Saturday, May 31, 2008
I just love the town of Durango. It has always been a pleasant respite from the heat of the desert on our summer field studies journeys. I would arrange for a grocery stop, giving the students a few minutes to wander about the town, getting t-shirts, and restocking their ice chests. I got to know the town even better when my son decided to pursue an Anthropology degree at Fort Lewis College.
The town occupies some glacial outwash plains along a river with one of the most poetic names of any I have ever known: the Rio de los Animas Perdidos, the River of Lost Souls. It flows out of the Rocky Mountains, joins with the San Juan River, and eventually merges with the Colorado.
Why the special day, and why Durango in today's post? My son met his fiancee at Fort Lewis College in Durango, and today they are getting married! So, postings were a little light this week for probably obvious reasons. I've been distracted....
Wednesday, May 28, 2008
The prominent cliffs in the lower part of the canyon are the Mississippian aged Redwall Limestone. The cliffs are about 500 feet high. The overlying redbeds are the Pennsylvanian-Permian beds of the Supai Group and the Hermit Shale. They are delta and floodplain deposits eroded from the Ancestral Rocky Mountains which existed at the time to the northwest in Colorado.
I had the privilege of seeing one of the last free-flying California Condors back in the 1980's in the hills north of Santa Barbara. When the population dropped to about 28 individuals, they were all captured and they started raising captive birds. As more and more of them matured, and the total number slowly rose, they began releasing the birds in the wild in a number of widely isolated locations in California, and in their old range of Arizona. A small population inhabits the North Rim at times. At the time of my last visit, I wasn't aware of the presence of these grand birds. But I did see some monstrously huge turkey buzzards flying around and finally realized that NOBODY was identifying turkey buzzards with number tags. These were condors, in range of my camera! It was a neat moment, although I kept trying to get a picture without the number tag, but getting a picture of a Condor with the Grand Canyon as a backdrop was thrilling enough.
Monday, May 26, 2008
I would have to start with the oceans. They cover 70% of the surface, hiding any structures in the rock, and providing an opportunity for life to arise. One of the first choices I would make is a shallow marine landing in the equatorial regions. It seems to me that vast areas of molten ice (that's how they would see it) would be mysterious and perhaps even inhospitable. I would leave it to the Martians to design a device that could explore the mysterious waters. Would it sink and sit on the bottom, or would they think to give it the mobility to explore different depths?
How would Martians see the chance of life developing? They live on a cold, dry planet with liquid water a rare phenomenom. Would they pick a landscape on Earth that is most like theirs, in hope of finding life there? How about the Dry Valleys of Antarctica? It might not tell them the most about the planet, but would it confirm their pre-conceived notions about Earth and the similarities it shares with their planet?
Erosional processes on Earth are clearly different from those on Mars. If I were them, I would aim for one of the boring places, such as the Central Valley of California, or the Mississippi River basin to get samples of soils that develop in depositional basins in order to learn something of the current and immediate past climate. What would they make of soil horizons?
On the other hand, vast eroded areas of bedrock would present an intriguingly new landscape for a Martian. I would pick a deeply eroded, but flat terrain that reveals as much geological history as possible. With a good eroded anticline and a rover, one could work out a geological history for an area quite readily. I am thinking maybe some of the anticlines in Wyoming, or the Virgin Anticline near St. George Utah, or the Kettleman Hills in the Central Valley of California. Another erosional landscape would be one of the shield areas such as those found in parts of Australia's Outback, or northern Canada.
The Martians would surely be curious about active river systems and stream erosion. There would be obvious benefits in exploring a river gorge that exposes a great deal of geology, like the Grand Canyon, but I wonder about the technological challenges of exploring such a place with an un-manned (un-martianed) craft.
Finally, wouldn't they be drawn towards active volcanoes? They will have studied their own ancient shields, and understand the rock chemistry, but they never will have seen an erupting volcano. Would they shoot for the Big Island of Hawai'i, or Mt Etna? Or would our shield volcanoes seem too pedestrian? Would they go for a big stratovolcano instead? What about Cleveland or Augustine in the Aleutian Islands?
