Monday, April 25, 2011

Trying not to see stars

I've commented before on Native American artifacts that resemble constellations near my home in Southern California (e.g., cupula rock). My comments weren't original: Ray Williamson, in his book "Living the Sky", refers to constellations in Great Basin petro glyphs. In searching for other examples of constellations in rock art, I found this paper: -- but the paper doesn't declare strong support for the constellation hypothesis, and in personal correspondence, the author offered his hindsight that he is now very skeptical of the constellation hypothesis. I've also sent photos of cupula rock to Anthony Aveni (Author of The End of Time: The Maya Mystery of 2010) who saw no reason to interpret the patterns as other than randomly distributed boreholes (see  Ok, I did do the nose).

So it is with caution that I share these photos of a rock at Joshua Tree National Park:

Six, similarly sized depressions, with four in a pretty straight line.

Here is a view of the area. I'm looking approximately South. Center in the photo (and you may need to click the photo to see ths) is the pattern:

 Here is a close up of the depressions, with my size-12 foot for scale:

The depressions look as worn as the surrounding rock and are even in size.

The rock at Joshua Tree is large-grained and crumbly. I believe it erodes quickly, and that people could easily make these depressions (now and thousands of years ago), but I saw no scratches or evidence hinting at human hands at work.

The depressions are in a popular camping and climbing area called Indian Cove. Joshua Tree has other Native American artifacts, so long-term human occupation is not in question. In the following photo, I noticed other patterns. The main group is in the center, but lower to the right you can see an alternating pattern of depressions:

 Here is a zoomed in view showing a right-left stepping pattern:

I see many natural depressions in the rock at Joshua Tree, but I've not seen any that are so consistent in shape as these.


Tuesday, April 19, 2011

Amboy Crater: 50 minutes North from my last post

Twenty-one years ago I drove across the great plains and southwest deserts of the United States on my way to California. Iraq had just invaded Kuwait and gas prices soared. I made a note of the highest price: $1.79 per gallon in Amboy California, which is near the southwest portion of the mojave desert. While in Amboy, I noticed a lava flow and prominent cinder cone and vowed to return. Twentyone years and over 2 dollars per gallon later, I returned.

Amboy Crater, viewed from the western rim (spliced together from three photos)

The drive north from Joshua Tree National Park to Amboy crosses classic alluvial fans. These alluvial features evelope the base of the mountains and form vast gradual slopes where you can drive for miles, barely noticing any elevation change.

The cinder cone rises 250 feet from the surface, making it unmistakable:

A mile-long trail leads from a parking lot to the cone and crosses the lava flow and it's varying features. Here, the flow's low, wavy shape is highlighted by the dry grass:

And here the texture is that of a pushed up parking lot, rock black as asphalt and cracked. Plants and sand exploit the cracks.

The composition of the cone has texture differences. Right is crumbly; and left, more of a charcoal color and texture comparable to graphite powders. The left also has distinct erosion channels.

A view looking down from the crater rim near the transition between textures.

A close up of the texture change:

After my visit, I found Amboy Crater on GoogleEarth, which is just like being there, unless of course, you've actually been there.

Notice the satelite photo from GoogleEarth shows streaks from the cinder cone and other features. These streaks weren't apparent to on the ground, and if they are real, my guess is that the streaks are wind deposits, darker grains blown from the cinder cone and other outcrops, and deposited onto the sand dusted flow. It is likely the winds blow consistently to the south east, something to follow up on.

Something on the sparse wildlife:

A very unusualy insect, unless I presume, you live here.

And a few plants:

Possibly a mallow or type of lilly growing among the lava rock -- another plant to identify.

Bright yellow encelia bushes peak around March and make a delightful contrast with the dark rock.

One last note: The best time to visit is Oct - March when the temperatures are mild. The lava flow heats up in the sunlight and would be dangerous for most people to cross when April-Sept temperatures start in the 90s.


Monday, April 18, 2011

Waking in the Desert to Anticrepuscular Shadows

Everyone should wake up in the Southern California desert once in awhile, especially during April. My first word upon waking is "ouch", but after recovering from sleeping on the ground, I can enjoy this type of sight:

The photo shows anti-crepuscular shadows converging on San Gorgonio (the white peak in the distance). It is common to see beams of light while looking toward the rising or setting sun -- these are called crepuscular rays. However, this is the second time I've photographed the anti-crepuscular effect -- e.g., shadows continuing to the vanishing point opposite the sun (also called the anti-solar point). The crepuscular effect comprises light rays, shadows or both. In the above photo, the ray would be the larger area between the shadows, but I can hardly call that a ray. Rather, I see only the anti-crepuscular shadows. I suspect that the conditions necessary to create the appearance of smaller light rays against a darker background are more rare than this.


Friday, April 15, 2011

Some redrawn illustrations for RealClimate

I redrew the illustration from Professor Ruddiman's post on RealClimate for the purpose of making them available: