The San Gabriel Mountains have been subject to quite a bit of deformation in their past. Some of which is still ongoing, such as the movements along the Sierra Madre and San Andreas Faults. Here, near Mt Wilson, the rocks exhibit multiple instances of deformation. The white vein is mostly composed of quartz, which has been offset by multiple faults. Slickensides can be seen as the reddish areas on the right side of the photo. The surrounding materials are complex metamorphic rocks.
A well-photographed portion of the Ridge Route, known as the Callahan Line Change, is now a part of the Virtual Tour of the Ridge Route. This is a section that had become somewhat obscure because of later freeway construction. For more detailed information –
Near the southern end of the Salton Sea in the Imperial Valley, you can find some very interesting geological features. Mud volcanoes, slowly “erupting” a fine muddy ooze, are some of the evidence of the extreme heat not far below the surface here. Gases, usually carbon dioxide, also emanate from the ground here. These mud volcanoes are more active in winter and spring, when groundwater is a little higher and the surface temperatures are a bit lower. I highly recommend a visit sometime.
This morning (2/21/2020) at 5:42 am, a small earthquake struck the Castaic area north of Los Angeles. Just looking at the maps, it seems near the San Gabriel Fault but it is a somewhat complex area. It was also a very deep earthquake as they go, 18.1 km. Shaking was felt in a wide area but wasn’t very strong.
For more information, check out the USGS Summary Page of the event.
https://earthquake.usgs.gov/earthquakes/eventpage/ci39079535/executive
Looking toward South Mount Hawkins in the West Fork San Gabriel Canyon from State 39. This road was planned to be improved but landslides prevented this work from being completed. In the case of this area, almost all of the low lying areas not covered in snow are landslides in one form or another. Even Crystal Lake, where this roadway is headed, exists because of landslides.