Sunday, May 25, 2008
The South Rim gets something like 90% of the visitation, which is reason enough to avoid it, but because more people are there, the rim has more trailheads, more facilities, museums and so on. The North Rim, in contrast, is around 1,000 feet higher, cooler, and more moist, and thus the forest is predominantly composed Ponderosa Pine (instead of pinon), and there are more meadows. One of the nicest aspects is the location of the group campground: it is only a few hundred feet from the rim (South Rim campgrounds are nearly a mile back). I prefer the views from the North Rim; the higher elevation offers a panorama of the landscape south of the rim, including the San Francisco Peaks volcanic field.
Today's picture is a morning shot looking south towards the San Francisco Peaks. I will have to leave it to others who know more about this kind of thing to explain why there is a gigantic composite volcano and associated volcanic field here. I imagine there is a sort of 'manhole' effect where lavas are leaking out from under the thick continental crust of the plateau country where it has been faulted by the current extensional regime, like a sewer system backing up. The high point on the rim, Humphrey's Peak is over 12,000 feet high (Arizona's highest mountain), but the original summit may have been several thousand feet higher. From the east, the complex looks surprisingly like Mt. St. Helens. The field is mostly Pleistocene, and at least one volcano erupted within the last 900 years (Sunset Peak National Monument).
Saturday, May 24, 2008
This is a geology blog, so I will point out that she graduated with a degree in geology. There is a grad school out there that will be lucky to have her in the program in a year or so, and later on, a company or school is going to have a very talented employee. Congratulations!
The syncline lies near exposures of the Calico fault, an active right-lateral strike slip fault. The Landers quake in 1991 ruptured part of the fault zone. A minor offset cuts the left limb of the syncline and other faults slice through the basin, making it an excellent place for mapping.
The layers exposed in the fold are terrestrial and fresh water sediments of the Miocene Barstow Formation, a critically important stratigraphic and paleontological element of southern California geology. The vertebrate fossils found here include early species of elephants, camels, antelope, three-toed horses, cats, and many others. In some nearby areas, silicified insects have been discovered as well. Because the layers of the formation are bracketed by dateable volcanic ash layers, they form the basis of the Barstovian Land Mammal Stage of the geological time scale. When similar species of animals are found in other parts of the country, they can be dated to around 15 million years by comparison to the Barstovian fauna.
Looking for a good example of an angular unconformity? Check out the layer of alluvium across the top of the fold! The region eroded to a relatively flat surface in Pleistocene time and was covered by alluvium, but more recently the land was warped upward and is presently being rapidly eroded.
The Barstow Formation was the host rock for barite and silver ores, as well as borate minerals, and a number of mining ghost towns dot the region. Calico is the most famous, and has been developed as a regional county park (read: tourist trap), but it is a nice enough place to visit. Kenny Rogers and the First Edition once actually produced a two disk record album full of songs about the ghost town. Farther to the east, the Calico Early Man Site offers evidence for the presence of humans in the western hemisphere far earlier than is accepted by most archaeologists.
Want to see Rainbow Basin? The Bureau of Land Management site offers the directions and information on camping and touring the region.
Update: It didn't take long to find out that others really love the place, too (and beat me to the blog post!). Ron Schott has a blog entry here (although I am having trouble following the link), and Dave Schumaker has one here. Thanks for the info!
Thursday, May 22, 2008
I prided myself on being able to outhike nearly all my students all through my 30's and 40's, but about ten years back, I was moving up the north rim trail so slowly, and so redfaced, that my concerned students turned back down the trail, and asked "Mr. Hayes, are you going to be ok? Can we carry your pack?". The week following the trip, I bought a gym membership and started working out. The results have been up and down, but in general I am still capable of outhiking some of my students.
