The Karst Topography...of California? A Look at California Caverns

We took a field studies trip a few weeks ago, and it turned into a mini-series on the karst terrain of California, a landscape that forms over limestone and marble. The development of caverns leads to distinctive features on the surface above, including sinkholes and disappearing streams. I've covered the sights we saw on that trip, but there are plenty of other caverns across the state, more than a thousand of them. I've only explored a relative handful, but the ones I've seen are spectacular. I'm going to explore a few more of them in coming posts.

Today's post is about some caverns in the Mother Lode of the Sierra Nevada named after the state. California Caverns have been known since the Gold Rush days, and etchings in the cave dating to the 1800s attest to the long history of human exploration. To no one's surprise, the well-traveled parts of the cave have been used and abused. It was standard practice in the old days to break off stalactites as souvenirs, and to use a cavern wall as a register.

This fact is what makes California Caverns a special treat. In the Gold Rush days, only about 300 feet of passageways were known, and the worst damage occurred in those passages. They are rather barren and unremarkable.

The deeper passageways are somewhat less damaged, and the cave becomes more interesting. Some of the higher ceilings escaped vandalism and retain some marvelous examples of cave bacon.

Our guide takes us into the deeper passages to the Bridal Chamber. There is an immense mountain of flowstone in the back that is just stunning. It is noticeably cleaner and white than speleothems in the previous passageways. In older days, this was the end of the cave. A debris-filled passageway behind the Bridal Chamber went unnoticed for many years. Several decades ago, spelunkers started moving the debris, and squeezed through an extremely narrow hole (which would have caused me to become unhinged, given my tendency towards claustrophobia in certain situations).

The explorers emerged into a stunning chamber, now called the Jungle Room. No human had ever set foot here before. I can barely imagine what that was like. Luckily, they kept the room a secret for years, safe from vandalism, before preparing the cave for public tours. Now, anyone can see what a pristine cave looks like. It's true that pristine caves don't have carefully placed lighting, but one can think of the situation as being like a museum exhibit: the art is carefully managed, and lighting is used for highlighting the best perspective.

The room is filled with incredibly delicate stalactites and soda straws, the kinds of speleothems that are the first to be broken off by vandals and souvenir hunters. There are thousands of them, each one a treasure. They are pearly white, having never been grimed up by torches and sooty lanterns.

Dark corners hint at additional passageways, and indeed California Caverns are now known to be one of the longest caves in California, at 1.4 miles (the longest in the state is Lilburn Cave in Kings Canyon National Park at 21 miles, 28th longest in the United States).

Every corner of the Jungle Room is a revelation...I could almost feel the joy that John Muir felt when he visited the caves before they had been so badly defaced:

Here we lingered and reveled, rejoicing to find so much music in stony silence, so much splendor in darkness, so many mansions in the depths of the mountains, buildings ever in process of construction, yet never finished, developing from perfection to perfection, profusion without overabundance; every particle visible or invisible in glorious motion, marching to the music of the spheres in a region regarded as the abode of eternal stillness and death.

The caven is still active. In wet years the lower passageways are filled with water and must be pumped to provide access. Seeing the water flowing across the surfaces of the cave decorations provides greater depth to their appearance.

California Caverns were in the center of the area that burned during the Butte Fire in September, and they lost power and water. Amazingly, the visitor center survived, but vegetation in the area was severely affected. The caves are open for visitation, however, and are being done temporarily as lantern tours. You can get updates concerning the caves by clicking here. 

California Caverns are another treasure of the state's karst topography. They are worth a visit if you are ever in the vicinity of San Andreas in the Mother Lode.

Intense November Weather in Central California...and Tornadoes?

Credit: Jacquetta Wehking

I tell my students on occasion that they live in a place that is relatively free of the most serious geological hazards. We are a fair distance from the earthquake faults that wreak havoc on the coastal cities (the San Andreas and Hayward faults, for instance). We mostly live on a river terrace so serious floods do not impact most of the city (the floodplain developments are an exception of course). We live far from volcanoes or steep slopes that can fail. But I also warn them that there is no place in the world that is entirely free of geologic hazards. I got reminded of that today. A tornado touched down just a few miles from my house, causing some serious damage, but thankfully no one was hurt. Friends were witness to the event. It was uncomfortably close.

