The Other California: A Bit of the Rarest Ecosystem in SoCal at the North Etiwanda Preserve

 

This is ultimately a story about what may be the steepest mountain in the world (although I cannot yet confirm this). But the story involves a little bit of a journey down memory lane if you can bear with me a bit!

When I was a kid in Ontario, California in the 1960s, we possessed one of those wonderful things that kids don't have enough of today: a big backyard. There was room enough for a big lawn for ball games, large hedges and trees, and climbable walls around the lot. And enough bare ground that a kid could dig nice deep holes, looking for fossils or buried treasures. But what I found when digging those holes was a lot of rocks. Big rocks, cobbles really, of granite and gneiss and schist, although I didn't know those terms at the time. But I did wonder where the rocks came from.

Earth science wasn't much of a thing in my primary education in the 1960s, but I knew enough to think the somewhat rounded rocks came from a river. But there were no rivers to speak of in the Inland Empire east of Los Angeles. I got an education about that in 1969 when the biggest floods in nearly two generations hit the valley. Streets turned into rivers, and numerous houses and buildings were destroyed by mudflows coming out of the nearby San Gabriel Mountains. Nearby Day Canyon recorded an outflow corresponding to 33 inches of precipitation across its small drainage basin in 24 hours on February 25, a state record. 

The perspective of this photo may deceptive; all the road you see here is sloping downhill for the entire 14 miles

And then, in the 1970s, it was high school and the cross-country team. A favorite training route was to run up Euclid Avenue in Ontario and Upland (AKA State Route 83). It still is one of the prettiest city roads in the state, with a wide median planted in Pepper Trees and numerous architecturally distinctive homes dating from the early 1900s. It runs for 14 miles in a straight line from San Antonio Heights to the Chino Hills. 

On the easy days we needed only to run a four-mile out-and-back practice to Foothill Avenue, but when the coaches were bearing down, we needed to run all the way up to Baseline or further (6-8 miles). The thing is, the farther one ran up the hill, the steeper it got. Thus was my introduction to the geometry of alluvial fans. During the mudflows and flashfloods that produce the fans, the coarser debris drops out first, and finer-grained materials get carried further out into the plains below. A fan has a concave profile, becoming steepest at the top. 

Some days, the coaches would drive us up into the barrens at the top of the fan, and our runs included a series of breathtaking terraces (and I mean this in the literal sense, as we were breathless by the time we climbed them). I had no idea at the time why they were there. It seemed like alluvial fans should have a smooth profile, not a terraced one.

In the late 1970s I was in college, and my education about alluvial fans and earthquake faults became a bit more complete. These alluvial fans that I had exhausted myself on during cross-country practice were textbook examples of alluvial processes, and maps of them were indeed a part of my laboratory exercises. I also learned that the terraces were actually fault scarps, produced in the last few thousand years by titanic earthquakes that have been lifting the San Gabriel Mountains. They've been uplifted so rapidly that the mountain ridge that includes Ontario and Cucamonga Peaks may be one of the steepest mountain slopes in the world (I heard this statistic at a conference, but I have not been able to locate the reference). The mountains are so steep that mass wasting is a far more dominant form of erosion than river flow. And the mountains are indeed massive, rising 7,000 feet from their base to the highest peaks.

Thus it was that when I left the region in the middle 1980s, the cities below were growing, but the alluvial fans above them had defeated attempts at agricultural development (the lower slopes were ideal for vineyards and citrus orchards). The surfaces were ignored, or used for garbage dumping, shooting, and off-road vehicle travel. They were considered wastelands. Someone had had the bright idea of putting Chaffey College up there, miles away from the main population centers in the valley (it's visible in the lower left corner of the map above), but the college stood apart, surrounded by scrublands.

