| Patagonia, Argentina y Chile. |
[07 Jan 2008|11:08pm] |
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In November, a friend and I went to Patagonia, including the far south. Down there, all things are Magellanic in some way. For example:
... the [[Strait of Magellan]] (Estrecho de Magallanes, left), of course. It seemed a bit tame compared to the [[Beagle Channel]] (right)
... [[Magellanic penguins]], which are rather frumpy little birds, totally lacking in the graces of their larger Antarctic relatives. (I fear the Chilean government tourist board will come after me for letting out the big secret, but these photos, just like all photos of penguins, entirely fail to capture how absolutely fucking miserable the weather is. This seemingly balmy romp on the beach was actually in a steady 40 knot wind with rain and occasional sleet, at about maybe 40degF in the sun if you thought warm thoughts.)
... and, my personal favourite, the [[Magellanic Clouds]] (left). These, along with the amazing intensity of the Milky Way at the negative latitudes (right), are worth a trip to the southern hemisphere all by themselves.
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| San Francisco Oakland Bay Bridge, East Span. |
[31 Aug 2007|11:41pm] |
 The Maze, free of mice.As I mentioned previously, the San Francisco Bay Bridge is closed this weekend, starting at 2000 tonight. My friend Paul suggested we go up for a bay tour around the closing time, to see, among other things, what a Bay Bridge looks like with no traffic on it. ( Read more... )
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| San Francisco Bay, California. |
[16 Jul 2007|03:00pm] |
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Last Friday, I was invited to tag along for a tour of the progress on the construction of the San Francisco - Oakland Bay Bridge East Span Replacement Project. ( Read more... )
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| Southern San Joaquin Valley, California. |
[21 Mar 2007|06:01pm] |
 Wheeler Ridge, as discussed previously. The anticlinal axis runs diagonally through the frame.
 The Elk Hills, another oil-rich anticline to the north of Wheeler Ridge. This was US Naval Petroleum Reserve Number One (here's a more succinct version, if you're already familiar with the Teapot Dome scandal) until President Clinton put it back into private production in the late 1990s. It's hardly recognizable from the air, since it has been completely and utterly reshaped by the oil industry. It is now just a maze of service roads and derricks; it looks amazingly like the side of a pet ant farm.
(These were taken at about 10,000 feet, from N9849L piloted by my friend Paul.)
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| Mojave Desert, California. |
[19 Jan 2007|01:39pm] |
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These are from a Phoenix-San Francisco flight (UAL1437) last weekend. Always interesting to see things from FL360, especially an area I've grown to know so well from the ground. The flight took a direct route from around Buckeye (Arizona) to the Walker Pass area across the Sierra Nevada, passing over Parker, Amboy, Barstow, and California City. 
Amboy lava fieldPrevious post (see also the Lavic Lake post). Also [[Amboy Crater]]. 
Harper (Dry) Lake and Luz VIII & IXPrevious post. Also [[SEGS]].
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| Providence Mountains, Mojave National Preserve, California. |
[25 Dec 2006|03:41pm] |
It's that time of the year again. This year I repeated what last year was supposed to be -- going out to Kelso Dunes. It was alright, but the sunrise was better last year.
I love this time of day in clear skies -- the time between astronomical twilight and sunrise proper. You really get a sense that the sun is just another star rising in the east.
It's a bit sad that in a year's time, I've only managed to post to this journal nine times. I'll try to work on that. Lately I mostly just post photos to my flickr stream and my own LJ (![[info]](http://l-stat.livejournal.com/img/userinfo.gif) midendian).
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| Sonora Pass, Sierra Nevada, California. |
[22 Oct 2006|01:43pm] |
Orionid meteor falling through Cygnus and the Milky Way
When Halley's Comet passes 'near' the Sun every 76 years, it melts a little, and debris trails behind, eventually diffusing into large clouds of dust. Earth passes through this dust twice a year -- once in early May as the eta Aquarids meteor shower and again in late October as the Orionids. Even the smallest particles create impressive streaks as they burn up from the friction of moving through our atmosphere. The comet hasn't disposed any new material in this spot since its last passing in 1986, but there is plenty left.
