Friday, October 31, 2014

The Airliner Chronicles: the San Andreas Fault in Southern California

The San Andreas fault at Cajon Wash and Lone Pine Canyon at the eastern end of the San Gabriel Mountains
Oh how I love flying. I don't get all that many chances to do it, and flying on days with clear weather happens even less often, but sometimes it works out. One of my first blog series was called the Airliner Chronicles, and in it I featured geology from an aerial perspective. I haven't flown in a number of years, but I had a brief trip to Southern California last month, I scored a window seat, and managed to chose the correct side of the plane, so I got to see some marvelous perspectives of the San Andreas Fault.
Mount San Antonio is the highest peak in the San Gabriel Mountains at 10,069 feet (3,069 meters). The highway in the foreground is Interstate 15 heading towards Cajon Pass.
What made the views so memorable was that they were in the San Gabriel Mountains, which just a few weeks ago were made into a National Monument. These were the mountains of my youth, the peaks and valley where I learned to camp, hike, and climb. I've seen these mountains from down in the canyons, and from the tops of the peaks, but never so well from high above in a plane. The flight was too short!
The San Bernardino Mountains are higher than the San Gabriel Mountains on average, but not generally as rugged. I was on the wrong side of the plane for good pictures, though.
The San Andreas fault slices through 600 miles of California, but the most rugged stretch of its path is along the northern edge of the San Gabriel Mountains. The fault actually crosses the Transverse Ranges, offsetting the San Gabriels from the San Bernardino Mountains at Cajon Pass. The presently active stretch of the fault has shifted at least 130 miles in a right lateral sense (when standing on one side of the fault, the other side shifts to the right; a left lateral moves the opposite direction). The grinding of the rocks along the fault produces a powdery material called gouge that is easily eroded. The fault reveals itself as a series of linear valleys that cut across the mountain ridges. I've provided labeled versions of most of the pictures showing the trace of the fault.
The San Gabriel Mountains are moving northwest along the fault.
I passed the small mountain village of Wrightwood, a town with a lot of geological problems. Not only does it sit directly on the San Andreas fault, it also lies at the base of a steep mountain ridge composed of deeply sheared Pelona schist. When wet, the schist is prone to failure, and there have been a number of serious mudflows over the years including an event in 1941 that buried 190 acres. The scars of the landslides were easily visible from above.

The village of Wrightwood on the San Andreas fault. The Heath Canyon Mudflow started at the scars on the left side of the photo.
The San Andreas has produced a number of very large earthquakes in Southern California, most notably in 1857, an event with an estimated magnitude of 7.9. The quake fractured the ground for a distance of 225 miles (350 kilometers) from Cajon Pass to Parkfield in the Central California Coast Ranges. The ground shifted as much as 30 feet (9 meters), with an average of 15 feet (4.5 meters). Trees that were damaged in the quake can still be seen in Wrightwood. The average recurrence interval over that last few thousand years has been about century, but it varies widely from a few decades to more than 300 years. It is considered one of the more likely faults to produce large earthquakes in coming decades.
Wrightwood on the San Andreas fault in the San Gabriel Mountains
A bit further I could pick out the Mountain High Ski Resort and the deep gorge of the East Fork of the San Gabriel River. The heart of the newly established San Gabriel Mountains National Monument, the East Fork is around 4,000 feet deep, almost as deep as the Grand Canyon.
Mountain High Ski Resort and the East Fork of the San Gabriel Canyon
The canyon is unique. It was the focus of a huge political battle in the 1970s over a wilderness designation that brought much of the canyon under protection from mining and development. There are herds of Nelson Bighorn Sheep and natural trout fisheries in the depths of the canyon tributaries. Development was always a dicey proposition. There is little in the way of flat terrain, and terrible floods have scoured the canyon bottom on numerous occasions. There is a paved "bridge to nowhere" in the lower canyon. The road it was once connected to was washed away long ago.
Further west there is a fine example of a shutter ridge. These are mountain ridges that have been moved laterally by the fault in such a way as to block of the river drainages from the other side of the fault, deflecting the streams sideways.
A shutter ridge along the San Andreas fault in the San Gabriel Mountains
The winding road in the picture is the Angeles Crest Highway, which was opened for traffic in 1956. It is an anachronism, built in a time when development was encouraged in the national forests. It goes for 66 miles from La Canada in the L.A. Basin to Wrightwood. In such steep terrain, keeping the road open is a challenge. Landslides and slope failures are commonplace along the highway.
Shutter ridge on the San Andreas fault
 A special geological treat from the air is Devils Punchbowl, a Los Angeles County Park. The park lies on an ancient strand of the San Andreas fault. The sandstone and conglomerate of the Punchbowl Formation was twisted into a plunging syncline, a downward pointing fold with an axis that slopes to the west (to the right in the picture below).
The Devils Punchbowl, a west plunging syncline in resistant layers of conglomerate and sandstone.
Devils Punchbowl is a marvelous little park with memorable hiking trails that explore the steep fins of sandstone. You can see some pictures from ground level of the region in this post from last year.
Offset stream near Palmdale. The dark line is the California Water Project.
As we neared the town of Palmdale, I could see examples of offset streams. These are stream channels which have been shifted and separated by the lateral motion along the fault.
My flight also included a stretch of the fault system a little farther north. I'll try to include it in the next post.

