Wednesday, April 30, 2014

Adventures Along California's San Andreas Fault: The Devil's Punchbowl (but no earthquakes today)

The Devil gets blamed for a lot of stuff, and who am I to say he isn't responsible for bad things? But one can hardly blame us for blaming him for massive earthquakes when he goes around leaving things next to major fault systems, like punchbowls.

Southern California is a tortured landscape, and it isn't just the pop culture. The entire region has been twisted more than 90 degrees from its original orientation, forming one of the very few east-west trending mountains ranges in North America. The rotation is a consequence of the crust being caught between the Pacific and North American plates along the San Andreas and related fault systems. The end result of the rotation and stepwise motion of the fault is massive compressional forces that have lifted the San Gabriel and San Bernardino mountains to great heights in a very short period of geologic time, just a few million years.
The San Andreas fault shifts sideways with the consequence that long ridge lines called shutter ridges offset stream channels and block drainages. The two foreground ridges run parallel to the San Andreas along the north side of the San Gabriels.
Our journey home this last weekend followed the path of the San Andreas fault as it passed along the north side of the rugged San Gabriel Mountains. These mountains are statistically one of the steepest mountain ranges on the planet, and the huge number of ancient and modern landslides in and around the mountains attests to their instability. The deformation of the crust is most intense in the immediate vicinity of the fault zone, so we encountered a mess of rocks when we arrived at Devils Punchbowl County Park outside the town of Pearblossom.
Devils Punchbowl is administered by the county of Los Angeles, and has a nice little visitor center with a couple of interesting trails that wind among the steeply dipping rock layers. The rocks exposed in the park are called the Punchbowl formation, and they were deposited in alluvial fans in basins that formed about 13 million years ago in the vicinity of the fault. They have since been twisted into a series of upward (anticlines) and downward pointing folds (synclines). The map below by Thomas Dibblee, a legendary California geologist, shows the generalized geology of the Devils Punchbowl region.

The axis of the most obvious fold in the main part of the park, a syncline, plunges into the ground to the west directly towards the park headquarters. It's on the map above and in the picture below:


If it is hard to pick out, take a look at the annotated picture below. In a syncline, the layers slope, or dip, towards the center (the axis) of the fold. The axis slopes towards the observer, i.e. water would tend to flow downwards along the axis of the fold.
A popular one-mile long loop trail winds through the center of the punchbowl, offering some nice views of the conglomerate and arkosic sandstones that make up the cliffs. I had a few moments to spare, so I walked quickly down the trail to have a look around (I moved considerably slower on the climb back up!).
If these rocks look a little like a place where Captain Kirk should be fighting Gorns, you aren't too far off, although it's a different formation, a different fault, and a different location. The Vasquez Rocks are along Highway 14 on the other side of the San Gabriel Mountains, but the rocks there also formed in alluvial fans, and were tilted by fault motions.
The trail started to climb steeply, and I realized that all my walking exercises over the last five months have done wonders for my leg muscles, but somewhat less for my aerobic capacity. I've got to spend more time on stairs! As an old favorite folk song says, I'd rather be huffing than not huff at all.
The Devils Punchbowl is a fascinating place to visit. You access the park from a turnoff at the east end of the village of Pearblossom on Highway 138 between Palmdale and Cajon Pass. There are picnic facilities, but no camping. The kids will love Squints the owl and the other animals in the visitor center.

Geologists sometimes seem to court disaster, in the sense that someone like me will stand on a major fault zone and think to himself that it would be cool to see the "Big One" happen just then.  Such an event is going to be a horrible tragedy, and I would never wish it on anyone, but we live here in California, and the quakes do happen. It's just that there is an intellectual curiosity about what it looks like when a fault ruptures and shifts 15 or 20 feet. It would indeed be a sight to see.
So we hung around near the fault trace just to see what would happen. Nothing did, of course, or everyone would have heard of it. The big earthquakes have a recurrence interval of around 100-150 years, and with the last major event in 1857, there is plenty of stress built up, but there was no compelling reason to think that it would happen while we were there. No, we just heard the light breezes, the buzz of busy insects, and watched the sun shining on myriads of wildflowers hiding among the shrubs.
We stooped down and started photographing flowers, including this one, a variant of the Mariposa Lily that I was not familiar with. It's stunningly beautiful, but if you are a small bug, it can be deadly as well, as you can see in the photo below...
There were just a few Beavertail Cacti blooming in the area.
There were lots of Coreopsis growing in isolated patches.
And there were lots of Desert Dandelions along the highways where they benefited from the little bit of extra runoff from the road surface.