This year's Orionids happened to fall near a new moon, for a nice dark sky. The peak was on Saturday morning, but there's still a night or two left if you haven't seen them. Orionids appear to radiate from northeastern Orion, near his shoulder, and so will be most plentiful when Orion is at the zenith (ie, straight up), which is around 0300 in California. That said, the most impressive are, like the one above, far away from Orion, since the longest streaks come from objects that hit the atmosphere at the shallowest oblique angles; though there are more of them, the ones near the radiant in Orion hit almost dead-on and burn out quickly.
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| San Francisco, California. |
[07 Oct 2006|12:41am] |
( +1 )
Much to the displeasure (and occasional horror) of some residents, it's [[Fleet Week]] in San Francisco. Most of the activities are inobtrusive (the usually co-incident North Beach Festival / Columbus Day celebration is far more of an inconvenience), except the [[Blue Angels]] practice and performances. The half-dozen F/A-18's spend about a half-hour each of the of the four days of Fleet Week buzzing the Financial District / North Beach / Marina area, usually very low and very very fast. When they're all flying past you in a single formation, the sound is particularly memorable.
But I enjoy it! This was the first time I've heard supersonic aircraft since Iraq. It's a very distinctive sound.
The first shot almost makes me let go of any regret about the thousand+ dollars I spent on lenses this week, including the Sigma 170-500mm I used for these. I've never used a lens that can go so long -- I found myself forgetting that it was able to zoom in more. It could be a little sharper, a little quicker to focus, and I really wish it had a zoom lock, but for less than a fifth of the price of the comparable Canon lens, it's a winner.
The weather was totally miserable today -- windy, wet, cold, and foggy, which combine into some unnamed weather condition that is even more unpleasant than the sum of its parts (the closest word I can come up with is "January"). It's supposed to be sunny for the weekend, so I'll probably try to brave the Fisherman's Wharf tourists again to try for blue backgrounds and higher contrast. The worst part about the tourists is that when you're carrying around a lens that is over a foot long, you get mistaken for a professional and therefore someone who would just love to take their picture. On the upside, you get to play with the latest in point and shoot cameras from tourists all over the world -- some of them are pretty awesome these days!
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| California Highway 108 / Sonora Pass, Sierra Nevada, California. |
[25 Aug 2006|01:50pm] |
Last week, I went on a short (day and a half) photo/hiking/driving excursion, and am finally making headway on sorting through all the photos. I don't have much to say about them, but it seems appropriate to post some of them anyway.
CA-108 near Dardanelles, looking east
There was a lot of smoke in the air that night; I could smell it, but I didn't quite realize how extensive it was until I saw the resulting photos -- note the especially soft edges on the mountains in the valley corridor. Where I took this photo, the highway runs along the southern wall of a gorge containing the Middle Fork of the Stanislaus River, as well as Donnelle Lake/Reservoir. My original target on this part of the highway was the Donnelle Overlook, so I was very sad to find it closed, seemingly permanently. From that overlook, you could see down into the gorge from the edge of the granite walls, unobstructed by trees.
This photo looks east, towards the peaks around Sonora Pass, from which long ago volcanoes released vast basalt flows. These rocks have been almost entirely removed by the glaciers of ten to fifteen thousand years ago (accelerated by the uplift of the range as a whole), but the occasional peak is still covered. Dardanelles Cone is such a mountain, and its flat brown mesa looks totally out of place in the smooth rounded granites of the western Sierra. You can easily make it out on the aerial photos -- a big brown smudge in a sea of grey, green, and blue.
( two more )
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| Del Puerto Canyon, Coast Range, California. |
[13 Jul 2006|10:39pm] |
I've been out of the area for the last couple weeks, and only happened to hear about this fire on the evening news from Los Angeles the night before. Normally when you're driving up Interstate 5 towards 580 and the bay area, there is a large finger of clouds that spill through the Delta region into the Central Valley, starting to be visible right about at the 5/580 split -- it's not uncommon for it to start raining at that point in the winter. When I saw these clouds, I just figured it was that typical weather (though a bit early). But it quickly became apparent that these clouds were orange, and that my trip would be delayed by my need to find backroads into the hills.
