Okay, not really to the center, but deeper than any drill or mine shaft ever went. Del Puerto Canyon in the California Coast Ranges provides a window into the Earth's mantle, while passing through more than ten miles of crustal material. Allow me to explain! We were there last weekend, a group of our students gathered together after finals to explore the canyon.
The Great Valley began as a forearc basin, a sequence of sedimentary layers lying on oceanic crust between a subducting trench and the edge of the North American continent. The sediments were derived from the erosion of the Ancestral Sierra Nevada, which at the time was a string of volcanoes not unlike the Andes or Cascades of today.
What a fascinating time this was! Huge volcanoes were erupting every few decades, while large rivers were constantly eating away at the mountains. A diverse group of dinosaurs roamed the forests on the flanks of the volcanoes including hadrosaurs (duckbilled dinosaurs). Raptors and carnivores similar to T-rex and Deinonychus (the American version of the velociraptors) lurked in the trees and along the rivers. Various species of Pterosaurs flew overhead.
The first dinosaur found in California was discovered on this ridge above the landslide.
The very first dinosaur fossil ever discovered in California was found in this very canyon, by a teen named Al Bennison in 1936. The creature was a Saurolophus, a plant-eater that had been caught in a river flood. The carcass floated out to sea, and was eventually entombed in the sediments of the Great Valley forearc basin.
Fall colors in Del Puerto Canyon. Unlike the rest of the country, we believe in enjoying the fall until winter actually begins on the calendar.
Like the adjacent coastline, the sea teemed with life. There were
creatures much like those of today, clams and snails (pelecypods and
gastropods), fish, and sharks. And then there were the sea-going
reptiles: the Plesiosaurs (the suspected "Loch Ness Monster" creature,
unfortunately), the Ichthyosaurs (large dolphin-like reptiles), and
Mosasaurs (35-foot-long swimming Komodo Dragon relatives). A new species
of Mosasaur was discovered by Al Bennison just a few miles away
from Del Puerto Canyon.
The sediments accumulated to an incredible thickness, more than 25,000
feet. The sediments were later twisted upwards to form the eastern flank
of the Coast Ranges. The road in Del Puerto Canyon winds for more than
10 miles through the sandstone, siltstone, and shale that once formed
the ocean floor. We were driving up canyon, but deeper down into the
crust. We were looking for the Tesla-Ortigalita fault that marks the
boundary between the so-called Great Valley Group, and the underlying
Coast Range Ophiolite, a slice of oceanic crust.
We soon reached the rocks near the base of the Great Valley Group, and found the exposure of the fault zone (it cuts diagonally upwards to the left in the picture above). I visited this spot nearly twenty years ago with Al Bennison, who by then was long retired. He described the structural relationships to us, and pointed out that ammonite fossils (cephalopods related to the Pearly Nautilus and the Octopus) could sometimes be found in the shale on the right side of the fault. He walked over, glanced at the cliff for a moment and said "here's one", handing me the delicate fossil. I've been to that darned outcrop another twenty times or so over the years, and I've never found one for myself!
So of course, what happens when I take our Geology Club students to the outcrop last Saturday, students who have never seen this spot, some of whom haven't even learned about ammonites yet? Yes, they found one. Durn it all....
At this point we've driven 10 miles into the canyon, and passed through five miles of seafloor sediments. We've reached the top of the oceanic crust, known in this area as the Coast Range Ophiolite, one of the most complete such sequences in all of California. For the next part of the journey we sought to pierce the crust and travel into the Earth's mantle below. We continued up the canyon...
Red-shouldered Hawk at entrance to the Sacramento National Wildlife Refuge
Every so often, I remember what an extraordinary place I live in. It's sometimes easy to forget while dealing with the air pollution, the lingering drought, and the seemingly non-ending recession, but California's Great Valley is one of the most important provinces in the United States. It provides something like 25% of the nation's fruits and vegetables, and is the world's leading producer of almonds and a number of other products. Despite being almost completely altered by agricultural and urban development, a few remnants of the original landscape survive. It's a reminder that America once had its own version of the plains of the Serengeti (translation: "endless plains").
Along the auto tour route at the Sacramento National Wildlife Refuge
The Great Valley extends for 400 miles from Redding to Bakersfield, averaging 50 miles in width. It is extraordinarily flat, with most parts lying below 300 feet in elevation. Practically the only exception is an extinct volcano called the Sutter Buttes north of Sacramento, which rise some 2,000 feet over the valley floor. The mountains loom on the horizon of the Sacramento National Wildlife Refuge, where I paid a visit a few weeks ago. It was like exploring the Great Valley in another geological age.