The secret to finding the treasures of the Bright Angel Trail is to outhike the burros. Most of the daily trips from the North Rim go to the springs about 2 or 3 miles down into the canyon. That part of the trail is dusty, full of flies, and very odoriferous. They do pay some poor soul to take a wheelbarrow down the trail, collecting "road apples". Below that point is a wonderous land. Today's picture is the passage of the North Rim part of the Redwall Limestone. I have not been on many trails that were more vertical!
The Redwall Limestone is a Mississippian-aged formation that records the presence of a shallow epicontinental sea that covered much of North America. It is full of fossils, such as brachiopods, corals, bryozoans, and numerous other creatures that inhabited the warm tropical sea. The limestone is a cliff-former that is easily visible from any point on the rim. The cliffs are generally so rugged that the location of literally all rim-to-river trails in the Grand Canyon is governed by the accessible passages of the Redwall. The Redwall is not red at all, as nearly every booklet and sign tells you, but instead is gray in most places. The surface of the cliffs are coated with iron oxide staining from the overlying Supai Group.
Another lesser known fact about the Redwall is the extensive presence of karst features in the layer. In late Mississippian time, the surface emerged above sea level, and numerous caves and sinkholes developed. Most were filled with intensely weathered red soils. A few caves (presumably much younger) are accessible for exploration, although most open into overhanging alcoves hundreds of feet from any horizontal surfaces. Grand Canyon Caverns are a tourist oriented attraction south of the park on the old Highway 66. One of the caves on Horseshoe Mesa has an access trail, and the exploration of that cave by myself in 1976 was one of the series of events that led to my becoming a geology major. Other caves were accessible to Pleistocene animals, and the dry conditions preserved many traces, including their droppings. The split twig figurines of the first human inhabitants of the region have been found in caves of the Grand Canyon.
Wednesday, May 21, 2008
The crossbedding in the Navajo Sandstone provided a natural separation point to quarry the trail out of the cliff. It is incredible to imagine the dune sea that existed here in Jurassic time. The desert even included oases, as indicated by small pods of freshwater limestone in between some of the dunes. Few bones have been found in the Navajo but numerous trace fossils have been found in the unit.
Monday, May 19, 2008
Sunday, May 18, 2008
Saturday, May 17, 2008
I am tempted to give it another try this year...the trail offers stunning views all the way up, although I need to spend more time in the gym before considering it.
Friday, May 16, 2008
One point for guessing the park or monument. Clue: The site made the list on Callan Bentley's Scary Map du jour
Two points for describing the stratigraphy, age and environment of the formation.
Five points for identifying the trail, because I remember it being one of the tougher trails I have ever hiked, and I don't think many people have been on it. But what a payoff at the end!
Have a nice evening!
Fast forward to the present day conflict in Iraq (and I fear, if the idiots in the White House have their way, Iran). A war being fought by "volunteers", for a longer duration than World War II. So many families have been financially and emotionally trapped by having a family member in the reserves, which have not been called up in decades, except for Iraq-related incidents. Soldiers being recalled to duty in Iraq, three and four times over. More than 4,000 Americans dead, not to mention hundreds of thousands of Iraqis. A horrific number of war wounded and maimed, and an incalculable future of post-traumatic stress syndrome that will affect our vets for decades.
Our soldiers are serving their country admiralbly and honorably, but it seems that they are the only people who are sacrificing any part of their lives and resources. What have we been asked to do? Buy more! Show the terrorists that we consumers can continue to spend and borrow so we can have more things! Put a "support our troops" bumper sticker on our SUV's. What else? Oh yes, we can be disturbed by the images of war that we see on tv. And then turn the channel. We aren't even paying for this war. We are paying for it by credit card; our grandchildren will foot the bill for us.
Did I say geo-political rant? Oh, yes. Why are we there? Would this war be happening if there weren't billions of barrels of petroleum under the sands of Iraq? Yeah, I know all those other justifications for being there: Sadaam was not a very nice person, he had weapons of mass destruction, etc., but the numbers are stark: Saudia Arabia, around 250 billion barrels, Iraq, around 105 billion barrels, Kuwait, around 95 billion barrels, Iran about 90 billion barrels. We use about 5-6 billion barrels a year in the United States. We have about 30 billion barrels in the ground. That's it.
