Monday, September 15, 2014

Northern Convergence: Finally Finding the Edge of North America at Yoho National Park...600 miles inland


Looking upstream on the Kicking Horse River at Field, B.C.
How strange geology is, and what wonderful journeys it provides for our imagination! So many geological processes are exceedingly slow, and yet over time incredible changes occur. How can I be talking about the edge of the continent when we are 1,000 kilometers (~600 miles) from the nearest shoreline?

I've called this narrative of our journey "Northern Convergence" because of the presence of a convergent plate boundary for the last 200 million years or so that has drastically altered and changed the continental margin of Canada and the Pacific Northwest. We had spent the previous four days traversing landscapes composed of exotic terranes, tracts of crust that originated someplace else and had been appended to the edge of the continent by way of subduction. The bits of crust were dragged into the trench, but were too buoyant to sink into the underlying mantle, so they mashed into continent instead, and intense deformation resulted. And the continent got bigger...lots bigger.
Looking downstream on the Kicking Horse River at Field, B.C.
We had crossed the Insular, Coastal, Intermontane and Omineca belts in our four days of driving, covering some 1,000 kilometers (600 miles), and we had finally reached the Canadian Rockies at Yoho National Park. It was here that we finally first encountered the ancestral edge of the North American continent. The limestone and and other sediments in the cliffs high above were deposited in a passive margin setting consisting of debris washed from the ancient continent around 900-400 million years ago. Everything west of our location was from someplace besides North America!

The scenery was on a truly grand scale. Yoho is contiguous with Banff National Park, and yet is rarely mentioned in the same breath (it's always "Banff and Jasper", maybe because they're on the Alberta side, and Alberta knows P.R.). Yet the park is spectacular, and even better, holds a treasure of worldwide significance.
The park protects mainly the upper watershed of the Kicking Horse River which includes several major icefields, including the Waputik and Wapta. The glaciers coming off the icefields contain finely ground silt and clay that stay suspended in the turbulent water. The rivers look like flowing milk at times.
Glacial "milk" also changes the appearance of lakes. In the calm water some of the clay begins to settle out forming a translucent turquoise color that is very striking. We made a stop at Emerald Lake to talk about the glaciers and have a look at the high ridge where the Burgess Shale was exposed.
Another road reaches up into the Yoho River drainage, providing access to Takakkaw Falls, the third highest in Canada at 254 meters (833 feet). The waterfall is a textbook example of a hanging valley, resulting when the main trunk glacier carved a deeper valley than the tributary glacier. The glacier feeding Takakkaw Falls is only a kilometer or so upstream of the brink.

If you need a sense of scale regarding 254 meters, look at the picture above where the water leaps outward from the cliff near the top of the waterfall. Let's zoom in on it. Those little dots to the left? Rock climbers!
All in all, Yoho National Parks is one of the most dramatic landscapes imaginable, but it's the rocks themselves that hold the real treasure. Although mining took place here last century, the treasure is in the fossils found in these rocks. About half of our crew were not with us as we toured the park, as they had left early in the morning to complete a tortuous 12 mile hike to see the quarry where the Burgess Shale fauna was discovered more than a century ago.

There is a problem with understanding the ecosystems that existed millions of years ago. Usually only the shells and bones are found, but the vast majority of organisms had soft bodies that are rarely preserved as fossils. They would invariably decay quickly. Fossil localities with the remains of soft-bodied organisms are few and precious, and our students were investigating one of the world's most famous. The Burgess Shale preserves the fossils of soft-bodied organisms that were present only a few million years after the dawn of complex multi-celled lifeforms.
How did they come to be preserved here? Just over 500 million years ago, the region was at the edge of the continent in relatively shallow water at the edge of the continental shelf. The shelf was unstable and occasionally a mass of mud would break off and sink into deeper water, carrying with it the organisms that were living there. The blocks sank into oxygen-starved water where the bacteria that would have consumed the soft body tissue could not survive. Mud covered and preserved the dead organisms. More than a hundred species have been described here.

