Journeys in the Back of Beyond: Wait, This is a National Park?

 

Pack up your stuff kids! We're going to a NATIONAL PARK!

Cool! Does it have big mountains?

No.

Oh, does it have deep canyons?

No.

Can we go swimming in a lake or river?

No.

Oh, will rangers give an interesting talk around a campfire?

No, there's no campgrounds.

Does it have trees at least?

Well, yeah, but they're all dead.

What kind of a national park is this???

It is of course the national park dedicated to a bunch of long dead trees, Petrified Forest in Arizona. It was the third day of our recent exploration of the Back of Beyond, the vast geological wonderland of the Colorado Plateau. We had traveled east of Flagstaff to explore the prairies and badlands that make up much of that strange landscape. 

To most folks it's all about the petrified wood. Some might even think it's a one-note kind of place, of some interest maybe, but not worthy of a full exploration. They couldn't be more wrong! The park is a showcase of geology, archaeology, and paleontology. And it has some unique and dramatic scenery to boot.

The wood was discovered first by indigenous people thousands of years ago (evidence indicates a human presence in the region for at least 12,000 years). They made use of the petrified wood as projectile points, knives, scrapers, and even building materials (there is a reconstructed pueblo in the park made almost entirely of the agatized wood).

Petroglyph at Newspaper Rock in Petrified Forest National Park

The European colonists who always get credited for their "discoveries" came along in the 1850s. The military investigated the region first, followed by ranchers and homesteaders. The area became better known as railroads were built through the region, taking advantage of the relatively flat terrain and availability of water along the Puerco River. A hotel stop at Adamana allowed passengers to tour what was then known as Crystal Forest, and walk off with tons of petrified wood samples. Later on a stamp mill was constructed to grind up the wood to be sold as an abrasive. It concerned some people.

Often the creation of a national monument, which can be established by presidential proclamation, is a controversial affair. Such actions were taken by presidents to protect endangered resources and archaeological sites that locals were often profiting from. It's only as tourism follows that proclamation that local folks begin to accept the presence of a monument in their midst. The story seems to be somewhat the opposite in this case, as the Arizona legislature unsuccessfully proposed a Petrified Forest National Park as early as 1895 in response to local concern about the disappearance of vast amounts of petrified wood. The passage of the Antiquities Act in 1906 gave Theodore Roosevelt the power to designate Petrified Forest as the nation's second national monument that same year. Congress waited until 1962 before "upgrading" the monument to national park status (monuments have the same level of protection that national parks do, although funding sometimes lags behind). Subsequent actions in 2004 more than doubled the size of the park to 341 square miles (884 sq km). 

Despite the protective actions, it's estimated that 12 tons of petrified wood disappear from the park every year (the thieves need to read up on the curse of stolen wood). It's ironic that so much is stolen, since it can be purchased legally just outside the park.

Being petrified is not the normal fate of most trees. Most of them decay and are destroyed, but in just the right circumstances petrifaction can happen. The tree has to be isolated from the atmosphere and destructive microorganisms by being buried quickly in fine mud and clay. There needs to be a source of silica (silicon dioxide), and the movement of groundwater. At Petrified Forest, the trees were ripped from distant forests by muddy flashfloods and volcanic mudflows and transported many miles, coming to rest in river floodplains and swamps. Layers of volcanic ash provide the silica and the swamps and rivers provide the groundwater. Over time the silica fills in the cells of the wood, preserving it. Oxides of iron and other metals provide the bright coloration.

But that's not what I'm really here to talk about!

The real value of Petrified Forest National Park lies in the story contained in its multicolored strata, the Chinle formation. It records a tumultuous period in Earth's history, the middle to late Triassic Period from about 225 to 208 million years ago.

When the Chinle formation is exposed to the elements, the mud and clay is easily and quickly eroded, preventing the development of soil and inhibiting plant growth. The resulting barren desert badlands hardly look like the remains of a tropical environment of large rivers and lakes, but that is what it is. And those barren sediments hide a wealth of paleontological remains (that's short for "fossils").

Exposures of the Chinle formation in the northern portion of the park

The Mesozoic Era (252-66 million years) is often called the Age of the Dinosaurs, and of its three periods, the Jurassic is best-known (perhaps because of a certain film series), and the Cretaceous only slightly less-known, since no one ever made a movie called "Cretaceous Park". It did however gain notoriety as the ending curtain-call on the reign of the diverse and occasionally gigantic reptiles, due to a massive asteroid strike in what is today the Gulf of Mexico.