Wednesday, October 29, 2014

Northern Convergence: America's Most Dangerous Volcano, and the End of the Journey


Northern Convergence as a name for this blog series was all about the role of a convergent plate boundary in the production of the scenery of the Pacific Northwest. The compressional forces that developed as the Pacific/Farallon/Juan de Fuca plate was stuffed under the North American continent formed range after range of complexly folded and faulted mountains hundreds of miles inland.


Perhaps the most vivid effect of plate convergence is the formation of a magmatic arc, a chain of inland volcanoes and underlying magma chambers. The oceanic lithosphere carries rock and water deep into the underlying asthenosphere where the rocks are heated, and the water liberated. The water has the effect of lowering the melting point of the mantle rock and plumes of molten magma form, which start moving upwards through the continental crust. Sometimes basaltic or andesitic magmas reach the surface. In other instances, the hot magma melts some of the continental granite, forming dacite or rhyolite.
Mt. Adams from Sunrise Ridge

Volcanism is one of the intense and spectacular geologic processes one could ever hope to witness (or avoid, if you not geologically-minded, or sane). Volcanoes are capable of horrific destruction and disaster, but they also provide rich fertile soils and incredible scenery. We had now been on the road for nearly two weeks, and an important early site for our investigations was to be Mt. Garibaldi and the Black Tusk, two of the northernmost Cascade volcanoes. As I wrote previously, rain and clouds obscured our views that day, and all we ended up seeing were some old lava flows (and, it should be said, some wonderful waterfalls).
Not a volcanic eruption, but instead a wildfire. Couldn't help imagining, though.

As we drove west on our final day, volcanism loomed. We would be passing through Mt. Rainier National Park, and it is hard to think of any mountain in the world that dominates the surrounding landscape the way Rainier does (Kilaminjaro comes to mind, or Mauna Loa in Hawaii, but few others). In stark contrast to our earlier visit at Garibaldi, the skies were crystal clear and sunny.
Mt. Rainier from the west

Rainier rises to an elevation of 14,411 ft (4,392 m), just a bit short of being the highest peak in the lower 48 states, but certainly the highest in the Cascades (only Shasta comes anywhere close at 14,179 feet). Glacial erosion has ripped away hundreds of feet of rock from the summit area, so at one time it was almost surely the tallest mountain in the lower 48 (one more contender though could be the San Francisco Peaks in Arizona, another stratovolcano missing thousands of feet from the summit).
Rainier from the air

For all of its grandeur, Rainier is an incredibly dangerous mountain. It contains roughly half of all the glacial ice to be found in the lower 48 states, around a cubic mile. That much ice and a tendency to have eruptions every few hundred years is a frightening combination. Many people think (perhaps influenced by bad Hollywood movies that involve volcanoes) that lava flows are the greatest hazard from volcanoes. They are not; lava flows would hardly be expected to get off the mountain massif itself. Andesite is just too sticky to flow far before congealing.

