Desert Skies, Hoodoos, and Really Big Rhyolite Explosions: An Innocent Abroad in Phoenix

Some places I don't know very well in the geological sense, and this makes no sense, because I've been in Phoenix a lot over the years. Oh, I glance at the guidebooks, but invariably my brother will get up and say "let's go explore (fill in a feature in any direction from Phoenix)", and it will be some corner of the landscape I've never seen or read about. And so it was that we headed southeast last week towards the towns of Superior and Miami. The legendary Superstition Mountains rose to the north, and we ended up driving through the heart of the Pinal Mountains.

The Superstitions are the home of the Lost Dutchman Mine, which was not exactly lost, and no Dutchman was associated with it, but people look for it anyway. I have a strong feeling that it was found a long time ago, and was mined under a different name with no one the wiser. There wasn't a lot of mineralization up high in the mountains, but a fair amount around the margins, and those areas were exploited a long time ago.

Copper was another story. Vast deposits have been found throughout the area, and Superior, Miami and Globe grew with the mines. I liked the street sign in downtown Superior (below). Magma was the name of one of the mines in the area. Still, it would be nice to see more geologically themed street names in my local town...

We drove east of Superior into the Pinal Mountains and soon encountered some very rugged territory. Although I was ignorant of the fine details, I quickly recognized that we were in the vicinity of some heavy-duty Neogene rhyolite calderas (that's "supervolcanoes" for the Discovery Channel writers). There were at least five calderas in the region. Each one was capable of producing massive explosive eruptions of hot ash in volumes exceeding 100 cubic miles. The pink rocks forming the cliffs around us are called rhyolite tuff which formed when the hot ash hit the ground and re-melted, but quickly cooled and solidified into rock.

I never get tired of photographing the saguaro cacti that are endemic to this region of Arizona. They seem to have unique personalities, if plants can have personalities.

The pinnacles of rock formed as the ash cooled and contracted. The ash flow had to shrink and so formed myriads of fractures, often at angles of about 120 degrees. The fractures provided avenues for water to get in and weather out the rock, often by freezing and expanding.

The towering pinnacles are sometimes called hoodoos. The slopes are exceedingly rugged, and the highway required a tunnel to get through the narrowest part of the gorge.

We took a deserted back road to try and get a view down into the Pinto Valley Mine, one of the region's gigantic open-pit copper mines. We only got a partial view of the upper terraces. Operations have restarted in the last year or two, with copper and molybdenum as the main products.

And then there were the skies over our heads. The clouds were diverse, with a beautiful band of mare's tails off to the west. It looked like sunset would be interesting...

It's winter, so ice crystals make up the clouds. When the sun hits the crystals just right, a prism effect produces brightly colored sun dogs. I've seen lots of sun dogs over the years, but I've never noticed the ray that runs beyond the sun dog away from sun itself (to the right in the photo below).

The sun was getting low in the west, so we headed back down the highway to the vast valley containing Phoenix and its many suburbs. The canyon nicely framed the setting sun.

As we rolled down the slope towards Florence Junction, the haze in the valley gave the low hills in the distance a mystical appearance.

What a beautiful day it was.

Out in America's Never Never: Desert Water...Gambling with 30 Million People

This water is flowing in one of the driest places in America (and naturally, too)

Water. Nothing in the world makes you appreciate it more than not having it.

In the desert, water is the factor that decides life. An organism adapts to the lack of it, or that organism disappears. The plants of America's Never Never either store it, have deep taproots, or they wither and die until the next flash flood. The animals either live near the few precious springs, or get their water from the plants that they eat.

Source: http://en.wikipedia.org/wiki/Colorado_River

The region between the Sierra Nevada and the western edge of the Colorado Plateau includes some of the driest landscapes in the world. Nearby Death Valley averages 1 or 2 inches of rain per year, and in some years receives none. The most it has ever received was 4.5 inches or so.