The refuge is a year-round home for many species, but it really comes alive during the winter, when tens of thousands of migratory birds arrive from the far north. A seven mile-long auto route allows for a leisurely exploration. It's a great place to be introduced to the natural landscape of the valley, although there are many others that are equally spectacular (the Merced, San Luis, and San Joaquin being other excellent choices). I just happened to take most of these pictures during my visit at the Sacramento NWR last month.
Gadwalls at the Sacramento NWR
The Great Valley originated as a shallow sea along the subduction zone and trench that dominated the western coast of the North American continent for more than a hundred million years during the Mesozoic Era, the time of the dinosaurs. The sea occupied a sedimentary trough called a forearc basin. As the basin filled with sediment, the weight of the layers pressed the crust downward, allowing more sediments to accumulate. Over time, vast thicknesses piled up, in places reaching 25,000 to 50,000 feet (7,500 to 15,000 meters).
Northern Pintails at the Sacramento NWR
The subduction zone began to transform into a new plate boundary beginning about 30 million years ago. Instead of the convergence of the crust, the plates began to slide laterally, forming the San Andreas fault system (this type of boundary is actually called a transform boundary). The crust along the transform crumpled, causing the uplift of the Coast Ranges just a few million years ago (the mountains are among the youngest ranges in the world). The shallow sea receded and became dry land in recent geologic time.
Ring-necked Pheasants are masters of camouflage...well sort of.
The valley has a Mediterranean climate, with warm dry summers and cool (but not cold) wet winters. The amount of precipitation ranges from very low in the south to relatively high in the north, but for the most part the ground cover is a grassland savanna, with oak woodlands in the wetter areas. Numerous rivers flowing from the adjacent Sierra Nevada supported mile after mile of riparian habitats and wetlands. Swamps and marshes dominate the delta of the Sacramento and San Joaquin rivers. These environments provide habitat for a staggering variety of wildlife.
The original prairies supported vast herds of elk and pronghorns, along with deer, and numerous smaller species of rodents. In earlier times, the landscape supported mammoths and mastodons, bison, ground sloths, horses, and camels. When humans arrived, this rich habitat was forever changed. Many of the species went extinct, or were driven elsewhere. Only about 5% of the original landscape remains.
Despite the horrible destruction of the original ecosystem, patches survived. The vast flocks of migratory birds, though much diminished, still flew into the valley and occupied what corners they could. Members of a subspecies of the elk endemic to the valley, the Tule Elk, were once common across the valley floor. They were hunted mercilessly for hides and meat until they were thought to be extinct around the 1860s. A single breeding pair was discovered in 1874, and after twenty years only two dozen of the elk survived in a single refuge in the south valley.
Ring-necked Ducks at the Sacramento NWR
In the early 1900s, a new ethos emerged, the idea that humans needed to nurture and protect the ecosystem that sustained life on the planet (although few at the time would have worded it this way!). In some cases, the actions came about because favored species had become depleted from over-hunting. In other cases, it happened because migratory birds were damaging agricultural fields because they had no other sources of food. Whatever the reasons and motives, the result was the establishment of hundreds of wildlife refuges across the United States. A series of refuges span the length of the Great Valley like a string of pearls. Animals once on the edge of extinction were brought back from the brink. The Tule Elk now number in the thousands. The Aleutian Cackling Goose, also once thought extinct (a flock of 600 survived on a remote and rarely visited island) number in the hundreds of thousands. The refuges have played a pivotal role in survival of dozens of endangered species.
It is an amazing privilege to experience a place like the Sacramento National Wildlife Refuge (and the dozens of others across the valley) in fall and winter as the migratory flocks arrive. I was stunned to find that this incredible movement of birds was taking place here literally under my nose (okay, over my nose) during the first 25 years I was living here. I was so busy exploring the more showy Sierra Nevada or California coastline that I failed to recognize the treasure that lay just a few miles away from my backyard. I can barely describe the noise of tens of thousands of birds taking flight all at once. It's not just their calling back and forth. It's the sheer compression of all those wings beating at once.
