stop at the Twain Harte Lake exfoliation site. I wrote about it back then, and it was picked up on Reddit and IFLS, links that led to the post being the most read ever on Geotripper (12,400 hits and counting). We emerged from the smoke and climbed the upper reaches of the Stanislaus River, approaching Sonora Pass, which after Tioga is the highest paved highway over the Sierra Nevada at 9,624 feet (2,933 meters). Tioga Pass in Yosemite is 9,943 ft. (3,031 m.).

In a series of ice ages, glaciers covered about 30% of the range, reaching as low as 3,000 feet or so in some of the deeper canyons. Yosemite is simply the most famous of the glacially carved gorges, and many others are of incredible and spectacular beauty. This was not always fully appreciated, and some of these wonderful wild canyons were dammed for irrigation storage and domestic use. Hetch Hetchy is the most familiar, but the canyon below Donnell Vista on Highway 108 has also been inundated. Still, the glacial heritage of Middle Fork of the Stanislaus is evident from the viewpoint. The steep canyon walls of granitic rock and the overall U-shape of the valleys are the result first of ancient river erosion and then modification by thick rivers of ice.

If you look at the second picture above, you can see some unusual looking mountain peaks. Their blocky flat aspect indicates they are composed of something different than the "expected" granitic rock. They are the remains of lava flows, ash flows and volcanic cones that once covered this part of the Sierra Nevada. Indeed, until 9 or 10 million years ago, the Sierra looked far more like today's Cascades Range than the lofty glacial peaks we see today. There were a number of snow-covered stratovolcanoes, but much of the remainder of the range was composed of lower hills. The upper reaches of Highway 108 where it crosses Sonora Pass cut through some of the volcanic rocks.

We stopped a mile or two short of the pass to get a detailed look at the granitic rocks. Depending on the relative proportions of plagioclase and orthoclase feldspar and quartz, rocks may be identified as granite, granodiorite, tonalite, diorite, or monzonite. The rock exposed just below the pass is called the granodiorite of Topaz Lake, dated about 89 to 83 million years ago, during the Cretaceous era. It was intruded in the deep crust about 4 or 5 miles down where it cooled slowly, forming visible crystals of feldspar, quartz and dark minerals like biotite mica and hornblende.

Glaciers scoured the surface of the granodiorite, polishing it and providing a nice view of the structure of the rocks. Some of the orthoclase (potassium feldspar) has formed huge blocky crystals easily visible in the shot below. Even better, during the intrusion process, blocks of the surrounding rock broke off and sank into the magma. Composed of minerals that had higher melting points, it didn't melt, but instead persisted as an alien mass in the granitic rock. Such inclusions are called xenoliths. They provide a peek at what existed here before the intrusion of the magmas.

We drove over Sonora Pass and headed into the barren lands beyond. Our destination was the site of a gold rush, but not the one that Californians are familiar with.

The Other California: Highway 108 and Donnell Vista - like Yosemite, only with Volcanoes!

Those of you who've followed my blog over the years may remember that I produced a blog series called "The Other California" which existed long before any Toyota commercials with a similar slogan. I come back to it time and again when I find (or rediscover) those places that don't always show up on the tourist postcards, but which have incredible geology and are scenic to boot.

Today we are exploring a few corners of the Upper Stanislaus River drainage in the country north of Yosemite National Park. People from outside the region can be forgiven if they think that the Sierra Nevada is just Yosemite Valley, Sequoia National Park, and Lake Tahoe. The range is 400 miles long, and pretty much all of it is spectacular, except Yosemite and Sequoia are just a little more so. I cannot doubt that if Yosemite Valley didn't exist, the upper Stanislaus would have been one of California's national parks. In some ways, Sonora Pass and the upper Stanislaus are even more interesting in the geologic sense. The reason? Volcanoes.

Donnell Vista Point on Highway 108 about 18 miles above Pinecrest Lake and Strawberry is the site of today's exploration. The parking lot and quarter-mile trail to the viewpoint were recently renovated with funds provided by the America Recovery and Reinvestment Act. The old worn-out trail was resurfaced, and a new ADA compliant trail winds along the western part of the slope, providing some new views to the west.

The first thing one notices from the overlook at Donnell Vista is the deep U-shaped canyon occupied by the lake behind Donnell Reservoir. During the Pleistocene Ice Ages, rivers of ice repeatedly scoured the gorge below, with the last glacial stage ending only about 12,000 years ago. The ice exposed the underlying granite, forming steep cliffs and numerous small rounded asymmetical domes called roches moutonnées. Some nice examples of glacial polish can be found in the region.

The ice in most places removed a cover of volcanic lava flows and any soils were stripped away as well. As a result, wide areas of granitic rock are exposed, and the forest grows only in fractures and joints where bits of soil can accumulate.

Glaciers also scour out basins where lakes can subsequently form, but the lake below the view point is clearly not natural. It is Donnell Reservoir, constructed in 1957 by the Oakdale-South San Joaquin Irrigation district for storage of water for agricultural irrigation and power generation. It stores a bit more than 60,000 acre-feet of water which today is only used to generate electrical power. Storage for irrigation now takes place downstream in the much larger (and more controversial) New Melones Reservoir.

The high peaks to the north and east of Donnell Vista preserve the evidence of the volcanic activity that took place here 10-12 million years ago. The few remnants not stripped away by the ice form the mesa-like peaks on the skyline. When the volcanoes were active, the region would have looked a great deal like the Mt. Lassen volcanic center, which remains active today.

The lava flows filled a fault basin near the present-day Sierra Crest in the vicinity of Sonora Pass, and at times spilled over into the adjacent river valleys. One lava flow traveled nearly sixty miles to Knights Ferry in the Sierra foothills above Oakdale. The landscape surrounding the lava flow eroded away during the uplift of the Sierra Nevada block, leaving the lava flow as a prominent ridge called an inverted stream.

The upper drainage and headwaters of the Stanislaus River up to and over Sonora Pass offers up some fascinating geology. I helped edit a field guide of the geology of the region for a meeting of the National Association of Geoscience Teachers in 2012. It's for sale through Sunbelt Publications and the proceeds support scholarships for geology majors in California, Nevada and Hawaii. Get more information about the book here.

PS: Ron Schott has a great gigapan shot of the view from Donnell Vista at  http://www.gigapan.com/gigapans/114032