Monday, October 6, 2008
Back from Sequoia and Kings Canyon
Out on another field trip this weekend; I took 12 students on a whirlwind tour of Sequoia and Kings Canyon National Parks on the western slope of California's Sierra Nevada. The parks are known well enough, but receive only a fraction of the visitation of Yosemite. I'm fine with that, actually; imagine having a valley that is as spectacular as Yosemite practically to yourself. That can happen this time of year at Cedar Grove on the South Fork of the Kings River.
Ask people what the deepest canyon in North America is, and you will likely get "Grand Canyon" as an answer. They would be wrong by nearly half a mile: a stretch of the Hells Canyon, Oregon/Idaho, and Kings Canyon both reach depths of more than 8,000 feet (Grand Canyon is about 5,500 feet deep, and Yosemite Valley is 'only' 3,000 feet). A spectacular highway winds down the steep canyon walls into Kings Canyon National Park at Cedar Grove. Junction View provides an outstanding view of the canyon in the deepest section. It is entirely formed by river erosion; the glaciers never reached the area shown in the first picture above.
Ask people what kind of rock makes up the Sierra Nevada and you will probably get a blank look, but some will mention "granite". It is true that most of the Sierra (three quarters or so) is made up of granitic rock (defined as plutonic rock with quartz and feldspar), but only about 10% is actually granite as defined by petrologists. Most of the plutons are composed of granodiorite and tonalite, which contain greater proportions of plagioclase than orthoclase. In addition, something like a quarter of the range is made of metamorphic rocks. Metamorphic rocks are visible in the upper parts of the first photograph. The exposures include quartzite, slate, schist and marble of the Boyden Cave Roof Pendant.
Cedar Grove is higher in the mountains, and the valley floor has been shaped by the glaciers that scoured the highest parts of the range (see the second picture). With the high cliffs and meadows, the valley is reminescent of Yosemite, though it lacks the dramatic waterfalls (Roaring River Falls are certainly memorable even though they don't have the height of Yosemite Falls). Trails lead to some of the most attractive alpine scenery in the world at places like Rae Lakes and Evolution Basin.
So where do you take a geology class when in Sequoia and Kings Canyon? Here's what we usually see (a fire closed Crystal Cave early this year, though):
Hospital Rock: Mass Wasting, and great river exposures of the metamorphic rocks
Crystal Cave: A dramatic marble cavern with a river, multiple levels and intricate passageways (fee waivers available for educational groups)
Moro Rock and Hanging Rock: Exfoliation and jointing, and a simply spectacular view of the alpine scenery of the Great Western Divide (12,000 feet and more).
Tokopah Valley: Glacial trough, and Tahoe/Tioga aged moraines exposed along the highway
Giant Forest and Grant Grove: Sequoia Trees, the biggest living things on the planet, with a paleontological record that spans the northern hemisphere
Panorama Point: (just outside Grant Grove) A dramatic view of the Sierra Nevada high country, extending to the Sierra Crest at North Palisade (14,242 feet; one of the highest peaks in the Sierra Nevada)
Junction View: A view of the deepest canyon in North America, river erosion and mass wasting
Highway 180 to Cedar Grove: Metamorphic rock exposures, Boyden Cave (public tours), plutonic rock exposures and numerous dikes
Cedar Grove: U-shaped valley, hanging valleys, numerous well-defined recessional moraines, glacial meadows, jointing, exposed plutonic rocks
The best, most accessible resource on the geology of the parks is Exploring the Highest Sierra by J.G. Moore. It includes detailed geology road guides and trail guides.
The National Association of Geoscience Teachers recently conducted several field trips in the two parks and published a road guide (including one vignette by yours truly) which is available here- A Teacher's Guidebook to the Southern Sierra: Sequoia and Kings Canyon National Park, the Great Western Divide and the Sierra Nevada Foothills
Oh, and take the warnings about bears seriously! They haven't killed any tourists in a century or more, but they are incredibly strong and intelligent, so they will find your food in your car, and remove it in such a way as to make your insurance agent sweat a little....