The Volcano That Wasn't There, and Two That Were...

Mt. Shasta and Shastina from the north

I hope that your holiday travels were safe and happy. I had a fine time visiting family across the Pacific Northwest, from Seattle to central Oregon, Northern California and home again. I had been looking forward to seeing a bevy of Cascades volcanoes, including Mt. Rainier, Mt. St. Helens, Mt. Hood, the Three Sisters, Mt. McLoughlin and the others. Of course, the Northwest had no intention of revealing its treasures, as clouds and rain dominated our trip from one end to the other. There was plenty of geology, mind you, as we saw all manner of flooding, landslides, and mudflows, but I admit to feeling a tiny bit of disappointment at finding the Cascades hidden from sight.

Mt. Shasta from near Weed (photo by Mrs. Geotripper from a fast moving vehicle!)

It wasn't until the last day of our travels, a 600 mile drive from central Oregon to the Great Valley in California that we saw anything of the high Cascades. We crossed the Siskiyou Mountains in a light snow storm, but by the time we reached the Klamath River in California the skies had almost magically cleared. As we turned around the ridge near Yreka, Mt. Shasta came into glorious view. Shasta is the second highest (14,179 feet; 4,322 meters) and most voluminous of the Cascades volcanoes, and the second most active (after Mt. St. Helens). It last erupted in 1786. The volcano consists of at least four volcanic centers, including Hotlum Cone, the highest peak, and Shastina, a parasitic cone on the west side of the mountain (on the right side of both photos above). Shastina is actually the third highest Cascade volcano at 12,329 feet (3,758 meters) .

Lassen Peak from near Red Bluff

Later, as the sun sank lower in the western sky, we were treated to a rare valley view of snow mantled Lassen Peak (10,463 feet; 3,189 meters). Lassen is a dacite plug dome that came into being during a series of eruptions around 27,000 years ago. It has the distinction of being the most recent volcano in California to erupt. After a series of nearly 200 phreatic explosions from May of 1914 to May of 1915, the volcano produced a dark viscous lava flow that melted much of the snow around the summit that resulted in a major lahar (volcanic mudflow). A few days later there was a large explosive eruption of ash, with a pyroclastic surge that destroyed about four square miles of forest.

Lassen Peak and the remnants of Mt. Tehama

I was even more pleased with the view of the volcano that wasn't there. If you look to the right side of the photo above, you can see a series of ragged peaks, which include Brokeoff Mountain, and Mt. Diller. They are the remnants of a large stratovolcano that would likely have towered over Lassen Peak. The peak, now called Mt. Tehama (or Brokeoff Volcano), grew during a long series of eruptive events between about 590,000 and 385,000 years ago. The eruptions grew silent, and erosion began to attack the extinct volcano. It is interesting to sit in the midst of these peaks (the main park road passes among them) and realize that one is looking out from the deep interior of volcano.

It was nice to see the coating of snow on the mountain peaks of northern California. The snow depths are still less than they need to be, but they are certainly better than the near lack of any snow at all that we saw last year during our holiday travels.

Northern Convergence: America's Most Dangerous Volcano, and the End of the Journey

Northern Convergence as a name for this blog series was all about the role of a convergent plate boundary in the production of the scenery of the Pacific Northwest. The compressional forces that developed as the Pacific/Farallon/Juan de Fuca plate was stuffed under the North American continent formed range after range of complexly folded and faulted mountains hundreds of miles inland.

Perhaps the most vivid effect of plate convergence is the formation of a magmatic arc, a chain of inland volcanoes and underlying magma chambers. The oceanic lithosphere carries rock and water deep into the underlying asthenosphere where the rocks are heated, and the water liberated. The water has the effect of lowering the melting point of the mantle rock and plumes of molten magma form, which start moving upwards through the continental crust. Sometimes basaltic or andesitic magmas reach the surface. In other instances, the hot magma melts some of the continental granite, forming dacite or rhyolite.

Mt. Adams from Sunrise Ridge

Volcanism is one of the intense and spectacular geologic processes one could ever hope to witness (or avoid, if you not geologically-minded, or sane). Volcanoes are capable of horrific destruction and disaster, but they also provide rich fertile soils and incredible scenery. We had now been on the road for nearly two weeks, and an important early site for our investigations was to be Mt. Garibaldi and the Black Tusk, two of the northernmost Cascade volcanoes. As I wrote previously, rain and clouds obscured our views that day, and all we ended up seeing were some old lava flows (and, it should be said, some wonderful waterfalls).

