The Other California: The Mountains of My Youth

I grew up under the east end of the San Gabriel Mountains, a huge terrane of Proterozoic and Paleozoic metamorphic rocks intruded by Mesozoic granitic rocks, and squeezed up like a watermelon seed between the San Andreas fault and the Sierra Madre-Cucamonga fault system. I have heard that the San Gabriels have the statistically highest average slope of any mountain range in the world, and having hiked and climbed these mountains in my youth, I find the statement plausible.

As with many things of youth, I kind of took the mountains for granted, thinking the far away Sierra Nevada as the "real" mountains. The Sierras were only accessible during summer vacation, so the San Gabriels served as a mere substitute camping and hiking locale while waiting for school to get out. Having made a few excursions into the region recently after a thirty year absence, I am reassessing that opinion. The San Gabriel Mountains are a rare treasure. How many of the millions of people in the Los Angeles Basin-Inland Empire region are aware that they have gorges that are nearly as deep as the Grand Canyon in their backyard? Or that the pebbles in their alluvial fan backyards are some of the oldest rocks in the state, at nearly 2 billion years? Or on a more menacing note, that those pebbles arrived in their backyards via numerous monstrous mudflow events? Actually, I think some people are aware of that last one, especially in light of some of the recent wildfire disasters in the region.

Today's first picture is of Cucamonga Peak, which rises to 8,859 ft (2,700 m) from the apex of the alluvial fans at the mountain base at about 2,000 feet. That's a gain of about 7,000 in a horizontal distance of three or four miles. These are steep and high mountains! The canyons that carve the deep gorges on the flanks of these mountains are dangerous environments in the long run. Mass wasting in the form of rockfalls, debris avalanches and slumps accomplishes much of the erosion, and the intermittent streams that run through these valley are prone to disastrous mudflows.

San Antonio Canyon is one of the steep canyons that is well known to locals, but not so much to those outside the region. It drains the slopes of Mt. San Antonio (10,064 feet) and a ring of 8,000 and 9,000 peaks tucked behind Cucamonga Peak in the photo above. A paved highway provides access to tiny Mt. Baldy village and a modest ski resort (did you even know that southern California has skiing?).

The lower canyon can be described quite accurately as ravaged by both nature and man, as the region is regularly swept by wildfires (natural and not). The 'floodplain' is choked with debris from numerous mudflows, and few trees can gain a roothold on the valley floor. The slopes above are almost impossibly steep.

The roadmakers tried to maintain the highway on the valley floor, but the picture above shows how that worked out. The highway today winds along slopes hundreds of feet above the creek. In the upper canyon, the high peaks are dramatically revealed, and conifers make an appearance, mostly Bigcone Spruce, Jeffery Pine, and Incense Cedar.

VW Bugs (1960s vintage) were wonderful cars, but my poor car had to drop into first gear to surmount the biggest obstacle in the canyon, the Hogback. It is just above and left of center in the picture below. Mt. Baldy Village is tucked into the area just beyond, and the major trailheads come a bit farther up the road.

For my fellow high school students, the Hogback was a test of one's manhood (and it was mostly guys). They would take their muscle cars up and down the highway at speeds approaching 90 mph, and some would make it out of the canyon. Others didn't. One morning a friend showed up at school sheepishly bearing bandages and scratches. A bit of questioning revealed that he had missed a curve and ended up 400 feet down the slope on the canyon bottom. I almost died at the top of the Hogback; I was driving my family up the road with my newly issued drivers permit when someone came down the highway passing on a blind curve and running us off the road.

As a pre-geologist in the early 1970s, I thought the Hogback was out of place and out of character with the canyon. I have come to realize that it is very much in character with the canyon, so I leave you with this question: What is the Hogback?

I should probably invoke some sort of Schott Rule on those geologists that live in the nearby towns, but I won't, so answer away!

The Other California is my continuing series highlighting the geology of the fascinating places in my fair state that don't often show up on the postcards that tourists buy. The state is a big place and I have yet to see it all, so if you have a favorite corner of the state and would like to put together a blog entry, I would gladly add it to the series.