One single thread of water winds its way through this parched land. From the Wind River Range in Wyoming and the Colorado Rocky Mountains, the Colorado River gathers the snow melt from countless high mountain ridges and flows for 1,450 miles through one of the driest environments on the planet. In the five million years that it has existed in its present course, the river has excavated untold cubic miles of rock, filled in the huge delta at the head of the Gulf of California, and filled numerous hidden groundwater aquifers. Only in the last 100 or so years has the river been altered from this condition, due to the intervention of a unique new species on the planet. We have changed everything about the river and the balance of water use in the region. But for how long?

We spent a day traversing this dry landscape between the Mojave Desert and the edge of the Colorado Plateau near St. George, where we got a sense of just how dry this land is, and also how we have altered the balance of water use in the region. Our stops included the aptly named Valley of Fire State Park, and Lake Mead National Recreation Area.

The red sandstones of Valley of Fire are called the Aztec Sandstone, a Jurassic layer that is related to the Navajo Sandstone that makes up much of the scenery on the Colorado Plateau. Here in Valley of Fire, the rock has been jointed and fractured, and spheroidal weathering has turned the rocks into a wonderland of jumbled rounded boulders. The rocks were caught up in a compressional event in Cretaceous time called the Sevier Orogeny. Older Paleozoic rocks were pushed up and over the Aztec along a series of thrust faults. When the Colorado River established its present course, headward erosion along the tributary streams (in this case, the Virgin River) exposed the deeply buried rocks.

Water was available along the Virgin River, so Ancestral Puebloans and other cultures have lived here for thousands of years. They left a visible record of their existence in the form of petroglyphs in the desert varnish that covers many of the rocks. Their villages were small, in keeping with the limitations imposed on them by the lack of water.

Hoover Dam and Lake Mead

Contrast the existence of these small villages with the huge metropolis of Las Vegas. Or Phoenix. Or Los Angeles. For in the same way that the Virgin River made a small villages possible, the Colorado River allowed huge cities to exist in the desert. Phoenix survived for years with groundwater, but the water accumulated in the ice ages, and can never be replaced. A water table that began at a depth of 30 feet now lies hundreds of feet lower. The Central Arizona Project allows Phoenix to put a big straw in the Colorado River and draw out large amounts of water. Los Angeles got along with water they accessed (stole) from the eastern Sierra Nevada and Owens Valley, but they grew too much and needed more. Canals draw water into the Imperial Valley and further towards reservoirs that ring the L.A. Basin. Las Vegas is the most dependent; groundwater provides only 15% of their water. The rest comes from the river's big storage facility, Lake Mead. To their credit, they put some of it back. A permanent river with a constant flow of thousands of gallons per minute flows from their water treatment plants back into Lake Mead (remember, downstream users, you get what Las Vegas flushed away!). None of the river's water flows into the Gulf anymore.

Photo by Mrs. Geotripper

We stopped briefly at Callville Bay (in part to "add" some water back to Lake Mead), and were shocked to see the problem that faces these cities, and all the other stakeholders in Colorado River water. All the white, bleached area in the photo above is supposed to be under water. It hasn't been underwater in a long time, due to a horrific drought that has gripped the region for the last decade (and the drought continues). Lake Mead has dropped to historic lows, less that 50% of capacity.

Lake Mead is the largest reservoir in the United States, holding around 28 million acre feet of water, equal to two years of "normal" flow for the Colorado River. The reservoir is perilously close to "dead pool" level where it won't be able to generate hydroelectric power. What happens when the water runs out?

Photo by Mrs. Geotripper

At Valley of Fire, we were amused by the antics of the small Antelope Ground Squirrels. When they got too hot, they buried themselves in the sand to cool off.

Unfortunately, we don't have the choice of burying our heads in the sand. We take for granted that we turn a knob and water comes out. It may not always be that way. The inhabitants of the American Southwest have some hard decisions coming as global warming continues to change our environment.

Oh, the dog in the opening photo? It's cooling off in Rogers Spring, one of the natural springs that flows out of a fault zone on the north side of Lake Mead near Valley of Fire. There is a bit of water to be found even in the driest places.

