Mojave NP - Hiking Hole-in-the-Wall and Banshee Canyon

Mojave National Preserve is huge - 2,500 square miles and is the third largest unit of the National Park System in the contiguous United States!  Three of the four major North American Deserts -- Mojave, Sonoran and Great Basin - come together in the preserve, supporting a surprising diversity of plants and wildlife. A rich geologic history and a wide range of elevations throughout the park make for unique landscapes.  We had no appreciation for the immensity and diversity of the preserve until we arrived.  Consequently, it has been very hard to explore all the aspects of this area from one location near Barstow.  We had to pick two or three interesting features and content ourselves with exploring those.  Next time, perhaps we'll camp in the preserve where we can get at everything a little easier.

The area immediately surrounding the Hole-in-the-Wall Visitor Center is a good introduction to the geology of this section of the preserve:  rhyolite cliffs riddled with holes and hollows:

Rhyolite is igneous, volcanic rock, and can have a variety of appearances and colors.  Here is how Wikipedia describes the rock:

Rhyolite can be considered as the extrusive equivalent to the plutonic granite rock, and consequently, outcrops of rhyolite may bear a resemblance to granite. Due to their high content of silica and low iron and magnesium contents, rhyolite melts are highly polymerized and form highly viscous lavas. They also occur as breccias or in volcanic plugs and dikes. Rhyolites that cool too quickly to grow crystals form a natural glass or vitrophyre, also called obsidian. Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations, spherulitic, nodular, and lithophysal structures. Some rhyolite is highly vesicular pumice. Many eruptions of rhyolite are highly explosive and the deposits may consist of fallout tephra/tuff or of ignimbrites.

What makes Hole-in-the-Wall so interesting is that multiple forms of rhyolite exist side by side and layered on top of one another, so that a walk through the landscape is an exploration of all the forms that rhyolite can take:

Below, Kathy pauses at the trailhead for the Rings Loop Trail to learn about what we will be seeing:

Our hike circled a large mesa.  As we walked, we had huge stone cliffs to our right, and large expanses of rolling land to our left:

The area was visited by native peoples over the millenia, and where the rock acquired a desert patina, petroglyphs testified to human habitation:

In many places, hard tuff formed from volcanic ash-fall were overburdened with pyroclastic flows of lava or other material, and after erosion over the millenia, left examples of those geologic layers:

Where tuff formed from volcanic ash, hot gases that had been trapped in the ash eventually escaped after the ash hardened, leaving honeycombs of round holes that were further widened and smoothed by wind and water.  David pokes around near some of the holes below.  (Watch out, David, the ranger sign warned that desert varmints can inhabit those holes!)

Why, indeed, here's one of those desert varmints right here in this hole!

Eagle-eyed Kathy spotted a huge boulder of breccia containing chunks of black obsidian:

We finally arrived at one of our objectives -- Banshee Canyon -- so named because the winds blowing through the canyon are said to scream like banshees:

The canyon becomes so narrow at the far end that it has to be traversed like any other slot canyon: slowly and carefully, hand over hand.  The National Park Service installed sets of climbing rings on two vertical ascents along our route.  Here, Kathy plans her climb up the first set of rings:

The geology of this place was fascinating, making it worth the 90-mile drive from our campground. However, when we learned that campground at Hole-in-the-Wall is an excellent Dark Sky star viewing location, we resolved to come back and camp here in a year or two.