Mojave Madness (part 1: the Geology lesson)

Speaking of rocks.....

A little under two weeks ago, a small group of us city folk decided to flee the cramped, damp urban life for a brief respite in the vast, dry Mojave Desert.  It was supposedly the beginning of wildflower season!  I left work early on Thursday with a sense of urgency.  I battled the wind as I rode my bike home eagerly to start our adventure.  Visions of orange California poppies, deliciously red cactus blooms, and yellow brittlebushes was my carrot on the stick.  I was so incredibly excited to be re-acquainted with that vaguely familiar place I'd seen so long ago.  Being the nerd that I was, I'd done a little research into the natural history of this magical place.  It amazes me how much change that little part of the world had seen over such an incomprehensible period of time - the Mojave and Death Valley region had once defined part of the western edge of the continent that now claims the United States.  Check out the image I borrowed from the Mojave Desert Geology website!  A very cool repository of geological info about the region. 

For about 800 millions years, the Mojave's oceanic margin was the junk yard of a large variety of marine sediments.  These marine sediments would eventually transform into rocks, known as sedimentary rocks - the oldest of them being over a billion years old!

About 250 million years ago the mid-Atlantic spread started to shove the North American plate into the oceanic Pacific plate. A pressure zone was created where the oceanic plate was forced down into the mantle. This is known as a 'subduction zone' for all you geologist semantic types like my father - Hi, Dad!  As the oceanic plate descended into the insanely hot/high pressure mantle, it melted into magma.  Magma is lighter than the material around it so it ascended to the Earth's surface.  If it reached the top before cooling down too much, it exited the upper crust via volcanic eruptions, thus explaining the origin of some of the mountains contained within the region.  If it didn't quite make it to the surface before cooling off, it solidified to form a huge rock or 'intrusion,' as referred to in the above figure.  Sprinkled throughout the Mojave are lots of these large intrusions that have become exposed over millions of years through uplift and erosion.  These intrusive rocks form the core of most of the Mojave mountain ranges.

After millions of years, the North American/Pacific plate subduction zone transformed into what many Californians are now quite familiar with: the infamous San Andreas Fault line, a strike-slip fault line that moves horizontally.  OK, I'll stop musing about geology now and move on to plants!
Not only is the geological history intriguing, but also the surprisingly rich diversity of vegetation.  There are over 1,000 different species of plants, which is pretty amazing considering the rather hot and arid climate.  The quirky Joshua Tree (Yucca brevifolia) is one of the most distinctive of all the plants, giving the landscape an extraterrestrial feel.  Being springtime, this was also that rare time of the year where many of the wildflowers take advantage of the amenable climate and gusty winds to bloom and advertise their sexy parts.  What a spectacle!  The swaying, seductive orange poppies popped back into my head as my bike tire hit the sidewalk in front of my apartment. 
All we had to do was brave the long drive to Barstow tonight so we could get some sleep and then start our journey into the Preserve tomorrow morning......