Not a volcanic eruption, but instead a wildfire. Couldn't help imagining, though.

As we drove west on our final day, volcanism loomed. We would be passing through Mt. Rainier National Park, and it is hard to think of any mountain in the world that dominates the surrounding landscape the way Rainier does (Kilaminjaro comes to mind, or Mauna Loa in Hawaii, but few others). In stark contrast to our earlier visit at Garibaldi, the skies were crystal clear and sunny.

Mt. Rainier from the west

Rainier rises to an elevation of 14,411 ft (4,392 m), just a bit short of being the highest peak in the lower 48 states, but certainly the highest in the Cascades (only Shasta comes anywhere close at 14,179 feet). Glacial erosion has ripped away hundreds of feet of rock from the summit area, so at one time it was almost surely the tallest mountain in the lower 48 (one more contender though could be the San Francisco Peaks in Arizona, another stratovolcano missing thousands of feet from the summit).

Rainier from the air

For all of its grandeur, Rainier is an incredibly dangerous mountain. It contains roughly half of all the glacial ice to be found in the lower 48 states, around a cubic mile. That much ice and a tendency to have eruptions every few hundred years is a frightening combination. Many people think (perhaps influenced by bad Hollywood movies that involve volcanoes) that lava flows are the greatest hazard from volcanoes. They are not; lava flows would hardly be expected to get off the mountain massif itself. Andesite is just too sticky to flow far before congealing.

Source: Mount Rainier - Living Safely With a Volcano in Your Backyard by Carolyn L. Driedger and William E. Scott, USGS -- from USGS fact sheet 2008-3062

The ice is another matter. A modest eruption of ash or lava could melt a vast amount of ice, mixing with the ash to form a fast-moving mudflow called a lahar. Over the history of the volcano lahars have had the greatest reach, extending as far as the Puget Sound. The cities of Tacoma, Puyallup, Sumner and others are built on lahar deposits from Rainier (see above). Tens of thousands of people along the drainages below Rainier will have a few tens of minutes to evacuate in the event of a major mudflow. For all its beauty, the mountain is a ticking time bomb. It's also probably one of the most carefully monitored mountains on the planet. I don't doubt that the slightest hint of activity will bring a flurry of evacuations.

Rainier from the air in 2007

We spent a few hours on Sunrise Ridge, but our time was limited. We had nearly completed our journey and some of our people needed to catch flights at SeaTac. We headed down the hill towards Puget Sound. We had seen many wonders on the roads that took us across the Olympic Peninsula, the ferry to Vancouver Island, a rainsoaked drive through the Sea to the Sky Highway, explorations of Banff and Yoho National Park, a sojourn among the ghosts of dinosaurs on the High Plains, and a drive home through the Rocky Mountains and the Columbia Plateau. I had gotten to know an extraordinary group of people, and a small corner of a most extraordinary country, Canada.

The Looming Volcanic Giant of Northern California: Mt. Shasta

So California is all about earthquakes, right? Oklahoma has tornadoes, Florida has hurricanes, Minnesota has blizzards,and California has the San Andreas fault (and all the other active faults that no one seems to remember the names of). But really, California has a "little" of everything, and we have a "big" of volcanoes. I was on my way home today from family Thanksgiving celebrations in Oregon, and while we traveled down Interstate 5, we had some simply awesome views of California's gigantic volcano, Mount Shasta.

Shasta is the second tallest volcano in the Cascades Range at 14,179 feet (4,322 m) after Mt. Rainier, but in bulk it is the largest composite cone/stratovolcano in the range (Medicine Lake Highland, also in California, has more volume, but is a shield volcano that doesn't even reach 8,000 feet in elevation). The mountain is composed largely of andesitic lava flows and ash deposits, but also includes outpourings of basalt and dacite. It has been active for more than half a million years, and may have last erupted in 1786. It has had eruptions on average every 600 years or so, making it the second most active volcano in the Cascades after Mt. St. Helens.