Sometimes, the lands that seem so barren do in fact have value, and the more they disappear, the more precious the remainder becomes. So maybe it is a good time to ask: what are alluvial fans good for anyway? Here are my thoughts in no particular order:

Artesian wells near San Bernardino in the early years of settlement. Source unknown, but found at you have water mail: artesian wells in San Bernardino, California

Alluvial fans are a vast sponge that could hardly be designed better to capture water and store it underground, safe from evaporation. The Inland Empire became an agricultural powerhouse in the last century on the basis of the citrus fruit industry. It was a desert climate that very rarely froze, and yet had a wealth of water underground. Sometimes at the distal end of fans, artesian springs produced fountains of water that could be easily utilized in the vineyards and orchards (artesian springs and wells are those that flow due to underlying pressure and don't have to be pumped to bring water to the surface).

Urbanization robs much of the fan surface of the ability to absorb water, given that pavement and buildings tend to shunt floodwaters into the concrete flood channels. They in turn are designed to carry water downstream without damaging buildings. If they have enough capacity, that is.

The south slope of Cucamonga Peak, Can anyone see a viable climbing route? I don't think chocks and pitons would work in the rotten rock, but I suppose you could anchor to the trees. That's how I climbed a similar (but shorter) canyon in my youth.

Alluvial fans are a buffer from huge mass wasting events. The mountains above the Inland Empire are, as pointed out previously, among the steepest mountains on the planet. In addition, the rocks that make up the steep cliffs are badly fractured and jointed from the intense faulting and pressure resulting from their uplift. I can't find many records of people climbing the mountain from the south other than up a ridge after a wildfire had cleared the brush. These slopes are exceedingly unstable, and landslides and slope failures are a constant hazard. 

The Blackhawk Slide on the north side of the San Bernardino Mountains. Credit: Kerry Sieh of the U.S. Geological Survey

It may be an extreme example, but the Blackhawk Slide on the north side of the nearby San Bernardino Mountains is a gigantic debris avalanche that traveled 5.6 miles across the surface of the alluvial fan about 17,400 years ago. It was probably set off by a large earthquake, and traveled on a cushion of compressed air. Such huge events are extremely rare, but not out of the realm of possibility.

Mudflows are also considered a form of mass wasting, and the upper parts of alluvial fans are the danger zone for the flows containing the largest boulders (which can be ten feet or more across in extreme instances). 

Mudflow that followed wildfires in the San Bernardino Mountains in 2004. Courtesy: U.S. Geological Survey

Wildland-urban interfaces are a rising concern as urbanization spreads into once wild landscapes. Among the greatest concerns are the incidences of wildfires spreading into cities because of their proximity to chaparral-covered slopes. I'm not speaking as an expert here, but it seems to me that alluvial fan surfaces are a more defensible surface than rugged slopes. Housing developments that butt up against the hillsides would seem to be in the greatest danger in our new normal of drought, rising temperatures and increasing wildfires.

Finally, alluvial fans are a unique and rapidly disappearing ecosystem. The alluvial fans hosted a wide variety of shrubs, grasses, and wildflowers, along with excellent habitat for all manner of mammals, birds, reptiles, and amphibians. Some of the Southern California species are found nowhere else in the world. This rare ecosystem has a name, the Riversidian Alluvial Fan Sage Scrub (RAFSS). It is limited to the alluvial fans along the southern exposures of the Transverse Ranges, including the San Gabriel, San Bernardino, and San Jacinto Mountains. Those fans are as much as 90% urbanized now. There is very little of the original landscape left.

Satellite image of the alluvial fans north of Interstate 210 at Upland and Rancho Cucamonga. The blue marker shows the location of the North Etiwanda Preserve

And so we come to the present day. I returned to the landscape of my youth on a trip last week, and the changes were astounding. I knew that urban development had been creeping up onto the fans, but I never had a good look at the magnitude of the changes. Housing developments and shopping centers have swept up like a tsunami onto the upper reaches of the alluvial fans. Chaffey College has been engulfed by the wave of development and is surrounded by housing tracts.