And what have we done in the last 30 years since the last gas crisis? Essentially nothing, and even worse, our vehicles have grown larger, consuming ever more fuel to get us around town for our absolutely essential errands. Detroit and Congress and the President can barely agree to slight increase mileage standards in the next ten or fifteen years.
Am I angry? I guess it sounds that way. I have been keeping a count of the war dead on my office door ever since the 700th soldier died. Someone, or more than one "patriot" has continued to tear down my tally month after month, somehow irritated that we should keep in mind the sacrifice being made by our heroes in the military. I have been at it for so long, I have become numb to the numbers. They almost lost meaning to me, until this week.
The idiot who occupies the White House revealed what he has sacrificed in the war effort. He gave up golf in 2003! He thought it would send the wrong message to be smacking a little white ball while good people were dying. What does he say to the fact that he has spent more time on vacation than any other president?
I fervently hope that you will vote for people who will extricate us from this futile war. I hope you will vote for people who will design an energy plan that plans for a future beyond the two years or four years to the next election. I hope you will vote for someone who can truly call on us and inspire us to sacrifice something of our lives so that there will be something for the children who come after us. Work now to make your own life a commitment to a greener future.
And the next time a politician, or a columnist, or a talking head on television tries to justify a war, make sure that they have their children on the front lines of the conflict. Because that can be the only measure of sacrifice that can justify taking sons and daughters away from someone else.
Wednesday, May 14, 2008
- Perhaps 100,000 people are dying in Burma as the result of a horrific cyclone (and even worse military meddling)...
- Tens of thousands of people have died in a terrible 7.9 earthquake in China...
- Dozens of people are dead in a series of record-setting tornadoes across the midwest and south...
- Nearly two thousand people die in New Orleans after a terrible hurricane strikes...
- Sea level is rising and polar ice masses are melting at an accelerating rate...
- Commodities are becoming scarcer, and the price of food and fuel is rising at rates not seen before...
In the past four years, I have reported several times about the incredible spike in tropical storm activity. Time and time again records have been shattered.
Global warming can't be an explanation for the upsurge we are seeing today. Cyclone Nargis had all the makings of a perfect storm. Packing winds upwards of 120 mph, the cyclone became one of Asia's deadliest storms by suddenly going from Category 1 to Category 3 and hitting land at one of the lowest points in Myanmar.
The storms seem to be intelligently guided to inflict maxim (sic) damage [italics mine]. If they were random, the law of averages would cause most to strike uninhabited areas or follow paths that lead to the open ocean.
There are many more quotes, and many more sites like this on all of these events, and the Rapture Index has been played for laughs on some websites. But a great many people pay attention because once again, the magnitude of some of these events is incomprehensible (while others, like gas prices, are irritating, but they are a symptom of a very serious coming problem of resource scarcity). Humans have always looked for an underlying cause, whether it is the anger of the gods, or the movement of massive plates, or the warming of the climate. Scientists use more sophisticated tools these days compared to divining rods and tea leaves, but we still try to explain those things that are unexplainable. Fair or not, many people see scientists as simply one more kind of priestly class that explains the mysterious, and our pronouncements are to be considered, and then "believed", or "not believed".
So, if you are from a non-scientific background, and you are wondering if we are entering "the last days", I ask you to consider that many of these disasters are the natural consequences of ever more and more people living in marginal and dangerous places. The earthquake in China happened at the margin of a violently active geological fault zone. Overpopulation and lack of arable lands inland lead to too many people living in hazardous coastal areas, subject to hurricanes and typhoons. Sometimes these disasters do happen nearly simultaneously, it is the nature of randomness.
And some events are unusual. But there are verifiable reasons. Global warming is real, and it is having profound effects on our environment and our weather, so we are living through strange times. But we are the cause of the warming. This is not something to have an opinion about, it is not a political issue, even though some have caused it to become one.
