Sunday, January 31, 2010

The Other California: Lassen Peak, A Volcanic Afterthought...

Getting back to our exploration of the "Other California", those places in our wonderful state that don't always show up on the postcards, and aren't the usual tourist destinations. I break my own rules every so often, and end up visiting a popular or well-known place, but only to emphasize things that a weekend tourist might miss on a quick run-through. Such is the case today, with a visit to Lassen Volcanic National Park.

The park's centerpiece, Lassen Peak, was perhaps more famous among geologists prior to 1980, when it reigned as the site of the most recent volcanic eruption in the lower 48 states. The eruption, from 1914 to 1917 (with a little puff in 1921) included lahars (volcanic mudflows), pyroclastic surges (explosions of hot ash), and a lava flow; in short, all the things a textbook writer would want to describe. One added benefit: it didn't kill anyone (although there were a few close calls). Those of us who had our first geology class before the St. Helens eruption in 1980 learned our volcanoes from the example of Lassen Peak.

Truth be told, Lassen Peak doesn't look much like a volcano. It is a miniscule peak compared to Mt. Shasta (1/2 cubic mile compared to 108 cubic miles). Although it tops out at nearly 10,500 feet, it rises off a plateau at 8,000 feet and thus is only a little more than 2,000 feet tall (Mt. Shasta rises more like 10,000 feet from its base). Visitors looking for a classic-looking symmetrical cone surrounded by lava flows will be disappointed. Lassen is a plug dome, composed of extremely viscous dacite-rhyolite lava. It erupted about 27,000 years ago by squeezing out of the ground in a manner not unlike toothpaste. Although it is a small volcano, for a plug dome it is huge; by most reports it is the largest of its kind in the world.

Lassen Volcanic National Park has a number of famous attractions, including the peak itself, Bumpass Hell and the Sulphur Works, two geothermally active areas, and a number of beautiful lakes including Manzanita and Summit Lakes. The Devastated Area records the result of the lahar and the pyroclastic surge in the main 1915 eruption. Our next few explorations will include several cones that are among the youngest mountains in the state, and a major volcano that has gone missing.

So why am I calling Lassen Peak an 'afterthought'? I'm kind of giving away the whole answer in the photo below, taken during a flight home from British Columbia a few years ago. At one time, Lassen would have been neither the tallest nor largest volcano in the park area. From about 600,000 to 400,000 years ago, that honor would have belonged to Mt. Tehama, a stratovolcano typical of the Cascades Range, similar to such peaks as Mt. Hood or Mt. Baker in Oregon and Washington. It may have reached heights of 11,000-12,000 feet. Following the last of its eruptions, the summit collapsed into a caldera*, or was simply eroded away, leaving behind a jagged ridge of peaks forming the rugged southwest corner of the national park. The Sulphur Works mark the approximate center of the extinct volcano. As can be seen in the photo below, Tehama would have dwarfed Lassen Peak.
The trail to Bumpass Hell provides one of the best ground-level views of the ancient volcano. Brokeoff Mountain on the left and Mt. Diller on the right mark the remaining flanks of the Tehama volcano. The lava flows exposed on each peak slope upwards towards the former summit above the center of the picture.

If any of my California Geology students have made it this far in the post, here is a free question from our Cascades quiz in a few weeks: Mt. Tehama is the most difficult mountain to climb in California, in fact no one has ever stood on its summit. True or False?

*How's this for a volcanic afterthought? As Donald Rumsfeld famously once said, "There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns." Forrest reminds of something that I knew, but didn't have ingrained enough in my brain pathways to recall as I was writing this post. There is no evidence that Brokeoff Mountain ended in a catastrophic caldera eruption, according to the latest research. Instead, the ash tuff (the Rockland Tephra) that was thought to derive from the destruction of Brokeoff actually predates Brokeoff. The volcano didn't form a caldera, but it did grew on top of an older caldera.

Saturday, January 30, 2010

NPS Web Page Chronicles Yosemite Valley Rock Falls

Via, here is a link to a new web page on the rockfall history of Yosemite Valley. Besides a report on rockfalls in 2009 (there were 52), the page includes a wealth of links to other resources about mass wasting phenomena in the region. The map above chronicles the location of all the major rockfalls from 1857 to 2009.

It was a big year in the valley for this sort of thing. The Ahwiyah Rockfall actually changed the appearance of Yosemite as seen from the Wawona Tunnel and Glacier Point forever, and was the largest rockfall in 22 years. Luckily no one was hurt or injured.

Friday, January 29, 2010

The Geologist was Crying Inside....