All in all, a beautiful day, courtesy of the Devil leaving his punchbowl lying around a major plate boundary.

Tuesday, April 29, 2014

The Antelope Valley California Poppy Reserve: Color in the Western Mojave Desert This Week

I admit I've taken artistic license, in that I took this picture of a busy hummingbird on the same day, but by the time I took the shot, I was two hundred miles north in the parking lot of a Black Bear Diner in Tulare, California on my way home. But it sure catches the eye, doesn't it?
We were in Southern California for the wedding of my god-daughter this last weekend (have a great life Megan and Richard!), and I must say they picked a good time to give us an excuse for hitting the road. On the way home we made our way along the San Andreas fault from Cajon Pass to the Grapevine, hunting for earthquakes, and hoping to see some colorful wildflowers, despite California's crippling drought. A drought, yes, and a huge water deficit, but we had a few good storms roll through the state in the last few weeks, giving a boost to the wildflower season.
We took a chance and headed out the Antelope Valley California Poppy Reserve to see if the poppies were blooming. They were. They are certainly a bit more limited in scope than in wetter years, but they formed a beautiful golden carpet across the desert floor. They were also mostly closed up in the fierce wind that was blowing through the area in the aftermath of the storm. The poppies are natural, but exist here for an unnatural reason, a topic I discussed back in 2010 in this post.
In that post I described how.the flowers are a natural phenomena, but a natural phenomena with a very human influence. About seven miles west of the Poppy preserve there is another state park: Arthur B. Ripley Desert Woodland State Park. The park preserves 580 acres of what turns out to be the native land cover of the Mojave Desert west of Lancaster and Palmdale: juniper woodland and Joshua Trees.

A century ago, this high end of the desert was cleared of Joshua Trees and Juniper, usually by chaining (dragging a huge chain between tractors that knocked down whole forests) or fires in order to put in thousands of acres of alfalfa fields and other crops. Large areas were reserved for sheep and cattle grazing as well. The natural plant cover was long gone. Much later, some of the abandoned fields started to recover, and the showy wildflowers are the pioneer species that are the first to recolonize disturbed lands.  Joshua Trees can no longer recolonize the valley floor; they don't have any method to spread their seeds widely (Joshua Trees were once spread in giant ground sloth poop...). Despite their incredible beauty, the wildflower displays are a monument to our extensive alteration of the environment that once existed here.

Many of the agricultural fields have been abandoned for lack of water and other economic reasons, but our utilization of the desert for our human needs continues. Notice in the picture below the huge windmills in the distance, and what I think is a large solar array.
After taking in the beautiful fields of California Poppies, we headed west along the San Andreas fault to Highway 138 and the Gorman cutoff. Suddenly the hills were alive again with what looked like the beginning of a nice blooming of lupines and some kind of yellow flower (we didn't have time to stop and investigate closely).
I imagine that in a week or so this will be a true wonderland of color, especially after the weekend dousing by the short but intense storm that rolled through California. The storm was too late to do anything about the drought, but it brightened the world just a little before the summer heat sets in.

Monday, April 28, 2014

Where are the Ten Most Incredible Places You've Ever Stood? My Number 7, Gubbio, Italy: Castles, Medieval Town, Roman Arena, Faults, and a Dinosaur Killer

It's not always easy, but travel whenever you can. See as much of the world as possible. I passed on both New Zealand and Hawaii three decades ago for reasons that seem trivial today. I didn't go overseas until 2001, but my life since then has been enriched in ways that I can barely comprehend. Few of us have resources enough to just leave and go somewhere, but there are sometimes cheap alternatives...like a geology field class! Yes, you have to work and stuff, but you will see wonderful things, and you'll be traveling with interesting people.