Tornadoes are not all that rare in California. No one could mistake our funnel clouds for the monsters that regularly roar down through Tornado Alley in the central United States, but there have been 403 confirmed events between 1950 and 2013. The majority have been weak, as only 25 of them reached EF2 or more. But they do happen, and there was enough energy in the latest storm to produce one this afternoon.

Source: http://thevane.gawker.com/maps-tornadoes-in-california-arent-as-rare-as-you-migh-1670728375

It's been a wild weather month here in central California. I went walking to see the retreating edge of the tornado-forming storm from the new parkway they're building along the Tuolumne River. It's looking very different than it has for most of the last four years. It's wet. Ponds of water covered parts of the recently aligned trail.

We've had three major storms in as many weeks, and they followed two weaker storms last month. The month is half over, but it is already the second wettest November in the twenty-five years I've been keeping records at my home east of Modesto in the Great Valley. We've received 2.48 inches, which is equivalent to nearly a fifth of year's normal precipitation. It would be nice if this were a harbinger of more storms to come. We've been in the throes of the worst drought in the historical record. Last year's snowpack in the Sierra Nevada amounted to less than five percent of normal. Our reservoirs are just about empty, and the shortfall would not be made up even if we had a record year of precipitation.

As much as we hope for an end to the drought, it's a clear case of being careful what you wish for. El Nino weather years are known for producing intense weather events, causing flooding and mudslides in central and southern California. And the El Nino that has been building in the Pacific Ocean this year is a record-breaker, a storm-maker on steroids. Our storms so far haven't even been warm storms out of the south. The main effects aren't really expected for another month or so.

As I walked this afternoon, I noted that there was already a small slope failure along the trail. It did no damage, but it's a warning of what may be coming.  I was reminded of the floods of 1997 when the Tuolumne River was flowing at 70,000 cubic feet per second, the highest ever recorded. The river threatened numerous bridges, and flooded more than 1,000 homes downstream. And the flood could have been worse had Don Pedro Reservoir upstream hadn't held back the highest flows (at one point, the inflows exceeded 130,000 cubic feet per second).

One thing I am anxious to see happen is a high enough runoff to scoop out the hyacinth plants that are threatening to cover the river. The invasive weed crowds out the native plants, blocks light from the river bottom, and lowers the oxygen content of the water. It's been around for years, but the infestation has been particular bad in this year of constantly low flows.

I turned around and reveled in the sunset and fall colors that have finally arrived. I know that a lot of you live in places where the fall colors are astounding and all, but California is simply a darn nice place to live, despite all her problems. Here I was walking in a light shirt and short pants, in the middle of November still enjoying the changing leaves of the trees. I can visit snow if I want to, but I won't be shoveling it. It's been a tough four years of drought, but maybe the tide is turning. A record wet November is certainly a good start. I can do without the tornadoes, though.

2.0% of the Tuolumne River Story, Courtesy of the Tuolumne River Trust. And 8-foot-long Saber-toothed Salmon!

Standing on the Dana Fork, close to the headwaters of the Tuolumne River in January of 2012 (when no snow had yet fallen)

Rivers often get used as a metaphor for life. Writers might compare the exuberance of youth with the dancing streams and waterfalls at the headwaters of rivers, and the calm deep waters of the big rivers denote adulthood. And of course, there is the "Old Man River". In a way, geologists once did the same thing, designating different stages of river erosion as "youth", "maturity" and "old age". On a planet that is so active, rivers rarely follow the script of such simplicity. Rivers undergo constant change, and some parts of river systems can be older than other parts. The watersheds can be altered by mountain-building events, lava flows, landslides, and other dramatic changes in a landscape. The Tuolumne River certainly fits that bill.

The Tuolumne River flows through the flat valley of Tuolumne Meadows, the location of a 2,000 foot deep ice sheet during the ice ages. The longest glaciers of the Sierra Nevada, 40 miles long, originated here.

The river seems "normal" enough. It has headwaters high in the Sierra Nevada in Yosemite National Park, it has carved a deep canyon along the middle stretches, it flows onto the plains of the Great Valley of California, joins up with other rivers, most notably the San Joaquin (although the San Joaquin hasn't contributed significant water to the system in many decades), and finally ends in the delta complex at the head of San Francisco Bay.

