Day 4: Circumnavigation of Mount Shasta

You promise sunshine but it looks like rain.

Low pressure is moving in and threatens to linger with us for a few days. This means rain. I said yesterday that the mountains make their own weather. This happens through several processes:

The most intuitive is that a large mountain forces air upward resulting in decompression of the air. Decompression leads to cooling. Cooling air holds less moisture. Air loses moisture via consensation, cloud formation and rainfall.

The second mechanism is that air obtains much of its heat from the earth suface beneath it. If a mountain is high enough up and absorbs enough sunlight the mountain at a given elevation will be warmer than the surrounding air. Air near the "warm surface of the mountain will rise, cool and condense as the mountain draws in more moisture from all directions.

The third is not so much the mountain itself as it is the air. Water vapor is lighter than Oxygen and Nitrogen. The greater the saturation the more likely air is to rise in the first place.

We are off to a late start. Disrupted sleep + class upkeep have had a way of throwing monkey wrenches into everything. There is a lot we are doing this trip besides driving and sightseeing. It all adds up.

When We finally left Weed at 10 AM the clouds were lifting. Maybe rain later, but this was our window of opportunity. We began with a drive to what we hoped would be timberline, only to learn that the road was closed at Bunny Flat, 2.5 miles earlier and 800 feet down. So we set out to climb at least a little bit. We are however both out of shape and the Altitude was getting to us. We made it maybe 1/3 mile to the top of the meadow, where enjoyed views of Avalanche gulch and Some of the ridgeline. Here the stratified nature of Mt Shasta is readily apparent: multiple lava flows of varying consistency stacked atop one anotehr. Some of these are, of course comprised of less stable material

As a consequence the land is in constant motion, evidenced by the bent trees all up and down the hillside. Classic Soil Creep. Some are even bent at 90 degrees.

At some point after tiring of sitting we agreed to drive around the mountain. On our way back to Shasta City we were treated to one of the most Sublime views. Shasta is the 2nd tallest cascade volcano and the elevation of its summit makes it one of the tallest in N. America. Even 1/2 way up as we were things around us looked small.

Circumnavigation

7 Years ago we took a very sketchy dirt road (Forest Highway 31) that nearly destroyed our Ford fiesta and oddly failed to get us to many good views. This time I had identified a road further out that appeared to be maintained to a higher standard, that started out near McCloud, CA. We were pleased at first to be driving a veritible tree tunnel. Indeed this road seems to service a large number of logging opperations, but unlike our previous route, this one afforded us a chance to actually see the mountain.

We stopped multiple times to snap pictures of different angles of the Mountain, picnicing in a lonely meadow with view of the summit and many of the glaciers. It was at one of these spots We remarked at how much whiter the North facing slopes are compared to the South facing ones. We are seeing very directly the influence of sun angle on climate. North facing slopes spread the sunlight over a larger area. South facing slopes at this latitude (~41 degrees) actually concentrate sunlight. East and west also matter as they determine when the slope receives energy. More energy when the air is already warmed up will melt snow and ice a little faster- such that western slopes tend to melt before eastern slopes. We marveled at the ever changing glaciers and clouds dancing over the peak.

Whitney Glacier

Whitney glacier pictured above is the largest glacier in the state of California. Nestled between Shasta and Little Shasta on north facing slope, it is somewhat buffered against the most rapid of climate change by some quirks of local geography and climate. So much so that it is one of the rare but not unheard of glaciers that will typically grow during warmer years. How does this happen?

Glacier mass is a function of snowfall and mass loss. While warmer years usually lead to higher melt rates, the extra evaporation off the ocean will also lead to increased snowfall. In most places the tradeoff between these two factors is such that the glacier still retreats in a warmer year, but at Whitney Glacier on the north face of shasta, it will actually grow. This is one reason not to cherry pick the dynamics of any single glacier when inferring global trends.

The Lava Caves of Pluto

After several hours of drivign our final stop was at the end of an short but scary dirt road and a rough and rocky short trail: Pluto's cave. In my classes we talk extensively about how limestone will dissolve into caverns. The other rock that readily forms caverns is Basalt. How? you ask? Lavas freeze first where they are in contact with the cold air at the surface and then thicken more deeply below. In the case of these lavas, that thick insulation allowed the lava below to continue flowing long after the surface had frozen. You can see a marked change in texture and crystal size as we get closer to the walls of the tube and the surface almost resembles glass in places.

Many Critters have also made their homes here. We saw numerous bird nests along the lava flows lining the walls. We Could SMELL numerous bats in the area, or at least their poop. In one cave the smell was so overpowering we got out quickly. You might also notice the degree to which the roofs of these caverns have collapesed. I confess I was not sure how safe it was to linger here.

We were getting tired and there was much work still to be done. So we Returned to Weed, grabbed some dinner supplies at the local market and watched the storm approach.