Shasta is a composite cone in the truest sense. At least five distinct volcanoes in various stages of disrepair make up the mountain. The earliest collapsed around 350,000 years in a gigantic debris avalanche that flowed 28 miles north to the vicinity of Yreka (the nature of the slide was not recognized until the 1980s after St. Helens produced a similar avalanche with a length of 12 miles). The Sargents Ridge and the Misery Hill cones erupted, became dormant and were deeply eroded by glacial activity. Shastina erupted around 9,800 years ago forming a large satellite cone that is actually the third highest volcano in the Cascades. Hotlum Cone is the currently active volcanic center, having erupted fairly often during the last 9,000 years.

Shasta has seven active glaciers, including the longest and most voluminous in California. Meltwater from the glaciers will occasionally cause destructive lahars or volcanic mudflows. Other dangers lurk on the flanks of the volcano, where some 20,000 people live. Ash flows, lava flows and even a caldera collapse are possible hazards to those who live in the shadow of the mountain.

The mountain is famous for mythology and legends as well. The native Americans certainly understood the power of the mountain, having witnessed some of her eruptions. The prominence of the giant edifice has resulted in all manner of speculation about the gods and aliens who call the mountain home. Many consider the mountain to be a "global power center" or "spiritual energy vortex". The existence of the mountain alone makes it magical for me, but folks seem to take this stuff seriously. I was in a crystal shop this afternoon listening to a strange and earnest conversation about chemtrails and spiritual vibrations. Books abound about the Lemurians and other societies that live inside the volcano. They've got it all figured out...

Shasta is a beautiful mountain, and a looming volcano that is capable of creating havoc. On this particular day, all was peaceful and serene. We enjoyed the sight during our long journey.

Rivers Appearing Out of Nowhere: McArthur-Burney Falls State Park

Note: Sorry for the odd character of the photos. My hike was at dusk, and lighting was difficult!

There's no doubt that McArthur-Burney Falls are absolutely spectacular, almost otherworldly. Burney Creek spills over a high ledge of basalt and is joined by myriads of whitewater springs bursting out of the cliff below. It falls into a gigantic deep blue pool of water before flowing down to the reservoir a mile or so downstream.

It is cool and moist even in the driest and hottest part of the year, because the springs that feed the fall are practically impervious to seasonal changes. A lot of water passes through the park each day, something like 100 million gallons every 24 hours.

The geology is interesting. The region includes horizontal flows of basaltic rock along with intervening layers of lake sediments and diatomite. The basalt is jointed and broken up and allows water to sink quickly into the ground (surface streams are surprisingly rare in this wet climate). The diatomite and siltstone layers are impermeable and don't allow water to sink deeper into the ground. It is instead forced to flow sideways until it flows out at a spring such as those in the face of McArthur-Burney Falls

What makes the falls more intriguing is the incredible contrast between the river downstream and upstream of the falls. Downstream, Burney Creek has a sizable flow, as seen below.

I decided to check out the river upstream of the falls and headed up the trail. Fall colors were just beginning to make an appearance.

I can now say I spent some time this summer on the Pacific Crest Trail. A whole mile of it, in fact! It runs through McArthur-Burney Falls State Park on the west side of the creek. It was quiet and quite devoid of other hikers on the Sunday evening when I was exploring.

At the upstream end of the park, Burney Creek is AWOL. There is only a dry channel lined with basalt boulders, aspens and willows.

Making my way downstream, I found a spot where the river appears as a series of pools, but at this point it is not yet flowing. The water table is intersecting the channel of the stream and rising to the surface.

Just a bit further downstream, the river has grown, and after a few hundred yards more, it is a large stream that makes the bold leap over the ledge of basalt.

This has been a strange landscape we have been traveling through, an entire shield volcano with no surface water beyond a glacial lake at the summit caldera, and a lava plateau, also with limited water. Yet the climate is wet, and is ultimately the source for much of the water flowing in the Sacramento River.

I headed back to camp. Tomorrow was the last day of the field class, and we were going to pay a visit to Lassen Volcanic National Park!

Seeing Volcanoes Inside and Out: Exploring California's Volcanoes

Our just completed exploration of Northern California's Volcanoes was a fascinating journey through the interior and exterior of several volcanoes. How do you explore the innards of a volcano? On the one hand, you can do a Brendan Fraser and fall thousands of feet or miles into a volcano ("Journey to the Center of the Earth", a movie I appreciated mostly for the living trilobite in the opening scene). Or...you can wait for the volcano to go extinct, be uplifted and eroded for millions of years, and then be established as Castle Crags State Park, and go stand at the viewpoint at the end of the park road. We chose the latter.