Source: Mount Rainier - Living Safely With a Volcano in Your Backyard by Carolyn L. Driedger and William E. Scott, USGS -- from USGS fact sheet 2008-3062

The ice is another matter. A modest eruption of ash or lava could melt a vast amount of ice, mixing with the ash to form a fast-moving mudflow called a lahar. Over the history of the volcano lahars have had the greatest reach, extending as far as the Puget Sound. The cities of Tacoma, Puyallup, Sumner and others are built on lahar deposits from Rainier (see above). Tens of thousands of people along the drainages below Rainier will have a few tens of minutes to evacuate in the event of a major mudflow. For all its beauty, the mountain is a ticking time bomb. It's also probably one of the most carefully monitored mountains on the planet. I don't doubt that the slightest hint of activity will bring a flurry of evacuations.
Rainier from the air in 2007
We spent a few hours on Sunrise Ridge, but our time was limited. We had nearly completed our journey and some of our people needed to catch flights at SeaTac. We headed down the hill towards Puget Sound. We had seen many wonders on the roads that took us across the Olympic Peninsula, the ferry to Vancouver Island, a rainsoaked drive through the Sea to the Sky Highway, explorations of Banff and Yoho National Park, a sojourn among the ghosts of dinosaurs on the High Plains, and a drive home through the Rocky Mountains and the Columbia Plateau. I had gotten to know an extraordinary group of people, and a small corner of a most extraordinary country, Canada.

Sunday, October 26, 2014

The Blind Men and the Elephant, as Told by Geologists: The Channeled Scablands of Washington

A dry channel in basalt on the Columbia Plateau in central Washington (photo by Mrs. Geotripper)
I'm sure most are familiar with the parable of the blind men and the elephant. Several men investigate an elephant, but each touches a different part, so one describes it as being like a snake (the trunk), and others as a wall (the body), a rope (the tail), a fan (the ear), or a tree (the leg). The story of the Spokane Floods and Channeled Scablands of Washington is pretty much the Blind Men and the Elephant as told by a Geologist. In this retelling, the geologist is just as blind as the others, but hearing the arguments among the others, decides to investigate further. He goes back, touches the trunk, the body, the tail, the leg, and ear, mulls on it for awhile, goes back to the arguing men and says "You aren't gonna believe this guys...".
Channeled Scablands and Palouse Soils near Davenport, Washington (photo by Mrs. Geotripper)
J Harlan Bretz was a Seattle-area high school science teacher in the early 1900s, and after receiving his doctorate in 1913 he became a professor at the University of Washington and later at the University of Chicago. He was interested in glacial features of the Puget Sound, but eventually started to explore the strange landscapes of the Columbia Plateau east of the Cascades. The plateau was volcanic (horizontal basalt flows), but it was covered by a fertile silty sediment called the Palouse Soil. The soils have been used for growing vast amounts of wheat over the years.

But the soils weren't everywhere. In many places they had been stripped away, leaving barren rugged channels across the prairie. Most of the channels could not be directly related to modern rivers, but geologists used the Pleistocene ice ages as an explanation. The vast ice sheets covered and changed the landscape, and river drainages would have been altered. The outwash from the melting glaciers could account for the apparently high volumes of river flow required to form the channels.

But to Bretz, these facts weren't adding up. As topographic maps were finally becoming available for the region, he was starting to see the bigger picture of where these channels were found. He was, as it were, becoming a bit less blind. A startling hypothesis was beginning to form in his mind, an idea that would eventually transform our perception of one of the central underlying assumptions of geology.

Geology made a giant leap forward in the early 1800s when James Hutton first articulated the principle of uniformitarianism, the idea that we can use our understanding of present-day processes to interpret what has happened on the Earth in the past. The idea that things happened according to the laws of nature in the past as they do today was a powerful model for understanding how rocks and structures came to be. As the science developed over the next century, the principle hardened into a sort of orthodoxy that all geological processes were constant, and generally slow. This was in part a response to the idea of catastrophism, a model that suggested that some geologic phenomena could be explained by unusual and violent events. To many geologists this smacked of religious explanations like global floods.
Boulder field near Moses Lake (photo by Mrs. Geotripper)

The more Bretz explored the region, the more he was convinced that something extraordinary had happened here. He documented the braided pattern of the dry watercourses, eventually referring to the rugged landscape as the "Channeled Scablands". He discovered gigantic ripplemarks in some of the channels. His research led him to suggest that a series of huge floods had affected the region, floods without precedent in the modern day. His hypothesis seemed to run counter to the principle of uniformitarianism and his proposal met with fierce opposition in the geological community.