Despite my dismay at the magnitude of urban development, I found out that a significant portion of the RAFSS has been preserved as the North Etiwanda Preserve. The relatively recent extension of the 210 Pasadena Freeway into San Bernardino had destroyed a significant part of the RAFSS, and as mitigation, 762 acres were given to San Bernardino County for preservation in 1998. Other land acquisitions brought the size of the preserve to 1,176 acres (nearly two square miles). Even better, the lands preserved were contiguous with the slopes leading up Cucamonga Peak, providing an intact ecosystem connected to the nearby trees and chaparral of San Bernardino National Forest.

A three mile long trail winds through the preserve, with numerous interpretive signs detailing the geology, biology, archaeology and recent human history of the region. I didn't have time to walk the entire route, but I was able to see (to my tectonic delight) a perfectly pristine fault scarp running across the preserve. You can see the terrace in the pictures above and below. The last major earthquake probably happened one or two thousand years ago, and may have ranged as high as magnitude 7.5.

Cucamonga Peak is a southern California treasure, a fact not always appreciated by those who live on the alluvial fans below. It is a dangerous neighbor as well, with earthquakes, fires, and floods a serious concern. The North Etiwanda Preserve is a wonderful resource for learning about this unique landscape, and is one of the few places where one can get a sense of the landscape that existed before urbanization swallowed it up. 

On a final note, when I was at Chaffey College in 1976, the geology department got a call from a gravel quarry just east of where the preserve is today. They had found a bone of some sort. It turned out to be a fragment of a tusk from a Columbian Mammoth, one of the many megafauna species that wandered these alluvial fans during the last ice age (although no glaciers came close to this place). One could almost imagine the Columbian Mammoths, Dire Wolves, Sabertooth Cats, Giant Ground Sloths, Short-faced Bears, Horses, and Camels that once roamed across Southern California while strolling the trail at the preserve.

For more information about the natural history of the North Etiwanda Preserve, check out this website at the The San Bernardino County Museum (sbcounty.gov).

This post is part of The Other California blog series I've been writing since 2009.

One of the Most Astounding Viewpoints in America: At the Outer Ring of Hell (but not really)

A place not to missed. That's what I have to say about Dante's View in Death Valley National Park. And if you ever get there, don't just stand in the parking lot. Short walks in several directions offer even better views of the incredible landscape surrounding the lowest place in North America. Death Valley may get hellishly hot sometimes, but it's not a view of hell but is instead a dramatic perspective of some of the most interesting geology in the American West.

The Black Mountains form the eastern margin of the deepest part of Death Valley, almost directly across from Telescope Peak, at 11,043 feet (3,366 meters) the highest point in the park. The viewpoint is a bit over a mile in elevation at 5,476 feet (1,669 meters). From the viewpoint one can take in almost the full length of Death Valley, a distance of more than 100 miles. Once also look east across the numerous mountain ridges of the Basin and Range geological province to Charleston Peak above Las Vegas, Nevada. A few summits of the Sierra Nevada peek out over the ridge of the Panamint Range across the valley.

Directly below one's feet is a steep one mile drop to Badwater on the valley floor. The slope is so steep that the parking lot and Badwater pond are not visible, but very small humans can be seen on the white trail leading out to the salt flats, and very small cars can be seen driving on the highway that circles the edge of the alluvial fan.

Here's a zoomed shot to see the people a bit better...

The Black Mountains are composed mostly of the oldest rocks in the region, a complex of gneiss and schist dating back 1.7 billion years. Similar rocks are found in the depths of the Grand Canyon in Arizona. They were once covered by several vertical miles of Paleozoic sedimentary rocks, but those rocks have slid westward to form the Panamint Mountains. The gap between became the graben of Death Valley itself.

The rocks making up the summit area are volcanic rocks, mostly rhyolite, which were erupted in violent eruptions around 6-7 million years ago. Such rocks have been found across the Basin and Range province, indicating extensional stretching and failure of the crust, which ultimately formed the grabens and horsts of the region.

I take my use of superlatives in describing viewpoints seriously. You can see my ten (eleven, actually) most precious "spots" in the world, and Dante's View is on that list. There may be other places in the world that allow one to see far, but I suspect few reveal a more stunning and fascinating landscape.

