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.

Former Seas and Oceans: Searching for the Past in the Great Valley

The world changes. It changes minute by minute as events happen in human society, the disasters, the eruptions (such as Sinabung this last weekend), the wildfires, the earthquakes. Other changes are more incremental, such as the rise of mountain ranges and their removal by the relentless forces of erosion. Given enough time, huge changes take place, but no one in the midst of these processes would ever notice a difference over the course of their lives.

Teaching geology and the earth sciences is often a challenge, especially when we talk about the history of planet Earth. The rocks on the slopes before us may look barren and innocuous, but huge events reveal themselves when we start observing them carefully. As a professor at a community college, my students are usually neophytes in the geological sciences. They are seeing the earth from a new never-before considered viewpoint.

I was on the road this last holiday weekend, introducing my students to the geology of Death Valley National Park. Some are currently in geology classes, some already had taken my courses, and some were entirely new to the science. Death Valley is a long drive from our campus, so we left on Thursday night to cover the 200 miles of the flat Great Valley, and to get a head start towards the desert. We camped at Kern River County Park outside of the town of Bakersfield, and at the foot of the southern Sierra Nevada.

After a cold night, we awoke to a panorama of barren grass covered hills with no rocks in sight. A layer of soil covers them all, except where roadcuts expose a small part. We talked in camp before leaving about how geologists see landscapes. Where a politician might see only city and county boundaries, geologists see provinces, regions with a unique geological history that contrasts with the areas around them. The Great Valley of California, for instance, is a vast 400 mile long trough that has been collecting eroded sediments from the Sierra Nevada and Coast Ranges. It's been going on for at least 140 million years, and the sediments have accumulated to depths as great as 50,000 feet. More recently, perhaps during only the last one or two million years, the land was uplifted and gently tilted, causing the sediments to start eroding again.

We further talked about how geologists organize the rocks they see into formations, members, and groups. We recognize that in specific environments (ocean bottom, river floodplain, delta, sand dune) specific kinds of rocks will accumulate, and we can recognize by a change in the rock that the environment changed at some time in the past. In other words, as one looks at a cliff, different layers with different rocks and different colors show how the depositional environment changed, such as a river flood plain being inundated by rising sea level, or becoming drier and changing to a desert with dunes and the like. These unique layers are called formations. Formations are distinguished by being mappable and by having precise definable contacts with other layers above and below. Thinner distinctive layers within a formation may be defined as members, while several closely related formations (such as desert dry lake salt layers and desert sand dune deposits formed adjacent to each other at about the same time) may be classed as a group.

At our locality along the Kern River, a shallow seaway once existed. Maybe that's not such a stretch, since a rise of sea level of only 300 feet would inundate the area again. The presence of the sea is indicated by silt and sandstone layers, and the presence of numerous fossils. 15-16 million years ago, in the Miocene epoch, this was an ocean teeming with life. The shoreline must have been relatively close by because the fossil assemblage includes an occasional bone of a horse or camel, indicating a carcass that floated out to sea after a flooded river overtook the animal. The animals preserved as fossils are whales, dolphins, seals, walrus relatives, manatee relatives, and more than two dozen species of shark. Sharks have rarely-preserved cartilage skeletons, but their teeth are species distinctive. The size of the teeth range from barely visible to monstrous daggers almost a foot long (from the gigantic Great White relative Megalodon).

The rock layer is called the Round Mountain Silt, a formation within the Temblor Group. The incredible accumulation of fossils at the locality has been something of a mystery; suggestions include a volcanic ash disaster (no evidence of volcanism nearby, though), red tide poisoning (perhaps, but no clear evidence), or a feeding ground of large sharks (but large sharks were among the dead as well). A more recent suggestion is that the bones and teeth accumulated over a long period of time (perhaps 700,000 years) at the bottom of a sediment-starved basin (a deep trough a little farther offshore; such basins exist today in Southern California around the Channel Islands). Whatever the reason, the idea of finding fossils for the first time in their lives held great appeal for the students!

They shot off up the hill and although finds weren't abundant, almost everyone found a fragment of bone or a small tooth. The strange rectangular tooth in the picture above was that of a manta-type ray.

It's clear that some people spend a great deal of time digging and collecting at the site (the hillside has a prominent ledge where the digging takes place. Two years ago, one of the "serious" diggers was there, and showed us one of his really excellent finds, seen below.

The largest tooth ever found by any of my students was probably this one from 2011 (below). The variety in shape and size is apparent from the selection seen in the photo.

One warning about hunting for fossils in the region. The south end of the Great Valley is prime habitat for the fungal spores that cause Valley Fever. It's a nasty disease that is caused when the spores (which are in the dusty soils) get into your lungs and reproduce. If you ever give it a shot, take precautions...it's not a disease to be trifled with.

We got in the vans and started over the hill (Tehachapi Pass) on our way to the Mojave Desert, and then onwards to Death Valley, where our explorations would really begin.

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.