But most of all, please consider that every time you are willing to call one of these disasters God's judgement, you remove the humanity and dignity from those who are suffering in horrible ways. If you allow yourself to belittle innocent victims, by calling them immoral, or illegal, or under God's punishment, you are defying the very tenets of your religion: that you love one another. The magnitude of these human tragedies is indeed overwhelming. But don't let the pronouncements of fools take away the humanity of the victims. Don't try to comfort yourself by thinking that these human beings are victims of God's judgement. Do whatever you can to help; the next time the victim may be you....
Sorry for an angry rant...
Another perspective (from a non-western view) on this subject can be found here.
Sunday, May 11, 2008
I partly blame Silver Fox for the distraction, too. Her picture of the San Rafael Swell brought to the fore that I will be on the road soon. So, I will be continuing a series of little known places, but that will include some of the wider world of geology out there. Today, we start simple: where is today's photo? Our class will spend two days on the north side...
Saturday, May 10, 2008
The view from the summit of Sentinel is superb, although it reveals little of the valley floor. Instead, it provides a sweeping view of the valley walls and the surrounding region of glaciated peaks, cirques, aretes, domes and cliffs. It stands only 700 feet shorter than Half Dome. It is visible from the classic view of Yosemite Valley, just behind the lowest of the Cathedral Rocks, and just to the right of Sentinel Rock.
Today's picture is looking west towards the portal of the valley, framed by the Cathedral Rocks and El Capitan. The granite that forms both of these edifices is mostly unjointed, and the glaciers that scoured the valley were unable to quarry deeply beneath the cliff faces. The sediment between the portal cliffs is only about 300 feet deep. At the upper end of the valley, in the vicinity of the stables and Stoneman Meadow, the sediments may be as much as 2,000 feet thick!
One may notice the near lack of cliffs beyond the portal formed by El Capitan and Cathedral Rocks. These are the Rockslides, and are composed of diorite of the Rockslides, which is Jurassic-Cretaceous in age, somewhat older than the other rocks in the valley. The rocks have been intruded by mafic dikes and joint more closely than other plutonic rocks in the valley, causing them to easily break down and form talus slopes. Roads built across this slope have been abandoned over the years due to constant rockslide damage.
Friday, May 9, 2008
Well, perhaps you have seen this view, if you have been to Yosemite. It is the view up the Merced River Canyon above Yosemite Valley, as seen from Glacier Point. The two waterfalls are the justly famous Nevada Falls (upper, 594 feet) and Vernal Fall (lower, 317 feet). Because they are on the Merced River, they have the virtue of not drying up in the late season, although they can shrink to insignificance in a dry year. The falls have formed along prominent joints in the Half Dome granodiorite. The glaciers moving down the valley plucked at the more jointed rocks down-canyon, forming these glacial stairsteps.
The hike to Vernal Falls is one of the most popular hikes in the park. In the early season, hikers will end up entirely drenched from the spray from the base of the falls. Unfortunately, there is an utterly beguiling green pool of water just upstream of the the fall that just begs to be soaked in on a hot day...it is fun right up to the point that one gets caught in the current and gets swept over the brink. Believe the signs and find somewhere else to swim!
Thursday, May 8, 2008
Wednesday, May 7, 2008
Today's view of the abyss comes from a familiar tourist stop: Glacier Point. It is accessible by paved road and trail, and is visited by hundreds of thousands of people every year. It is easily one of the greatest scenic vistas on the planet. The view is dominated by Half Dome and the Tenaya Canyon, as well as the cliffs around Yosemite Falls. Between the two is an interesting view of a pair of exfoliation domes called North Dome (left) and Basket Dome (right). From the valley floor they are barely visible above Royal Arches and Washington Column.
Exfoliation takes place when the weight is removed from homogeneous rock like granite, and the rock expands. It fractures parallel to the surface and this leads to a tendency to remove corners and edges of otherwise rectangular rocks. A great many domes grace the Sierra Nevada, and a vast number of them have never been touched by glaciers.