But the Triassic Period gets less attention. There are few if any dinosaurs from the Triassic in children's plastic toy collections, and yet the Triassic is the period in which the dinosaurs appeared on the planet for the first time. Few of them were large, and they didn't dominate their habitat the way their progeny in the Jurassic and Cretaceous did. There were other creatures inhabiting their world, all of whom were survivors of the greatest extinction event ever to strike our planet. And from within their ranks the first mammals emerged.

The Permian-Triassic mass extinction event was the worst devastation ever visited upon life on planet Earth, wiping out as much as 80-90% of existing species. The cause is not precisely known, but a vast outpouring of lava and ash in Siberia is thought to be a main contributor to a sudden change in the climate that caused a spike in temperatures and acidity in the oceans (carbon dioxide rose from 400 to 2,500 ppm, compared to our current historical rise from 280 to 420 ppm). A total break-down in ecosystems followed, both on land and at sea. It took millions of years for the survivors to rebuild any kind of stability (only to be disrupted again at the end of the Triassic).

And this is why Petrified Forest is so important. It gives us a picture of conditions in the middle and late part of the Triassic when some semblance of stability had returned to the world. The Chinle formation, which is exposed over most of the park, has yielded up to 200 species of plants and around 60 species of animals. Nearly a hundred of them were first discovered at Petrified Forest National Park.

The Triassic world looked little like the subsequent Mesozoic era. The Jurassic and Cretaceous periods saw the dominance of terrestrial habitats by hundreds of species of dinosaurs big and small, plant-eaters and meat-eaters alike. Mammals and smaller reptiles scurried in the underbrush while small amphibians continued to thrive in rivers and streams. 

Diorama of animals and plants of the Chinle formation, Petrified Forest National Park

The Triassic was characterized by several animal groups that competed with each other in the aftermath of the great Permian extinction. There were still large predatory amphibians up to 10 feet long, including Metoposaurus. Many years ago, one of my students found an odd specimen in the Chinle (outside the park, for the record). It looked so odd that my guesses ran the gamut from coral to alien, but it wasn't until I saw this exhibit at the park museum that I thought of Metoposaur (see a picture here and here). To be fair, some paleontologists thought of phytosaur scutes as another possibility (see below).

There were some "not-quite-reptiles" called therapsids that were once called "mammal-like reptiles" but they actually represent a distinct group of organisms that shared a common ancestry with the reptiles. They were destined to become the ancestors to the first mammals later in the Triassic. In Permian time, the Therapsids and their related groups dominated terrestrial environments with hundreds of species, but they were decimated during the extinction. A few survived into the Triassic, including the Placerias hesternus, seen below. It was a plant-eater which at up to 11 feet and a ton in weight, was one of the larger creatures of the time.

Placerias hesternus, a dicynodont therapsid, a large plant-eater

The pterodactyls made their first appearance (and no, they aren't dinosaurs either; they had a common ancestor with them). There were in fact some dinosaurs too, but they were mostly small, and most certainly didn't dominate their ecosystem. Some found in the park, like Coelophysis and Chindesaurus, were predators but being 3 to 7 feet long they were hardly the gigantic terrifying creatures of the Jurassic and Cretaceous periods.

Artist: Dr. Jeff Martz, NPS

The creatures that brought terror to the ecosystem were the Archosaurs, the reptilian line that led to the crocodiles, birds and dinosaurs. The sediments of Petrified Forest National Park have yielded up specimens of Postosuchus, which at upwards of 23 feet in length, was gigantic by Triassic standards. It was a formidable predator.

Artist: Dr. Jeff Martz/NPS

Another member of the archosaurs found in the park are the Phytosaurs. They strongly resemble the crocodiles, but are not that closely related. They are instead a marvelous example of convergent evolution, by which different lineages evolve to similar shapes (think sharks and dolphins).

Artist: Dr. Jeff Martz, NPS

Petrified Forest is far more than a collection of petrified wood pieces lying around. It's a very different world and a fascinating place to visit and explore. It's one of the best places in the world to understand the time that gave rise to the mammals, and as such, to us.

Airliner Chronicles: Stuck on a Plane with a Proselytizer...