The Snow, Ross's, White-fronted, and Cackling Geese are the very visible and charismatic parts of the ecosystem of the valley, but they are only part of a chain that includes many other species of plants and animals. The challenge of the refuges is in re-creating and sustaining the entire "circle of life", as certain Disney movies might put it. With this basic challenge there is a myriad of conflicts and compromises with the many other stakeholders of our valley, especially when it comes to the issue of water.
Ross's Geese at the Sacramento NWR
My videos from the Sacramento NWR didn't quite work out, but a week later I caught the same species of geese at the San Joaquin National Wildlife Refuge. There are thousands of them taking to the air all at once.
There is another critical part missing from this ecosystem. It's the loss of predators. There are still birds of prey like the Red-shoulder Hawk at the beginning of the post, and the Red-tailed Hawk below. There are the occasional foxes and coyotes that have learned to survive among the human invaders. People have brought their cats and dogs. But the valley was once home to the California Grizzly Bear, the much-larger Short-faced Bear, the American Lion, the Sabertooth Cat, and the Dire Wolf. These animals died out at the end of the Ice Age, although the Grizzly survived into the 20th century. When the large grazing animals disappeared, so did the larger predators.
Red-tailed Hawk at the Sacramento NWR
The Great Valley is a challenge. It's a challenge to live here, it's a challenge to fully understand. In the face of so many land-use issues, it is challenge to one's sanity. But it is also a fascinating place, one that retains a precious link to the past, when it was a functioning ecosystem with a diversity of animals and plants that was the rival to any African savanna. It's worth the effort to explore and understand this landscape.
If you are one of my Modesto-area readers, please be sure to pay a visit to the Great Valley Museum of Natural History. The new museum is a wonderful resource for beginning to understanding the valley as it is and how it once was.
Being on a volcano isn't too bad,at least if it isn't erupting. In Hawaii, I've even enjoyed being on an erupting volcano. "On" isn't too hard as a rule. You just drive or walk on it. Being over a volcano takes a little aerial technology, but flying to Seattle on a clear day does the trick. I've occasionally posted aerial shots of the Cascades volcanoes.
Getting under a volcano is a bit trickier. One needs to find a place where the magma chambers feeding a volcano have cooled and solidified, and then wait a few tens of millions of years while the crust rises and is stripped away by erosion. The exposed rocks would include granite, granodiorite, tonalite, and diorite. There are some very nice places to see such rocks, especially in my backyard, at Yosemite, Sequoia, and Kings Canyon National Parks in the Sierra Nevada. Needless to say, I've writtenjust a little bitabout these places...
Getting into a volcano is pretty much like getting underneath one. It takes less time, since only thousands of feet of erosion are needed, instead of miles. The trick is finding an accessible deeply eroded volcano. One of the most scenic of all eroded volcanoes has to be the half volcano of Pinnacles National Park in California's Coast Ranges. I don't mean "half" in the sense of half eroded away. Half of the volcano is missing for other reasons (read on...).
We took our last official field trip of the semester a few weeks back, and our destination was Pinnacles, being our nation's national park, and one of the most scenic and geologically interesting parts of the Coast Ranges (although there are many things that are geologically interesting about the Coast Ranges). Of course, as is my wont, I lectured and talked about the geology, but no lecture can ever compete with field experience. I sent the students up the trails to see the geology up close.
I headed up the Condor Gulch Trail. It connects after 1.7 miles with the High Peaks Trail, which is one of the finest short hikes in North America. My heart was there, but not the time. I made for the Condor Gulch Overlook, and continued another half mile to gain some wonderful views of the surrounding territory.
The volcano at Pinnacles National Park was a composite cone with at least five vents or domes composed of rhyolite lava and breccias. I imagine the closest analog to the volcano in California today wold be Mammoth Mountain in the eastern Sierra Nevada, although Pinnacles was situated much closer to the ocean, and may have been partly under water. Most of the rocks exposed along the trail began as mudflows on the flanks of the volcano, the summit of which was located a couple of miles south of the trail I was following.
From the Condor Gulch Overlook, one can look into a series of potholes where the intermittent stream flows over the volcanic bedrock. Boulders in the swirling currents have eroded the holes, which may hold water for weeks or months after major storms. The water is can be critical for wildlife in the area.
