|Fields of lupine atop Table Mountain (Tuolumne County)|
Though wildflowers abound during the spring, the year round draw of Table Mountain is its geology. Located in Tuolumne county, Table Mountain can be viewed while driving along highway 108, between Knight's Ferry and Jamestown. (Heading east on highway 108, you will begin to see Table Mountain shortly after passing the Red Hills area.) The formation is obvious: a dark, flat-topped mountain with nearly vertical sides, rising above the surrounding foothill landscape. The mountain that seems to wind sinuously through the foothills is a lava flow, the cast of an ancient riverbed.
|A portion of the "back" or northwest side of the mountain, as seen from along the hiking trail.|
The basaltic lava erupted from the vicinity of the Sierra Nevada crest about 9 million years ago and flowed west along an old river channel, the Stanislaus riverbed. The basalt displaced the water, cooled and solidified. Over time, erosion stripped away the older, softer rock surrounding the riverbed. Because basalt is more resistant to erosion than the surrounding rocks, the cast of the river was eventually left to stand above the landscape, an example of inverted topography. Basalt from this eruption can also be found atop high ridges in other locations north and south of the river, from the Table Mountain area all the way to the river's headwaters in the Sierra.
|Source: Google Earth|
The image above is borrowed from Google Earth in order to lend a sense of perspective. Seen from above, the outline of the ancient riverbed is clear. Northwest of the highway, notice a portion of Table Mountain, seen as a brown ribbon. This is the solidified river of lava, flowing south and west from its source in the Sierra along the course of the ancient river.
|The flat, mesa-like top of Table Mountain|
As one might expect, the top of Table Mountain is flat, like the mesas of the southwest (though geologically very different). The width of the lava flow in the vicinity of Jamestown varies from 100 to 500 yards or more; in some places up and down "stream" remnants of the flow become patchy. Portions of the lava flow can also be seen atop the bluffs upriver from Knight's Ferry. A trailhead off of Rawhide Road in Jamestown gives hikers access to the top of Table Mountain.
|Harlequin Lupine (Lupinus stiversii)|
Vernal pools and wildflowers grace the top of Table Mountain in the spring. There was quite a bit of water present when we visited a week or two ago, with a few small waterfalls cascading over the steep sides of the lava flow. White-throated Swifts (Aeronautes saxatalis), which nest on steep, rocky cliff faces, darted through the air above us, and lupines spread out in vast fields around us.
|Sky Lupine (Lupinus nanus)|
|Harlequin Lupine, growing in a protected spot beside basalt boulders.|
|Lupine and Clarkia|
|Butter 'n' Eggs (Triphysaria eriantha formerly Orthocarpus erianthus)|
The hike to the top of Table Mountain is about 4 miles roundtrip, beginning at the end of Shell Road (off of Rawhide Road in Jamestown). The first mile of the trail meanders through beautiful oak woodlands, verdant and flowery at this time of year. Near the beginning of the second mile, the trail begins to ascend, gradually at first, through dense Chamise (Adenostoma fasciculatum) and a lovely, cool little stand of Western Spice Bush (Calycanthus occidentalis). The path enters a heavily wooded area, and hikers welcome the shade of oaks as the trail becomes progressively steeper, ending in a final steep scramble over basalt boulders. The view from the top is a pleasing reward. Watch out for Poison Oak along the trail!
After wandering along the lava flow and enjoying the scenery as long as you wish, return via the same trail. It's not a very long trail, so you should have plenty of time to stop and enjoy the beauty of California's oak woodlands!