The fossil quarry lies high on a ridge above Emerald Lake between Field and Wapta peaks. You can pick it out in the picture below, as the horizontal gash in the hillside with the lowest patch of snow. The hike is not easy, really an all-day affair. The quarry is a World Heritage Site and access is strongly restricted, and obviously collecting is not allowed. I've heard they've even gone after fossil sellers active on E-Bay.
I did the hike in 2005, so I didn't try it this time, opting instead to let my fellow professor hike with the students (she might forgive me the blisters one of these days...). The hike was one of the great adventures of my life, though, and I described it in detail in a post last April: you can read it by clicking here. There just aren't many times in life when you can be so close to the ancient past.
Holding a specimen of Marrella splendens in the Burgess Shale quarry, 2005

We visited with the local wildlife, and then headed over Kicking Horse Pass into Banff National Park. More adventures lay ahead!
A Black-billed Magpie (Pica hudsonia) at Field, B.C.

I hope that somebody appreciates that I made it through an entire post about a place named "Yoho" with nary a single "Pirates of the Caribbean" joke.

Friday, September 12, 2014

Northern Convergence: Mt. Revelstoke, Where the Columbia Mountains Reach to the Sky (and right into the clouds)

Thanks for all the attention to the post on exfoliation in Twain Harte! 4,000 hits and counting, it's been my most read blogpost in five years (about 10 or 15 times normal traffic). Today we are getting back to our tour of British Columbia and Alberta, one of the most beautiful regions in the world. We last looked at Craigellachie, the site of the completion of the Trans-Canada Railroad. As we continued down the highway, the mountains around us were becoming dramatic.
We had been traversing the Intermontane Belt, a region of high plateaus and relatively modest mountain ridges, and were now entering the Omineca Belt, a series of increasingly rugged mountain ranges, including the Purcell and Selkirk ranges, subdivisions of the Columbia Mountains. Yes, the Columbia, as in Columbia River. That's the Columbia in the picture below (actually a reservoir on the Columbia), a long distance upstream from the thread of water between Oregon and Washington in the Cascades. It is a huge watershed!
Our main goal for the day was to explore Mt. Revelstoke National Park, and the best way to do it on a tight schedule is to drive to the 1,938 meter (6,360 feet) summit. A beautiful 26 kilometer paved highway switchbacks up the flank of the mountain and ends at a parking lot just below the peak. From there one can walk a short trail to the summit area, or catch a van to the upper parking area. A network of short trails explores the alpine environment.
Storms had been wreaking gentle havoc with our trip for three days. We certainly didn't get the worst of the weather: a day before we arrived in Kamloops there had been intense thunderstorms and some areas of town were unexpectedly flooded. Drumheller, a town we would visit in a few days, was hit with a storm of golf-ball sized hailstones. Mostly we were rained on, and clouds obscured some of the views we had hoped to see (most notably at Mt. Garibaldi in the northernmost Cascades). We woke to sunshine in Kamloops, but as we drove east into the higher mountain ranges, the clouds seemed to be gathering on the higher peaks.
We reached the summit of Mount Revelstoke and had a look around. In a "cup half empty or half full" moment, the cloud deck lay just above us, so we had extensive views into the valleys below while the rugged high peaks above us were obscured. Even if partially hidden, the view was spectacular.
Mt. Revelstoke was the eighth national park in Canada, having been established in 1914. The park preserves a swath of alpine scenery from the shores of Lake Revelstoke on the Columbia River (around 500 meters, or 1,640 feet) to the summits of Revelstoke (1,938 meter, 6,360 feet) and Mt. Coursier (2,646 meters, 8,681 feet). The park encompasses four vegetation zones, an interior rain forest, subalpine Hemlock and Engelmann Spruce forest, subalpine meadows, and alpine tundra on the highest peaks. The region receives prodigious amounts of snow, and skiing was an early form of recreation on the mountain. One of the first ski jumps ever constructed was used in the park for years.
The park is not really notable for extensive rock outcrops in the most visited areas. In the very humid environment, vegetation and soils are widespread. The underlying rock is part of the Shuswap Metamorphic Complex, a series of Proterozoic and Paleozoic rocks that were deposited in the Pacific offshore of the North American Continent. The rocks were crushed into the edge of the continent in Mesozoic time, intruded here and there by Mesozoic granitic rocks, and exposed during mountain uplift in the early Cenozoic era. 
The growing season on Mt. Revelstoke is exceedingly short, essentially from late June to early September, but the plants are well adapted to bloom fast and die. The park is famous for the August wildflower display, although we were a bit early to see the best of it. There were some beautiful Glacier Lilies (no good pictures, but wait for my post on Glacier National Park), and some colorful Indian Paintbrush.
As always seems the case, the clouds were starting to lift, but our time was slipping away. We enjoyed several high peaks to the north clothed in wispy clouds, but we had to start down the mountain. And of course, the sun emerged!