And really, I felt sorry for the poor guy who was stuck sitting with me on the plane flight from St. Louis to LAX. Oh, I wasn't trying to convert the poor guy into some religion. No, he got the full-court press from me about the importance of understanding what was going on 35,000 feet below us on the ground. He was being proselytized into the world of geology.

People who fly a lot for whatever region may be forgiven for not paying attention to the grand panorama unfolding below them, but to a geologist, the extra dimension is pure gold. Seeing a large swath of the Earth's surface grants a whole new perspective to understanding geological processes.

I didn't have a working GPS on the flight, so I had to guess our location for the first two hours of the flight, somewhere over Missouri, Oklahoma, or Texas. But it was unmistakable that we were over oil and gas country. The drilling rigs and their connecting roads could not be missed. Some politicians once described the "footprint" of oil and gas drilling on a landscape as just a few acres being torn up. Seeing the scene from above suggests that the footprint is "small" in the sense that a spider web is a few strings of dragline silk.

I was lost until the mesas and plateaus appeared. I knew at that point that we were in New Mexico, and I correctly figured out that we passed Sante Fe and Las Vegas, New Mexico. My seatmate, a Pittsburgh resident, got a bit confused about the Las Vegas part; "We're in Nevada already?". I crushed his hopes (that is NOT the way to proselytize, by the way).

The landscape turned into a rainbow of color, and I suddenly knew our precise location better than a GPS unit. We had reached the Painted Desert area of Petrified Forest National Park in Arizona. A plateau covered by basalt flows was breached by erosion, exposing the brightly colored layers of the Triassic Chinle Formation. The Triassic rocks reveal the beginnings of the dinosaur domination of our planet, and the floodplain and river deposits contain some of the earliest dinosaur species known. There is the wood, of course, and a stunning variety of amphibians and reptiles, including Phytosaurs, huge crocodile-shaped creatures that exceeded 30 feet in length.

Just west of Petrified Forest, I got the finest treat of the day, a perfect view of Meteor Crater. I put the best of the pictures up in yesterday's post.

A short time later, more colorful rocks came into view, but they were older than the Chinle of Petrified Forest. We had reached the Pennsylvanian and Permian rocks of the Supai Group. These rocks are the same ones exposed in the walls of the Grand Canyon, about eighty miles to the north. This is the edge of the Colorado Plateau, where the high flat landscape gives way to the deep fault valleys of the Basin and Range Province. Because the valleys are so deep, erosion eats away at the edge of the plateau, forming scenic deep gorges like Oak Creek Canyon, north of Sedona.

I was distracted by some wildfires burning in the thick forests of the plateau. I finally realized I was missing one of the more extraordinary features of the Colorado Plateau, the San Francisco Peaks Volcanic Field. The field is a vast basalt lava plain populated by hundreds of cinder cones, and an immense stratovolcano that reaches more than 12,000 feet in elevation, the highest point in all of Arizona. The edifice of the San Francisco Peaks has been altered somewhat by erosion; it was once 4,000 feet higher. It would have been the highest point in the lower 48 states.

The existence of the volcanic field is somewhat of an enigma. There's no obvious reason for it being here. There are suggestions that it is the result of an incipient hot spot, but the idea is not wholly accepted. The field is active; an eruption took place less than a thousand years ago.

Somewhere near the end of the flight, my poor beleaguered seatmate asked a geological question. He was wondering why there was a gigantic hole in the ground that wasn't a meteor impact crater. It was an open pit mine, probably for copper. I almost had a convert to the ages of rock!

Dreams of Summer: This is Where and When...Wait, They Made a National Park Out of This?

Why, yes. Yes they did. About two posts ago, I pointed out that there are some places where the geology is kind of...monotonous. One of those places is the vast sage plain east of Grand Canyon and Flagstaff, around the towns of Holbrook and Winslow (yes, that Winslow). The land is flat, windy and barren, hardly looking like a place of geological inspiration. And yet it is.

In the last post, we were stuck in a wayward time machine, emerging in a nightmarish swamp and river floodplain populated by strange and frightening reptiles and other creatures. I asked for help in explaining where and when we were, and the readers responded quickly and accurately (strangely enough, a bunch of readers share the same name: Anonymous!). We had landed in the Triassic Period, about 225 million years ago, in Petrified Forest National Park, Arizona.