I've been this close (or closer) to probably a half-dozen forest fires (like in Yosemite, driving right next to the flames along the road, or at the North Rim of the Grand Canyon, where I had to turn around because the road had melted). The most striking thing is not the smell, not the heat, but the utterly bizarre quality of light. Smoke has a light transmission range rather unlike air and, more subtly, depends on whatever is being burned and the temperature at which it's burning -- it makes experiencing fire in every region quite unique. Ponderosa needles at the Grand Canyon are nothing like range grasses and Oak leaves in the California coastal mountains, not to mention the regional atmospheric differences affecting cloud dispersion, or the inclination of the sun which in turn affects so much else.
I'm a bit sad about this. This fire has entered one of my favorite parts of the Bay Area: the San Antone Valley on the back side of Mount Hamilton. Driving across CA-130, eastbound from Mount Hamilton, everything suddenly seems so remote. A nice barely-maintained road running along a lovely creek, rarely anyone else around -- nothing at all like just ten miles to the west.Although I'll complain about being told to leave: Much thanks to the CDF and the property owner on who's land I was trespassing for putting up with me.
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| Rainbow Basin (BLM), Mojave Desert, California. |
[05 May 2006|07:41pm] |
What brought me to geology in the first place was my love of mountains. They are spectacular things, from the overall shape of a range down to the minor faults and folds of their orogeny exposed alongside the road. Until a few years ago, I didn't even pay much attention to rocks themselves, just the shapes they've been made into. It turns out lots of people have this particular interest. It's called structural geology, and one of the best places to play is in the desert. Not only do things get preserved longer in the precipitation-free climate, but there's only a few pesky plants obscuring the shapes -- you get a bigger, clearer window on the past.
Rainbow Basin is a small chunk of BLM land about ten miles north of Barstow, California, accessible by a long dirt road, the end of which is a strange one-lane dirt road through the basin, and a pretty good campsite. The rainbow name comes from the colorful weathered strata exposed in the various outcrops -- largely sedimentary, with a few periods of volcanic ash mixed in to hold it all together. It has variously been an inland sea, a lake, a rain forest, and now a desert. In the pluvial times, it had abundant wildlife, dinosaurs of the land and of the sea, some of which are still preserved as the random fossil. At some point between the rain forest and the desert, the surrounding continent underwent major changes, and the sediment beds experienced compression under the colliding pressures from opposite directions. Once horizontal strata now form great sine waves of rock -- alternating anticlines and synclines -- now exposed by erosion.
This area is most famous among geology students for the Barstow Syncline, as in the photo above. Imagine holding a sheet of paper horizontally, one end in each hand, then moving your hands slowly together as it forms a wave. Now imagine only seeing one of the downward periods of the wave, the rest having eroded away or still encased in a mountain -- that part is a syncline. The Barstow Syncline is a very obvious structure, largely because it is so fresh -- very little else has happened this rock. After seeing this, everything in Rainbow Basin looks like a syncline or anticline. Like this:
( Read more... )
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| 300 (Spear|Main), San Francisco, California. |
[29 Mar 2006|08:37pm] |
Remember the construction site with the old ship? Well it's progressing. The remaining half of the ship is still buried under Folsom, behind the concrete wall, near the spotlight and scaffolding just right of center. The elevator shaft under construction in the left back corner will eventually be the center of The Infinity Tower II, 35 stories tall. It will be the shorter of this particular pair of residential towers -- all part of a large forest in the works for the continued yuppification of the new "South Beach" neighborhood. (Isn't it great that all these buildings like to say that South of Market and South Beach are "the height of urban living in San Francisco"... totally ignoring that (a) these neighborhoods are becoming nothing but really tall suburbs; (b) you can find plenty of real urban living in, well, the rest of San Francisco?)
The excavation went down about twice as far as I expected. (It's going to be parking, I hope-assume.) The crane they erected of course required a large crane of its own: with all counterbalancing, that crane weighed enough to make the asphalt on Main St subside and a huge crack to form (it's been patched, but I really hope they plan on entirely resurfacing that street once they're done playing). They still want to be ready to start pre-selling in May (meaning not that the building has to be done, but that it does have to generally resemble some place a human would want to live), which means they've had to ignore one of the wettest winters in SF's history, and work day and night. I'm sure the pay is more enjoyable than the work.