But there are significant deviations. In the high country of the Sierra Nevada, the river flows across a mostly horizontal landscape for a number of miles. Tuolumne Meadows could almost be described as a swampy stretch of river, especially during the spring runoff in wet years. Then the river plunges headlong into a deep gorge, complete with waterfalls and cascades that would be more characteristic of the headwaters.

Into the river at LaGrange Bridge

Along the ridges and slopes high above the present day river, there are stretches of river gravels from a long-gone ancestral Tuolumne River, one that may have had its origin in central Nevada. Other ancestral Tuolumne Rivers lie within the sediments of the Mehrten Formation that form bluffs around the present-day river in the foothills. These mudflow deposits (and occasional lava flows) record a time when volcanoes erupted near the Sierra Nevada crest only 9-10 million years ago.

I had a marvelous opportunity to explore 2% of the river last week, courtesy of the Tuolumne River Trust. The trip was a three mile long canoeing expedition (the river is 149 miles long, thus 2% of the river), from the Old LaGrange Bridge to the Old Basso Bridge. It was a yearly event, the "Paddle with the Salmon" trip. This part of the river flows among the lowest foothills of the Sierra Nevada, just a few miles upstream from where the river emerges onto the floor of the Great Valley at Waterford.

2% of a river doesn't sound like all that much, but there is a lot of geological history wrapped up in those couple of miles of river. Old LaGrange Bridge was built in a spot where the granitic and metamorphic rocks of the river disappear beneath sedimentary layers. There are three named formations in this part of the Sierra Nevada foothills: the Ione, Valley Springs, and Mehrten formations. They encompass around 40 million years of geologic history.

Around fifty million years ago, the region was very different. The Sierra Nevada, which had been an Andean-sized mountain range throughout most of the Mesozoic Era (the age of the dinosaurs), had been deeply eroded to what amounted to low hills (in many interpretations anyway; the issue is "under discussion" in research circles). Large rivers with a source at least as far east as central Nevada flowed across what would later become the crest of the present-day Sierra Nevada. These rivers flowed into a tropical coastal complex that included swampy estuaries and extensive sandy beaches. The resulting Ione formation has been mined for low-grade coal called lignite, for clay (used in ceramics), and the beach sand has been mined for glass-making (you can tour one of the old mines at Black Diamond Mines Regional Preserve near Antioch). We drove past exposures of the Ione where we got onto the river.

The river sediments, called the Auriferous Gravels were also mined, much to the detriment of the riparian habitat of the Tuolumne River. "Auriferous" means gold-bearing (Au is the chemical symbol of gold). Miners turned the river upside down in their search for the elusive metal. They used pans and other placering methods at first, but by the early 1900s they were using large floating barges called dredges. The dredges would be floated in a newly dug pond (filled by seepage from the high water table), and giant shovels ate away at one edge of the pond. They processed the sediments for the gold on the barge itself, and then used a conveyor belt to dump the waste rock at the other end. In other words, the dredges were sailing across the landscape, carrying their ponds with them.

The biggest terrifying rapid of the day! When one of the canoes got hung up on a rock, the trip leader hopped out of her raft, walked over the canoe, and moved it along. Yeah, the river was kind of low...

The dredges remained active through the early 1970s. The dilapidated remains of an abandoned dredge can be seen just a couple of miles from our section of the river, off LaGrange Road. The remains of a dredge maintenance camp can be seen on a bluff above the river at Old Basso Bridge. One of the old dredge fields has been preserved as a county park called the Joe Domecq Wilderness.

Many of the efforts of the Tuolumne River Trust involve the rehabilitation of the riparian habitat along the river, to assist in the recovery of the population of Chinook Salmon and other native species. There is a lot of work to do. The dredges were terribly efficient, with the emphasis on "terribly". The heritage of the mining efforts are barren fields of boulders. The fertile soils are long gone.

Near the end of the rafting trip we passed buff-colored exposures of the Valley Springs formation. The layers contain volcanic ash and tuff from gigantic eruptions of rhyolite calderas (so-called "supervolcanoes"). Incredibly, the eruptions took place in central Nevada. These ash layers traveled hundreds of miles! There were Native American grinding stone holes in some of the exposures.