Barren plains may be uninteresting to look at and explore, but they make for great transportation corridors, and the land that eventually would become Petrified Forest National Park was the site of a road in the 1860s, a railroad in the 1880s, and a national highway (the legendary Route 66) in the 1920s. The petrified wood was discovered by surveyor Amiel Whipple and geologist Jules Marcou, during explorations in the early 1850s (discovered by Europeans, anyway; there are ruins in the park made hundreds of years ago out of petrified wood!).

Once the railroad was constructed, travelers began to visit the area, and many removed huge amounts of petrified wood. There was even a business at one time that was prepared to ground up the "wood" for use as an abrasive. Local people began to fear that the precious mineral would disappear, and they began efforts to establish a national park to protect the resource. The first effort failed in 1895, but the passage of the National Antiquities Act in 1906 led to the proclamation of Petrified Forest National Monument the same year (Congress can establish parks, but the President can proclaim national monuments). It wasn't until 1962 that Congress established the area as a national park. In 2004, the size of the park was more than doubled, to 341 square miles (884 square kilometers). Despite the legal protection, it is estimated that tons of petrified wood are stolen every year. This, despite hefty fines and the easy availability of petrified wood outside the park boundaries.

I called the park plain and barren, but that's not at all true. The rocks here have been gently lifted and erosion has exposed the underlying shale, siltstone and mudstone layers into rapidly eroding badlands. Metals in the rock have oxidized into a veritable rainbow of colors. The northern regions of the park are known as the Painted Desert. The rocks are almost exclusively part of a single formation, the Chinle, representing a complex of river channel and floodplain deposits dating from the Triassic. Variations in the rocks have led researchers to organize the rocks in the park into four members: Mesa Redondo, Blue Mesa, Sonsela, Petrified Forest, and Owl Rock. The Chinle (or equivalent rock) is found throughout the southwest. There are something like 50 members identified, and the precise definition of the unit is controversial. To get a sense of the conflict, check out this overview: http://chinleana.fieldofscience.com/2008/11/chinle-confusion.html 

Petrified wood is one of the prettiest of Earth's minerals and rocks. The wood was originally buried in mud and volcanic ash. As the wood slowly decayed away, it was replaced by silica (the mineral quartz, SiO2), and stained by oxides of iron, manganese, copper, and other metals. The trees, some of which reached heights of 200 feet, are classed into at least three species, and as many as nine. Araucarioxylon arizonicum is the most common, and as such has been designated as Arizona's state fossil.

It turns out that Petrified Forest National Park preserves far more than fossilized wood. The extensive exposures of the Chinle have provided not dozens, but hundreds of fossil species, and not just plants. The Triassic Period was a pivotal time in the history of the Earth. It was established on the basis of a mass extinction that wiped out some 90% of the species living on the planet. The extinction decimated the dominant reptiles at the time, the mammal-like reptiles, allowing a group of diminutive archosaurs to gain ascendance in the ecosystem. The archosaurs include today's crocodiles and birds, and some relatively famous animals called dinosaurs. The late Triassic deposits of the Chinle contain some of the earliest dinosaurs known, including Coelophysis and Chindesaurus bryansmalli, a small carnivorous dinosaur found for the first time at Petrified Forest.

The rich fossil record and incredible exposures of the rocks of Chinle provide an important look at a time when the planet was getting back into some kind of ecological balance after the greatest catastrophe of all time. Petrified wood was the original attraction, but the park preserves a significant part of Earth's history.

The protection of the park has revealed another important resource. The explorations of the 1850s were hardly the first incursion of humans into the region. The presence of a secure source of water (the Puerco River) and a prairie environment populated by numerous grazing animals meant that people have lived in the region since the end of the last ice age 13,000 years ago. The park preserves hundreds of archaeological sites, including the ruins of entire villages.

The 2004 additions to the park didn't add all that much in the way of wood resources, but it did include a significantly large area of badlands wilderness in the Painted Desert. It used to be that no camping was allowed in the park, but there is a trackless region in the northwest part of the park now where one can got lost in the past.

So yes, they made a park out of this. For so many good reasons.

It's One of the Most Spectacular Landscapes on Planet Earth: Come and see the Colorado Plateau in Person! June 11-26, 2015

For once I am not discussing a trip I have taken...I am talking about a trip that you can take.

Grand Canyon from Powell Point on the South Rim

I spend a lot of time on my blog trying to convey the sense of wonder that comes from exploring the wild places of the Earth. I have to say, though, that nothing comes close to the actual experience of being there, seeing the rock, hearing the wind and feeling the heat, watching the night-time skies, and walking within the ruins of villages of people who lived on this land thousands of years ago (and meeting their descendants in the region today).