It's amazing to think about all the human energy that goes into a project like this (and it's a pretty small project in the grand scheme of real estate development). Finding and acquiring the right lot, raising money, designing the building / "lifestyle", lobbying for permits, lobbying for community support, etc -- not to mention the actual construction effort.
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| Ivanpah Valley, Nevada/California. |
[05 Feb 2006|04:14pm] |
Ivanpah Valley from old Ivanpah settlement; Stateline/Primm, Nevada at base of mountains on left
Las Vegas' current commercial airport ([[McCarren]]) is projected to be over-capacity in a couple years. In addition to building another terminal at McCarren, they've determined they need a second airport.
About two years ago, Nevada's Clark County purchased the majority of this valley (including the dry lakebed which fills most of the valley) from the BLM[1], for about 20mln USD. They're looking to have the first flights from the tentatively-named [[Ivanpah Valley Airport]] in 2017.
I decided to visit the valley, just to make sure I saw what it was like before it became one of the country's busiest airports. As Chris says, it's only a few miles from the popular Cima Dome area of Mojave National Preserve. The place will never be the same.
Why Ivanpah Valley? Well it's "close", in suburban America terms -- it's only a 40 mile drive from Las Vegas. It's initially going to be for large, mostly international flights "where the passengers will not mind an extra hour of drive time". Long term, they are, of course, planning a monorail. That is Nevada's solution for everything now -- even Stateline/Primm, a town with three casinos, an outlet mall, and nothing else, has a monorail to cross the freeway (though with the airport moving in next door, that monorail might just get extended all the way to Las Vegas).
Instead of essentially stealing part of California (airspace and pollution-wise), they could have gone to some other area around Las Vegas, but it's tough finding space for airports in Nevada. There is tons of restricted airspace, due primarily to alien autopsies, Apollo moon landing simulation, and flying saucer experimentation.
I hate to admit that I will probably find entertainment in watching A380's full of Europeans land in the middle of nowhere in the Mojave, but mostly in that the-world-is-so-fucked-up sort of way. But that's Las Vegas.
[1] The Bureau of Land Management is basically the default owner of all of the United States. If you own land in the US, it was at some point purchased from the BLM, either with actual transfer of money or through assumption (via the widely-accepted squatter's rights prior to the Homestead Act). Most important to this part of the country was the Mining Land Act, which was basically a Homestead Act for metal mining claims. (The BLM is not to be confused with the other Department of Interior divisions like the National Park Service and the US Forest Service. Those are protected lands (to varying degrees), as opposed to BLM land which is mainly just 'administered' -- which just entails making sure it doesn't entirely burn during wildfires and selling it to the highest bidder at the approval of a congressman.)
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| Wheeler Ridge, Kern County, California. |
[31 Jan 2006|11:06am] |
As you drive south through the ever-boring San Joaquin Valley, the flat valley suddenly becomes very steep above 70 miles before Los Angeles. To the left, through the smog, are the southern Sierra Nevada; to the south and east, the Tehachapi; to the south and west, the San Emigdio; to the far west, the Coastal Ranges. In the foreground between the last two is a series of small hills, awkward and severely broken. This is Wheeler Ridge. The overall structure is that of an anticline[1] -- the top half of the sine wave of folded rocks, a hill with young rocks on the outside and older inside. (Some times the younger rocks at the crest of an anticline erode, leaving a structure with younger rock layers angling towards each other, but older strata exposed at the top.)
Anticlines are well-loved by the petroleum industry. The theory goes that oil is seeping up all over from (the direction of) the center of the earth -- much of it, in fact, ends up evaporating. Oil deposits, then, are discovered where that seepage is trapped, due to hard, impermeable rock layers (as opposed to the somewhat porous layers of whence it came). In flat areas, the layer where the oil is trapped could still allow it to flow horizontally[2] and hence not become entirely trapped. But when other structures exist, the oil becomes trapped in all directions, and a deposit develops. In anticlines, the deposit forms in the arched ceiling of the fold.