The Castle Crags are an especially scenic part of the Klamath Mountains province, a region tucked between the Coast Ranges and the Cascades at the north end of the Great Valley (I've written about them previously, click here to see). Most of the Klamaths are composed of dark colored metamorphic rocks, many of them derived from the mantle, but at Castle Crags the rocks are different. The light colored cliffs are composed of granitic rock (mainly granodiorite, a plutonic rock containing lots of plagioclase feldspar), dating back to around 160 million years ago. The granodiorite was once molten, feeding volcanoes that would have existed several miles above where we were standing. Some of the magma remained in crust, cooling slowly and allowing for the growth of visible crystals. Standing among the granitic towers of Castle Crags is to be standing in the interior of a volcano.

The dramatic spires are the result of exposure at the Earth's surface, and the resulting release of pressure (remember that these rocks formed at a depth of three or four miles in the crust). As the pressure is released, the rock expands and fractures, sometimes in vertical cracks called joints. The joints are exploited by water and ice, leading to the erosion of the steep sharp cliffs.

Sometimes the expansion of the granitic rock is outwards, parallel to the surface of the cliff. This causes fractures that act to remove corners and edges, resulting in dome-like cliffs, much like those found in Yosemite and elsewhere in the Sierra Nevada. This process is called exfoliation.

Even as we stood at the viewpoint appreciating the underside of a volcano, we could turn to our right and see a rather astounding view of the outside of a volcano. A very big volcano. Mt. Shasta is the second tallest peak in the Cascades Range, exceeded only by Mt. Rainier, but it is the most voluminous stratovolcano in the Cascades, and perhaps even the world.

At 14,179 feet, it dominates the scenery from all directions in Northern California. A stratovolcano is composed of alternating layers of ash and lava, but the details of Shasta's structure contradict that description. It is actually the remnant of at least five different volcanoes which developed on more or less the same site. The term "composite cone" is perhaps a more accurate moniker.

Shasta was our next stop of the day. At over 14,000 feet, no roads approach the summit, but in years past a ski area had been constructed at the 8,000 foot level on the south side of the peak. The ski resort was removed long ago because of avalanche danger (a wide swath of fallen trees highlights the hazard), but the paved road remains.

We took the highway out of Mt. Shasta City and headed up the mountain...

Hitting the Road: California's Volcanic Lands

There are lots of volcanoes in California, in the deserts, the eastern Sierra Nevada, even in the Coast Ranges, but the most recent and most diverse volcanoes are in the north state, in the Cascades Range and the Modoc Plateau. I'm headed up there tomorrow with my students.

 We are spending our time in Lava Beds National Monument which sits on the flank of California's biggest volcano (surprise! It's not Mt. Shasta...or Lassen Peak either).

We'll have a look at Mt. Shasta, which is the tallest volcano in California, and probably the biggest stratovolcano in the Cascades...

We'll finish our studies at Lassen Volcanic National Park, site of the last eruption in California, in 1914-17. With a bit of luck maybe a small cinder cone will erupt harmlessly somewhere near us along the way! Geotripper will return in a few days...

The Other California Compilation Updated

I posted several entries in my long-running blog series on the "Other California" and realized that I was linking to a compilation page that was woefully out of date. I went through and added more than two dozen entries that I posted over the last two years, including a lot of material for the Sierra Nevada, the Transverse Ranges, and the Coast Ranges. If you are curious about some of areas I covered in the past, check out the compilation on the Other California on this page.

Searching for the Perfect Volcano...And visiting some state parks for the last time

It's September, the start of a new semester, and time for a last stab at field work in the high country! I'm heading out with one or two dozen students for an exploration of the California Cascades, the southern end of major chain of volcanoes that includes such luminaries as Mt. Rainier, Mt. St. Helens, Crater Lake, and Mt. Hood. We will be taking an in-depth look at Lassen Peak, Mt. Shasta, and Medicine Lake Highland, some of the most intriguing volcanoes to be found anywhere.

We will also be taking a last look at a couple of California's state parks that are slated to close within a matter of weeks. For the lack of less than a dollar from each resident of the state, we are losing 70 of our state treasures, including Woodson Bridge State Recreation Area, and Castle Crags State Park above the Sacramento River in the Klamath Mountains. I hope to be posting some new pictures of what we are about to lose of our state heritage because of the dereliction of duty by our state legislators.