Searching for the Lost (not actually lost) Dutchman (not actually Dutch) Mine: What a blast, literally

I've been to Phoenix quite a few times over the years, but somehow until last week had never taken Highway 88 to one of the most familiar sights in Arizona, the Superstition Mountains, home of the fabled Lost (not actually lost) Dutchman (not actually Dutch) Mine. It's probably fair to say that I wasn't trying very hard to find the legendary gold mine. I was having too much fun drinking in the stunning scenery and enjoying the fact that I was standing under a massive caldera ("supervolcano" in popular culture).

The Superstitions are...abrupt. The sheer cliffs are fascinating; they are composed of volcanic rocks that once made up the core of a vast caldera complex not unlike Yellowstone. Several massive explosions rocked the region, and so much ash was blasted out of the magma chamber that the chamber collapsed in on itself, forming a series of vast 'craters' 10-12 miles across. The calderas of the Superstitions are 15-25 million years older than Yellowstone, are extinct, and have been deeply eroded. The high peaks and spires were once part of the resurgent dome of the caldera.

As we drove east we reached the marginal area of the caldera, where vast blocks of tilted ash and tuff are exposed in deep rugged canyons. Highway 88, the Apache Trail, winds upwards from the Phoenix suburbs to a series of three reservoirs that were constructed a century ago to provide dependable water supplies for the vast city (it wasn't enough, though). The reservoir below is Canyon Lake, the lowest of the three. Thick rhyolite flows form the bold cliffs.

By the time we reached Fish Creek Canyon, the landscape had attained an other-worldly appearance. It seems just like the kind of place that one could hide...a secret gold mine! The Lost Dutchman Mine is the stuff of legend, as in it is probably more legend than fact. The Dutchman wasn't lost for one, and he wasn't a Dutchman, he was German. And as far as lost mines...the old miners left little to chance. There isn't much mineralization in the rhyolite tuff exposures, and since a few gold mines were developed around the margins of the old caldera, I'm willing to bet that the Jacob Waltz's mine was found long ago. But that's taking all the fun out of it, I guess.

Gold just doesn't grab me the way the imagination does...I stood among these rocks reliving the vast explosions that rocked this place, protected by the safe distance of time. Imagine an explosion so big that it incinerates all life for miles in all directions, a blast 500 times larger than the eruption at Mt. St. Helens in 1980. Imagine watching as the crust gives way and falls for one or two miles into the void. Imagine watching as the dust slowly clears away to a new and vastly changed landscape that will be void of life for years. Imagine as the volcanic activity in the caldera declines and ends, and over millions of years, the rocks are exposed by uplift, mountain-building, and erosion.

What an incredible place! Thank you dear brother and sis-in-law for the great trip!

Dispatch from the Road: Life Can Change in an Instant

The sky turned yellow and dark today in Casa Grande, Arizona, near the metropolis of Phoenix. A major winter storm was blowing through the desert, and as we left Tucson the wind was already whipping up. By the time we reached Picacho huge billowing clouds of yellow dust obscured the freeway. It was a dangerous day on the road. A chain reaction accident involving 13 cars and 9 trucks killed three and injured many others. A fire had started, and when we passed the scene a few hours after the crash, the trucks were still smoldering. A second chain reaction involved a dozen cars or so, and happened only a few minutes ahead of us on the highway. It was a stressful day for us, and a tragic day for some. My heart goes out to those who lost family members in the accidents.

Dust storms are a normal phenomenon of deserts, but they are made worse by poor agricultural practices and droughts. According to news reports, the worst dust of this particular storm was the result of plowing in nearby agricultural fields. I find myself wondering if the agribusinesses take high winds into account when they plow potentially dusty dry fields near major transportation corridors. A sign on a highway warning of dust is too easily ignored, and does not absolve those responsible when things go terribly wrong. This sort of tragedy is too common in the Phoenix region, as well as back home in the Central Valley.