Everyone Needs a Good Scapegoat: Molokai Certainly Has One

Mohi at the AGU Blogosphere reports on research done on Molokai by Jonathan Stock and others concerning damage done by feral goats which were released on the island in the 1500's. The stripping of the vegetation in the island's tropical climate has led to extreme levels of soil erosion. The muddy mess pours into the sea and is having a drastic effect on the coral reefs. I've yet to visit Molokai, but the report immediately made me think of some striking images I caught while flying over the island on my way to the Big Island from Oahu. The muddy water provides a sharp contrast to the normally deep blue water along the island coast.

I've talked about problems with invasive species on the Hawaiian Islands in the past (the three posts can be seen here). The native plants adapted to conditions on the islands, and have few defenses against pigs, goats, and cattle, and often cannot compete against other plant species that have been brought to the islands by early colonizers, and much later, by gardeners and landscape architects. The extinction of these native plants is one issue. The research by Stock and others highlights of the problems of having all vegetation stripped away, and how this effects ocean ecosystems as well.

I've said it in tweets, and I'll say it here: I sure wish I was at the AGU meeting in San Francisco right now instead of grading finals and lab reports! 18,000 geologists and earth scientists in one place has got to be a lot of fun...

California's First Dinosaur Discovery and Finding a Tiny Bit of Inspiration

I meet with 72 5th-graders on Friday. The occasion was our SEEK (Science Education Encounters for Kids) day, a program NOT sponsored by NSF, GSA, NAGT, or any other acronym. It is a volunteer affair that has been running at our college for the last year or so. We bring students from local elementary schools to the campus where they can see science in a college setting. We do a lecture presentation and a pair of laboratory experiences. It was, as always, a lot of fun doing science with the kids. Something happened this time that really set me to thinking, though.

I asked them what school they were from, and so many of them shouted their answer that I didn't really pick out a school name from the cacophony, but I moved on with my intro about the prehistoric animals found in our region. And I got to the dinosaurs.

It seems like dinosaurs always capture the imagination of kids. I can talk about ancient sharks, sabertooth cats and giant cave bears, even mosasaurs and plesiosaurs (we've had them all around here), but they really perked up when I mentioned that a dinosaur was discovered in California too. Then I mentioned where, and their eyes grew wide, and a bunch of them shouted "that's where we live!".

They were, as it turned out, from Patterson, a small town at the west end of Stanislaus County, where California's first dinosaur was discovered in 1937. A 17-year-old young man by the name of Al Bennison was exploring nearby Del Puerto Canyon, and he found bones near the ridge-top above the farm and landslide seen in the picture above. It proved to be a species of hadrosaur, a Saurolophus, a large plant-eater of the duck-billed dinosaur clan (according to story related by Richard Hilton in "Dinosaurs and other Mesozoic reptiles of California", a femur from the creature was being used as a doorstop by a local rancher).

What struck me is that no one knew this. No one ever does. It seems that one of the most fundamental scientific facts about our county remains unknown by children, teachers, and just about everyone else. We teach our children their all-important math and English so they can pass their multiple-choice competency tests but this is an example of how we are falling short in the arts, the sciences and history. Math and English become more or less meaningless without the context of these other disciplines. But we are told that there just isn't room in the budget for these "frills" of education. It's more important to preserve our tax breaks than to take care of our vulnerable and young. According to recent news reports, American students have fallen to the bottom of the heap among leading economic powers in science and mathematics. And California spends less per student than just about any other state. And the cuts keep coming. Our summer session is about to be cut again this year. Sometimes I come close to despair.

I asked the kids what they wanted to be when they grew up. Their answers included the usual policeman, firefighter and other normal kid answers. One indicated she was going to be on "Dancing With The Stars". But one of them said "scientist". Maybe it was because they were on a science field trip, but it gave me that little bit of hope for the future. I hope we can give them the opportunities they deserve and the inspiration they need.

Postscript: I found a report of a discovery of a Hadrosaur in Orange County in 1927, but it was not actually identified as a dinosaur until decades later.

