Tioga Pass: a lesson in geology

At 10000 feet, the scenic 46-mile-long Tioga Pass in Yosemite National Park is the highest highway in California. We finally got our chance to go in May of 2021, when the COVID-related restrictions meant few people in the park and even fewer on the Tioga Pass. There were stretches of road where no cars passed us for over 30 mins, and we were mostly alone on the trails. We were so isolated that we inadvertently startled a deer grazing in a meadow.

In the winter, the snow buries the pass over 10 feet deep. The opening of the pass, which is possible only in the summer, is an impressive feat by the National Park Service. Equally impressive are the geological features along the road. For example, How did large round boulders reach the Olmsted point? Round rocks are formed in flowing water. Glaciers, which flow like water, erode and shape the landscape around Yosemite. These boulders were left here by glaciers plowing through the area during the last ice age. The rounded half-dome peak is another example of such erosion. Yes, the glaciers flowed hundreds of feet ABOVE the half-dome. This fact, while looking up at the tall half-dome from the Olmsted Point, is just incomprehensible. 

If you are wondering where does the water from the melting snow go? It collects in the many lakes of Yosemite, one of which is the clear, green-blue, and serene Tenaya Lake. This lake is a must-see place along the pass.

My favorite place on the pass is the large, flat & beautiful Tuolumne Meadows. A short hike along the meadow took us to a small waterfall on the Tuolumne River. We had the place to ourselves & enjoyed a peaceful lunch here while enjoying the picturesque scenery. This is a great place to spot wildlife. We saw a large herd of deers grazing in the meadows. From the meadow we saw pointy peaks like the Cathedral Peak. Naturally, the question beckons, why are these peaks pointed, when half-done is not? Because the glaciers never reached the height of these peaks! They eroded their bases but not the tops, which left them sharp!

Before descending towards the Lee Vining area, the Tioga Pass crests near Dana Meadows. This is a subalpine zone where only shrubs and grass grow. Curiously, unlike the typical black granite mountains Yosemite, the mountains here are red, why? When lava cools beneath the Earth’s surface, it becomes granite. The glaciers moving through Yosemite eroded the soil above & exposed the granite. These reddish mountains were formed by lava that erupting on the Earth surface and transforming into reddish metamorphic rock.

Here we saw people going off the trails and stepping into the meadows despite signs warning against it. Meadows are delicate ecosystems, and plants take much longer to grow at these heights. Always heed warnings and do not walk into meadows.

We delayed visiting Yosemite for years because we wanted to do both: the Valley and the Tiago Pass; It was well worth the wait. Although we spent an entire day here, there is still so much left to explore. I hope we go back sooner next time.