July 18, 2012
Photographer: Dave Lynch; Dave’s Web site
Summary Author: Dave Lynch
Vegetation lineaments are natural lines of vegetation, or boundaries, between high and low vegetation densities. They can be caused by a variety of mechanisms, but faults are a common source. "Veg lines" occur primarily where soil moisture is locally enhanced. Faults can produce them by hindering the flow of subsurface groundwater. At the fault plane, rock pulverized by earthquakes is often so fine that it impedes water flow on the uphill side and this water ponds to or near the surface. Even when the seed distribution is random, more plants are able to sprout where soil moisture is enhanced. In some cases, water will reach the surface and flow out as natural springs. Where this happens, as shown above, the vegetation lineaments are marked by lush plant growth along the fault, with relatively little plant enhancement on either side.
Vegetation lineaments are most evident in the desert. Indeed, any oasis in a desert is almost certainly the result of a fault. Near the southern California town of Desert Hot Springs, many vegetation lineaments are prominent. They’re produced by the San Andreas Fault and the Banning Fault, both being part of the plate boundary between the North American and Pacific Plates.
This photo shows Thousand Palms. Subsurface water is flowing from right to left. Note the enhanced growth of vegetation to the right, with the highest plant density occurs along the San Andreas Fault (vertically through the picture).
The photo below shows Willis Palms. Subsurface water is flowing from right to left. Here water seeps from the ground and plant growth is abundant, including native Washingtonia Palms (Washingtonia filifera). This vegetation lineament is along the Banning Fault.