Postscript #2: One of those moments of irony...after making a crack about students aspiring to be dancers on television, our local paper has a front page article on a student at a local school...dancing on television (MTV). To their credit though, there was a science story too, about how Saturn got her rings...way back on page B-5. I'm glad we have our priorities straight.

Finding Faults and Bottomless Lakes in Southern California

My previous post on the geologic hazards of living at the eastern edge of the San Gabriel Mountains resulted in a fair number of comments, essentially all correct, pointing out that the local inhabitants are threatened by earthquakes, landslides, mudflows, floods, fires, and...pet-munching critters. Some also pointed out that every locality faces natural hazards, which is very true, but not all places are equal! One of the serious hazards of living in California is the ever-present threat of major earthquakes, due to the proximity of numerous active fault systems. But ask a Californian (or anyone else for that matter) the name of a fault in our state, and the answer is invariably "the San Andreas". Ask for the name of another, though, and most people blank. The next question one might ask is "how close do you live to the San Andreas, or any other fault?" Unfortunately, that question may result in a blank stare, too.

So, today's post is about finding fault in California. If one thinks he or she has never seen the San Andreas or any other fault, they might find that they actually have, but just didn't know it. The San Andreas in particular is spectacularly exposed along several major freeways leading out of the Los Angeles Basin, along Interstate 5 at Gorman, Highway 14 at Palmdale, and on Interstate 15 over Cajon Pass. That's where we are exploring in today's adventure. A few miles north of the junction of I-15 and I-215, the Interstate climbs a hill, and an exceedingly straight valley appears to the northwest (the picture above). It is called Lone Pine Valley, and it is one of the better exposures of the San Andreas. One can leave the highway at Kenwood Avenue or Cleghorn Road and follow the original Route 66 to see some interesting fault features, including an exposure of the rocks in the fault zone at the Blue Cut.

But first we have to find the Bottomless Lake! It is not clear to me how the whole thing started, but a short Google search reveals discussions of the mysterious bottomless lake in Cajon Pass, including this delightful little excerpt:

"I was there swimming not to long ago and saw a man catch a fish that looked like a bass but the eyes were huge and almost popping out! He was gonna take it home to find out what it was but released it fearing it might die and it turn out to be a pre historic fish. I just believe that its a bass that was way deep down under and its eyes popped out as it was surfaced. But what has my attention is the rumors of lost lake having no bottom! Any info?

Anonymous (not verified) on Mon, 09/06/2010 - 9:32pm.
THATZ TRUE LOST LAKE HAVE NO BOTTOM THEY CHECK ALREADY"

I always find myself wondering who the mysterious "they" are...

Anyhow, Lost Lake is a sag pond along the fault trace, which is fed by springs (groundwater is often forced to the surface along fault lines). I am guessing that the "bottomless" rumor came along when the association of the lake with the fault became locally known... a line of thinking that might go... "faults go to the center of the earth, or something like that, so a lake on the fault won't have a bottom either". Of course one can see the bottom of the lake in the GoogleEarth image, and the crime report I read noted that divers looking for the body mentioned that the the lake is barely 20 feet deep.

The lake has been a trash heap and hangout for undesirable people over the years, but it looked on my visit like the Forest Service was trying to improve the situation. There was not as much trash as I remembered from the past, and signs noted that a recreation fee was required for parking. The cattails were healthy too.
A short walk up the hill provides a view of the fault scarp and the Blue Cut, an exposure of the mangled and broken rock within the fault zone. In the picture below, the San Andreas cuts through the left flank of the hill in the distance and crosses the freeway in the left margin of the picture. Lost Lake is the small pond in the center of the picture.
The GoogleEarth image below shows the fault relations at Lost Lake, including a very nice example of an offset stream. The San Andreas is a right lateral fault, meaning that an object across the fault from the observer is moving to the right (note the arrows in the picture at the bottom). Terraces, scarps and channels at Lost Lake have been extensively studied to construct a chronology of past earthquakes at this site, and there have been some big ones (an older reference is included below). Two historical events involved nearby portions of the fault, the 1857 Ft. Tejon earthquake (with a magnitude in the vicinity of 8), and possibly in 1812, an earthquake that caused serious damage as far away as Mission San Juan Capistrano. The average recurrence interval may be as little as 100 years.