First, a big shout-out to all the geoblogs out there who provided such first-rate coverage of the Haiti Earthquake over the last few weeks. I appreciate Chris at Highly Allochthonous and for the feeds that got all the information in one place. I was participating in a community symposium tonight about the earthquake in Haiti and needed a powerpoint presentation in a hurry on the geology of the quake, and I found all the info I needed in a few minutes.

The presentation went pretty well. 150 people came out on a rainy Friday night and most stayed for the whole two hours. We had a historian who spoke about Haiti's difficult birth and the difficult conditions that have held Haiti back over the centuries. I was speaking on the geology of the quake, and the implications for a place like California, so towards the ending I tossed up the graphic shown above to see the relative scale of plate boundary relationships in the Caribbean and California. There is no direct correlation, with California part of the American mainland and Haiti an island on oceanic crust, but the idea of a complicated boundary of multiple strike-slip faults leading into a convergent boundary is valid.

It was the last part of the evening that got to me. On the one hand, I was talking to a bunch of Californians and Americans who were interested and upset about what happened in Haiti when the earthquake struck, but despite anything we could say, the country is still pretty much remote from our everyday concerns. On the other hand, three young women sat in the front row listening to our academic discourse. They are MJC students, attending under the auspices of the Cooperative Association of States for Scholarships, the goal of which is to prepare foreign students to return home with personal, academic, and technical skills which will enable them to continue growing professionally, share the benefits of their training with others, and make positive contributions to the development of their countries. Needless to say, these three young ladies were from Haiti. They had lost friends and relatives in the quake, and had to live in fear for days before finding out the fates of their own parents and siblings.

They spoke briefly to the crowd, telling of their pride in being Haitian, and showing pictures of the best of their country, the places of beauty and magnificence, many of which have been lost. I can't imagine what it was like for them; in this country for only a little over a year, learning English almost from scratch, and hearing of the devastation of their home country from afar. And then trying to describe their feelings to an audience of strangers. Sympathetic strangers, but strangers just the same. I tried hard to understand what it was like for them, but the best I could do was to try and imagine what it would be like if the if the situation was reversed. And I felt the tears...

Not to be cynical, but Haiti is going to be gone from the news headlines soon. Some Hollywood star is going to divorce another Hollywood star, or some pro athlete is going to do something stupid, or some politician is going to make some colossally hypocritical assertion. And our collective short attention span will wander to other places. Please don't let it happen. A donation that feeds a few people for a few days is wonderful, but we need to look to the future of the country, and the efforts to help Haitians rebuild an infrastructure that can support the people in the long run. Please consider donating to Habitat for Humanity or other groups that will be participating in the rebuilding of the country.

Friday Field Foto: A Field

A geology professor I much respected was famous for saying "I wouldn't just take you ANYwhere!", no matter how plain and uninteresting the site looked. Invariably, the story told in the drab rocks was far more interesting than the original view suggested, a phenomenon familiar to many of my geologist friends. So today, for all the places I take you on Geotripper, here is a plain and uninteresting...field.

It's not just any field, though. In three years, if the stars align correctly, this will be the Modesto Junior College Community Science Center, and it will be a wonderful facility for advancing the sciences in our educationally-challenged Central Valley of California. Besides housing the Chemistry, Biology, Physics, and Earth Sciences departments, it will also include an observatory, a planetarium, and the Great Valley Natural History Museum.

The project is being funded by our own community through a bond issue that was passed several years ago, and much of the credit for the design and impetus for the project belongs to some very talented and tenacious people in our division. It's going to be a great facility! Construction bids are coming in at the end of the next month, and construction should begin soon after. Expect to see some updates as the building grows.

Wednesday, January 27, 2010

The Other California: A Mystery Solved, and One of the State's Prettiest Little Waterfalls

Monday's post was a bit of mystery, in that a dry channel turned into a rushing stream in less than a half mile. The answer is sort of mundane, but quickly leads into the story of one of the finest, most attractive waterfalls that I know of. It's on a lot of postcards, but I don't think many visitors from outside of the state know much of it. Welcome to McArthur Burney Falls State Park, the second oldest state park in California.

At the hard to define boundary between the Modoc Plateau and the Cascades provinces, basaltic lava flows are interspersed with lake sediments, and a series of fault lines cross the region. Basalt lava contracts as it cools, forming numerous fractures and joints that provide an avenue for surface water to sink into the ground. Consequently, streams and rivers can disappear and reappear in unusual places, sometimes in spectacular manner. Some of the largest springs in the country are found nearby (At Fall River Mills, a group of springs have flows of around 1,400 cubic feet per second, an instant river). Another spring rises on the Burney River (below), forming the river of our little mystery. It's what happens just a short distance downstream that makes this place special.