In the hills above us we could see ledges and cliffs of the Mehrten formation. From about 11 million to 7 million years ago, eruptions from andesite volcanoes near the crest of the present-day Sierra Nevada produced huge lahars, or volcanic mudflows that choked old channels of the ancestral Tuolumne River. The river would shift in response to the disruption and establish new channels. The rivers flowed across low plains populated by various species of camels, horses, antelope, and mastodons. There were also large Galapagos Tortoise-sized turtles, and strangest of all, 8 foot long salmon with large teeth variably described as tusks or saber-teeth. Despite the fearsome teeth, they probably fed on small prey. If you would like to learn more about the salmon and the turtles, check out the new exhibit at the Great Valley Museum at Modesto Junior College.

We only saw a few salmon during our float trip, but that was okay. We know they're out there. What we did see was 40 million years of Sierra Nevada history exposed along just 2% of the river's length. What a marvelous adventure in the past (and in the present day as well)! I deeply appreciate the kindness of the Tuolumne River Trust for allowing me to join in on their journey.

The Great Valley Museum at Modesto Junior College is Seeking a Director

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.

The Karst Topography...of California? Into the Black Chasm

California is not really known for her expanses of karst topography, the landscapes that develop where limestone or marble lies underground. In my short mini-series about the karst of California, we've seen the gold-fields of Columbia State Historical Park, the grinding stones at Chaw'se State Park, and the Natural Bridges of Coyote Creek. Today we are going underground to see the reason for the sinkholes and disappearing streams: the caverns of California. Believe it or not, there are more than a thousand of them! There are about eight of them that have been developed for tours. We'll have a look at some them over the next few posts.

On our recent trip exploring the karst topography of the Sierra Nevada Mother Lode, we visited one of the most unique: Black Chasm Cavern, near the Gold Rush town of Volcano. Black Chasm was opened for tours around 1990, but it has been known since the Gold Rush days.

An early discovery by miners is usually the death-knell for a cave. The early explorers tended to be careless, and they thought nothing of breaking off cave decorations (speleothems). Such caves eventually became muddy holes in the ground, bereft of any beauty. But Black Chasm had something going for it, something that protected the cave: it was the Black Chasm itself.

Just inside the very step entry passage, there is a 100 foot deep fracture that halted any further exploration of the cave unless the spelunkers had technical climbing gear. Far down at the bottom of the chasm, there is a turquoise colored lake. When the cave was developed, the owners affixed a stairwell across the upper part of the chasm, providing access to the Landmark Room at the far end of the cave (the tour covers several hundred feet of the cave, which has a total of about 4,000 feet of passageways).

The Landmark Room is a true revelation for cave enthusiasts: it's almost completely untouched by vandals and sloppy cavers. The speleothems (cave decorations like stalactites, stalagmites, columns, draperies, and flowstone) have never been snapped off or otherwise damaged.

The stalactites and draperies are spectacular. The owners have done a good job of lighting the cave to highlight the most interesting decorations. I've toured the cave a dozen times or more, and I always find something else to photograph.

It's quite amazing to see draperies that have never been stained by the grime of torches and candle lanterns.

The speleothems could be easily snapped off, but it has not happened. It's a marvelous privilege to see untouched caves. But Black Chasm has achieved National Natural Landmark status for a different reason: the helictites. National natural landmarks are established by the federal government, but the land where these landmarks have been established are privately owned. The status represents an agreement to protect the landmark from damage or development. 

The helictites at Black Chasm are extraordinary. They can be thought of as stalactites on an acid trip, as they seemingly have completely disregarded gravity as they have grown. They may start growing in the style of stalactites, but water can be squeezed from the interior under hydrostatic pressure, and grow in random directions. They aren't immediately apparent on the conducted tour, because they actually keep the lights in that corner of the cave off (we look where we are directed, after all). One begins to notice the helictites here and there in dark corners, a few dozen on the cavern walls. I'm perhaps giving something away here, but I am surprised every time the lights come on.

Because that's what happens. The lights come up, and there is a wall covered by thousands upon thousands of helictites in a chaotic pattern that is simply stunning.

Helictites are among the most delicate of cave decorations, the first to be destroyed by vandals and careless cavers. But this cave was protected for a century by the Black Chasm, and the owners have been careful to preserve this incredible resource. They were never broken off, and as such, this wall of crazy stalactites is probably the most complex and spectacular group of helictites that can be seen in any show cave in the country, maybe in the world.