There is a myth sometimes repeated that one can see Mt. Whitney from Badwater, which is simply impossible because the Panamint Mountains rise 7,000-8,000 above the adjacent valley floor. One can see the tips of several Sierra Nevada peaks from the hill north of the parking lot at Dante's View, but I think the highest peak visible is Mt. Williamson at 14,389 feet (4,383 meters). It is possible to simultaneously see both the highest and lowest points of the conterminous United States, but you have to find your way to the summit ridge of the Panamint Mountains and Telescope Peak to do so.

It's truly a place and a view not to be missed.

Out of the Valley of Death: Geology at Fifty-five

One of the first things I tell my students (and occasionally even with some success) is "don't sleep while traveling in the vans". Death Valley National Park is the largest national park in the lower 48 states, and no matter how much time one has, it's hard to take it all in. When you only have four days, it's pretty well impossible, but there is still much to see in transit between stops. On our third day out we were set to explore the northern end of Death Valley, which in a park that is mostly desert wilderness, feels even more isolated and lonely (despite the presence of Scotty's Castle up one of the side canyons).

The day started with a stunning sunrise as seen from one of the most isolated RV parks in the American west, Stovepipe Wells. The campground is literally a parking lot, but it's a parking lot with one of the most incredible views possible. The resort is situated on the distal end of the huge alluvial fan that emerges from Mosaic Canyon on Tucki Mountain, which we'll check out in a future post. The elevation is sea level, but it somehow feels higher, given the spectacular and far-ranging view.

Two great desert mountain ranges form the boundaries of the northern reaches of Death Valley, the Cottonwoods on the left and the Grapevine Mountains on the right in the picture above. The mountains tower over the valley floor, reaching nearly 9,000 feet above a valley floor that is barely above sea level. The view extends thirty miles or more.

A drive north towards the end of the valley reveals a series of classic desert features, starting with the Mesquite Flat sand dunes, sometimes known as Death Valley dunes. Sand dunes are picturesque enough by themselves, but in Death Valley they have a dramatic backdrop of high barren mountains.

We raced by at 55 miles per hour ("Honest, officer!"), but cameras these days are versatile, capturing the image as if we were standing still. And this is the sort of incredible sight one could miss if one is snoring away.

The dunes have formed here because prevailing winds sweep down the northern reaches of Death Valley (and a number of destroyed tents over the years can attest to the power of these winds). The vast bulk of Tucki Mountain at the north end of the Panamint Mountains stands in the path of these winds, causing them to break up and form eddies. The sand accumulated in the region as the powerful winds lose energy and drop their load of sand and dust. They are sometimes referred to as star dunes, or modified sub-barchan dunes. Even if you've never been to Death Valley, you've probably seen these dunes anyway; they formed the backdrop for the droids lost on the planet Tatooine in the original Star Wars movie.

In the picture above, one can see the valley floor beyond the dunes is interrupted by a terrace of some sort. This is the scarp for the Furnace Creek fault zone which is one of the important structural features of the Death Valley graben.

A closer look provides a view of light-colored sedimentary rocks exposed in the face of the scarp. The fine-grained mud and silt layers are part of the Furnace Creek formation, which was deposited into a fault trough similar to present-day Death Valley, but oriented in a more northwest-southeast direction. Crustal stretching has effected the crust in the region more than once. The erosion of the Furnace Creek formation in this dry environment produces badlands topography, which we will explore in greater detail in another post.

The fault system interrupts the surface of the alluvial fan, shifting it in an right lateral direction (the rocks across the fault are displaced to the observer's right). These faults roughly parallel the San Andreas fault, which lies far to the west. The fault is presumably still active, but has not produced a major earthquake in modern times.

Another incredible sight visible from the road is the series of alluvial fans that extend from the edge of the mountains down to the valley floor. They build up as the rare but violent flash floods and mudflows carry boulders and debris across the valley floor. They have a somewhat convex slope, becoming steeper near mountain front. Death Valley is famous for the variety and number of fans it has.

The fans reveal variations in color. The darker surfaces on the fans result from desert varnish, a mixture of manganese oxides and clay that coat the exposed surfaces of the rock. It accumulates over time, and the origin is debated. Bacteria are likely involved in the process.