The Pinnacles volcano erupted near the newly forming San Andreas fault system, and the volcano was actually split in half by the fault motions. One part of it remained in southern California where the exposures are called the Neenach Volcanics. They can be seen in the Lancaster area quite close to the Antelope Valley Poppy Preserve. The rocks on the other side of the fault were carried north some 195 miles (314 kilometers) over 23 million years. It wasn't wasn't fast...maybe 2 inches per year, but the manner in which it happened was pretty violent. Every century or so there would be an earthquake in the range of magnitude 7.5-8.0 that moved the fault 10-20 feet all at once. The process continues today, with the San Francisco earthquake of 1906, the Fort Tejon earthquake of 1857, and the Loma Prieta earthquake of 1989. Enough stress is built up on various segments of the faults to produce large and damaging earthquakes, events that California needs to be prepared for.
From the ridgetop, the landscape appears gentle and serene. The thick brush and Gray Pines hide evidence of a violent past: volcanic eruptions, earthquakes, mudflows, and landslides. Today, the park is a delightful place to explore, with 30 miles of trails. I certainly enjoyed the three miles I traveled the other day.
If you are having trouble visualizing what 195 miles looks like, check out the fault map below that shows the location of the San Andreas, the Pinnacles volcano, and the Neenach volcanics.
It's hard not to feel depressed or hopeless when terrible things happen, when people do horrible things to those around them, and when innocent people die needlessly. The latest of far too many attacks hit close to home, near where I grew up, and where I still have connections.
I have no profound words or insights, there have been plenty of such discussions on the social media that I follow. I do hope that some action will finally be taken to prevent future massacres. It's so easy to feel hopeless.
Sometimes, the Earth presents us with such beauty that we can forget the evil for a few moments. It was raining today, a blessing in itself after four years of lingering drought. The sky seemed to be completely overcast, but out west, the light from the setting sun found a path through the clouds, and for a few short moments we had a spectacular rainbow, a double bow that extended across the sky. We don't really get a lot of them around here (given the general rarity of storms, period), so this was kind of an exceptional moment.
I don't know where our sense of beauty comes from, but there is something so pleasing about the spectrum of color that appears when sunlight is refracted through water droplets. It's high in the sky, and seemingly distant and unattainable, kind of like the ideals of being human. There is a sort of perfection we can hope to reach as individuals and as a society. I don't mean this in the sense of some religious belief that is "better" than the belief of someone else. There's too much conflict there. I mean it in the sense that we might one day find a way to treat each other with kindness, respect and equality, a recognition that we have a limited time in our own existence to make the world a slightly better place.
It's maybe kind of odd to think of it this way, but in geology we describe a form of "perfection". We call it a "graded stream". Rivers flow to the sea. The longer a river exists, the more it molds a landscape so as to achieve the most efficient flow, using the least amount of energy. If there is an obstruction, a landslide, say, or a dam, such things are ultimately removed by the erosive force of the fast-moving water. If there are pools, the stream slows, and dumps sediment in such a way as to fill in the gaps. As long as the water moves, the river approaches a form of physical perfection, with a channel that transports water to the sea in the smoothest manner possible (subject to the laws of physics). Perfection is never reached, because landslides and earthquakes will always happen, but the river works through these interruptions. It never stops changing the channel through which it flows.
Humans can never be perfect. But we can change the world we live in. We can choose to be the disasters, the landslides and other catastrophes, or we can be part of the constant never-ending flow that smooths out the imperfections. We can take away the hate. It takes patience, courage, and empathy for others.
This is a reposting of my note from last month. The deadline for applying is Friday, Dec. 4! From personal experience, I can say that Modesto Junior College is a pretty nice place for a career.
The Science Community Center at Modesto Junior College is a monument to the importance of science education, with state-of-the-art labs and classrooms for biology, astronomy, chemistry, physics, and the earth sciences, as well as a fully equipped observatory, and the most technically advanced planetarium projector in the United States (seriously, it's the newest generation, and we were the first to have it installed). The Great Valley Museum has exhibits emphasizing the unique biology, paleontology and geology of the Great Valley, and includes the unique teaching tool called Science on a Sphere. Construction will begin soon on the Outdoor Education Laboratory in the open space north of the Science Building.
We are currently seeking a permanent director of the museum
The position announcement can be found here: https://yosemite.peopleadmin.com/postings/1826. If you are a talented person who knows and loves science, but can also navigate the depths and passages of a college and state bureaucracy as well as excelling at fundraising, you may be the person we need to lead our school and our valley into a new era of science excellence. Contact the Human Resources office at Yosemite Community College District if you have questions.
