Boulders

We usually associate erosion with wind and rain, but the fantastic shapes of the rocks in Joshua Tree National Park were created underground. The granite outcrops originally formed from upwelling lava deep under the surface. As the softer rocks on top eroded away, that released the pressure on the granite; coupled with the constant shifts along the fault lines running through the area, the changing stresses caused the rocks to fracture vertically and horizontally, forming largely rectangular boulders. Over millions of years, groundwater and abrasive clays eroded the boulders into the rounded shapes we see now. Once the overlying rocks were themselves eroded away, rain and flash floods washed away the clays, leaving us with this impromptu sculpture garden.