Tuesday, October 15, 2019

Its Really Been That Long? 30th Anniversary of the Loma Prieta Earthquake on Thursday

It's Earth Science Week, and "Geoscience is for Everyone" is the theme for this year. Geoscience IS for everyone, because geology dominates the lives of everyone. No one can escape it, for better or worse. Better, when we find inspiration in the awesome forces that have made our planet, and worse for the geologic hazards that exist everywhere on the planet in one form or another. Here in California, one of the premier hazards are the earthquakes that occur here with disturbing irregularity (it would be so much nicer if they followed schedules so we could prepare). I'm writing about the anniversary of the Loma Prieta earthquake a few days early, but we had two moderate earthquakes in less than 24 hours in Northern California (magnitude 4.5 and 4.7), so seismic things are on my mind.
No photo description available.
Two good-sized earthquakes as recorded at Modesto Junior College
We can only share our stories to keep that knowledge at the forefront that will allow us to survive and recover from the major earthquakes to come. Here's my story from 1989, when my teaching career was just beginning.
No, this isn't what happens (credit: A. June)
On October 17th, 1989 at 5:04 PM, my physical geology laboratory had just finished and almost everyone had gone home to watch the World Series. A couple of students were helping me (it was Maureen and Sonny; funny how I remember the names of the first students I had better than the ones I had last semester). We were 100 kilometers from the epicenter, so when the seismic waves started to shake our building, the movement was a strong rolling motion instead of sharp vibrations. We looked at swaying TV monitors, and commented that it was an earthquake. It was a most scholarly discussion, actually. We realized the shaking was not stopping, and we thought we could sense the direction of the quake as well. We started to guess where it might be happening, but when the shaking reached the 40 second mark (the energy was spreading out, it lasted only 10 seconds or so near the epicenter), we realized it was a major event, and that fatalities were probably occurring (and unfortunately we were right). The deodar trees out the window were whipping back and forth as if they were in a high wind. The strangest part for me was the unconscious decision I was making as the shaking progressed. Despite having a quiet scholarly discussion, my body was moving from the front of the podium to the back, where there was a nice solid space to hide under. I would have dived under if the quake had lasted any longer.
Well, this can happen, but most people survive, even in the worst of quakes (credit: A. June)
In hindsight, I should have been a bit more aggressive about taking shelter under the desk. An analysis of our building a year or two later revealed an architectural weakness that suggested the building could collapse if the seismic waves hit it from a particular direction. A seismic retrofit a decade later included some massive shear walls in the lab I taught in.

Meanwhile, at the city library, my children were making me proud. At the time of the quake, there were huge sailing ship models on display, in some cases right on top of the book stacks. The stacks were not reinforced or braced, so there was a real potential for injuries if the quake was strong enough to knock those stacks over. I was told that most people were just standing there watching the bookstacks swaying, but my kids, my well-trained and intelligent kids were the only people in the room to take shelter under the sturdy study tables. Luckily, as I said before, we were on the fringes of the effects of the earthquake and no one was hurt.
The double-decker freeway in Oakland. It was not designed for the amount of shaking that occurred.

The Loma Prieta earthquake, a magnitude 6.9 event at a depth of 11 miles, was a tragedy: 63 people died, and 3,700 were injured. If the World Series game between the A's and the Giants hadn't been about to start, the death toll would have been much higher. Traffic was stunningly light that afternoon. Despite this, the Bay Area was in chaos for days, and months passed before life got back to normal. We were on the fringes, so instead of pain and suffering, we had a profound learning experience that was remembered by my students for the next decade and a half. But it has been 30 years now, and many of my students weren't born when the quake happened. Few of them have felt a quake at all. The large quakes like Loma Prieta and Northridge are ancient history, and there is less of that innate knowledge of what they should do when one hits. Few admit to having any kind of emergency kits at home, and they have no plan for what to do when the next big one hits.

Fault studies across California make it clear that more big tremors are coming, almost surely within the next decade or two. We educators must keep these past events alive in the minds of our students so they will be ready for these events when they come.

This is an abridged version of a blogpost from 2009.

Monday, October 14, 2019

Travels in Cascadia: The Toughest Hike I'll Ever Do...Stawamus Chief in British Columbia

Note that I didn't say the toughest hike YOU will ever do. Every hiking experience is individual, and this one left me...breathless. Stawamus Chief is one of the most popular hikes in the Vancouver-Squamish region of British Columbia, and when we passed through the area last July, I knew I needed to give it a shot.