The water spills over a 129 foot edifice, which in a state that has dozens of high waterfalls might seem insignificant.

From farther back, we see that the water splits into two channels, but we also see that something is going on below the rim. Some of the water is coming is flowing out of the cliff face itself. In fact, a lot of it, perhaps more than is spilling over the edge.

The lip of the fall is a basaltic lava flow. The rock beneath the cliff is much softer, consisting of clay-like diatomite and volcanic breccia. The groundwater can't sink through the underlying layers, and is forced to the surface just under the basalt rim. It makes for a unique sight.

A short trail descends to a deep pool at the base of the falls, and provides another perspective. The amount of water is stunning. The flow of groundwater at the falls is far less affected by seasonal differences in precipitation, so the discharge remains fairly constant all year. If you are visiting California in the late summer, McArthur Burney is a dependable place to see flowing water.

My only (mild) complaint about the falls is that the basin opens to the north, so the sun doesn't shine on the falls much, except maybe mid-day (when I never seem to be present). Photographers do pretty well catching rainbows in the spray rising over the falls, but at the base, pretty much everything is in the shadows. It's a cool place to be on a hot day, but difficult to photograph (at least for amateurs like myself)!

The park offers a nice campground, incredible fishing, and a nice network of hiking trails (the Pacific Crest Trail passes through the park). Information can be found in the park brochure. The California state budget crisis threatens the park's future. For info on how you can help out, check out the California State Parks Foundation. The parks don't deserve to be constant budget footballs; please get involved!

Monday, January 25, 2010

The Other California: A Monday Mystery (and a gratuitous cute deer picture)

Today's entry into the Other California series lies in the Modoc Plateau/Cascade Provinces, and presents itself as a bit of a mystery...

How is it that this dry creekbed...

Becomes this river, less than 1/2 mile downstream?

There are no tributary streams. There aren't any storms in the area. The elevation is about 3,000 above sea level. An inadvertent clue of sorts is buried in an earlier post, found here.

This river is related to one of the prettiest sights in California that is not part of the National Park System, although a visiting president once called it one of the natural wonders of the world.

Oh, and here is your gratuitous furry creature picture for the day. I saw them along the upper dry creek while trying to avoid stepping into the prevalent poison oak.

Sunday, January 24, 2010

The Other California: Five for the Price of One

The Other California is the story of the places in the state that aren't found on all the postcards. I'm finding some subject material in the familiar places that turn out not to be so familiar. Mt. Shasta is an example. The mountain is one of the most famous sights in the state, and people come to the mountain for many reasons: contemplation, climbing, skiing, hiking, and searching for errant Lemurians and Atlanteans. Everyone seems to refer to Mt. Shasta as a single mountain, but a brief look at the peak shows it to be actually five distinct volcanoes.

Mt. Shasta is often referred to as a stratovolcano, due to the alternating layers of volcanic ash and andesitic lava flows making up the structure of the mountain. It is often compared with symmetrical cones elsewhere in the world, such as Fujiyama in Japan and Mayon in the Phillippines. A different term, composite cone, is probably more descriptive. At least five major cones make up the edifice, erupted at different periods over the last 600,000 years.

The two youngest volcanoes, Hotlum Cone and Shastina are the most obvious of these multiple cones. Shastina, at 12,330 feet, is technically the third tallest volcano in the Cascades even lumped as it is with Shasta (it is the prominent peak on the left side of the photo above). It erupted during a series of eruptions around 9,800 years ago.

Hotlum Cone, the highest summit of the volcano, began erupting about 9,000 years ago, and has erupted numerous times since, including a possible eruption only 200 years ago. It is the most likely source of renewed activity on the mountain.

A drive to the end of the Everitt Memorial Highway at Panther Meadows provides a look (above) at two of the older cones. From the parking area Hotlum Cone is not visible. Instead, the upper flank is Misery Hill, and the jagged peaks to the right are Sargents Ridge. The Misery Hill Cone began erupting around 50,000 years ago, while Sargents Ridge is closer to 200,000 years old. Both cones are deeply scored by glacial erosion, and retain little of their original shape. I've outlined the cones in the photo below, including an approximate guess about the location of the Sargents Cone summit (note the slope of the layers).

The fifth volcano is the most enigmatic of all. It pretty much doesn't exist. The mountain developed prior to 360,000 years ago, but for a long time, no one knew where it went. Erosion could explain why it is gone, as could a massive explosion. It wasn't until 1980 that the actual explanation became apparent.