From midway down the mountain we had a fine view across the valley to the Monashee Mountains, home to some of the oldest rocks in British Columbia, at around 2.2 billion years. The town of Revelstoke could be seen on the narrow plain below.
Glaciers cling to the high peaks, a kind of a preview of the spectacular icefields that we would be seeing in a few days in the Canadian Rockies. We intended to visit parts of Canada's Glacier National Park, but active wildfires had closed off access to most parts of the park.
About an hour later we pulled into the small town of Golden and checked into our hotel. The storm continued to break up, giving us a beautiful sunset over the Purcell Mountains.
Tomorrow would be the beginning of the climax of our trip, an exploration of Yoho and Banff National Parks in the Canadian Rockies.

Monday, September 8, 2014

Ongoing Exfoliation Event at Twain Harte Lake in the Sierra Nevada


There is an ongoing geological drama going on the Sierra Nevada that may be unique (to the extent of my knowledge, which is admittedly limited in this area). Exfoliation, a process long recognized as the shaper of granitic domes and monoliths, is presently busting up the surface of a small dome at Twain Harte Lake a few miles east of the Mother Lode town of Sonora. The process has been captured on video, and is presently being monitored, due to the effects it is having on a reservoir abutment.
The event burst into the news in August when a possible dam failure warning was issued following a loud popping sound and the leakage of water from the edge of the reservoir. Once the site was investigated, a decision was reached to drain the lake until the full extent of the damage was clear. There have been at least three 'events', the last on August 3.

An employee of the lake association was very kind and allowed me to have a look at the dome and the new exfoliation shells. It was fascinating. The first thing to catch the eye was the lifeguard tower. It's tilted at an odd angle because the rock it is sitting on has been pushed upward into what is called an "A-tent" joint. My erudite and learned comment was "wow"!
Exfoliation is the breaking and fracturing of hard rocks like granite in slabs parallel to the surface of the rock. It removes corners and edges, resulting in the familiar domes found in regions like the Sierra Nevada where lots of granitic rock is exposed. It has traditionally been described as the result of 'unloading', whereby erosion strips off the overlying rock, releasing pressure and causing the rock to expand outwards, and fracturing in the process. There are some alternate explanations involving a certain amount of compression, which makes sense looking at the 'A tent' in the picture above.

There were freshly loosened slabs all over the surface of the rock, with lots of chipped edges. From the videos it is clear that the chips often snapped loose before the major slab event, like foreshocks to an earthquake (and given that earthquakes are also an example of stress release, the analogy is appropriate).
How incredible it must have been to see this happen!
The worry, of course, is the proximity of the exfoliation slabs to the abutment of the dam. A geological consulting firm is monitoring the activity, with stress meters set up in several places.
I admit I never gave it any thought, but it seems clear that the fractures are occurring in a swarm, as the stress regime changes with each break, placing new pressures in different sectors. Like a series of aftershocks following an earthquake, the rocks will continue to shatter for a period of time until a new stable regime or equilibrium is reached. I don't know any details of how or if this process has been witnessed in the past, so I couldn't even speculate on how long these rock 'pops' will continue. Maybe they are already done, but I wouldn't count on it.
The picture below shows a series of fresh parallel fractures running perpendicular to the edge of the dam.
We took a closer look at the dam abutment. So far the damage is limited to the top few feet of the south margin of the dam.
In the picture below we are looking down on the edge of the dam and on the left one can see the fresh exfoliation fracture. It leads into the dam abutment.
In this next picture, we are looking closer at the edge of the dam and can see a crack running through the concrete, going down about three feet or so. The dam is around 70 years old, and had been inspected only a few months prior with no signs of problems.
No one can say that the episode is over with, but it was fascinating to see. As I said before, I'm not aware of whether this process has been monitored in real time before, and I can't find any examples of exfoliation being captured in action on film or video, although it most assuredly is happening all the time somewhere in the world. If I hear of any developments, I will pass them on.
Picture by Mrs.Geotripper
I certainly hope the good people of Twain Harte get their lake back. It looked pretty sad without any water. It is a popular swimming and fishing hole.