Mesa Verde National Park in southwestern Colorado

The Colorado Plateau, encompassing parts of Arizona, New Mexico, Colorado and Utah, is one of the grandest geological showplaces on the planet, and at the same time it is an archaeological treasure. Our geology department is combining forces with our anthropology department to offer a unique course on the archaeology and geology of the Colorado Plateau and other spectacular sites in the American West. The courses (Geology 191 or Anthropology 191) will take place on June 11-26, 2015, beginning and ending at Modesto Junior College in Central California. The cost will be about $160 for registration (for California residents; out-of-state tuition is higher), and $850 for food, transportation, and camping and entrance fees. The only additional costs would be for laundry, showers, and souvenirs.

Wupatki National Monument and the San Francisco Peaks volcanic field

Although these two courses are directed towards geology and anthropology majors, our travelers will also include teachers, life-long learning participants, and anyone who is fascinated in the geology of this stunning region. If you are a science teacher, you will come home with a collection of photographs that illustrate most of the important principles of geology, and a selection of rocks, minerals and fossils that will make great classroom teaching tools (legally collected, of course; there are many localities outside of protected parks from which to collect samples).

Kashua-Katuwe National Monument in New Mexico

What will you see?

Six states: California, Nevada, Arizona, New Mexico, Colorado, and Utah.

Eight national parks: Grand Canyon, Petrified Forest, Mesa Verde, Zion, Pecos, Chaco Culture, Great Basin, and Yosemite.

Nine national monuments and preserves: Mojave Desert, Wupatki, Sunset Crater, El Morro, El Malpais, Kashua-Katuwe, Bandelier, Jemez Caldera, Aztec, Natural Bridges, Horseshoe Bend at Glen Canyon Dam, and many more state and tribal parks including the pueblos of New Mexico!

Horseshoe Bend on the Colorado River near Glen Canyon Dam

Sound interesting?

If you are in the Modesto region, we will have an organizational meeting on Monday, April 6, at 7:30 PM at MJC in Science Community Center 326 (West Campus). Previous experience in geology, earth science or archaeology is recommended, but not required. You will need to be healthy enough to camp and deal with rugged terrain, although long hikes are not required (opportunities for hikes will be common, however). If you are not able to attend the meeting, please contact me, or our anthropology professor, Susan Kerr, and we will get in touch with the information that you will need.

The trip itinerary and basic information is on the web at http://hayesg.faculty.mjc.edu/Geology_174_Colorado_Plateau.html (my site for the course), or http://kerrs.faculty.mjc.edu/anthro_191_193.html (my fellow professor Susan Kerr).

The Abandoned Lands...A Journey Through the Colorado Plateau: There is at least one forest in the Southwest that won't burn this year...

We continue our journey through the Abandoned Lands, the empty landscapes of the Colorado Plateau. We arrived at the national park the next morning and got a look at one of finest places to study Triassic history anywhere...the Chinle formation (or Group) is a complex sedimentary sequence that preserves a record of river floodplains and lakes that spread across Arizona, Utah, and several other states at the dawn of the age of the dinosaurs. Some of the earliest dinosaurs ever discovered have been found here.

But the neat thing about the Triassic is not the little dinosaurs. They had not really reached their dominance of the terrestrial ecosystem at this point in time. There were other creatures, some of them absolutely terrifying...like the phytosaurs.

Can you imagine wandering lost through a swamp and running into one of these? Phytosaurs resembled crocodiles, but were different in a number of ways. Some of them were also big...like 35 foot long in some instances.

There are lots of other creatures found in the sediments of the Chinle. The odd looking creature below is a Placerias hesternus, one of the therapsid reptiles, sometimes called the mammal-like reptiles. Huh? Since when is a reptile anything like a reptile? Well...when they have a more upright stance than reptiles, when they have differentiated teeth including fangs, and when they may even have been endothermic, i.e. warm-blooded. The therapsids were in fact the ancestors to the mammals, who appeared in latest Triassic time (they then presumably provided the dinosaurs with protein for the next 100 million years before an asteroid wiped out the reptilian overlords).

All told, the park is one of the richest Triassic fossil beds in world, with 200 kinds of plants, and dozens of therapsids, phytosaurs, amphibians, and early dinosaurs. But wait (as they say in late-night TV ads), there's more!