There is a vast area of knobs (called hummocks), small valleys, and ponds extending for 28 miles north of the volcano, almost to the town of Yreka. Geologists didn't quite know what to make of it, and it was mapped as a cinder cone field, which strangely had a consistent composition. Then Mt. St. Helens happened.

The St. Helens eruption was precipitated by an earthquake that shook the north side of the mountain loose into the largest debris avalanche ever witnessed by human beings. It traveled twelve miles down the Toutle River valley, and produced a unique topography: hummocky. As the dust settled at St. Helens, geologists knew they had an explanation for the strange landscape north of Shasta. Between 360,000 and 300,000 years ago, about 11 cubic miles broke loose from the volcano and flowed 28 miles, more than twice the distance of the 1980 event. So far as I know (I'm open to corrections), it remains the largest landslide known in North America.

The hummocky avalanche is visible in the aerial photo below (another view can be seen in one of my earliest blogs here).

Friday, January 22, 2010

The Other California: A Land of Fire and Ice (but mostly ice today)

I'm breaking my own rules here. My latest series is exploring the places in California that aren't on the postcards, but are worth a visit. The thing is, Mt. Shasta is one of the most familiar sights in the state of California. The gigantic stratovolcano, the largest of its kind in the Cascades Province (and one of the largest in the world) reaches an altitude of 14,162 feet, and can be seen from over a hundred miles away in some directions. It's on a lot of postcards. But most people see the volcano on their way from California to Oregon along Interstate 5, and in doing so have a hard time seeing one of the most remarkable things about the volcano that isn't volcanic.

California, the sunny, mostly arid, almost semi-tropical state is not known for its glaciers, but it most certainly has them. The Sierra Nevada has between a dozen and several dozen glaciers, depending how one defines them. The largest Sierra glacier lies beneath the peaks of the Palisades, and is a mile wide and half a mile long. But farther north, Mt. Shasta has at least seven, including both the longest, and the largest glaciers in the state. They are most easily seen from viewpoints along State Highway 97 between Weed and Klamath Falls, Oregon.

Whitney glacier is the longest glacier in the state, with a length of about two miles. It is also the only valley glacier in the state. It zigs, then zags down the center of the photo above. Most all the other glaciers occupy the cirques at the head of glacial valleys. Whitney displays many classic glacial features, including bergshrunds, ice falls, crevasses, and moraines.

Whitney is the longest glacier in the state, but it is fairly narrow in its valley. The honor of the largest glacier in the state is nearby Hotlum Glacier, which coats a slope on the northeast flank of the volcano. It is about 1.3 miles long and 0.7 miles wide. In the picture above, Hotlum can be identified from the rounded cracks (the bergshrund) on the left flank of the volcano. Bolam Glacier is in the center of the photo, and bits of Whitney are on the right.

The glaciers of Shasta have a unique distinction: they are one of the few glaciers in the world that are actually growing in size. Before any global warming deniers get excited, the growth is actually a consequence of the rise of world temperatures. Warming of the northern Pacific is causing an increase in evaporation, and is increasing the amount of precipitation on the mountain. The increase of snow is able to offset the loss of ice due to melting during the 1.8 degree Fahrenheit rise of average temperature in the region over the last century. Continuing increases in global temperatures will eventually overwhelm the glaciers, and they will most likely be gone in a century or so.

See them while you can!

Tuesday, January 19, 2010

The Other California: Cries from the Past

Continuing a web tour of Lava Beds National Monument, a place to go when you've seen all the postcard places...

Wounded Knee, Little Big Horn, Sand Creek. The relationship between the indigenous people of the Americas and Europeans has not been a positive one, to say the least. Battles and conflicts were fought across the country over centuries, and invariably the losers were Native Americans. The history of the California is no exception, and many tribes who lived in the state for thousands of years were annihilated, often without even memories of the people being preserved. Whole cultures simply went extinct, whether from warfare, disease or neglect. A story is preserved in one place at least, at Lava Beds; a last stand for the culture and livelihood of the Modoc people, in 1872-1873.

The Modoc people had lived in the Klamath Falls-Tule Lake region from time unremembered, and made first contact with Europeans in the 1840's as settlers arrived on the Oregon Trail. Relations between the cultures were rocky and sometimes violent, and eventually the Modoc people were forced to move to the reservation of their ancestral enemies, the Klamath people. After several years of intolerable conditions of neglect, some of the Modocs left the reservation and returned to their homeland on the Lost River near Lava Beds, led by Kientpuash, known to the settlers as Captain Jack (picture below).