If you haven't seen the video, there are some very good ones on the web, courtesy of Condor Earth Technologies (click here for the link) and Dotysan, who is a local resident. Check them out!




Sunday, September 7, 2014

In Case You Haven't Seen It: Shock-wave from Volcanic Blast at Papua New Guinea's Tavurvur Volcano


This has been making the rounds on Facebook and Google+, but just in case you missed it, have a look at the shock wave from an eruption at Papua New Guinea's Tavurvur (or Rabaul) volcano. The footage was captured by an Australian couple, Phil and Linda McNamara. The shock wave is astounding.

Tavurvur is a small stratovolcano on the island of New Britain that has been highly active and dangerous. It nearly destroyed the town of Rabaul in 1994 and killed more than 500 people during an eruption in 1937. It is part of a larger (8x14 km) caldera that formed about 7,000 years ago.

Shock waves are nothing new, but good video images are. The cable television show Mythbusters has gotten a lot of mileage showing the effects of shock waves. In geology, I've been showing a satellite photograph from the eruption of Mt. St. Helens in 1980 to my classes for years that shows the shock-wave from that eruption. But a static shot doesn't capture the dynamic nature of such explosions. Closer to home, an explosive shock-wave from a 1996 rock fall in Yosemite Valley destroyed hundreds of trees in the area around Happy Isles.

It's astounding stuff.

Saturday, September 6, 2014

Northern Convergence: A Different Kind of Convergence More Than a Century Ago in Craigellachie


There was a time in this fair land when the railroad did not run
When the wild majestic mountains stood alone against the sun
Long before the white man and long before the wheel
When the green dark forest was too silent to be real
Canadian Railroad Trilogy - Gordon Lightfoot

As we crossed the mountains of British Columbia on our geological journey through western Canada, I was becoming aware that whenever we stopped I seem to hear trains in the distance. It makes sense; in mountainous country, highways tend to follow railways, which were sometimes constructed along ancient trails, which followed the gentlest passes. Railways had a somewhat special role in the settlement and development of North America. Completion of the railway across the United States, culminating in the ceremony of the golden spike at Promontory Summit, Utah in 1869 transformed travel across the country. It turned overnight from an arduous dangerous journey of months by horse, oxen, and foot, to a comfortable ride of several days.

