Out of the Valley of Death: Explorations in Red Rock Canyon

The next stop on our way to Death Valley National Park was one of the most ideal locations for learning the basics of stratigraphy to be found anywhere: Red Rock Canyon State Park in the El Paso Mountains along the Garlock Fault. The park protects exposures of the Miocene deposits of the Dove Springs formation (formerly the Ricardo formation), aged at about 8-12 million years. The formation of conglomerate, sandstone and claystone was laid down in alluvial fans, floodplains, and lakes in a semi-arid savanna environment. The region was home to a vast array of grazing mammals and predators, including extinct elephants, rhinos, three-toed horses, giraffe-like camels, saber-toothed cats, and bone-crushing dogs as well as smaller animals like ancestral skunks, martens, alligator lizards, rodents, and shrews. (follow the links to descriptions of each type of animal on the Los Angeles Natural History Museum website).

The park has stunning exposures of the sedimentary and volcanic rocks that illustrate many of the basic principles of stratigraphy (superposition, original horizontality, lateral continuity, and cross-cutting relationships). I worked with the students to observe and identify the rocks, and to work out a sequence of events that led to the formation of the exposures. And then I turned them loose to produce a rudimentary map of the geology of the area around the beautiful red cliffs.

It was February, and the sun was blazing! The temperature topped out at about 90 degrees. In a sense it was quite pleasant, especially compared to the frigid conditions back in the eastern United States, but it was also a reminder that we never had winter this year. There has been so little rain that there are parts of the Central Valley that have received less precipitation than Death Valley. It was a bit disturbing to realize how dry conditions are across the state.

Red Rock Canyon State Park has been the setting for numerous movies over the years, including old-time westerns, but my favorite movie scene was the opening sequence of Jurassic Park, where the protagonists were excavating velociraptors from Snakewater Creek or some such place in Montana. I sometimes find myself thinking "your cute little velociraptors wouldn't stand a chance against our bone-crushing dogs and sabertooth cats!".

Out in America's Never Never: Getting There

Photo by Mrs. Geotripper

A journey into the Never Never of America has to have a beginning in the green lands. From our base in the fertile Central Valley, we traveled through 200 miles of irrigated farmlands. They would be part of the desert were it not for a massive water project drawing water from northern California. We crossed the Sierra Nevada at Tehachapi Pass and continued into the Mojave, a desert that exists because of the rain shadow effect. Pacific storms are wrung dry by the imposing walls of the Coast Ranges, Sierra Nevada and Transverse Ranges.

Photo by Mrs. Geotripper

The western Mojave could hardly be mistaken for wilderness outback. Los Angeles has spilled over the mountains, with hundreds of thousands of people living in towns like Palmdale and Lancaster. Power lines and railroads crisscross the desert, as well as numerous paved highways.

We made a short stop at the massive open pit mine at Boron, one of the world's largest sources of borate minerals. The mine, operating since the 1920s, is now 500 feet deep, a mile long, and half a mile wide. A visitor center perched on the edge provides a marvelous view of the operation.

As we continued eastward, the trappings of civilization began to fall away. Barstow is a crossroads town of just over 20,000 people. At the north end of town, a road provided access to Fort Irwin (eerily accompanied by a lot of white crosses from traffic fatalities), but our route took us on a side road to Rainbow Basin.

19 to 13 million years ago, the Barstow region was not a desert. It was a savanna, with wandering streams and ephemeral lakes. The grasslands included groves of palm trees, and numerous grazing animals that were the ancestors to the elephants, antelope, horses, and camels that are familiar to us today. The grazers were preyed upon by a collection of primitive canines and felines, as well as amphicyon, a large carnivore that can visualized as an ancestor to the bears and dogs. The sediments that collected in the isolated basins accumulated to a depth of more than 3,000 feet, with a brightly colored assemblage of freshwater limestone, sandstone, siltstone, conglomerate, along with a series of volcanic ash layers that made it possible to date the formation.

The layers were later caught up in the deformation that began as the San Andreas and other faults warped and twisted the crust. In the center of Rainbow Basin, the Barstow Formation was deformed into a textbook example of a syncline, a downward pointing fold in the rocks. This is the syncline I wrote about a few weeks ago. I used the outcrop as an introduction to basic stratigraphic principles, and the students sketched the relationships, and outlined a sequence of events to account for the scene ahead of us. Here is the sketch as I would have done it...

The principle of superposition tells us that the oldest rocks will be found at the base of the sequence, so the Barstow Formation is the oldest rock visible. The principle of original horizontality tells us that most sediments are laid down in flat layers, so we can state that the Barstow Formation has since been twisted from its original position. The principle of lateral continuity shows us that the red and green layers of the Barstow have been eroded, because they end against an overlying layer instead of the edge of the original basin. The erosion surface is termed an unconformity. The principle of cross-cutting relationships tells us that the faulting took place after the deposition of the Barstow Formation, but before the erosion that produced the unconformity. And after all of this, erosion exposed the rocks for us to see on a warm Saturday in June at the start of our long journey.

