The name "Las Trampas" or "the traps" in Spanish, is derived from the indigenous SaclanBay Miwok peoples' technique of using the area's steep canyons to trap herds of Tule elk and other game species for hunting.[2]
Las Trampas Creek and its tributary Grizzly Creek begin on the mountain. Las Trampas Creek is one of the largest sub-watersheds within the Walnut Creek Basin, comprising an area over 17,000 sq acres in size.[3]
Geology
Like much of Contra Costa County, Las Trampas peak and its surroundings are largely composed of fossiliferous sedimentary rocks from the Great Valley Sequence.[2] These formations have been heavily altered by millions of years of faulting and rifting, a process that is still ongoing.[4]
The region around Las Trampas Peak is tectonically active, with earthquakes being a common occurrence.
Certain bands in the area contain abundant fossils of prehistoric sea life from the Miocene epoch (~23 mya to ~5 mya)[4][5]
^Contra Costa County Watershed Atlas(PDF). Contra Costa County Community Development Department, Contra Costa County Public Works Committee. 2004. p. 79.