Stawamus Chief is a granite dome that rises more than 2,000 feet above the east end of Howe Sound, the southernmost fjord on the west coast of North America. The dome actually has three summits, the 1st, 2nd, and 3rd, and the trail climbs to the first summit in a little over a mile. That doesn't sound so bad, does it?
The beginning of the trail is pleasingly flat, rising gently through the Stawamus Chief Campground. The wide flat trail offered no clue about what would follow. I know it sounds dramatic, but from the moment one takes the first step upward as the trail starts the climb in earnest, the trail is relentless and steep.
Some of the steps are on wood stairwells, but the rest of them are large uneven stone blocks that I found challenging. And there are no breaks. Many trails are steep, but most all of them have short breaks were the trail is level for a few steps. Not this one. It never stops climbing.
I climbed higher and higher, and grew more exhausted with each step. The thought was slowly building in my head that I was no longer young, and that some trails were simply too tough for overweight 60-somethings. But then another thought immediately followed: this quite probably was the only chance I would ever have at making the summit. Who could know if I would ever be here again, and with time marching on, my ability to climb would no doubt degrade with age. It was probably the toughest hike I would ever do (in the future sense). I decided I had to do it, and kept going. And going.
Everyone's experience will differ, of course, and some younger and healthier people would not have that much of a problem on this trail. Part of my own worries weren't so much the climb, but the descent. All of those huge steps had to be repeated, but going down, and I worried about the impact on my knees and ankles. But I had already come so far.
Stawamus Chief is a granite dome, and the resemblance to Half Dome in Yosemite Valley is unmistakable. One of the things about Half Dome is that it was never covered with glacial ice. The dome took it's iconic shape from exfoliation of the outer slabs of granite. The corners and edges snapped off as the pressure of burial was released upon exposure to the surface. Glaciers at the base quarried away the fallen rocks.

Stawamus Chief was different: as I approached the summit, a most unusual rock emerged from the trees. It was a boulder perched on a granite platform. It was a classic example of a glacial erratic, a rock left behind as the glaciers that flowed over this surface melted away. Unlike Half Dome, the summit of the Chief had been covered by glacial ice. And not just a little...the ice here was over a mile thick!
In the end, I didn't make the true summit. The young men in our group reported that another twenty minutes and 200 feet of hard climbing remained ahead. I just wasn't up to it. But I did make it to the summit ridge, which provided a stunning view of the eastern end of Howe Sound. From this elevation, the glacial origin of the fjord was obvious. And I was happy to be where I was. Elated, even. And thrilled to be alive (literally!).
The knees and ankles took the expected pounding on the way down, but no lasting damage was done. I would live another day, and take on the next challenge. It could well have been the toughest hike that I would ever do (in the future sense; I've done some really tough hikes over the years), but the neat thing about life is that you never know what comes next. Maybe I won't do this trail again, but there are many other trails and challenges ahead. Again, that sounds dramatic, but finding one's limits is always an exercise in drama.

Saturday, October 5, 2019

Travels in Cascadia: Howe Sound and the Challenge of Living in Vertical Places, Part 1

We didn't fly over it, so I've clearly needed to borrow this image from Google Earth.

We have (slowly) been reviewing our geological exploration of British Columbia back in July, and when I last posted we had reached Howe Sound, the southernmost fjord on the west coast of North America. We arrived by ferry at Horseshoe Bay (from Vancouver Island), and then spent two days exploring the museums and parks of the city of Vancouver. But now we were headed into the interior, and needed to follow Highway 99 along the south side of Howe Sound.

Howe Sound is, as noted earlier, the southernmost fjord in western North America. A fjord is a glacially carved bay, and as such has nearly vertical rock walls sloping down to the waters of the bay. This kind of topography entails serious engineering difficulties for anyone who wants to live in, travel through, or mine in the fjord. Prior to the 1960s, the only form of transportation to the inlet of the bay at Squamish was by water. A railroad was completed between Squamish and Vancouver in 1956 (after a delay of something like 40 years), and the first iteration of Highway 99 was carved out of the walls of the sound between 1958 and 1969. When Vancouver was selected as the site of the 2010 Winter Olympics, the highway was widened to four lanes to provide access to Olympic venues in the Whistler area.

