Friday, October 31, 2014
I love numbers and statistics. I've lived in the same location for the last 23 years and the first year I was there I got a nice rain gauge for Christmas. I've been using it to keep track of precipitation in my Great Valley town about 13 miles east of Modesto. We are roughly at the middle of the valley (the center of the Central Valley!), about 200 miles north of Bakersfield, and about the same distance south of Redding. The valley climate ranges from Mediterranean in the north to desert in the south (Redding averages about 34 inches of rain per year while Bakersfield averages just over 6 inches). Modesto's 108 year average is 12.15 inches. The highest recorded rainfall was 26.01 inches in 1983 with the lowest at 4.3 inches in 1913.
The most rainfall I recorded in a single day was 2.32 inches on January 2, 2006, and the wettest single month was February of 1998 with 8.64 inches. Some of you in wetter climates may find these numbers amusing (I note a day in 2010 when Big Sur got 22 inches of rain...in 24 hours!). But as I've said, we live in an arid climate. Irrigation is all that keeps most parts of it green.
The scary part of the story is that of the last decade. There were a few wet years, but six of the last eight years have been well below average, only about 75% of what was once normal. Last year was the driest I've recorded. Our reservoirs are functionally empty and there has been little or no snowpack. We actually drove over Tioga Pass in January of 2012, and it was t-shirt weather. Tioga is usually closed from November to May because of snow, but not these days.
Here's hoping that tonight's storm, as disappointing as it is for the Halloween trick-or-treaters, is a harbinger of wetter times to come. It's a frightening situation all around.
|The San Andreas fault at Cajon Wash and Lone Pine Canyon at the eastern end of the San Gabriel Mountains|
|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.|
|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 Gabriel Mountains are moving northwest along the fault.|
|The village of Wrightwood on the San Andreas fault. The Heath Canyon Mudflow started at the scars on the left side of the photo.|
|Wrightwood on the San Andreas fault in the San Gabriel Mountains|
|Mountain High Ski Resort and the East Fork of the San Gabriel Canyon|
|A shutter ridge along the San Andreas fault in the San Gabriel Mountains|
|Shutter ridge on the San Andreas fault|
|The Devils Punchbowl, a west plunging syncline in resistant layers of conglomerate and sandstone.|
|Offset stream near Palmdale. The dark line is the California Water Project.|
Wednesday, October 29, 2014
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
|Rainier from the air in 2007|
Sunday, October 26, 2014
|A dry channel in basalt on the Columbia Plateau in central Washington (photo by Mrs. Geotripper)|
|Channeled Scablands and Palouse Soils near Davenport, Washington (photo by Mrs. Geotripper)|
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|
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.
Friday, October 24, 2014
|The view north from Logan Pass in Glacier National Park|
|How many animals are in this picture?|
|I suppose Bighorns could kill you, but I was thinking more of bears...|
|Clements Mountain near Logan Pass in Glacier National Park|
|Glacially carved valley east of Logan Pass|
|Glacier Lilies at Logan Pass|
|The meadows above Logan Pass in Glacier National Park|
|Horns and aretes north of Logan Pass|
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
Wednesday, October 22, 2014
|How will we deal with the hordes of people from the U.S. trying to invade our borders?|
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?"
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!