The hostilities began on November 29, 1872. On that day, the U.S. Army tried to round up the Modocs at their Lost River encampment, north of Lava Beds, in order to return them to a reservation in southern Oregon. Shots were fired, both sides suffered injuries, and the Modoc people fled south, led by Kientpuash. A separate party, led by Hooker Jim, went on a rampage, killing 14 settlers. The bands made their way by canoe and horse to the site that came to be known as Captain Jack’s Stronghold. The band included 53 men of fighting age, and about a hundred women, children and aged Modocs.

The Stronghold was the site of two major battles and a long siege by U.S. troops and militia of the small band of Modoc peoples during the long winter.

The conflicts that took place on this barren surface reveal much about the need to take into account the geology and geography of the battlefield. Although outnumbered at least ten to one, the Modoc warriors were able to take advantage of the landscape to execute their defense, and in the two major battles that took place, they inflicted many casualties on their opponents while suffering very few among themselves. During the January 17, 1873 conflict, the attacking army did not kill or injure a single Modoc warrior, while suffering 37 casualties, including 9 dead.

The Modocs could hardly have chosen a better spot to make their stand. The trail through the stronghold reveals a series of schollendomes (pressure ridges) and scarps that almost completely encircled the Modoc encampment. The fractures and fissures along the tops of the schollendomes were natural trenches that allowed quick access to any point along the defensive perimeter, and the Modocs had an excellent view of the flat open landscape that the U.S. Army had to cross in order to attack. In addition to defensibility, the stronghold included access to water and food along the shoreline of Tule Lake, a natural corral where cattle could be kept, and lava tube openings that provided shelter for the Modoc families.

Another advantage of the site was the presence of an escape route. After suffering a long siege and cold winter, the Modoc people prepared for another assault by the Army, now numbering more than 700. On April 11, during a peace parley, the Modocs shot and killed General E.R.S. Canby, in the hopes that by killing the Army’s leader, the soldiers would go away. The opposite occurred, and on April 15 the Army forces began bombarding the stronghold and advancing past the outer perimeter of the Modoc lines. After two days of attack, with 6 dead and 17 wounded, the Army poured into the stronghold to find…no one. On the night of April 16, the entire Modoc party, 160 men, women and children, along with dogs and horses, had deserted the stronghold, moving south along a smooth area of the lava flow, only a few hundred meters from some of the Army encampments.

Despite their successful escape, the Modoc people were now caught in the open, and it was only a matter of time before they were captured. Within a few weeks, Hooker Jim betrayed Captain Jack’s location in return for amnesty. Ultimately the Modoc people were moved to Oklahoma, and Captain Jack, along with three others, was hanged. The last major conflict in California between the U.S. Army and the aboriginal peoples was over. As the park brochure notes: “The cultural identity of an entire people was lost here…so settlers could graze a few cows”

About 200 Modocs remain in Oklahoma, descendants of seven of the survivors of the war, and about 500 Modocs still live in Oregon. The Modoc people returned to Lava Beds in 1990 for the first time in 117 years to perform ceremonies on their ancestral lands, and now do so yearly.

Aaron Waters (1992) has provided the most detailed account of the geology of the battlefield (Figures 5 and 6). A double-looping trail provides a choice of routes through the stronghold, one of 0.6 miles (1 km) and one of 1.1 miles (1.8 km). Either route reveals many interesting aspects of this unusual and tragic moment in American history, when a small band of Modoc people resisted a much larger force of U.S. soldiers.

Monday, January 18, 2010

The Other California: Whispers from the Past

Continuing our exploration of the places to go in California when you've seen all the places on the we visit one of the largest petroglyph panels in the United States.

The Modoc Plateau is a high, flat geologic province in northeastern California. It is a lonely region that was formed by numerous horizontal flows of basalt lava, and then split (by stretching of the crust) into a series of fault grabens (valleys formed by fault movements instead of river erosion). One of these grabens lies at the north end of Medicine Lake Highland, and until 1905 or so it contained a huge shallow body of water, Tule Lake. Rivers were diverted, levees were built, and most of the valley was developed for agriculture. In the GoogleEarth image below, all the green fields were under water a century ago, and the black areas are the only remnants of Tule Lake.

About 270,000 years ago, basalt erupted on the lake floor, and the interaction of the hot lava and water was explosive. These phreatomagmatic eruptions caused large clouds of steam and volcanic ash that reached heights of 15,000 feet, during hundreds or thousands of individual explosions. As the explosion columns collapsed, powerful pyroclastic surges formed layer after layer of ash and lapilli on the flanks of the growing cone. Later, when water interactions slowed, basalt flowed from vents on and around the cones.