The development of transportation corridors led to the development of a few small towns and villages along the route. And that caused problems in this steep countryside. We stopped in the little village of Lions Bay to have a look at a perilous situation.
The dangers of the steep mountain slopes are clear. In 1915 and 1921 a short distance to the east at the Britannia Mine and Britannia Beach, mudflows killed nearly a hundred people. The community at Lions Bay faced the same danger, and in 1981 a debris flow took out highway bridges, leading to several fatal accidents. In 1983, boulders and mud roared down Harvey Creek, destroying a number of buildings and killing two people.
Thus it was that we were looking at a strangely shaped Harvey Creek as it appears today. The channel is lined with boulders, but they are cemented in place. Upstream, a dam is visible, but the dam has holes at the base, and is not capable of holding back water. It's not designed to store water at all, but to stop the forward movement of debris flows coming down Harvey Creek.
In our next post, we'll have a look at the Britannia Mine, the largest (and perhaps steepest) copper mine in western Canada.

For more details about the geology of the Sea to Sky Highway and the engineering challenges, check out: http://quimpergeology.org/wp-content/uploads/2018/03/Sea2Skytour.pdf

Thursday, September 19, 2019

Travels in Cascadia: The Southernmost Fjord in Western North America: Howe's that Sound?

Our journey through the Pacific Northwest and British Columbia continued. We had spent several days on Vancouver Island, exploring Goldstream Provincial Park, Mt. Douglas and the Mutton Rocks of Victoria, Sitting Woman Falls, and the gabbro oceanic crust of East Sooke Park. It was now time to head back to the mainland and our goal was to explore the geologic environments of Howe Sound, the southernmost glacial fjord in western North America.

We would spend several days looking at this fascinating geological environment. To get there we would need to take a ferry from Nanaimo on Vancouver Island back to the mainland at Horseshoe Bay inside Howe Sound. We just missed an earlier ferry, so we cooled our heels for a couple of hours in the tourist traps at the ferry terminal. Our attention was distracted by a pair of otters hiding out in the shade beneath the ferry building.

After a few hours we were underway, leaving behind the fairly muted glacial topography of Vancouver Island, and heading towards the decidedly more mountainous country of the mainland. The main contrast was that glacial ice sheets covered Vancouver Island, but the mountains rose above the glaciers on the mainland. We could see the city of Vancouver off to the south.

As we scanned the horizon from the upper deck of the ferry, we could see that we were still definitely in the land of volcanoes. Off to the east we could just make out the lower flanks of Mt. Garibaldi, one of the northernmost of the Cascades Volcanoes. Garibaldi is one of the most unusual of the Cascades because a large portion of the edifice was erupted onto a glacier. When the glacier melted away at the end of the ice age, the flank of the volcano collapsed into the adjacent valley in a series of huge debris flows.
Mt. Garibaldi, with Howe Sound in the foreground

The clouds were playing hide and seek, and mostly 'hide' with the summit of Mt. Baker off to the south in Washington. The glacier-covered peak of Mt. Baker is geologically young, and the mountain seemed on the verge of erupting back in 1975, but it fizzled out to the disappointment of geologists and to the relief of everyone else.
Mt. Baker, partly hidden by clouds, from Howe Sound

My favorite sight from the ferry ride was of the Black Tusk or t'ak't'ak mu'yin tl'a in7in'a'xe7en in the language of the Squamish people, who considered the strangely shaped peak to be the landing place of the Thunderbird, a principle figure in First Nations mythology. In geological terms, the mountain is a deeply eroded stratovolcano, once like Mt. Baker or Mt. Hood, but now a spikey remnant of the original cone
The Black Tusk from Howe Sound

As noted before, Howe Sound is a glacial fjord, a deep bay with steep flanks that was carved by glaciers. It is a bit difficult to pick out the entrance from the Strait of Georgia because it includes several islands. The sound is 26 miles long, ending at the town of Squamish at the upper end. The urban center of Vancouver is just south of Howe Sound where there is more level ground.

The sound is full of geological delights. We would spend the next four days in the immediate vicinity. That's where we'll pick up the story next time.

Monday, September 9, 2019

The Way It Was: Yosemite on a September Saturday

Not what I was expecting...

I generally avoid Yosemite Valley in the summertime, and I try to avoid Saturdays especially, but I was a glutton for punishment; we hadn't been to the valley since last spring and were kind of curious about how it would be. We expected crowds and dryness and dust.
That's not what we found. In September, the meadows are often brown and the waterfalls dry. Instead, Bridalveil Meadow was green and filled with wildflowers, and Bridalveil Fall, while not roaring by any means, was flowing nicely. The wind occasionally picked up and blew the water in odd directions.
Even Yosemite Falls had a trickle. I don't know if it was left over from the spring, or if it was from the recent thunderstorms, but it was nice to see.
Half Dome is spectacular, no matter the time of year. The afternoon cumulus cloud buildup provided a nice backdrop.
Sentinel Rock is another towering cliff that is an incredible sight no matter the season. It's one of those rocks on the "wrong" side of the valley that is not noticed as often because it is opposite of Yosemite Falls. If it were anywhere else on the planet besides Yosemite, it would be a national landmark all on its own.
A late afternoon treat is the Valley View at the west end of Bridalveil Meadow. There's a small pullout, but it is often ignored by people rushing home from their day in the valley. We found a spot despite the traffic, and simply sat for awhile.
The wonderful thing about late summer is that the low water on the Merced River is often calm and provides a wonderful reflective surface. It was gorgeous and serene.