The construction of the transcontinental railroad was a huge accomplishment, crossing the prairies, the Rocky Mountains, and Great Basin, and the Sierra Nevada. It was one of the more significant events in U.S. history. But on our journey through Canada, I began to wonder if there hadn't been an even more impressive event north of the border.
We pulled into Craigellachie at the border of the Shuswap Highlands and Monashee Mountains. We were visiting the small park commemorating the driving of the last spike of the Canadian Pacific Railroad in 1885. Having just come through hundreds of kilometers of rugged mountainous terrain, we could understand why the "last spike" was so far to the west. The explorations and route planning of the architects of the railway must have been challenging to say the least.  For one, there was the winter. Many of the high passes presented special challenges from avalanches, or spring flooding in the river canyons. Farther to the east, the railroad had to pass through kilometer after kilometer of muskeg, the soft spongy swamplands of near-Arctic landscapes.
A monument to the last spike was erected at the centennial in 1985. We noticed that there is no lack of activity on the rail line, as at least five trains barreled through during our short visit (including the one above; the picture doesn't give the sense of motion, but it was moving fast).
I couldn't help but notice in the commemorative painting of the driving of the last spike that the person driving the spike was a dignitary who I suspect had rarely lifted a hammer in his life. It's not that I bear any animosity towards him (his name was Douglas Smith, a main financial backer of the railway), and in fact he was quite a philanthropist. But why is it that the dignitaries always get to shovel the first bit of dirt on a major project, and then let thousands of hard-working and hard-living workers (the "navvies") struggle for years to complete the project? Then, when the job is done, they come back and pretend to do a hard thing like driving the last stake? I guess it would be too much trouble to remember the names of the navvies, especially the ones who gave their lives in the service of the railways.
The centennial monument had something interesting on the flanks: representative rock samples from each of the Canadian Provinces. Above is a piece of anorthosite from Newfoundland. Anorthosite, a plutonic rock containing a large proportion of plagioclase feldspar and a few dark minerals, is known mostly from very ancient rocks, generally a billion years or older. It was also found on the Moon, making up the lunar highlands.
The Saint George granite out of New Brunswick is another plutonic rock that apparently is an excellent construction stone that has been quarried for years. It is Devonian in age, about 380 million years old.
The granitic gneiss from Wollaston Lake in Saskatchewan is an ancient rock, around two billion years old. The region has produced uranium.
British Columbia provided a chunk of jade from Mount Ogden. The jade is representative of rocks that formed in a convergent plate setting under great compressive stresses. Jade is of course valuable as a semi-precious gemstone. The outcrops are associated with exposures of serpentinite, a rock we are familiar with back home in California.
The visitor center offered up a chance to pound stakes into a railway, though I had more fun using their equipment as a rock hammer...

One of my favorite songwriters of all time, Gordon Lightfoot, wrote a song commemorating the centennial of the building of the railway, the Canadian Railroad Trilogy (the first stanza is quoted above). I like how he honored the navvies, those who did the actual work (the song was the first place I ever came across the word). Here is a YouTube of his performance of the song in Reno in 2000. Enjoy!




We are the navvies who work upon the railway
Swingin' our hammers in the bright blazin' sun
Livin' on stew and drinkin' bad whiskey
Bendin' our old backs 'til the long days are done

Thursday, September 4, 2014

Register for the Fall Meeting of the National Association of Geoscience Teachers! Oct. 10-12 at CSU Sacramento

The 2003 meeting sponsored by CSU Sacramento: Exploring the Malakoff Diggings

The fall meeting of the Far Western Section of the National Association of Geoscience Teachers is taking place on Oct 10th-12th in Sacramento at California State University Sacramento. Trip opportunities include the Sierras, Delta and local Sacramento geology.  Professors, K-12 teachers, and students (official and unofficial) of the earth sciences or geology are encouraged to join us. You do not have to be a member of the NAGT to attend, although we would love to have you join our organization. We encourage and support the teaching of the earth sciences in California, Nevada and Hawaii, and try to sponsor meetings that are not a great stress on teachers and students on limited budgets. You do not have to live in these three states either. These meetings are a great way to become acquainted with the geology of this fascinating region!

Here is a sampling of some of the exciting field trips that are planned:

1.    A Traverse of the Sierra Nevada from Sacramento to Donner Summit-Eldridge Moores, Emeritus Professor, Geology Department, UC, Davis  

2.    Bay Delta Hydrology and Geology-Rob Barry, Chief Project Geology Section, California Department of Water Resources; John Suen, Professor Emeritus, California State Univ., Fresno; Mark Pagenkopp, Geologist, Calif. Dept. of Water Resources

3.    Gold, Aggregates, and the Yuba Dredge Fields, California Mineral Education Foundation, Cynthia Pridmore, Engineering Geologist, California Geologic Survey

4.    Miocene, Pliocene, and Pleistocene Stratigraphy near Sacramento, CA. Tim Horner, Chair CSU, Sacramento, Geology Department, CSU, Sacramento

5.    The Legacy and Effects of Mercury in California Gold Rush Streams -Mike Hunerlach, Regional Mining Geologist and Liaison US Forest Service, Charlie Alpers, Research Chemist, United States Geologic Survey. 
Speakers:
Stephen Testa, California State Mining Board-Oil, Gold, Earthquakes and Higher Education in the latter half of the 19th Century.

