Loch Leven Trail

Temperatures in the nineties in the Sacramento Valley are driving hikers to higher elevations in the Sierra. Today I hiked a very popular trail, the Loch Leven Trail, which starts near Interstate 80, at an elevation of 5,680 feet. I arrived early, before eight o'clock, to avoid the crowds, and only a few vehicles were in the small parking lot. When I returned a few hours later, the lot was full and vehicles were parked in any available space nearby.

The trail was covered in snow just a few weeks ago. Patches of snow were still about. Water from snowmelt ran down some sections of the trail. Several large trees felled by the weight of snow over the winter lay across the trail. They will eventually be cleared.

The elevation gain is only 1,070 feet. The rocks and tree roots on the trail add some difficulty to the hike, particularly on the descent. There is a bit of scrambling in places. A hiking staff helps with stability.

The geology is interesting. The trail crosses the boundary between two rocks. The rock in the Rattlesnake Creek Pluton is granodiorite, a relative of granite, and is 120 million years old. This rock intruded as magma into the older Jurassic volcanic arc rock (Early Jurassic, about 200 million years old) during a subduction process. This pluton was essentially a large blob of molten rock that moved upward from the subduction zone far below. The magma followed fractures and melted overlying rock. Some magma reached the surface and erupted as volcanoes. But most stayed five to ten miles underground in a large chamber, and slowly cooled to leave the crystals in the rock we see today.

Where I stood on the granodiorite, the rock went several miles below me, and it once went several miles overhead. What eroded came to rest in what is now the Sacramento Valley.

There is no distinct line between the Cretaceous granodiorite and the Jurassic terrane rock. The two slowly melded together until one gave way to the other.

I continued up the trail, crossing the railroad tracks, the original ones being built by the Chinese for the Transcontinental Railroad. Further up I encountered snow. I scrambled about trees fallen across the trail. I passed granodiorite outcrops polished and scraped by glaciers. I passed the first two Loch Leven lakes and had lunch at the third.

 

A wonderful day in the Sierra.