The industry refers to the Wheeler Ridge anticlinal deposits as the North Tejon Oil Field -- the field office is on the right of the photo. Shallow oil was first discovered here in the 1920s, and deeper oil in the 1950s. As can be imagined by the sharp edges, there is still movement going on[3]. In addition to the Wheeler Ridge fault spanning the hills, there are also two transform microfaults running across the photo, one forming the Wind Gap and another forming the smaller Water Gap (where the California Aqueduct passes through).
I came across an interesting article this morning: How They Find The Oil, published in a 1966 edition of a magazine from Saudi Aramco (previously Arabian American Oil Company). Most of the article is more detailed, but this opening is entertaining:At the present moment there are over 25,000 "explorationists" roaming six continents in an unremitting search for oil. They include geologists, geophysicists, paleontologists, mineralogists, stratigraphers, geochemists, hydrologists and many other specialists. Also today there are proved world-wide oil reserves estimated at about 350 billion barrels already located underground. This would be enough to last more than 30 years—at the present rate of consumption. But oil economists, looking into the future, predict that consumption rates will not remain steady. Taking into account population growth, heightened economic activity, rises in the overall standard of living, as well as increased use of petroleum in petrochemicals, new protein food additives and other products, they foresee continuous growth in demand. The growth numbers were a bit larger than they projected, and their mention of petroleum-based protein additives scares me. But I like the assumption that "more than 30 years" is basically forever, so why not base your entire society on it?
(Sorry for all the photos in this post being crap. I just got a new camera last week and it ended up set badly from when I was messing around with it a few days earlier, and it didn't show up on the LCD preview of course. In conclusion, "ISO 1600" is grainy.)
[1] A glossary straight from the horse's ass.
[2] Simplification!
[3] Lots of "recent" faulting has caused lots and lots of sharp edges; the San Andreas fault system is viewable here simply as the fantastic almost-cliffs that separate the San Joaquin Valley from the Los Angeles area.
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| Rhein-Main Air Base, Frankfurt am Main, Germany. |
[02 Jan 2006|08:13pm] |
Passenger (pax) terminal at Rhein-Main Air Base
[[C-5]] on the loading ramp, runways 7/25 and the commercial terminal in background
[[Rhein-Main Air Base]] was formally established at the close of World War II and had become something of a legacy for the United States and the Air Force in the sixty years following -- a reminder of the War, and of Allied victory, but also a sort of extended American embassy (however ominous that may be). It brought many, many Americans to Germany, and sent a good number of those off to war and related policing initiatives.
Way-back-when, the US/NATO agreed that eventually the base should be handed back over to Germany, to demonstrate that yes, we really do regard you as sovereign now. This was supposed to have happened around 2001, but then the US decided to have wars again, so that agreement was sorta forgotten. They did, however, try to avoid using Frankfurt when they could, and, for example, significantly expanded the US presence at [[Rammstein]] (which before, I think, was kind of a pathetic air base, but I guess didn't fall under the hand-over agreement because it's not a WWII-leftover).
The Air Force ceased operations at Rhein-Main Air Base last October, and last Friday (30 December 2005) they finally handed over the keys to the Frankfurt Airport Authority. (Thanks to rezendi for the heads-up.)
The base shared runways with Flughafen Frankfurt am Main, Germany's largest airport (see this image, with the commercial airport on the top of the runways and the military base on the bottom). They're going to demolish (the sign on the building says "Scheduled for demolition 2006") all the old air base facilities to build a third passenger terminal and new maintenance hangars large enough to house the ridiculous [[A380]].
I didn't know any of this until I arrived there last February, and everyone was talking about the closure. The place was sort of falling apart. Since it'd been doomed for so long, I'm not sure it had much of a maintenance budget. (For example: the pipes in the men's restroom in the pax terminal had pipes leaking inside the wall, and it had seemingly been like this for a while -- they'd brought in a couple of oscillating fans instead of fixing the pipes.) It's all very boxy, very industrial, very much how you'd expect a low-cost facility built in the 1940/50s to look.
( more personal )
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| Granite Pass, Mojave National Preserve, California. |
[25 Dec 2005|04:27pm] |
High clouds over van Winkle Mountain
Granite Mountains
I decided to continue the tradition I started last year of making a point to be somewhere nice for sunrise on December 25th, a holiday which I don't celebrate in any other particular way.
