Seeking the Savanna instead of Seas: "Saturday Night Live" and Geology??

Historical geology is a real head trip (remember that term?). Stick geologists in the desert against a cliff like the one above, and they will make a few observations, pick up a few stones (and/or fossils), and in their mind's eye, they will be exploring a long-ago prairie that would have looked much like the one in the picture below (a bit of the rarest ecosystem in California, the prairie at Merced National Wildlife Refuge).

There would be differences of course. This current-day prairie is populated by a diverse group of birds and small mammals like ground squirrels and rabbits. But it lacks some of the components of a healthy modern wild prairie, mainly the larger grazing animals like deer, antelope, and bison, and the large carnivores that would prey on them. Coyotes and foxes still inhabit the region, and cattle or sheep are sometimes brought onto the prairie to help maintain the quality of the grasslands. But the larger canines and cats, i.e. the wolves and the lions, are long gone, as are the bears.

We were on the first full day of our exploration of Death Valley National Park. We weren't there yet, because we had a hundred miles of Mojave Desert to cross before we reached the park. Along the way we made a stop at one of California's most spectacular state parks, Red Rock Canyon (not to be confused with the Red Rock Canyon National Conservation Area outside of Las Vegas). Red Rock Canyon is on Highway 14 between the town of Mojave and Lone Pine, southeast of the Sierra Nevada. The place will look familiar to many, as the striking red and white cliffs have formed the backdrop to dozens if not hundreds of Hollywood movies (including some the opening scenes of the original Jurassic Park).

The plain hills to the south of our parking area (in the picture above) are composed of Paleozoic and older metamorphic rocks that have been displaced and uplifted along the Garlock Fault just south of the park. The rocks have been moved some forty miles from their original location by the left lateral movements of the fault zone. They have their own fascinating story, but what catches the eye are the much more colorful sedimentary layers that were deposited on the eroded surface of the metamorphic rocks between about 8 and 12.5 million years ago, a time period called the Miocene epoch.

For many of our students, this is the first real-world example of the basic principles of stratigraphy. We spent a few minutes talking about the birth of the science of geology in the observations of Nicolas Steno (superposition, lateral continuity, and original horizontality), and James Hutton (uniformitarianism). Then I unleashed them onto the rock exposures so they could evaluate the origins of the rocks and the sequence of events that produced the spectacular cliffs in front of us.

Understanding the changes of a prairie ecosystem through time is as easy as understanding "Saturday Night Live" (which for a fact might not be that easy). For more than forty years the underlying structure of the show has remained much the same; there's a guest host, there is a cold open ("It's Saturday Night!"), there are skits, there is the weekend news, there are fake ads, there are musical numbers. But cast is constantly in flux. There have been many people over the years who have filled in the niches: those who could mimic political figures, those who could act as the "straight man/woman", those who could sing. Sometimes the actors were so unmemorable that they disappeared without a trace after a few weeks or months. Others were successful, and remained for years. Others went on to greater things, like Hollywood movies. And that's how the prairie savanna has worked over the years.

Once our students have looked closely at the rocks, they've identified that there are fine layers representing deposition in lakes, other layers that formed on floodplains or alluvial fans. The terrestrial origin of many of the layers is supported by the bright red color, formed as iron in the rocks oxidized into natural rust. What we don't have time for (or permission for that matter) is a search for fossils, because it is the fossils that tell the fullest story of these rocks. Are these fossils the John Belushi-Dan Akroyd period of the grasslands? Or the Joe Piscopo-Eddie Murphy period? Or Kate McKinnon?

Grasses emerged as a dominant plant species in the middle of the Cenozoic period around 30-35 million years ago. The low-lying plants had a novel method of survival: instead of broad leaves easily chewed by forest-dwelling animals, the blades of grass incorporated silica into their structure, and the hard silica would soon destroy the teeth of most animals that tried to subsist on it. A general warming and drying of the world climate led to the expansion of the grasses at the expense of woodlands and tropical rainforests. Animals either adapted to the new conditions or went extinct. The early part of the Oligocene and early Miocene saw many changing species, especially in the horse clan. The ancestors of the horses were small browsers in the forests. As they adapted to the open grasslands, they became larger, and their feet went from three or four toes to hooves, which gave them great speed to escape predators. Their teeth evolved to grow throughout life, allowing them to survive nicely while grazing the grasslands.