I'll be out of touch for a few days, but you might watch for updates on Twitter: @Geotripper.

It's Collect Rocks Day, What Shall I Do to Celebrate?

Well, I think I shall take a group of college students to the California Cascades, look at some volcanoes, and see if there are any rocks there. By a miscalculation of planning, we aren't leaving until next week, but the importance of this very special day will be close to our hearts as we wander around Northern California!.

I blogged about Collect Rocks Day a couple of years ago, and almost missed it, again. I'm not sure where this all originated, but I'll take any excuse!

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!

The Other California: Exploring California's Biggest Volcano

So we begin our exploration of Medicine Lake Highland, California's biggest volcano. As noted in a previous post, it is essentially a basaltic shield*, about 30 miles long in a north-south direction, and 22 miles stretching east-west ("stretching" is a particularly apt term in this instance). Starting from the plains of the Modoc Plateau at about 4,000 feet, the volcano rises to a high point of 7,913 feet above sea level.



The summit region on the volcano is a basin just over seven miles long and 4 miles wide, containing Medicine Lake itself (about 0.6 by 1.2 miles, and up to 143 feet deep). The basin formed when eruptions emptied the magma chambers beneath the volcano, causing the summit area to collapse inwards, forming a caldera. Crater Lake (over the border in Oregon) is a similar-sized feature, but it formed more recently, and far more catastrophically (a single devastating explosion rather than a series of eruptions over time). The caldera at MLH is topographically indistinct, having been modified by subsequent eruptions, and shaped by glaciation.

The volcano has been producing lavas for less than a million years. They are generated in the mantle as east-west stretching of the crust has caused numerous normal faults to form, providing a conduit for the basaltic lavas to reach the surface. A certain amount of mixing and other chemical interactions occur in the crust as lavas rise, causing some magma chambers to change composition. Many of the younger flows on the volcano are rhyolite (in the form of obsidian and pumice) and gray andesite. Comparatively speaking, Medicine Lake Highland is one of the most active volcanoes in the western United States. It has erupted hundreds of times during its growth, with at least nine eruptions in the last 5,200 years, with the most recent only 950 years ago.

Medicine Lake Highland sits astride the ill-defined boundary between two of California's geologic provinces, the Cascades and the Modoc Plateau. Although it is often lumped with and compared to the volcanoes of the Cascades, the north and eastern sides of the volcano clearly lie on the flat terrain of the Modoc Plateau, especially at Tule Lake.

The Cascades Province extends from northern California to British Columbia, and includes some of the most famous volcanoes in the world, including Mt. St. Helens, Mt. Rainier, Mt. Hood, and Mt. Shasta, and Lassen Peak (the last two being California's best-known volcanoes). The volcanoes derive their magmas from the melting of rock in the Cascadia Subduction Zone, where the oceanic crust and upper mantle of the Pacific Plate Juan de Fuca and Gorda plates are being driven beneath the North American Continent. The magmas are primarily andesitic in nature, forming a type of lava that is capable of explosive, devastating eruptions. The explosion of St. Helens in 1980 and the formation of the Crater Lake caldera around 7,000 years ago provide vivid examples.

The Modoc Plateau is less familiar. Sparsely populated and relatively flat, the region is mostly "drive-through" country, unless one is looking for an interesting geologic story. The oldest rocks of the Modoc Plateau are the basalt flows of the Cedarville series, which are best exposed in the Warner Mountains on the eastern edge of the province near Nevada. The rocks are several tens of millions of years old (Oligocene to Miocene). Subsequent faulting disrupted the crust, resulting in the formation of fault grabens and lake basins, including those containing Klamath and Tule Lakes (see the diagram above).

I will be writing about some of the unique sights on the highlands in coming posts, but if you can't wait and want some great online resources, check out the following:

A USGS geologic road trip through the region

A 2007 Volcano Hazards Assessment of Medicine Lake Highland and a very nice poster based on the same research

Information from the Cascades Volcano Observatory on the Medicine Lake Highland

Latest research on age dating of the youngest flows on Medicine Lake Highland

*UPDATE: A definitional thing here: the latest research, sourced below, describes Medicine Lake Highland as a "shield-shaped" edifice that can be better described as a "composite volcano" or "central volcano". This follows from new revelations about the interior of the volcano, which is more silica-rich than expected, and not primarily basaltic. I'm going to continue to call it a shield, based on the geomorphology, with full recognition that it is quite unique, and certainly not all that much like classic shields such as those in Hawaii. Thanks to Forrest for the heads up!