Among the weaknesses of his proposal was the source. Where had so much water (an estimated 500 cubic miles) come from? Bretz didn't have a good answer. At first.
Gigantic ripplemarks on the Camas Prairie of Montana

There were really two "blind" geologists looking at the Scablands problem. At the same time that Bretz was working on the Columbia Plateau, J.T. Pardee of the U.S. Geologic Survey was documenting evidence for a huge ice age lake that flooded canyons and plains in western Montana. It is said that he leaned over during a conference in the 1920s where geologists were eviscerating Bretz's hypothesis, and told his colleague "I know where the water came from". It was a number of years before the two put their ideas together as a comprehensive model, and it took even longer before the hypothesis gained widespread acceptance in the geological community. 

Our understanding of uniformitarianism had to change first. There was actually no logical reason to insist that geological rates were constant, slow, and unchanging. The current understanding of the principle is that the natural laws that govern any phenomena are the constant. If it looked like a river had transported boulders, then if channels existed with much larger boulders, then a much larger river was required, even if no such river exists in the present day. If a "small" crater like Meteor Crater in Arizona was produced by a fifty-foot wide meteorite, then a 130 mile wide crater like the one in the Gulf of Mexico would be produced by a much larger rock, maybe ten miles wide. Such a collision with the Earth would surely be catastrophic, and the available evidence suggests strongly that this one destroyed the dinosaurs and many other species on the planet. Catastrophism can be an acceptable explanation if it doesn't disobey the laws of physics and chemistry.

Bretz and Pardee had put together an amazing geological story: during the ice ages about 15,000 years ago, a massive glacier had blocked river drainages in Montana, producing a lake of 3,000 square miles and 500 cubic miles. In places it would have been 2,000 feet deep. On a number of occasions the dam had collapsed and the water rushed out in a catastrophic flood with a flow ten times that of the Amazon River. The floodwaters rushed across the Palouse prairie, carving the Channeled Scablands during the headlong rush to the sea. No modern historical flood comes close
Ripplemarks on the Camas Prairie in western Montana

We were on the last stages of our exploration of Canada and the Pacific Northwest, making our way back to Seattle via the Camas Prairie in western Montana and across the Channeled Scablands in central Washington. Our first stop found us on the Camas Prairie at Markle Pass.

The Camas Prairie was one of the spots where J.T. Pardee was able to document the existence of glacial Lake Missoula. Not only were there shoreline terraces carved into hillsides (below), but ripplemarks covered the valley floor. These were no normal ripples. They were as much as 30 feet high with wavelengths of 200-300 feet. The hydraulics suggest that the lake was draining fast enough to produce currents of 45 mph on the valley floor.
Ripplemarks and wavecut shorelines on the Camas Prairie in Montana

We left the Camas Prairie and drove west through canyons that had once contained a lake 2,000 feet deep. At Coeur d'Alene and Spokane we broke out into the plains of the Columbia Plateau, and our route passed through hills of Palouse Soil interspersed with jagged channels of basalt. In the afternoon we arrived at one of the most astounding results of the flood, the Dry Falls at Sun Lakes-Dry Falls State Park.
Dry Falls State Park in Washington

The park preserves a 400 foot deep valley that was carved in a matter of days by the flood that was probably 300 feet deep at this point. The waterfall was 3.5 miles wide. It is one of the most astounding pieces of evidence for the gigantic floods. I can only imagine what the scene would have been like on one of those days 15,000 years ago. A day like any other except for the rising fog in the distance and the dull roar of the coming waters.  What a sight it would have been.
Dry Falls State Park in Washington
In the early years of his research, Bretz did not have the benefit of maps or aerial photographs. Today hundreds of thousands of airline passengers pass over the Scablands yearly, often without looking out the plane window. It's quite a sight when you realize what you are seeing. I took a couple of shots a few years ago.The Palouse Soils show clearly in the upper part of the photo, while the dark basalts of the Scablands dominate the lower part. Note the small village on the lower right for a sense of scale.