And all of this can be seen from a quick detour off the freeway! It's a great place to learn about faults.

Weldon, II, R.J., and Sieh, K.E., 1985, Holocene rate of slip and tentative recurrence interval for largfe earthquakes on the San Andreas fault, Cajon Pass, southern California: Geological Society of America Bulletin, v. 96, pp 793-812

What's Wrong With This Picture? Travels in Southern California

Southern California is ... unique. I grew up down there, along with several tens of millions of other people, and I watched my town grow from a little community of 20,000 people to something like 100,000 when I left thirty years ago. I've had occasion to return more than a few times and I see seven or eight cities which have merged and overlapped to form an urban center that isn't called Los Angeles or San Diego, yet has more than 2 million people. They have to live somewhere, and that's forced many to live in places that have to be considered sort of marginal.

In my high school days, I ran cross country, and we trained in the foothills and across the alluvial fans at the base of the San Gabriel Mountains beneath Cucamonga and Ontario Peaks (8,859 and 8,693 feet respectively). I liked exploring the chaparral country, especially after the spring rains, and in those days, the fans were undeveloped. They were considered sort of a wasteland, too rocky to grow citrus or graze cows, as was done in the flatter valleys below.

It was quite a shock, then, to visit some relatives who lived in one of the newer developments, tucked right up against the mountains. In many third-world countries, people live in the marginal environments in shanties. In Southern California, they live in two story mansions.

So here are my questions for the day: How many natural hazards can people in the developments above, at the base of the eastern San Gabriel Mountains, reasonably expect to experience at some point in their lives? What is the geological cost of living in beautiful Southern California? And how many of these hazards are spelled out in the mortgage papers these folks sign?

Making a Final Stand: Friday's Mystery Photos

The answers to Friday's Mystery Questions came fast and correct! The answers:

What is wrong with the poor tree? Answer: Nothing.

And why is that the wrong question to ask? Answer: Because nothing is wrong with the tree. It is indeed a Dawn Sequoia, which is a deciduous tree that drops its needles every fall.

How can this tree be related to the one discussed above? The second tree is a gingko, and both trees are "living fossils". They both occur in the fossil record, and the gingko is a familiar ornamental tree, but it occurs in the wild in only one or two groves in China and the 'wildness' of those groves is disputed. The trees must have been virtually extinct before a few of them were discovered and cultivated by humans. The Dawn Redwood was thought to be extinct until a small grove was identified in China in the 1940's.

And what does any of this have to do with geology? In the fossil record, the trees are found on widely separated continents, indicating previous connections between the landmasses, connections that have been sundered by the movements of continents, or by changes in sea level.

I've discussed the story of the redwood trees here and here. One of the most spectacular places to see redwood species as fossils is Petrified Forest National Park in Arizona, but other preserved forests occur in Yellowstone National Park, and in the Calistoga area in northern California (below).

So why the title? What 'last stand'? The trees were reduced to a final stand, small groves that could have been destroyed by fire or logging. Unlike the usual outcome when humans are involved, the trees were saved and now are found throughout the world. That's gonna be an interesting mystery for paleontologists a hundred million years from now!

Another Friday Mystery Post

I'm on the road again today, seeking out the mysteries of Life, the Universe and Everything, and I have my towel in hand (literary allusion), but sometimes the best little mysteries come from the home territory. I was out walking on our campus, and realized there seemed to be a problem with this tree that is situated next to the soon-to-be Student Services Building (the construction of which has been very loud; my lab is next door). I took a closer look at the foliage (below).
So the mystery has two parts. What is wrong with the poor tree? And why is that the wrong question to ask?
A short stroll to the other end of the building revealed an extra dimension: how can this tree be related to the one discussed above? And what does any of this have to do with geology?