SAN BERNARDINO AND SAN GABRIEL MOUNTAINS: COMPARING THE RATE OF EROSION AND POSSIBLE CAUSES FOR FASTER EROSION AT THE SAN GABRIEL MOUNTAIN RANGE

Research studies show discrepancies in erosion rates between the San Bernardino and San Gabriel Mountain Ranges. The two Mountain Ranges, located in the Transverse Ranges in Southern California, might seem similar but exhibit different geological characteristics (USGS et al, 2006). According to research studies, the San Gabriel Range is experiencing higher levels of erosion than the San Bernardino mountains. This is evident in its unpredictable and jagged topography compared to the smoother, broad plateaus of the San Bernardino mountains (DiBiase et al., 2009). Contrasts in tectonic movement, rock composition, precipitation, and topography can be seen as possible causes for elevated erosion rates. The topography and distribution of slope and elevation are key factors to erosion as the extreme slopes exacerbate deterioration and increase the runoff from precipitation. Despite the barren conditions of the mountains, they receive significant levels of precipitation, especially the San Gabriel Mountains, which receive 7 centimeters more precipitation annually than the San Bernardino range (Spotila et al, 2002). With the mountains being adjacent to the San Andreas Fault, damage from tectonic activity to the mountains is expected. Considering the information discussed previously, two questions come to our mind. 1. If in fact precipitation is more abundant at the San Gabriel mountains, could this be one of the main reasons for faster erosion rate? 2. Is tectonic activity along the San Andreas Fault detrimental to the durability of the rocks comprising these mountains? Our hypothesis is that both of these factors contribute greatly to the overall erosion rate of the San Gabriel mountain range. In the future, we will visit the two mountain ranges. We will acquire rock hardness from both sides using the Schmidt hammer (rebound test). We will collect rock samples from every place a rebound test was taken and we will conduct a petrological analysis of the rocks to determine mineralogical composition. Elevation will be examined to see if this factor plays a role in the mountains' erosion rate as well.