The fossil-bearing rocks at Red Canyon are called the Dove Spring Formation (formerly the Ricardo Formation). The cast of characters are familiar in the sense that they fill the roles of many species on the prairies and wetlands today, but there were some unfamiliar characters as well. More than a hundred species of plants and animals have been found, making this one of the richest and most diverse fossil assemblages in the American West. They include the smallest mammalian members of the ecosystem such as mice, ground squirrels, rabbits and even a pika. The larger grazers were represented by ten (yes, ten) species of horse (compared to the three existing in the present day), four camel species, and three species of antelope. There were the surprising ones, two rhinoceros species, and two elephant ancestors (gomphotherium). The carnivores are represented by eight species of canine ancestors (some are called the "bone-crushing dogs"), and three species of felids (cats), including an early saber-tooth. There is a fair candidate for the ancestor of bears and dogs called a "bear dog" (Amphicyon). For a complete listing of the fossils found at Red Rock, check out this technical report from 2009.

So our investigation of an ancient savanna prairie revealed some of the early players in the drama that has played out across North America over millions of years. Some of the players (genera) were diverse and widespread but ultimately died out in North America (the horses and camels, rhinos and elephants). Other lineages survived, including the deer, the pronghorns, and predators like the wolves, coyotes, mountain lions, and foxes. The bears still lurk nearby in the mountains and would no doubt reoccupy the grasslands if the farms disappeared. Like "Saturday Night Live", the show continues and hasn't suffered cancellation, but a great many changes have taken place. The prairies of 12 million years ago can still be found in California today, but with a new cast and a different look.

Cartoons Come to Life: The Value of Field Studies at Red Rock Canyon

I spend a lot of time in classrooms drawing cartoons. Lots of them, diagrammatically representing folds, faults and stratigraphy, trying to communicate to my students how these structures tell the story of the Earth. The problem for many of my students is that these are just cartoons. Cartoons on Saturday mornings (do ANY of you remember when that was the only time one got to watch cartoons?) do represent life in a way, but only if you have a real life to compare them to. And that's the problem for many students these days. They have no real-life experiences in the outdoors with which to compare these drawings.

And thus, the value of a field studies course. There is nothing quite like having the privilege of standing beneath a cliff, enjoying and appreciating the scenery, yes, but also being able to understand the story it tells. Our trip to Death Valley a few weeks ago included a fossil hunt at the first stop, but our second was a site where basic principles of geology stand out in stark relief, without a need for a chalkboard cartoon (I forgot the chalkboard this trip anyway). We had arrived at Red Rock Canyon State Park in the Mojave Desert. Just stepping out of the vehicles presented us a cliff face that was a physical representation of the diagram at the top of the post, a series of brightly colored layers of sand, siltstone and volcanic tuff transected by a fault.

The order of the layering provides a fine example of "superposition", the principle that layered rocks are stacked oldest to youngest, unless they have been overturned. This is one of the earliest principles of geology, described originally by Nicolas Steno in the 1600s. Looking east along the cliff we could also see the physical manifestation of another Steno principle, that of original horizontality. Most sedimentary environments produce horizontal strata (think floodplains or lakes, or shallow seas). If layers are tilted, some kind of force has acted on them, and being here in southern California, faults might be at fault.

A discussion of these basic principles was followed by a short "mapping" project. We weren't quite to the proficiency of working with maps, but the students set out to propose how they would organize the layers into formations and members that could be used to tell a logical story as to how these rocks could have come to have the structure and appearance they have today.

Red Rock Canyon does have a fascinating story as it turns out. The red and brown layers, called the Dove Springs Formation, record deposition of silt and sand in river floodplains and ephemeral lakes between 12.5 to 7.5 million years ago. The semiarid savanna environment supported a diverse ecosystem that included extinct elephants (gomphotherium), ancestral rhinos, three-toed horses, giraffe-like camels, saber-toothed cats, and bone-crushing ancestors to the bears and dogs. There are also numerous smaller fossils like ancestral skunks, alligator lizards, and shrews, with a total plant and animal species count of more than one hundred. The ecosystem suffered the occasional catastrophe as it was buried by volcanic ash. Basaltic lava flowed across the region.

One of the student's discoveries was a somewhat less visible fault that shifted the layers. It was a great introduction into the mind of field geologists, seeing the world the way earth scientists do. It was an interesting spot, but there were many more to come on the road ahead.