Number seven on my list of most incredible places is Gubbio, in the Umbrian Province of Italy, between Rome and Florence. What's not to like about Gubbio? It has castles, monasteries, medieval fortresses, Roman arenas, plus active faults and beautiful mountains (the Apennines). Plus one of the most significant geologic outcrops in the world (more on that a moment).
Back in 2007, we conducted a joint anthropology/geology field studies journey through Italy and Switzerland. I had never been to Italy before, so I had a lot of book learning to accomplish before I could lead students in mastering of the geology of the country. And because I had never been there, we had a tour company make the logistical arrangements. They had a canned tour which visited all the famous sites (the Colosseum! the Leaning Tower of Pisa!) and it was sometimes a bit tricky to see some of the important geology (although Pompei was a stunning exception; the trip included a hike to the summit of Vesuvius as well as a tour of the ruins). On the day that we drove from Rome to Florence, there was a scheduled visit to the Basilica of St. Francis of Assisi. 

I suppose that some people would have preferred to see the church, but we had noticed that it wouldn't be much of a diversion off our route to see Gubbio instead. It lies east of the main highway high in the Apennines Mountains, the nearly thousand kilometer range that runs down the boot length of the Italian peninsula. The mountains have risen in response to compressive forces related to a convergent boundary in the Mediterranean Sea. In the vicinity of Gubbio, late Mesozoic and early Cenozoic limestone layers have been lifted high into a mountain ridge. In more recent time, faulting formed the valley containing Gubbio. The downdropped crust is called a graben. The eroded fault scarp above the town is called a triangular facet (much of the town is built on the fault surface; see the top picture). That the faults are still active has been shown in dramatic manner, as several deadly earthquakes have shaken the region in recent decades (one of them severely damaged the Basilica of St. Francis in 1997; the L'Aquila quake in 2009 killed 300 people and resulted in some geologists going to prison).
Gubbio has been a crossroads on the Italian peninsula for thousands of years, and numerous cultures have controlled it at one time or another. Its origin dates back to at least the Bronze Age, and some tablets discovered there contain the most extensive known examples of the Umbrian language. The Romans invaded in the 2nd century BCE, and the Roman theater/arena is the second largest known.
The city became powerful and changed hands often during the Medieval period, being on the main transportation routes of the time, but today it is sort of a backwater town, retaining a great deal of its Medieval heritage, including defensive walls, castles, monasteries and churches. But as interesting as these things were, we were there for something else.

The canyon leading down into the town of Gubbio is called the Bottacioni Gorge, and it cuts deeply into the Cretaceous and Paleogene limestone deposits of the Apennines Mountains. In the late 1970s, the father and son team of Luis and Walter Alvarez were here trying to gain some insight on the rate of extinctions at the end of the Cretaceous period, the mass extinction event that did in the dinosaurs about around two-thirds of the species of life on Earth at the time. They decided to test the marine sediments for concentrations of iridium, an element rare on Earth, but relatively more abundant in meteorites. The values were small, a few parts per trillion, and it was hoped that they might provide data on the rate of sedimentation across the Cretaceous-Paleogene boundary (or the Cretaceous-Tertiary K/T boundary).

They got a big surprise. A clay layer at the boundary exposed in the Bottacioni Gorge spiked at around 3,000 parts per trillion, a huge number. In the years that followed, a similar iridium-enriched clay layer was discovered at numerous sites around the world, and researchers soon suggested that a gigantic asteroid perhaps 6 or 7 miles across hit the planet and ultimate caused the extinction of the dinosaurs and other large creatures.