Sue McClurg, Deputy Executive Director, Water Education Foundation The Bay Delta Conservation Plan: How did we get here, and where are we going? 

Lots of other activities and field trips are scheduled!

Register now! Information can be found at the links below:
    Register Online, using credit card or PayPal! http://nagt-farwestern2014.bpt.me/ 
    Registration form: http://nagt-fws.org/New_Registration_Form-1.pdf
    Conference Information: http://nagt-fws.org/NAGT_fall_conference_info.docx.pdf
    Conference Agenda: http://nagt-fws.org/NAGT_FWS_2014_Conference_Agenda.pdf
    Accommodation Options: hhttp://nagt-fws.org/Accommodation_Options_Fall_2014.pdf


Hydraulic mine in the California goldfields.

Tuesday, September 2, 2014

Here We Go Again: Yellowstone is Going to KILL US ALL! Wait a minute...


I'm going to start with the conclusion (I've highlighted some parts using the bold font):
Geological activity at Yellowstone provides no signs that a supereruption will occur in the near future. Indeed, current seismicity, crustal deformation and thermal activity are consistent with the range and magnitude of signals observed historically over the past century [Lowenstern et al., 2006]. Over the past two million years, trends in the volume of eruptions and the magnitude of crustal melting may signal a decline of major volcanism from the Yellowstone region [Christiansen et al., 2007; Watts et al., 2012]. These factors, plus the 3-in-2.1-million annual frequency of past events, suggest a confidence of at least 99.9% that 21st-century society will not experience a Yellowstone supereruption. But over the span of geologic time, supereruptions have recurred somewhere on Earth every 100,000 years on average [Mason et al., 2004; Sparks et al., 2005]. As such, it is important to characterize the potential effects of such events. We hope this work stimulates further examination of ash transport during very large eruptions.
The reason I am doing so is because the media is reporting on the body of the report that came out recently concerning the possible effects of a major caldera eruption at Yellowstone National Park. That means we are getting the usual headlines like:

If Yellowstone Supervolcano Erupts, Ash May Reach NYC

Yellowstone Supervolcano Eruption Would Doom the United States

Eruption of the Yellowstone Supervolcano will turn the US into a Third World Country

Eruption of Yellowstone supervolcano could spell the end of the US


For the most part, the reports themselves aren't too bad (there ARE exceptions). The thing is, we've always known that a Yellowstone caldera plinian supereruption would be devastating. That's old news. The purpose of the research was to model the potential effects of such an event. I get that disaster and omens of disaster are what sell newspapers or put eyes on advertising, so headlines go over the top, just like they always have. But this approach leaves the readers with the wrong impression, and they are going to worry about whether eruptions of Yellowstone need to be added to their fears of terrorist attacks, Megalodon shark attacks on their Caribbean cruise, or whether vaccines cause autism. In other word, useless levels of stress based on incorrect or blatantly wrong information.
 
I want to send kudos to a couple of media outlets with less sensationalistic headlines, such as those from the Billings Gazette: Researchers predict ash fall if Yellowstone supervolcano erupted or the Daily Digest: New computer models show likely fallout of a volcanic eruption in Yellowstone.
These kinds of headlines actually communicate accurate information without the terror-inducing yellow journalism.

This report from the U.S. Geological Survey serves a useful purpose. It is part of the kinds of research that can help cities, states, and nations plan for and cope with natural disasters when they occur. The authors were careful to state in their conclusions the extreme unlikelihood of a rhyolite caldera eruption, but their computer model might be useful in predicting the effects of lesser eruptions elsewhere in the world, eruptions that are far more likely.

You can see the report here:
Mastin, L. G., A. R. Van Eaton, and J. B. Lowenstern (2014), Modeling ash fall distribution from a Yellowstone supereruption, Geochem. Geophys. Geosyst., 15, doi:10.1002/2014GC005469

But don't fret. There are still the Yellowstone WOLVES to worry about!