First some basics. Take a 5-gallon bucket of water, pick a fairly flat surface anywhere in a desert landscape and gently pour it out. You will observe that your water, if given a chance, will always flow downhill (as if it were playing a game of how low can I go) until it can no longer do so, forming a puddle; unless, of course it has either evaporated or soaked into the soil first.
The same basic scenario plays out whenever precipitation falls on ground that is not sloped and usually results in a puddle, a pond, a lake etc. before it either evaporates or soaks into the substrate (sand, gravel or soil). However, give that standing water body any slight irregularity in its margin and water will physically, chemically and biologically eat away at it until it can flow past the original barrier. Rest assured, the entire process will start anew when the freely flowing water reaches another barrier that forces it to puddle up again. Eventually, in time, if any of the original surface water remains, it will find itself all gathered up at the lowest spot on the terrain it has been traversing. In most cases the path that water takes on our planet can be described as generally equatorial with long westerly or easterly meanders. As for the "low spots", well those are generally the margins of some bigger puddles that are called seas and oceans.
From time to time, forces from beneath (see plate tectonics) can significantly change the elevation and surface terrain of the "playing board" that water has been slowly modifying in its quest for "low spots". The terrain can be lifted to form mountains, stretched to form valleys or titled in any direction. Sometimes, existing mountain ranges can even be moved long distances, like giant land cruising ships, into, through or alongside a previously and relatively level landscape, resulting in havoc on the paths of existing water courses and the stable watersheds that they have meticulously forged over time. To view the theorized sequence of geologic events that has led up to the present geographic configuration of California, view the sequence of animation at this site.
Compared to the landscape features like Rocky Mountains, the Sierra Nevada and even the San Andreas fault and the resulting Transverse Ranges of Southern California (see California's Coastal Mountains), the Mojave Desert and its landscape is relatively young (an effect of faulting and mountain building) and still in a state of flux. To view the theorized sequence of geologic events that has led up to the present geographic configuration of California and the present day landscape of the Mojave desert, view the sequence of animation at this site. A careful study of the Mojave's water courses, watersheds and flora and fauna can also point to a relatively recent and turbulent origin of its present landscape.
Stay tuned... More to follow...
No comments:
Post a Comment