The cliff in the picture below, Petroglyph Point, is one of these phreatomagmatic cones (a second cone is visible in the distance). It was shaped by lake water into a wave-cut abrasion platform which exposes the tuff layers in spectacular fashion. Each shelf-like ridge represents a different level of the lake. Differential erosion highlights variations in grain size and induration of the sloping tuff layers. Cavernous weathering, on the other hand, has produced tafoni, the distinctive hollows high on the cliff that are utilized by the many birds found here, especially the raptors.

Between 2,500 and 4,500 years ago, the humans in the region rowed canoes or rafted across the lake to this island cliff (the lake was eliminated in 1905 as noted above), and carved more than 5,000 messages on the stone. It may be the largest single petroglyph panel in the United States.

Some of the symbols are obvious in their meaning, especially the animal forms, but there are many more whose messages are lost to time. Unfortunately, the petroglyphs themselves are disappearing. Vandalism has destroyed many, and resulted in the construction of the chainlink fence. Even more insidious is the destruction by windblown sand. It was not a problem until the lake was diverted, but now abrasive particles blast against the soft rock on windy days, causing serious, irreversible damage.

Petroglyph Point is managed and protected as an isolated part of Lava Beds National Monument. It is easily accessed by a short gravel road off the main highway through the small village of Tulelake, and is well worth a visit.

Saturday, January 16, 2010

The Other California: Exploring the Volcano Underground

Continuing our series of where to go in California once you've seen all the places on the postcards....

As discussed in the previous post, California has a place with possibly the greatest concentration of lava tubes in the continental United States, some 700 of them, with around thirty miles of passageways: Lava Beds National Monument, on the flanks of California's biggest volcano, Medicine Lake Highland. Today's post is a brief photo essay on some of the kinds of things you can see underground at Lava Beds.

Two lava flows produced essentially all the lava tubes in the park. The first of these is the basalt of Mammoth Crater, which erupted around 30,000 years ago. Most of the caves occur in this unit. Mammoth Crater is a 1/4 mile wide, 340 foot deep pit at the south edge of the park which produced lavas that traveled as far as ten miles, producing a complex, multi-pronged tube system, shown on this map from the previous post. The Heppe Caves, above, are found just a few hundred yards from Mammoth Craters. The collapse pit in the picture is 168 feet across and 68 feet deep.

One oddity about Lava Beds is the total lack of open water in the monument: no creeks, no rivers, no lakes. Basalt flows become highly fractured as they cool and contract, and any water on the surface sinks quickly into the subsurface. Heppe Cave is one of the few exceptions, in that it often has a small pool at the bottom, probably maintained and sealed by underlying ice layers (the pool had disappeared when we visited in September).

The largest opening in the park is found at Skull Cave, near Schonchin Butte. The opening, seen above, is 60 feet in diameter. Though relatively short, the cave has one unfortunate attribute: just at the point where it turns totally dark, it drops into a second underlying tube system. This natural trap led to the cave's name, as early explorers found numerous skeletons of animals and two humans who had fallen in the darkness to their deaths. A metal stairway makes for a safer journey today.

These tubes-over-tubes have another interesting feature. In the frigid winter, cold air sinks into the caves. When the surface over the caves warms during the summer, the cold air stays put, so some of the caves in the monument maintain ice all year long. The deepest part of Skull Cave contains a frozen pond and a number of icicles (the ice in the photo below was taken in September). Another cave in the park, Crystal Ice Cave, is renowned for complex ice formations it contains. Special arrangements must be made to visit the cave, and it has some challenging passages.

The basalt of Mammoth Crater covers two-thirds of Lava Beds, but another flow about 10,000-11,000 years ago produced some fine lava tubes as well. This is the basalt of Valentine Cave. Valentine Cave itself is one of the cleanest and easiest caves to explore, with high ceilings and few breakdowns. It has about 1,600 feet of accessible passageways and displays many of the typical features of underground lava flows, including branching passageways, lava pools and cascades, pahoehoe flows, lava benches, pillars, and lavacicles.

Photographing lava tubes is a challenge. Dark colored rock in total darkness does not show well when you use a flash. For amateurs like myself, the best results come from photographs near entrances (as above), or by using a time exposure, and "painting" the walls with flashlights as seen below (pros use strobes of course). I like the cave ghosts in the picture below; several people walked through the scene during the 30 second exposure.

This other photo doesn't include ghosts, but shows the pahoehoe floor of the final lava flow in the tube, and some lavacicles on the ceiling. They can form as part of the ceiling melts while lava flows below.

Below are some sharktooth stalactites (lavacicles) in another cave. They are one to two inches long. They are also a really good reason to wear a helmet when exploring these caves. Your head can damage these by breaking them off, but I fear a great deal more damage can happen to your skull (the park sells some nice "bump caps" for a couple of dollars).