Even the view from a plane fails to communicate the full size of the flood. Satellite images are the only ones that can reveal the true scale of one of the world's great catastrophic events.
Palouse Soils and Scablands Channel in central Washington

One can say that the flood seems obvious when seeing the satellite view, but Bretz and Pardee had only the ground perspective to work with, and their years of detailed research and careful documentation. They were the blind men touching the different parts of the giant elephant, but they had the insight and evidence to put the whole story together. Decades passed before their model was accepted by the geological community, but they did receive recognition in the end, and the science benefited from a new perspective on the principle of uniformitarianism. It is one of the great stories of geology.
Source: http://www.cr.nps.gov/history/online_books/geology/publications/inf/72-2/sec5.htm
We pulled into our motel at Moses Lake for the final night of our Northern Convergence tour of Canada and the Pacific Northwest. We still had some incredible sights ahead on our last day on the road.

Friday, October 24, 2014

Saying Good-bye to the Glaciers of Glacier National Park


The view north from Logan Pass in Glacier National Park
Make no mistake about it. Glacier National Park is one of the most spectacular parks in the United States, and indeed is one of my favorite places on planet Earth. That said, it's losing something important, and the change is profound.
How many animals are in this picture?
When I was a child, I loved museums, but I knew there was a big difference between seeing a stuffed animal in a quiet exhibit hall versus seeing one in the wild. A living, breathing animal trumps a stuffed one every time, especially if said animal is capable of killing you!
I suppose Bighorns could kill you, but I was thinking more of bears...
And that's my problem with what's happening in Glacier National Park. It's hard to put a glacier in a museum. In 1850, there were around 150 glaciers within the park boundaries. Today there are only 25. And they will be gone soon, probably by 2030. The sights we've been enjoying over the years with our visits to Glacier are disappearing at a rate that is heart-breaking. Of all of the signs of climate change, the loss of glaciers is the most vivid. Glacier will always be a beautiful park, and I will keep going back for as long as I am able, but it will soon stand as a monument to glaciation rather than a place where one can experience glaciers. And that is a shame.
Clements Mountain near Logan Pass in Glacier National Park
The changes will go beyond just the loss of glacial ice and scenery. The balance of river flows will change, both in the patterns of volume, but also temperature. Some native species depend on the year-round cold flows that emanate from glaciers. Some streams without a glacier at the source will be drying up before the next winter comes around. Habitats of all animals will be driven to higher elevations, and those at the higher altitudes in the park may find themselves without any habitat at all. We are already seeing the kinds of devastation wrought by pine borer beetles in Colorado and Wyoming. Devastating wildfires have already affected large parts of the park. We are now living the predicted changes in our global climate.
Glacially carved valley east of Logan Pass
The primary purpose of our trip was an exploration of Canada, so our visit to Glacier National Park was a short one as we drove west. We usually stay two nights and spend some time on the trails. We traveled along the spectacular Going to the Sun Highway over Logan Pass, and spent several hours exploring the alpine meadows above the pass. 
Glacier Lilies at Logan Pass
As every climatologist will tell you, there is a big difference between climate and weather. Weather is the day-to-day conditions outside ("It's cold outside") whereas climate is the long-term patterns of temperature and precipitation. Climate changes slowly over time while weather happens daily. Yet it is hard not to notice the daily extremes. When we climbed out of our vehicles at Logan Pass (6,647 feet; 2026 meters) it was 86 degrees. We were surrounded by rapidly melting snowbanks, and it was uncomfortable 86 degrees. The herd of Bighorn Sheep noticed. Some of them were laying in the snow to keep cool.
The meadows above Logan Pass in Glacier National Park
The geologic story of Glacier National Park bears some resemblance to that of Banff and Yoho National Parks in Canada, but there are big differences as well. Like the Canadian Rockies, large blocks of sedimentary rocks have been thrust eastward over softer Cretaceous rocks of the High Plains. Unlike the Canadian parks, the rocks at Glacier are older, closer to a billion years of age (Banff and Yoho sediments are around 500 million years old). They are part of a sequence of rocks called the Belt Series. They contain fossils, but they are of algal deposits called stromatolites. Multicelled creatures did not yet exist.
The peaks were high enough to stand above the vast continental ice sheets that covered the adjacent plains. The glaciers plucked and abraded the flanks of the high peaks, leaving behind outstanding examples of horns, aretes, and cirques. But unfortunately, many of the banks of ice are no longer considered glaciers, as they have shrunk and stagnated. When the chunks of ice no longer move, they aren't glaciers anymore.
Horns and aretes north of Logan Pass
We headed down the incredible west side of the Going to the Sun Highway very slowly, both to avoid plummeting to our deaths down the steep cliffs, but also to avoid running into the beautiful Rocky Mountain Goats who were licking up salt off the roadway.
We reached beautiful Lake McDonald, had a last look at the high glaciated peaks, and then headed west to Kalispell to our hotel. We would be making our way to Washington the next day on our way home. The Northern Convergence tour was reaching the final stages, but there was still much to be seen on the road ahead!
Lake McDonald at the west end of the Going to the Sun Highway.