Latest research: Eruptive history and tectonic setting of Medicine Lake Volcano, a large rear-arc volcano in the southern Cascades (abstract)

The Other California: California's Biggest Volcano

In reference to yesterday's question of the day, well, there was a bit of trickery involved. Mt. Shasta was correctly identified in the photo by several readers, and Mt. Shasta is a huge volcano. It is certainly the tallest volcano in California, it is the largest stratovolcano (composite cone) in the Cascades Range (second in height behind Mt. Rainier, but bulkier), and by some accounts could be the biggest stratovolcano on the planet (I can't confirm that one). But...it wasn't the biggest volcano in the picture. On the boundary between the Cascades and the Modoc Plateau provinces are several shield volcano complexes, including Newberry Volcano in Oregon, and the broad dome of Medicine Lake Highland in California. Even though the highest summit on MLH does not exceed 8,000 feet, the volume of the complex is more than 130 cubic miles, as compared to Shasta's 108 cubic miles. It is California's biggest volcano.

Shields are largely composed of basaltic lavas, which tend to be less viscous, and thus less likely to develop steep slopes as they congeal. So the slopes of the mountains are usually quite gentle, and rarely produce strikingly high mountains (here is a photo of Mauna Loa, one of the biggest shields on the planet). In yesterday's photo, MLH takes up most of the photo, with Shasta on the far right-hand side. In the photo above, I was standing on a cinder cone on the flank of MLH, and couldn't fit the whole mountain in the frame.

As far as my biased self is concerned, MLH is one of the best places to visit a volcano in California. It will take a number of blog entries to cover all the fascinating features scattered around the mountain. Most of the volcano is under the jurisdiction of U.S. Forest Service, but a significant portion of the northeast flank is preserved as Lava Beds National Monument.

A picture from one of the summits of the complex, Little Mt. Hoffman, shows one of the oddities of the giant shield of MLH. The gray edifice in the foreground is Little Glass Mountain, a dome of pumice and obsidian of rhyolitic composition. On a volcano largely composed of black basalt, viscous flows of rhyolite (a completely different lava) should be deemed a bit strange. That's Mt. Shasta in the distance.

The Medicine Lake Highland sits astride an ill-defined boundary between the Cascades and the Modoc Plateau. For purpose of these blogs, I'm going to lump it with the Modoc Plateau, as some of the story I will be telling about the mountain will spill into Modoc territory. The Modoc Plateau is a lonely flat region in northeastern California floored by thousands of feet of basaltic lavas and intervening layers of lake and river sediments. The region is sliced by a lot of normal faults, and punctuated by numerous small cinder cones. The area is not considered all that volcanically active in the present day, except for the Medicine Lake Highland, which has cones and flows that are no older than 900 years. If you watch late-night television, you have seen the Modoc Plateau; it's that real estate that Erik Estrada tries to sell in the infomercials...hey, it's pretty country, but it's really isolated and lonely.

Stay tuned!

Geologists Travel...Part II

Continuing one geologist's travels in 2009...

Three weeks were spent on the Hawaiian Islands, an absolutely glorious journey with enough sights (and pictures) to last a lifetime. Here, Halemaumau crater on Kilauea is belching out tremendous amounts of sulfur dioxide and other gases into the atmosphere. The eruption began only a year or so earlier, with a vent 300 feet across and 600 feet deep. Lava is bubbling inside.

A July trip to Balboa Beach in Southern California saw the arrival of unusually large waves from a tropical storm off Baja. A couple of people were actually killed by them.

July also saw a trip to Lake Tahoe, the giant subalpine lake (1,700 feet deep) formed as a huge fault valley (graben) was dammed by lava flows. Mount Tallac, on the skyline, is composed of metamorphic rocks intruded by Mesozoic granitic rocks.

September included a field studies journey to the Cascades of Northern California and southern Oregon. We toured Mt. Shasta, Crater Lake (above), Lava Beds, and Lassen Volcanic National Park.

October was a field studies trip to the central Mother Lode, including an exploration of Black Chasm cave.

November included a tour of Pinnacles National Monument (above), and a Geology Club tour of Natural Bridges near Columbia in the Sierra Nevada Mother Lode.

And for December, a lot of family, and a quick look at the Grand Canyon!