"... the western landscape is more than topography and landforms, dirt and rock. It is, most fundamentally, climate--- climate which expresses itself not only as landforms but as atmosphere, flora, fauna. And here, despite all the local variety, there is a large, abiding simplicity. Not all the West is arid, yet except at its Pacific edge, aridity surrounds and encompasses it. Landscape includes facts such as this. It includes and is shaped by the way continental masses bend ocean currents, by the way the prevailing winds blow from the West, by the way mountains are pushed up across them to create well-watered coastal or alpine islands, by the way the mountains catch and store the snowpack that makes settled life possible in the dry lowlands, by the way they literally create the dry lowlands by throwing a long rainshadow eastward.
"Aridity, more than anything elase, gives the western landscape its character."
-from "Thoughts in a Dry Land", by Wallace Stegner