And that's the way it was...

Monday, September 2, 2019

Travels in Cascadia: You Can Have Your Niagara Falls, and I'll Have Mine...Goldstream Provincial Park, B.C.

Our journey through British Columbia last July continued. We were on Vancouver Island and were leaving the city of Victoria to catch the ferry back to the mainland at Nanaimo. But there were still some sights along the way. The town of Victoria was built on the lowlands at the south end of the island, but as we began traveling north the landscape grew more rugged and mountainous. The vast ice sheets of the last ice age covered the entire island, but the ice could not remove the tougher bedrock of the island's interior. Looking south from Malahat Summit (l,155 feet/352 meters) we could see the hills we had just explored, including the delightful Goldstream Provincial Park.
The park hosts a surprising variety of plant and animal life, due to a wide variety of habitats. Part of the value of the park is that it has not been logged, and thus preserves old-growth forests, including 700 year old Cedar trees. It includes an estuary/wetland at the end of the Finlayson Arm of the Strait of Georgia, part of the Salish Sea. The long inlet exists because the glaciers were able to exploit a fault zone that left the rocks weakened and broken. The Leech River Fault, a major terrane boundary, cuts through the park, dividing the Pacific Rim Terrane (the Leech River Complex) from Wrangellia. Wrangellia is made up of igneous intrusive rocks and metamorphic rocks from the Mesozoic Era, the age of the dinosaurs.
Looking south from the Nature Center one can see Mount Finlayson (below), another feature that indicates the presence of glaciers in the past. The rounded form of the mountain identifies it as a roche moutonnée, a larger-scale version of the rounded forms seen at Mt. Douglas and Mt. Tolmie in Victoria.
The title of today's post refers to one of the small delights of the park. The erosive action of the glaciers was oriented mostly north to south, and the ridgelines drop steeply into the valley containing the Finlayson Arm. Small creeks and rivers occasionally form modest waterfalls, including the easily accessed Niagara Falls. Visiting the waterfall, one realizes it was not named for the similarity of its volume to the better-known falls back east, but to the height. At 155 feet, it's just a bit shorter than Niagara's 167 feet (note the people at the bottom of the canyon for scale).
One might wonder why Goldstream Park has the name it has. The rocks of the Leech River Complex were altered by superheated mineralized water, and quartz veins with minor amounts of gold were emplaced in the area. The gold was discovered in 1858, and a minor rush involving perhaps 300 miners ensued a few years later. There was not a great deal of gold to be had, and the boom soon petered out, but the name remained. A few old tunnels and mines can still be seen in the park.
I know this is a geology blog, and most of the time I don't have much patience for trying to get pictures of deer, but as I was walking up the trail to the falls, I broke with tradition. Up ahead of me I could see some kind of four-footed animal, and it turned out to be the cutest little fawn ever. It was happy to share the trail with me for a few moments, until the rest of the crew caught up with me. It then took off into the underbrush.

Goldstream Provincial Park is west and north of Victoria on the Trans-Canada Highway 1. We were there on a holiday weekend and the parking lots filled quickly (we made some people very happy when our four vehicles left all at once). If you have the time and energy, a trail climbs to the summit of Mt. Finlayson.

Thursday, August 29, 2019

The Seismometer Has Gone Crazy! What's Going On?? (Don't worry, no disasters)

Nothing like putting up a seismometer going crazy to be accused of click-baiting. I mean, what's going on? Is it harmonic tremor, the movement of magma near the surface, ready to cause a catastrophic eruption? Is it a new earthquake swarm? Nah, it's not any of those things. It's education in action.

Our seismometer is a simple version, and the detector is right there in the geology storeroom on the third floor of our science building. It picks up the foot traffic in the corridor outside, so when classes began this week, the unit faithfully recorded the arrival of hundreds of students for the new semester. The large "earthquake" at the very bottom is the exodus of my students at the end of the evening from their class in physical geology.

Welcome all to the new semester!