And here we were, ready to lay our hands on the epic moment recorded in the rock when the way was cleared for mammals to take over terrestrial ecosystems on planet Earth. Except there were a few minor problems. For one, we didn't exactly know precisely where it was. And we didn't know if the spot would be marked or if there would be room to park a bus. And though it seems a minor issue, there were 35 people on the trip, and we didn't know where we were going to eat lunch (as all field trip veterans know, the two most important issues are "where and when do we eat?" and "where is the next bathroom?"). I had figured out that the spot was about 2 kilometers upstream from Gubbio, and that there was some kind of old medieval water canal close by.
So I was on pins and needles watching for the outcrop. The first problem cropped up on the edge of Gubbio. The sign on the road quite clearly said "no buses". Our Italian bus driver solved that problem in fine Italian style by ignoring it and driving right on past. We headed up the gorge, rounded a bend, and there was the canal, but I noted with a sinking heart that we had already passed the outcrop on the narrow road, which was pretty much not appropriate for buses (which is what the sign said, I think...). We drove for an interminable number of kilometers up the canyon (I figured about 80 kilometers, but the reality was probably 10), where the driver found a pullout that might be big enough to turn the bus around in.

Those of you who've seen the Austin Powers chase scene where he has a bit of trouble turning a golf cart around will appreciate what our bus driver did on that mountain road with a narrow pullout and a steep canyon wall. This wasn't a Y-turn. This was a Spiro-graph turn, for those of you who remember that toy. Back and forth for what felt like an hour, but was probably more like five minutes. But it finally happened and we headed back down the canyon.
The outcrop containing the iridium layer was in fact marked with a metal placard and an interpretive sign. We gathered around to have a look.
It was not unexpected I suppose that there would be precious little of the clay layer left at the site. Souvenir hunters have produced a huge cavity in the rock, but still, it was a great moment to lay one's hand on the surface where by most accounts, the dominance of the world by the dinosaurs ended. Medieval stories abound of brave knights sallying forth to slay dragons, but it seems the deed was done some 65 million years before we arrived on the planet.
One could see the drill holes left in the rock by the researchers. It is amazing that such a modest outcrop could contain a few atoms of a substance that could reveal a clue towards solving one of the greatest mysteries of the geologic sciences.
Now about the lunch and bathrooms issue. We had been driving for hours and people were getting hungry and, um, uncomfortable. It turned out that there was a single business in the Bottacioni Gorge, but it happened to be a restaurant, and the owner was quite happy to have a crowd of hungry geologists descend on his establishment. He's been catering to geologists for decades as it turns out, enough so that we were asked to sign the geologists register that was first signed by the Alvarez and his assistants!

And the food? By all accounts, the pasta and mushroom dish was the finest lunch we had on our entire journey. It was delicious! If you ever have the chance to visit the Gubbio locality, plan on eating at the Ristorante Bottacioni.

Thursday, April 24, 2014

Where are the Ten Most Incredible Places You've Ever Stood? My Number 8: The Burgess Shale in British Columbia

The journey continues through the ten most incredible places where I've ever stood. Every person's list will be different; I'm hoping to hear of great ideas for future travels! Number ten for me was the Alaka'i Swamp of Kaua'i. Number nine was Frame Arch in Arches National Park next to Delicate Arch, Frame's better-known counterpart. This next one was an easy post because one of the Accretionary Wedge topics asked a similar question, i.e. What is your geological pilgrimage – the sacred geological place that you must visit at least once in your lifetime? What follows is a slightly abridged post from the wedge topic in April of 2012. Keep in mind that no order is implied with these posts, except for number one.

I've had a rich life, being able to link my favorite activities, traveling and photography, with my career as a geologist and teacher. It means I have been to a lot of places, so determining a list like this leads to a lot of introspection. I've been enjoying reading some of the other entries...I like new ideas of where to go!

I settled on this one particular site because of the emotional impact it had when I reached the goal. It was indeed remote and difficult to get to. It was the Burgess Shale fossil quarry in Yoho National Park in British Columbia, Canada. Besides being one of the most important fossil sites in the world, it involved one of the most beautiful hikes I've ever taken. Just look at the scenery from the edge of the quarry:
Fossilization is a chancy process. Everything has to happen just right, and most of the time organisms are immediately scavenged or quickly decay. Even when things happen just right, it is exceedingly rare for anything besides bone or shell to survive. As a result, the fossil record is highly biased towards creatures with shells. When one considers how many soft-bodied creatures exist in the world's ecosystems, and how rarely they are preserved, we realize how poor our picture of the past really is. This is especially true of the "dawn" of complex life in the Cambrian period, just over 500 million years ago. Something 75% of the record is made up of the various species of trilobites, and most of the rest are sponge-like archaeocyathids and brachiopods (simple bivalved creatures which are not as "advanced" as clams). Although we know that plenty of soft-bodied forms existed, they have not been preserved, except in a precious few places.