Or maybe, more properly, the beginning of fifty miles of sand. It's generally moving south from this point. The west coast of North America is mostly mountainous, with dramatic cliffs sloping almost directly into the sea. Where the east and south coasts of the United States might have strands of sand that run for hundreds of miles, sand is rare enough in the west to be a curiosity. If fifty miles of sand is found in one place, it is extraordinary. That's where I spent my Thanksgiving, next to Oregon Dunes National Recreation Area.
I've always made a point of resisting the orders of our superiors to go out and buy things the day after Thanksgiving, being a firm supporter of the the idea to "leave no child (or anyone else) inside" as a form of personal education. We went exploring the coastal area around Florence this weekend.
As I've noted in previous blogs, the so-called Coos Bay dune sheet extends for 56 miles (90 kms) from
Coos Bay to Florence, and it is a strange and bizarre landscape that
contains 85% of Oregon's active dunes. It's mostly protected as Oregon
Dunes National Recreational Area. It isn't that there is simply a long
expanse of sandy beach; the sand has been blowing and migrating inland,
in some places nearly 3 miles, covering forests in some cases, and in
other situations, stabilizing and becoming forest. This odd
environment makes for unique ecosystem and geological landscape, mixing
ocean, swamps, rivers, forests, and lakes.
You can get a hint of the transition of dune to forest in the pictures here. I was quite literally standing above the very last dunes of the system, about eight miles north of Florence, where cliffs once again dominate the shoreline. The irregular hills are sand dunes that have been stabilized with European Beachgrass to augment
the stabilization of migrating dunes. The native grasses have been
pushed aside in many instances as the European non-native takes over.
Because of the spread of grasses, 80 % of the dune sheet is covered by
vegetation. In 1939 it was only 20% (US Forest Service data).
Only a few hundred yards inland, conifers have started to take root. The rivers and streams that flow into the dune fields, along with a high
groundwater table, have created a network of swamps, and more than two
dozen ponds and lakes (before I began exploring this region I would have said that lakes form only from glaciers, sinkholes, landslides, or oxbows on floodplains; dune lakes were new to me). The complex provides a rich environment for
wildlife.
The sand has several origins. The quartz rich sands have been eroded
from distant sources in the Klamath Mountains and Idaho Batholith and
carried to the shoreline environment by one of Oregon's many rivers.
Other sand is locally derived, eroded directly from the sea cliffs, or
carried onshore from offshore bars, sediment that may have originated
during the ice ages when sea level was lower. Wave action produced the
flat platforms on which the dunes accumulated.
It's a beautiful and dramatic landscape. If you ever get the chance...well, make the kind of choices that will get you chance to explore places like this!
Here's hoping that you all have a fine Thanksgiving holiday and that your travels are safe and fun. I offer up one of the things that I am truly thankful for: politicians that put aside their many differences and agreed to establish Pinnacles National Park in 2013. Maybe we can all learn something from the shock of actually working together and compromising: Democrats, at dinner this week be kind to your Republican relatives, and Republican relatives, be kind back. Be thankful that we can still argue politics without fear of reprisals.
Pinnacles National Park has provided us with our picture of a turkey for this Thanksgiving season. I doubt this one will be gracing anyone's table, as he was well inside the boundaries of the park. Maybe a coyote's, but this one looked like it wasn't going to take any crap from anyone.
Pinnacles has been one of my most dependable localities for seeing Wild Turkeys (which are not exactly a native species, but they have become naturalized in this region). I've seen dozens at a time there. The turkeys can be seen throughout the Coast Ranges. It's not well-known, but the Wild Turkey was almost hunted to oblivion a century ago. Aggressive efforts at conservation and introduction of captured wild birds to new regions (including California) brought them back.
A few years back, I caught a bit of a conflict, a love triangle if you will, in Morro Bay.
Pinnacles National Park is a beautiful place with fascinating geology. Look for a couple of posts soon from our recent trip there.
Short story of the geology: it's half of a large composite rhyolitic volcano that has been deeply eroded. Where the other half is today is part of the exciting story. The rest is the idea that you can wander around in the middle of volcano in the Central California Coast Ranges.
Pinnacles is a treasure. If you ever have a chance to explore central California, be sure to add it to your itinerary! In the meantime, have a safe and happy time wherever you may be. I'll be on the road, so posts may be scarce.