As we drove further north, the valley floor narrowed, and we soon reached an area where the alluvial fans from the two mountain ranges merged in the center of the valley. We were approaching the end of the Death Valley graben. In the distance we could see dark-colored rocks coating the surface of the alluvial fans. We had reached the volcanoes of Death Valley.

In the next post: the Ubehebes!

From Little Treasures Come Big Stories: Travels Through Death Valley National Park

Photo by Mrs. Geotripper

I returned from Death Valley to a load of work back on campus, but over the next few days I'll be posting on some of our adventures. On Saturday morning, we awoke to sunrise on the Mesquite Dunes east of Stovepipe Wells. We grabbed our packs and notebooks and hit the road. We had a lot of ground to cover.

Oddly enough, for having spent two days getting to Death Valley National Park, one of our first stops was outside of Death Valley National Park. This was for the simple reason that we were looking to understand the nature of the rocks that make up the mountain ranges surrounding Death Valley. Because we didn't have enough time to climb most of the mountains, we would need to see what had rolled out of the mountains during the many flash floods and mudflows that had scoured their flanks over the countless centuries. I have honest students, but their conscience would have had a tough time dealing with all the little treasures they were about to find. So we made sure we were outside the park boundaries when we let them out onto the alluvial fans coming down from the Funeral Mountains. For many of my students it was their first experience in finding a fossil.

Fossil crinoid stems. These are rare in oceans today (they are known as sea lilies), but during the Paleozoic era, they covered the sea floor like fields of wheat, and entire rock layers are composed of their fragments.

To most normal people, 300-400 million years of nearly continuous mud deposition is perhaps not the most exciting process to consider. But if that 300-400 million years covers the latest Proterozoic eon and the all of the Paleozoic era, such activity is irresistible to a paleontologist. A rock sequence that covers that time period contains the evidence of the rise of multicelled life on Earth, as well as the first appearance of all of the extant phyla known (plus a few extinct ones). A phylum, as a biologist will tell you, is one of the broader divisions into which all life can be organized. One phyla, the chordates, contains all the familiar animals with a notochord or backbone (fish, amphibians, reptiles, birds, and mammals). There are dozens of others, including the arthropods (bugs and crustaceans) and the molluscs (snails, clams and squids) which make up most of the species known today. A more or less continuous record of deposition makes it possible to detect patterns and trends in the evolution of life on the planet through time.

Grand Canyon National Park has a similar range of rocks exposed in the depths of the gorge, but huge pieces of the story are missing because of episodes of erosion. Where the Grand Canyon has about 4,000 feet of Paleozoic sediments, Death Valley has more like 20,000 feet! How can 20,000 feet of sediment fit into a mountain range that rises no more than 5,000-6,000 feet above Death Valley and other grabens in the region? If you look at the photo of the Funeral Mountains below, the answer is apparent: the sediments in the mountain range have been tilted. To walk through 400 million years of Earth history, we need only to walk a few miles along the base of the mountains.

How is it that sediments could accumulate for such a long time in such stable conditions? Most parts of the crust of the Earth are wracked by extreme tectonic activity like volcanism, folding, and faulting. The Paleozoic rocks of Death Valley accumulated in one of the most geologically "gentle" environments on the planet: a passive continental margin. A billion or so years ago, most of the world's continents were combined in a supercontinent we now call Rodinia. The continent began to break up at the end of the Proterozoic, which is a process that involves severe faulting and rifting, along with vigorous volcanic activity, but as the continents moved further and further apart, the processes became less active and finally stopped. The edges of the continents became a site of more or less continuous shallow marine deposition, and as more sediments were laid down, the crust slowly sank beneath the weight, allowing even more sediments to accumulate.

So, from a bit of wandering across a stony desert surface picking up random fossils, a story is told of massive supercontinents breaking apart and forming huge wedges of sedimentary rock that tell the story of 400 million years of evolution of life on planet Earth. In short, this is why I love teaching geology.