We headed east from Barstow on Interstate 40, and all evidence of civilization disappeared, with the exception of the narrow strip of pavement we were following. The desert spread out for miles in every direction. As the sun disappeared beneath the horizon, we made the turn north to Hole in the Wall within the Mojave National Preserve, a national park for all intents and purposes except for the right of a few to shoot wild "game". When the vans were parked, the silence was striking. We had reached the land I'm calling Never Never.

For the first time in many months, I just stared at the sky. Early on, the sky was dominated by the quarter moon, but later, when the moon had set, the sky filled with stars. I did a time exposure over Woods Mountains...

It was a beautiful and peaceful night, the first for me in a long time. It was dreamtime.

A Quiz on Earth History: Can You Pass? A Comment on Science Education

Which is older, the dark dike, or the lighter sedimentary rocks?

How would you do on this test (taken from a chapter in Carlson, Plummer and Hammersly's excellent Physical Geology: Earth Revealed textbook)?

1. “ Geological processes operating at present are the same processes that have operated in the past” is the principle of a. correlation b. catastrophism c. uniformitarianism d. none of the preceding

2. “ Within a sequence of undisturbed sedimentary rocks, the layers get younger going from bottom to top” is the principle of a. original horizontality b. superposition c. crosscutting d. none of the preceding

3. If rock A cuts across rock B, then rock A is rock B. a. younger than b. the same age as c. older than

4. Which is a method of correlation? a. physical continuity b. similarity of rock types c. fossils d. all of the preceding

5. Eras are subdivided into a. periods b. eons c. ages d. epochs

6. Periods are subdivided into a. eras b. epochs c. ages d. time zones

7. Which division of geologic time was the longest? a. Precambrian b. Paleozoic c. Mesozoic d. Cenozoic

8. Which is a useful radioactive decay scheme? a. 238U-206Pb b. 235U-207Pb c. 40K-40Ar d. 87Rb-87Sr e. all of the preceding

9. C-14 dating can be used on all of the following except a. wood b. shell c. the Dead Sea Scrolls d. granite e. bone

10. Concentrations of radon are highest in areas where the bedrock is a. granite b. gneiss c. limestone d. black shale e. phosphate-rich rock f. all of the preceding

11. Which is not a type of unconformity? a. disconformity b. angular unconformity c. nonconformity d. triconformity

12. A geologist could use the principle of inclusion to determine the relative age of a. fossils b. metamorphism c. shale layers d. xenoliths

13. The oldest abundant fossils of complex multicellular life with shells and other hard parts date from the a. Precambrian b. Paleozoic c. Mesozoic d. Cenozoic

14. A contact between parallel sedimentary rock that records missing geologic time is a. a disconformity b. an angular unconformity c. a nonconformity d. a sedimentary contact

If you have a degree in geology, these questions on earth history should give you no problem; they represent basic principles in the science. If you are a student in a basic geology class, they would be challenging, but with a bit of study, you should get most of them right. And if given as an open-book test with no time limit, they should be no problem at all...except if you are a student in my distance learning class. They barely break 50% most of the time. It isn't that they are bad students; they do fine on most of the other chapters. It mystifies me why they do badly on this one chapter, year after year, but I suspect the reason lies in the student's previous K-12 education.

Earth history and evolution have always been a required part of the primary and secondary curriculum, especially in California, but I get the feeling they don't get a strong emphasis in the classroom, perhaps out of fear of controversy from creationist parents, or due to the beliefs of the classroom teachers themselves. Because we end up not teaching our students why science accepts the evidence for an ancient Earth, students are left with statements like "scientists believe the Earth is millions of years old" as if it were a 50-50 choice. It's this idea of belief in scientific findings that has brought us to this dismal moment in our country's history when we can't mobilize to fight global warming because politicians and their followers choose to believe it isn't happening. Because people like Rush Limbaugh, Glen Beck and Senator Jim Inhofe are accepted as climate experts. They aren't; they are appallingly ignorant or devastatingly cynical (or both).

There was an interesting moment last weekend at our Wild Planet Day celebration, though. A father was showing his daughter our skeleton of the sabertooth cat. She wasn't much more than 7 years old, but he said to her, "is this creature millions of years old, or thousands?" I kind of sat back, waiting for the assumed explanation of how scientists are wrong and that the earth is only 6,000 years old. But, to my surprise, he said "the dinosaurs lived millions of years ago, but the mammals like this sabertooth lived thousands of years ago". A small but satisfying moment to be sure. And too rare these days.

If you haven't had a class in geology, don't feel bad if you don't know the answers. I've listed them in the comments.

What do you think about the earth science education our children are getting these days? Am I totally off base?