The cave is operated by the Sierra Nevada Recreation Corporation, and the cave is generally open all year for tours. They offer discounts for educational tours like the one we took two weeks ago. If you get a chance to tour the Mother Lode, Black Chasm is certainly worth a look. For more information, check out their website at http://caverntours.com/black-chasm-cavern-national-natural-landmark

The

The Karst Topography...of California? California has Natural Bridges, and not Just in Santa Cruz

I've been reviewing some of the stops on our recent field studies course through the karst country of California. This landscape is the portion of the Sierra Nevada Mother Lode that is underlain by the marble of the Calaveras Complex. The marble originally formed as limestone on the floor of the Pacific Ocean, and was mashed into the western edge of North America as the ocean floor was thrust beneath the continent along a subduction zone several hundred million years ago.

The marble was eventually uplifted and exposed at the earth's surface by erosion. The term "karst" refers to the tendency of such landscapes to develop sinkholes as underground caves collapse. Rivers have a tendency to disappear in such places. In today's post, we look at a creek that disappears, and reappears. Twice.

There is a place called "Natural Bridges" that is familiar to many Californians. It along the coast at Santa Cruz, and is actually a sea arch eroded by wave action. Less familiar are the Natural Bridges that span Coyote Creek between Columbia State Historical Park and Vallecitos on Parrot's Ferry Road in the Mother Lode.

In geologic terms, a natural bridge is usually taken to be an arch that has formed as a result of stream erosion. The epitome of such arches are found in Utah at Natural Bridges National Monument in the state of Utah. The bridge at Santa Cruz is more properly termed a "sea arch". Karst processes can also produce bridges, as an erosional remnant left behind as caves collapse, leaving openings through which water is flowing.

The Natural Bridges of the Mother Lode are certainly karst related, but in a slightly different manner. At Coyote Creek, springs of carbonate-laden water emerged from the hillside above the river, and calcium carbonate, the mineral that makes up limestone and marble, was precipitated into large masses called flowstone (a great deal like Mammoth Springs at Yellowstone National Park). They blocked the creek, but eventually water worked through the base of the spring deposits. Eventually the creek carved a course under limestone dam. The cavern has since been decorated with all manner of speleothems, stalactites, stalagmites, columns, curtains, and others. As can be seen in the pictures above and below, the springs are still active. There is a constant music of dripping water at the entrance to the upper bridge.

You can get a sense of the falling water in the shaky low resolution video below.

There are two bridges on Coyote Creek. Most hikers visit the upper cave, which is at the end of a relatively gentle one mile trail. It takes a bit of scrambling to get to the upper entrance to the cave, but it's apparently a fun float or swim through the several hundred foot long cave. I haven't had the privilege, as I've visted most often during the late fall season when the water has been cold.

It is possible to walk well into the entrances without getting too wet.

The bridges have suffered quite a bit of damage over the years. Tourists have been visiting the site for more than century. A hotel even was constructed on top of the upper bridge for a time. Many of the cave decorations have been broken off. Luckily, floods flush out the cave every so often, and it is high enough that some decorations are out of reach of vandals.

The lower cave lies several hundred yards downstream. Far fewer people know about it, and it is a bit of a challenge to get there. One can follow the creek for the most part, but the way is blocked by brush here and there, so trails of use climb the canyon walls in a few illogical-seeming spots. It's worth the effort, if just to get away from the occasional crowds at the upstream caves.

It's a bit shorter and the downstream exit is visible from the upper entrance (which makes some a challenge of some picture angles).

The bridges are on public lands administered by the Bureau of Reclamation (New Melones Reservoir lies just downstream), so the caves are nominally protected by ranger patrols, though I've never seen one. Mostly those of us who enjoy the caves need to be vigilant for vandals. Check this link for directions and maps to the caves: http://www.usbr.gov/mp/ccao/newmelones/planning_visit.html.

One of the nice things about the walk to the lower cave is the smooth exposures of marble along the creek between the two. It is white marble streaked with gray, and has been polished by numerous floods. The Calaveras marble originated as coral reefs or carbonate muds in tropical environments in the tropical latitudes of the Pacific Ocean. Strangely enough, the marble was featured on the front page of our local newspaper this week. It's about a marble quarry just a few miles away from the bridges. Check it out: http://www.modbee.com/news/article43637292.html.

These rocks have been on an incredible journey.