Table Mountain (Tuolumne County, California)

Table Mountain is composed of Table Mountain Latite, which formed from potassium-rich lavas erupted from a center of volcanism near modern-day Sonora Pass around 10.4 million years ago. The lava flows followed the course of the ancestral Stanislaus River, filling the river valley. As the Sierra Nevada Mountains were uplifted, the softer sediments surrounding the flows were eroded away, leaving behind an inverted river valley. Although the formation stretches for miles and rises hundreds feet above the surrounding landscape, its width rarely exceeds a few hundred feet. Most outcrops on Table Mountain reveal flow-top breccias, while some outcrops show distinctive columnar jointing.[3]

The lava flow which covered the ancient river bed trapped auriferous, or gold-bearing, gravels beneath it, some of which have been accessed by mining operations dating back to the 1850s.

A variety of flora and fauna are found on Table Mountain. In the spring, many wildflowers can be found atop the mountain including several species of lupine and the yellow mariposa lily, Calochortus luteus.[4] Vernal pools form on the flat top after heavy winter and spring rains, providing habitat for many uncommon plant and animal species. The harsh conditions found on top of Table Mountain generally prevent invasive plants from surviving, resulting in a landscape which is composed primarily of native plants.[5] White-throated swifts nest on the cliff faces that flank the mountain.[6]

• Inverted relief