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blog series on the "Other California" and realized that I was linking to a compilation page that was woefully out of date.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.

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: Whispers from the Past

Continuing our exploration of the places to go in California when you've seen all the places on the postcards...today 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.

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!