The floodplain and channel deposits make for some incredibly colorful badlands scenery. The bright colors result from the oxidation of metals in the clays, especially of iron. The clays are so easily eroded that soils don't develop easily, leaving behind a maze of gullies and channels.

There is a whole section of the park devoted to wilderness. No trails to speak of, but lots of interesting places to wander.

The park's riches extend to the human history as well. Abandoned lands? Yes. Few people live in the region today, but there is an 8,000 year history of human habitation. 600 archaeological sites are known within the park boundaries.

 There are some outstanding petroglyphs as well. Lots of them...

 Including this one. What do you see? Some think it is a dinosaur eating an unfortunate Puebloan, but others see a heron eating a frog. Of course, why would someone draw a bird eating a frog? Seems kind of ...ordinary to me.

Hmmm...I think I'm forgetting something. What is it? Oh yeah, I don't think I've mentioned what park we were exploring. It was actually originally established to protect some unique fossils: the petrified wood. I wonder how many parks have been missed because someone thought it was a sort of "one-note" place? Petrified Forest National Park? Why stop there? I see petrified wood in the curio shops all the time. Someone who thinks that is really missing out. The park is a fascinating place.

Most of the fossilized trees were carried from forests in surrounding highlands during floods. They were buried and the wood decayed away but was replaced by silica (quartz, in the form of agate and chalcedony). The wood is strikingly colorful; a lot of petrified wood from elsewhere occurs in pretty plain colors, but here there is a veritable rainbow in practically every sample. Entire trees, 100 feet long or more, are common in many parts of the park.

Petrified Forest is another place that suffered a lot of abuse before it became part of the national park system. Train passengers in the late 1800s stopped at the nearby station and walked off with tons of rock. A company once proposed to grind up the petrified wood to be used as an abrasive. Local citizens sought park protection as early as 1895, but it was 1906 before Teddy Roosevelt designated the site as a national monument. It became a national park in 1962.

Photo by Mrs. Geotripper

Theft is still a problem...apparently something like 12 tons of petrified wood get stolen every year. For what it is worth, stealing wood from the park carries a pretty serious curse. If you ask, the folks in the visitor center will show you the notebook filled with letters from people who had bad things happen to them while they possessed the stolen contraband. Legally collected wood can be purchased outside the park (they even give some away free; to get you inside the store, of course). If you are willing to do the legwork (mapwork?), you can find hundreds of square miles of Chinle formation on public lands (BLM) where non-commercial collecting is allowed.

In the meantime, if you are ever flying by on Interstate 40 and wonder if Petrified Forest is worth your time, well, I say yes, it is. And this is a forest that will never burn down, no matter how bad the droughts get...

Here is the explanation of my "abandonment" theme for this series: http://geotripper.blogspot.com/2012/06/abandoned-landsa-journey-through.html

Even More Beautiful Trees, and a Sequoia Story

The mini-meme on trees grew larger today when I wasn't looking....here are some more that I noticed when I got online tonight (in addition to the links mentioned in my previous post). I am really enjoying your contributions; it's great to see that we geologists can sometimes step back and appreciate the "overburden" that sometimes obscures our all-important outcrops. Of course, all these trees exist at the consent of geology, and I can't help but add some geological notes at the end of the post tonight...

Hypo-theses offers some beautiful tree shots from the Lake District in England (including some Norwegian pegmatite to keep things geological)

Eric at Dynamic Earth added two posts, one of some Junipers, which are also high on my favorites list, for the same reasons, and the other a case of some trees squeezing the life out of some boulders.

Chris at Highly Allochtonous contributed some great pictures of trees growing on very old rocks in South Africa (including one of my favorite landscaping species, the Jacaranda)

Callan Bentley at NOVAblog has some beautiful fall colors here. I haven't had the privilege of seeing fall colors in the northeast US yet, and would very much like to some day.

Pools and Riffles provides some more information about species in the eastern U.S. that I am not too familiar with.

In Terra Veritas offers some photos of trees revealing something out of whack with the underlying geology (really, though, you weren't obligated, but I appreciate the contribution!)

UPDATE: RockGlacier at Cryology and Co adds some comments about the role of dendrochronology in geology studies.