Tickner Cave (below) is also formed in the basalt of Valentine Cave, and is found close to the flows source at the south boundary of the park. It has a great many nice cave features, including a natural bridge.

Lava Beds tubes are full of surprises. One special example is Fern Cave, in an isolated section of the park. The monument lies within the rain shadow of the Cascades and is classed as semi-arid. The tube openings sometimes provide humid micro-climates, and a lush growth of ferns native to the other side of the range is found just inside (below). The interior contains numerous pictographs from the original human inhabitants of the region. The site is sacred to the Modoc People, and special arrangements must be made to explore the cave.

So there you have've explored five lava tubes at Lava Beds National Monument! Less than one percent...looks like you will simply have to visit the park if you want to see more!

Friday, January 15, 2010

Hey, I'm Changing Religions: Get Rich Quick!

I'm changing my religion...and there's a really geological connection here, involving earthquakes, gold mining, and diamond mining. You can get really rich if you align yourself with the right deity...

It's taken me a little while to understand the theology here, but apparently there's this God who gets all in a pique about an apocryphal story about the devil from 200 years ago, and sends four hurricanes and a horrific earthquake to smite out the lives of 200,000 great-great-great grandchildren of the person who insulted his sensibilities. On the other hand, a man of "god" spends his life conning money from widows and gullible old people through his television show, and invests the money in gold mining in an African country with the blessings of a bloodthirsty dictator currently on trial at the Hague for vicious war crimes. He also arranges to mine diamonds in another African country with the blessings of another vicious dictator, and uses the planes of his so-called "Operation Blessing" relief organization to ferry the mining equipment. The upshot is that this man, Pat Robertson, is worth $400 million to $1 billion.

OK, I'm not sure I really want to be associated with this kind of god. In fact, all I can say is that Pat Robertson is a repugnant human being. A man who takes credit for diverting hurricanes from his broadcasting center, which goes on to kill or injure many people where it does hit. A man who blames the 9/11 terror attack on liberals and homosexuals (along with another repugnant man, Jerry Falwell, who is dead now). He is a hateful bigot and a charlatan.

I kind of doubt that many of my readers send money to Pat Robertson, but if any do I have to say this: geologic disasters happen. They happen to evil people, they happen to good people. When you start judging people who are the victims of natural disasters, you dehumanize them. It makes it easier to ignore the terribly real pain and suffering that is going on, and will make you less inclined to help.

Please help out. There are many organizations on the ground in Haiti, including OxFam, Doctors Without Borders, and Habitat for Humanity (remember that months from now when we've collectively forgotten Haiti, rebuilding will still need to go on). Give now, and remember to give later when another story steals the headlines. All people are precious, and remember, you could be next. The earth doesn't judge us, it just continues doing the things it has for a long time. Sometimes, unfortunately, people get in the way.

"I hear the crying of the hungry
In the deserts where they're wandering
Hear them crying out for Heaven's own
Benevolence upon them
I Hear destructive power prevailing
I hear fools falsely hailing
To the crooked wits of tyrants when they call

I hear them all"

Old Crow Medicine Show

Thursday, January 14, 2010

The Other California: The Volcano Underground

Can you name the deepest cave in the United States? The answer can be a little tricky. Some sources will say that Lechuguilla cave, the recently discovered wonder in Carlsbad Caverns National Park is the deepest at 1,604 feet (the cave is also incredibly long, with 127 miles of passageways). But if one defines the depth of a cave as the vertical distance between the highest passageway to the lowest passageway, the deepest cave in the United States is in...Hawaii! Kazumura Cave has a measured depth of 3,614 feet. Caves in Hawaii? Actually, 5 of the 10 deepest caves in the country are in the Aloha State. And to add to the confusion, if you explore the full length of Kazumura, you will travel some 40 miles and probably go no deeper than 40 or 50 feet below the surface of the earth. Confused?

When thinking of caves, it is common to think of voids under the earth's surface that formed as acidic water ate away at rocks like limestone or marble, and filled with stalactites and stalagmites. Hawaii has no layers of limestone to speak of, but it does have volcanoes. How can a volcano make a cave?

The more relevant question is: how can basalt lavas flow for miles from the erupting vent? Wouldn't the lava cool after just a few hundred yards and become solid? As it turns out, lava does cool quickly, but it also forms a crust, and volcanic rock is a great insulator. The lava can continue flowing beneath a solid crust for miles without any significant temperature loss. The molten rock travels through an extensive network of lava tubes to extend the length of the flow. An active lava tube system can be seen in the pictures below from Pu'u O'o on the Big Island of Hawaii.