The original plan was to walk up Kelso Dunes, which are notoriously beautiful at sunrise and sunset, but I hadn't gotten enough sleep, and even more importantly, I'd forgotten to get gas before I left civilization and getting to the dunes would have significantly risked running out at some extremely inconvenient point (ie, any point). What I'd neglected to remember was that pretty much everywhere around here is beautiful at sunrise.
Others on: flickr, or my gallery (including older snapshots).
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| Hunter's Point Generating Station, San Francisco, California. |
[07 Nov 2005|11:55pm] |
PG&E's Hunter's Point generating station seems to have been reviled by the residents of San Francisco since its construction. It's a visual and environmental blight in a neighborhood that already seems unfairly blighted. At least since 1998, the opinion has been unanimous that the plant needs to go -- it's the phase-out schedule that no one can quite agree on.
The plant no longer operates on a regular basis -- it is a 'peaker' plant which is only operated when the grid needs it. In all of California's power problems over the last few years, it's been easy to get the message from the politicians that our power problems are entirely about generation. It really is easy to believe that, and it really is true that if you compare the load versus the generation, there is a shortfall. But lack of generation rarely causes the infamous "rolling blackouts". The problem is regional transmission capacity. The 'pipes' sometimes aren't big enough, or even more frustrating, they're in the wrong places.
Distributing anything into San Francisco is tricky -- it is a city that (like most cities) tends to consume vastly more than it produces, and that is fundamentally hard to get to (it's at the tip of a mountainous peninsula[1]). The Hunter's Point plant and its sister Potrero generating station are the only source of power the city has within its borders; the rest comes up the peninsula through a small number of large transmission lines. Unfortunately those lines do not (yet) offer the capacity to fill transmission gaps to meet CalISO's standards, so they (CalISO[2]) require the HP and Potrero plants to be available, despite the agreement that they be shut down.
Half the HP plant's generators are permanently decommissioned -- this occurred a few months before I took these pictures a year ago. The shutdown of the other half is waiting on the completion of nine new transmission lines to increase capacity into the city. That is, instead of generating electricity when the capacity into the city is too low to meet demand, they will just not run out of capacity (we hope). In the ISO algebra, this works out.
The Potrero plant a couple miles away is staying, though. During the debate over the Hunter's Point plant's future, the Potrero plant (which is not owned by PG&E) underwent emissions upgrades (giant catalytic converters!, etc) to avoid the HP plant's fate. Up until then, they'd been able to stay in environmental compliance only through liberal use of the law that allows dirty plants to literally buy the right to pollute from other, much cleaner plants that otherwise "underpollute"[3].
More: the 115kV line to connect the terminations at the HP substation to the Potrero substation, the 230kV Jefferson-Martin line to increase the capacity available to entire peninsula, an old, but still useful article, including a rough substation map of the peninsula.
[1] A point made all the more painful by the rest of the peninsula being run by different counties, one of which is the infamously isolationist County of San Mateo, who basically single-handedly ruined any hope the Bay Area had for good, unified regional transit by refusing to participate in BART and any other regional project. Santa Clara County to the south has always wanted to participate, for example, but because a direct rail link with San Francisco would need to pass through San Mateo, the cost to connect them (via a indirect route) has so far been prohibitive (though it has been in the "planning" stage for twenty years now). (San Mateo did however make the concession a few years ago to allow BART to pass through their county in order to connect San Francisco with its exclave San Francisco International Airport, which sits in the marsh off the County of San Mateo.)
[2] The California Independent System Operator. The "system" is the state's power grid (transmission network), the "independent" refers to their role as a third-party overseer who neither buys nor sells power, and the "operator" refers to their ability to be bureaucratic jerks whenever they feel like it.
[3] This has always been one of my favourite laws of all time. So absurd!
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| Apache Trail (AZ-88), Superstition Mountains, Arizona. |
[25 Oct 2005|09:04pm] |
The superstition around the Superstition Mountains is never-ending. The most famous myth is the long, silly story of the Lost Dutchman's Mine. Another (related, and even sillier) myth is that of the Peralta Stones.