I especially appreciated the return of Ron Schott and his Gigapan camera view of a Sequoia Tree in the Lost Grove within Sequoia National Park (along with a great macrogigapan shot of the underlying granodiorite). I love the Sequoias, and have included their geological story in two of my trip guides (for Fall 2006 Tuolumne Meadows and and Fall 2005 Kings Canyon).

In short, the Sequoias have existed as a genus for 200 million years or more and once existed in groves across North America, Europe and Asia. The trees of Petrified Forest National Park were probably a related species, and I have this wonderful image in my mind of giant dinosaurs wandering among the giant trees. Today the genus exists only as 60 or so groves of Sequoia trees in the Sierra Nevada, as the coast redwoods in northern California, and as the Dawn Redwood in the smallest corner of China, in a single grove of no more than 5,000 trees that was only discovered in 1944, and described in 1948. It had been thought to be extinct in the Miocene epoch.

The Sequoias were apparently wiped out elsewhere by climate change, especially the Pleistocene ice ages, but in the Sierra, they survived, barely, by propogating up and down the gentle western slope of the mountains as the climate alternated between glacial and interglacial periods. Some pollen work suggests they may have been on the very verge of extinction, but luckily for us they survived, and now are appreciated as the largest living things on the planet. Nearly all of the existing groves are protected in National and State Parks, including the recently created Giant Sequoia National Monument.

I have ideas for two or three more blogs on the subject of trees and geology, but I have vigorously been avoiding the pile of grading in my living room, so keep watching later this week....thanks again to everyone for your contributions!

Time Beyond Imagining - A Brief History of the Colorado Plateau: The Real Jurassic Parks

As we move forward in time, we reach the geologic period called the Jurassic, one of the few units of the geologic time scale that is familiar to many laypeople. We have Steven Speilberg and Michael Crichton to thank for that, and yes, dinosaurs rose to prominence in the terrestrial landscape, but lots more was going on as well, including a lot of interesting non-dinosaurs, including our own small furry predecessors creeping about in the underbrush (the mammals first appeared in the late Triassic, about the same time as the first dinosaurs).

So what are the real Jurassic Parks? In the movies, the park was an island populated by reconstituted dinosaurs that ate people and each other. The Jurassic Parks of the Colorado Plateau are the ones in which the most dramatic scenery is provided by Jurassic-aged rocks, which include the Wingate, Kayenta, Navajo, Carmel, Entrada, Summerville, and Morrison formations. The parks include the familiar Zion, Arches, Capitol Reef, and Canyonlands national parks, and the less familiar Grand Staircase-Escalante, Navajo, Rainbow Bridge, Vermilion Cliffs, and Colorado national monuments. Notable state parks include Kodachrome, Goblin Valley and Dead Horse Point, all in Utah. Many of the dramatic cliffs included within the Glen Canyon National Recreation Area are also made of Jurassic rocks. And let us not forget the actual Dinosaur National Monument, the one that actually has dinosaurs (although at last report, they did not eat park visitors).

Today's photos include a parting shot of the Chinle Formation at Petrified Forest National Park, simply because I came across it in a lost file and liked it, and a picture from near the head of the Schafer Trail in Canyonlands National Park, which is cutting across ledges of the Kayenta Formation as it prepares to plunge down the Wingate cliffs to the White Rim, discussed in a previous post.

The Schafer Trail leads to the White Rim Trail, which winds for a hundred miles or so through the heart of Canyonlands National Park. It is one of the life-list goals that I haven't accomplished yet. It pretty much requires at least two days to travel, and three or four days by bike. The Schafer Trail was originally carved by cattlemen and improved by uranium miners (they worked pretty hard...).

So, why the dramatic colorful cliffs? Something important had changed, causing the Triassic floodplains to disappear. The silts and clays and river channels were replaced by desert dune sands, which quite often form prominent cliffs when hardened into solid rock. The deserts formed because Pangea had begun to break apart, and North America was now moving northwest, into the subtropics where the prevailing air circulation results in dry conditions. We see a similar situation in the Middle East and Sahara Deserts today.

Mid-week Mystery Sample: What is it?

So what is it? In the early 1990's, I was conducting one of our first field trips through the Colorado Plateau region, and at a stop to observe the sediments of the Chinle Formation, one of the students picked up the sample seen in the picture. I am admittedly not a paleontologist, but I looked and looked and couldn't make heads or tails of it. It sat on my desk for seven or eight years, until I walked through the visitor center at Petrified Forest National Park (the park is a showcase for the Chinle Formation), when I got it! Can you?