Thursday, October 23, 2014

Partial Solar Eclipse from California (and What a Sunspot!)

Wow. Just wow. Yes there was a partial solar eclipse today that was visible across much of the country, and yes, it was pretty spectacular. But what caught my attention was the huge sunspot. It is the first time I've ever seen a sunspot with the naked eye, and it was incredible in the zoom lens. I'm told that it is more than 90,000 miles across, the width of 12 Earths. Sunspots are essentially gigantic solar storms. They look dark, but they are simply a bit less bright than the rest of the Sun's surface.
It was so big that even my camera was able to catch some detail. I had my camera on a tripod, and held a solar telescope filter over the end to catch these shots. The zoom was about 60x.
There was a lot of interest on campus, and so our astronomers and Astronomy Club had a number of scopes set out on the roof of the new Science Community Center. I wish I could have photographed one of the views through the most powerful scope. We could see the granules of the Sun's surface, and solar prominences, the arcing jets of plasma shooting out from the surface.
A great day!

Wednesday, October 22, 2014

Northern Convergence: Leaving a Beautiful Country

How will we deal with the hordes of people from the U.S. trying to invade our borders?
Our trip, the Northern Convergence tour, was not over, but the time had come to cross the border back into the United States from Canada. The trip thus far had been an eye-opener. We had been exploring the "crowded" part of Canada in British Columbia and Alberta, but the land itself exuded wildness and isolation.
We were on the High Plains east of the Rocky Mountains, and had spent the morning at the Head Smashed In Buffalo Jump World Heritage Site, and as gruesome as the name was, it was a fascinating place. From there we headed south to the border crossing at Carway. We figured since it had a name that there would be a town and facilities. We got there, and there was...one building. It was a duty-free souvenir/liquor/tobacco shop, and thank goodness, it had a restroom. Still, there were some picnic tables so we stopped for lunch and had a look around. We also wondered if the authorities were going to let us back into the United States. You never know...in the innocent days before 9/11, we were interrogated about whether we had any "Beanie Babies" in our luggage. I laughed at the question, and the border agent got very serious: "Sir, DO YOU have any Beanie Babies?"
We were not exactly in the High Plains, as the land was broken up into swales and shallow valleys underlain by very soft Cretaceous shale deposits. The shales had been deformed and twisted by the same convergent forces that had lifted the nearby Rocky Mountains, but erosion had smoothed off the sharp edges. The land was semiarid and treeless. More verdant lands could be seen in the distance as we looked westward towards the Rocky Mountains and Waterton-Glacier International Peace Park. Glacier National Park was our next destination.
Chief Mountain was especially prominent on the western horizon. The peak is an outlier of the Rocky Mountains, an isolated upper plate of a thrust fault that had pushed the hard Paleozoic limestones over the softer Cretaceous rock. Erosion had then isolated Chief Mountain as a klippe (see the diagram below).

The mountain was a dramatic welcome back into the United States. We only had a few more days left on our journey, but there was still much to be seen. The story will continue in another post!
Source: http://en.wikipedia.org/wiki/Klippe