Speaking of roads and cartoons come to life...here's the Roadrunner (pic is actually from Joshua Tree National Park)....

...and Wiley E. Coyote. Despite living in the most desolate driest place in North America, it looks like this one has actually caught a few roadrunners! Seriously, this coyote lives only a few miles from Badwater, the hottest and lowest part of Death Valley.

Barren Cliffs Reveal a Rich and Violent Past: Red Rock Canyon State Park

Deserts have such a fearsome reputation around the world, but deserts can be both beautiful and at certain times of the year a pleasant place to visit. The dry lands of the American Southwest are no exception. For geologists, the treat is made better by the marvelous exposures of barren rock that tell stories of the past when the landscape was very different. This is one of those places: Red Rock Canyon State Park in California. We paid a visit on our way to Death Valley a few weeks ago.

The Garlock fault cuts across the boundary between the Basin and Range province and the Mojave Desert, forming a high linear ridge called the El Paso Mountains. Erosion has stripped away the alluvial cover, exposing the underlying continental sedimentary rocks. The rocks, candy-striped in tones of red, pink and white, formed in a deep basin between 12.5 to 7.5 million years ago, accumulating to a depth of more than a mile. The sediments include arkosic sandstone, siltstone, shale, along with volcanic ash and lava flows recorded several dozen eruptive events. The environment was perhaps semiarid, but certainly wetter than the current day. The fossil record suggests an Upper Sonoran paleobotanical zone, with Black Locust, Mexican pinyon pine, cypress, California live oak, red-root, acacia, desert thorn and palm. Similar plants are found today in the high mountain ridges between San Jacinto and Santa Rosa Peaks in southern California (a region I explored often in my youth).

The steep cliffs have attracted filmmakers for decades, making appearances in all manner of movies, including a lot of westerns, and one of my favorites, the opening scenes of "Jurassic Park".  But instead of dinosaurs, paleontologists have discovered a treasure trove of late Cenozoic mammals, reptiles, amphibians, and birds. More than 100 species have been found thus far.

What kinds of animals lived in the western North America around 10 million years ago? It was a diverse ecosystem with many unexpected species for those who think that deer, antelope and buffalo cover all the bases. Thanks to David Whistler, we have a rather comprehensive list of the animals who lived here.

On the open plains, one would have seen two different rhino species, ten species of horse, four kinds of camels, three antelope species, two elephant-like gomphotheres, vultures, two large land tortoises, pika, two ground squirrel species, deer mice, and rabbits. 

In the brush covered woodlands, one would have found two oreodonts (extinct sheep-like animals), peccary, three-toed browsing horse, short-legged camel, ringtailed cat, skunk, two weasel-like animals, wolverine,  four distinctly different spiny lizards, night lizard, rosy boa, racer snakes, hedgehog, chipmunk, two gopher-like rodents, two different pocket mice, a bat, three small perching birds, mole, four different shrews, a small, rear-fanged snake, and two alligator lizard species.

This rich selection of plant eating animals represented a huge source of walking protein, so there were predators, lots of them. There were six different species of canids (ancestors to the wolves, foxes, and coyotes), a very large bear-like animal, and three large ancestors to the cats including a an early form of sabertooth.

We spent our time learning the basics of stratigraphy, practiced a rudimentary form of geologic mapping, and interpreted the environment of deposition from the nature of the sediments exposed in the cliff. I wandered between groups of working students, answering questions, but my eyes kept ranging across the cliffs, thinking how incredible it is that we live in a time when we can discern the past history of our planet, and in so doing, understanding how we came to be. We are both a part of the Earth's ecosystem, and yet exist outside that ecosystem (for better or worse).

This rich variety of animals in Miocene time occurred because the climate provided rich sources of food, and diversity of the ecosystem was the result. Today, if a climate is not to our liking, we alter the ecosystem to our own ends. We build our shelters, we travel in little cocoons with air-conditioning and stereophonic sound, and we import vast amounts of resources and fuels to maintain our chosen lifestyle. We tend to ignore the other elements of the ecosystem where we live and visit. We don't embrace our environment, we cut ourselves off from it. It's when I'm in a place like Red Rock that I am reminded of where we come from, our ultimate heritage. We are children of the Earth. And there are limits.