One of these is the Burgess Shale, in British Columbia. The shale accumulated as masses of mud slid into oxygen-poor water. The organisms living in the environment were killed immediately, as were the scavengers and microbes that would have consumed them. The outcrops were discovered by Charles Walcott in 1909, and over the years tens of thousands of specimens have been collected and analyzed. The rocks were full of diverse and sometimes bizarre species that would have otherwise been lost to all time (see this article for examples).

The Burgess Shale is high on a ridge in the Canadian Rockies, and it is a tough six mile hike to the quarry. As a World Heritage Site, and being within a Canadian National Park, access is highly restricted (and believe me, they know when someone is there illegally!). To see the quarry one must go with a conducted tour through the Burgess Shale Geoscience Foundation.
I made the hike in July of 2005, one of the first hikes that year in this cold alpine environment. The sun played hide and seek with the clouds, and rain occasionally threatened (I have the distinct impression that that situation occurs just about every day up there). Glacier Lilies were everywhere, providing a great deal of color along the trail. There were also several steaming piles of grizzly bear poop, so we stayed pretty close together on the trail...
It was a long uphill hike, but after 5 1/2 miles, we passed a sign that let us know we were drawing close.
I walked a little slower than the others, and I paused at the last few steps. Most of the other hikers were not geologists, and were only beginning to understand the importance of this site to paleontology. I gathered my thoughts and emotions, and stepped into the quarry for the first time.
It was still half-filled with snow and ice, but there were plenty of slabs of rock around. Trilobites were all over, and I almost immediately found a delicate sponge fossil. The others gathered at the far end of the quarry, so I walked over.
The foundation knows that random searching in the quarry will not reveal some of the rare creatures, so they keep some pretty decent samples in the red lockbox on the site. Gazing at the specimens, I realized all over again what a wondrous treasure this site this really is for paleontologists.
Collecting of course is not allowed here, but we were allowed to search among the slabs for fossils that we could "own" for ourselves through the magic of digital imagery. I quickly found a nicely preserved Haplophrentis, a primitive mollusk related to snails and clams.
My favorite find was a complex little Marrella species, which is actually the most commonly found fossil in the Burgess Shale. It was the most delicate fossil I've ever found. And hard to photograph!
I tried photographing the fossil from a couple of angles. The brown spot is a stain of fluids that escaped when the organism died. In case you are wondering, no, the specimen didn't "accidently" fall into my pocket. I put it in the pile next to the big red box, so look for it if you ever get up that way.
If you are having difficulty making out the specimen in the pictures above, check out the reconstruction in the picture below to get an idea of the complexity of the little creature. Something close to 180 species of creatures have been found in the shale, and perhaps only 2% would have been preserved in Cambrian sediments anywhere else in the world. The fossil record certainly has a bias that favors animals with hard shells or skeletons.
Marrella splendens Source: http://burgess-shale.rom.on.ca/en/fossil-gallery/view-species.php?id=80&m=3&
The rain started to fall, so we started down the barren slope. It's not a very smart place to be in a lightning storm! During the hike down, I was no longer so anxious about reaching the goal. I strolled along, enjoying some of the finest alpine scenery I have ever laid eyes on.

Emerald Lake, thousands of feet below, really looked more turquoise in color, due to the fine clay particles suspended in the water. Glaciers are still carving these mountains.
After about ten hours and 12 miles on steep trails, I arrived back at the parking lot, tired but happy. It was indeed a place worthy of a geological pilgrimage, and easily made my top-ten list of the most splendid places I've ever stood.