The mountain on the skyline is Mt. Hoffman, which is a high peak close to the geographic center of Yosemite National Park. N. King Huber used the view from the summit as the springboard to a discussion of the geology of the park in his excellent Geologic Story of Yosemite National Park. It is a great hike, and is likely to be the subject of future posts.
El Capitan Meadow is visible on the valley floor. One of the most prominent Tioga Stage glacial moraines lies just west of the meadow. It dates to about 13,000 years before present. For thousands of years, natural wildfires and intentional burnings by Native-Americans cleared the conifers from the valley floor, and over time it evolved into an open oak woodland with wide meadows and a few widely scattered conifer trees. The size of meadows in Yosemite Valley has dramatically decreased in the past century. Josiah Whitney and his crew calculated meadow area in 1866 to be 745 acres. By 1937, meadow area had dwindled to 327 acres. Today, meadows cover 65 acres, leaving only 6.8% of the original 1866 meadow area. With the advent of national park status, fires were suppressed and the shade-loving conifers flourished. The forest is now dense with young trees, and the possibility of disastrous wildfires is very real.
The distant skyline shows the relatively gentle westward slope of the mountain range, leading into the Central Valley. The mountains have risen by fault motions on the eastern margin of the range, leading to a westward tilt that has mostly developed within the last 9-10 million years.
Sunday, May 4, 2008
Jointing occurs as removal of the overlying rocks by erosion releases pressure, and the rock expands and fractures. It provides an avenue for water to enter the interior of the rock face and start the chemical weathering process, leading to the loosening of the boulders in the cliffs. The Three Brothers, with their intersecting joint sets, are a constant rockfall hazard. The white scars are recent slides and falls, including the 1987 Middle Brother slide, which with an estimated volume of 600,000 cubic yards, was the largest historic mass wasting event in the valley. Luckily, the National Park Service had closed the road below in anticipation, and no one was injured in the event. Other rock falls have produced injuries and deaths, including on the nearby trail to the top of Yosemite Falls.
Saturday, May 3, 2008
Still, they are crowded, noisy and fences and paved trails make it clear where you have to go. There is nothing quite like standing on the brink and staring into the abyss below, alone, with nothing between you and the whole expanse of cliff and valley floor but empty vast space. I am only beginning to discover those places. Today's pictures are taken from Taft Point, a viewpoint at the end of an easy one mile trail. Although the trailhead parking lot is often full, when I was there I saw only 3 or 4 other people on the trail, and I had the clifftop view all to myself (I think most people must have been climbing Sentinel Dome; more on it later).
Yosemite Valley is abrupt. There is no other way to put it. One walks through a gentle landscape of soil and forest, the occasional outcrop of weathered granitic rock, noticing flowers and greenery. A few steps later comes several feet of barren horizontal rock, and then suddenly the world falls away into oblivion. The land is of two ages. The flatness is old and gentle, ancient and unglaciated, a hint of the shape of the land before the mountains began their long and relentless rise into the sky. The other is youthful, brash, a place of action and change. First carved by river, then undercut by glacier, and shaped finally by mass wasting, the cliff is a temporary adjustment, a stand off between shear forces, friction and gravity. It is hard to stand on two feet and look over this edge; the feeling is to crawl towards the cliff, a form of supplication to the vast forces at work here.
The cliff across the valley in the picture above, if you don't recognize it, is El Capitan, the 3,000 foot-high cliff that dominates the west opening to the valley. The chockstones in the photo below have dropped into the Taft Fissures, joint openings caused when the previously deeply buried granitic rock expanded and cracked. The drop-off below the fissures is thousands of feet.
Friday, May 2, 2008
The camera I had was not versatile enough to allow the spinning of the stars, but a 30-second exposure was enough to bring out the ghostly details of Yosemite Falls with a star-studded sky above. No particular aspect of geology to discuss today, aside from pointing out the fact that we live in an extraordinarily beautiful world, a single unique planet wandering through the cosmos. It is a place of wonders.
It was cold, I was shivering, but there was not another soul moving on the valley floor that night. We had the entire place to ourselves. How many times will that ever happen in this lifetime?