Yet another myth is that the Superstition Mountains (Weaver's Needle in particular) are volcanic necks: when some volcanoes go dormant, the last bits of magma that would have been expelled remain in the network of tunnels that brought them there (the magmatic system), thus hardening and remaining in place. These would then be more robust than the rest of the volcano and would be the last part to erode. These things do happen. There are volcanic necks elsewhere in the region -- most famously, Shiprock in the Navajo Nation. But this, just like the Dutchman's gold, is too ridiculous of a story. Such orogeny would prescribe that the column be entirely consistent in composition, but you can pretty clearly see several different layers in these mountains. They are, in fact, just erosional leftovers; pieces of rock that through some chaotic chance, didn't get eroded[1]. This is far more common and likely than the volcanic neck theory.
But they are volcanic. Between 17 and 21 million years ago, there was a 30 mile wide caldera here, which greatly afflicted central Arizona, including the area that is now Phoenix. It spewed rhyolite and ash everywhere, many meters thick in places. Like here, for example, in this big whitish strata overlooking Canyon Lake[2] to the northeast of the once-caldera:
Obviously there's been faulting going on -- which there's been a lot of ever since the San Andreas decided to start this whole Basin and Range extensional business a couple dozen million years ago.
[1] The rocks look "cut up" and fractured because of calcreting, which I'll post about later.
[2] Part of the water reclamation system that supports the Phoenix metropolis.
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| Little Painted Desert, Navajo Nation / Arizona. |
[11 Oct 2005|09:03pm] |
nibot posted a few days ago about his starlight walk up Mount Sinai, which, among other things, made me think of one of my favourite photographs. It's hanging at Sabuddy, an Israeli restaurant in Tempe, Arizona; it's a very simple image of the barren badlands, somewhere, I assume, in Israel. Thinking about badlands and Arizona of course got me thinking about the Painted Desert.
This is not the Painted Desert. That's technically north of here. This is the Little Painted Desert; it's not a National Park, and is barely a park. It's about ten miles off I-40 near Holbrook, on the border of the Navajo Nation. It is little, I suppose, but it is also totally devoid of humans, and can be appreciated in silence.
Several parts of the Colorado Plateau are covered in badlands terrain like this. Their origin is in easily-eroded deposits (clay, claystone, mudstone, etc) that were then, post-fluvially/post-lucastrinely (river/lake), exposed to a very dry climate with infrequent but extremely heavy rainfall (such as pretty much all of the southwestern US). Flash flooding causes deep erosion, forming gullies and ravines. (The Arabic term wadi probably best describes this sort of water flow.)
The lack of vegetation comes from the high clay content of the soil. Clay can absorb a lot of water, and expand while doing so, but as it dries, it sort of evaporates more than consolidates -- it has trouble returning to its old size when the water goes away. Cracking and the general instability when drying cause it to erode quickly through the omnipresent force of wind (if you've ever been on the open plains of the Plateau, you can probably recall how it almost feels like it could erode your skin if it wanted to). The time right after a big rain is the most important time for a seed attempting to grow in the desert; even low-moisture desert plants require a lot of water during germination, and it's very important that they germinate and reach a decent size before they're forced to go into low-moisture mode. Since in the badlands areas, the ground is busy literally blowing away during this key time, it's pretty impossible for anything to grow. If the soil is very high in clay, it can be impossible for anything to grow for purely chemical reasons: water binds readily to clay particles, preventing the water from being used by plants. (This property of clay also causes it to form a sort of protected barrier, which makes it useful as a liner in landscaping and landfills.)
In a few places, flat-topped buttes have formed (such as in the background of the second picture). This is due to a harder rock layer withstanding erosion better than the surroundings. Generally, and particularly in this region, these are ash deposits from the nearby volcanoes, or perhaps even basalt flows themselves.
Although defined by severe erosion, badlands also harbour some of the best fossils. The water stays in the paths of the gullies, leaving the sections in between totally dry and preserved. The badlands in South Dakota are particularly famous for this, and the (real) Painted Desert in Arizona less so. (Though it has lots of fossilized ("petrified") trees, which are something else altogether.)
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