In the picture above, the lava emerges at Pu'u O'o on the far right side of the picture. It immediately flows into the lava tube system, traveling for seven miles down the slope, to emerge on the coastline on the far left side of the picture. No active lava flows are visible in any part of the picture.

The picture below is from a point above the Pu'u O'o vent looking towards the ocean entry in the distance. The roof of the lava tube has collapsed in several places giving rise to the steam vents.

The caves form when the eruption ends and the lava tubes drain. The tubes are often big enough to walk (or crawl) through, and because they can split into multiple passageways, they can be a lot of fun to explore. Kazumura Cave starts near the summit of Kilauea at almost 4,000 feet, and has continuous passageways that reach the coastline near Hilo, 40 miles away. It is the longest known lava tube in the world.

Hawaii has a number of pretty incredible lava tubes, but isn't this post supposed to be about California? It turns out that the continental United States has numerous lava tubes, and California has some world class examples. The most extensive collection of lava tubes to be found is in Lava Beds National Monument, on the flank of Medicine Lake Highland. I've been exploring some of the surface features of the monument in recent posts, but the main attraction of the park is the system of lava tubes, some 700 of them totaling more than 30 miles of passageways. Many are open to exploration by park visitors.

Map from: Waters, Donnelly-Nolan, and Rogers, 1990, Selected Caves and Lava-Tube Systems in and near Lava Beds National Monument, California: U.S. Geological Survey Bulletin 1673

We will explore some of California's Volcano Underground in coming posts!

Tuesday, January 12, 2010

A Tale of Three Quakes

There have been a number of earthquakes in the last week, some benign, and one an unfolding tragedy. I want to use my lab recordings of three quakes to make a point about the magnitude scale. The first recording, above, was a little 4.1 shaker on January 7 in the San Jose area, about 50 miles from my lab in Modesto. It just barely reached the threshold to be recorded on my unit. No damage was recorded.
The more serious California quake was the 6.5 magnitude event offshore of Eureka and Ferndale in Northern California. The magnitude scale is exponential, in that the energy release increases by a factor of about 30 for every number on the scale. A magnitude 6 quake is 30 times more powerful than a magnitude 5, and 900 times (30x30) more powerful than a 4. Therefore, the Eureka event was over a thousand times more powerful than the San Jose event. This shows on the seismograph record above: the recording was offscale for nearly 10 minutes, and waves recorded for over an hour (about four minutes are recorded on each screen shot). This was despite the fact that the quake was several hundred miles away from the seismometer. Eureka and the other communities suffered some minor damage, but few injuries have been reported.

Today's 7.0 magnitude quake in Haiti is a far more serious matter. It was several times larger than the Eureka event, and was centered beneath a crowded urban center where architecture standards are far less stringent. Preliminary reports are not sounding good, and prayers are probably in order for the people who live there. It's not like bad things haven't been happening to Haitians over the years. Even though the event was thousands of miles from my lab seismometer, it still was nearly off-scale, and the shaking lasted more than an hour.

It was a striking introduction to geology for my students, who were sitting down for their very first laboratory section today when the waves arrived from the Haiti event.

The recording unit is a simple lab seismometer that I got from Ward's Scientific about 15 years ago for around $3,000. It has done a fine job of catching most of the significant events (magnitude 7) around the planet, and most of the magnitude 4 and 5 events in California.


I've noticed some deskcrops on the geoblogosphere of late, and since I missed one of the early Accretionary Wedges on the topic, I want to "show and tell" some of my deskcrops too. Geologists are notable hoarders and collecters of shiny objects (not unlike crows and packrats), and our desks and workspaces get cluttered quickly. My most treasured single item is a highly crystalline sample of azurite, one of the ores of copper. I'm a sucker for deep blue...
Decades ago in a different job, I was tasked with cleaning out a bunch of old senior exercises in a basement storage area, and a lot of rocks got tossed. This one caught my eye, though, because of the color. The pink crystals are the gemstone tourmaline, and the lavender flakey crystals are a form of lithium-bearing mica called lepidolite. My best guess is that it came from one of the mines in the San Diego region of southern California.

Some deskcrops are not eye-catchers, but have special significance. These bladed crystals are samples of anorthoclase, from the pool of lava on at the summit of Mt. Erebus in Antarctica. It was collected by a researcher who spoke at our campus a few years ago, and was kind enough to donate the samples to the department.

It was kind of hard to choose my favorite deskcrops! The photo above is about a fifth of the total space on my desk, and the rest is similar to this. Books? Not so much. That's what bookcases are for.