Category Archives: Geology

Featured Image – 4/7/2021

Today’s featured image is a video. This was taken just a few days ago on the Old Ridge Route near Swede’s Cut. A rockfall in January 2021 has partially blocked the roadway with more material coming down in the near future. The rock, located in the Ridge Route member of the Ridge Basin Group, isn’t all that stable. Landslides still plague I-5 despite more modern construction methods.

For additional information check out the
Ridge Route Preservation Organization

Featured Image – 2/8/2021

1970 view of the I-5 / SR-14 Interchange construction. This “build” would partially collapse on February 9, 1971 while still incomplete. Courtesy – Caltrans

To commemorate the 50th anniversary of the February 9, 1971 M6.6 Sylmar / San Fernando Earthquake, our featured image shows the construction work in progress on the I-5 and State 14 interchange in 1970. This work would be halted abruptly in the early hours of February 9, 1971. After this, it would be reconstructed two more times. The earthquake changed the way freeways such as this were built and did further seismic codes throughout the state.

For further information about the interchange:

Featured Image – 11/23/2020

Along the San Andreas Fault

Near Valyermo, California, outside of Palmdale, the locals have placed signs where Pallet Creek Road crosses the San Andreas Fault. They picked a really nice spot too, as you have a sag area, fault scarp, and offset streams all easily visible from there. I recommend a visit!

Featured Image – 4/17/2020

Step faulting, slickensides, and heavily fractured rock

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.

Featured Image – 3/3/2020

Mud Volcanoes near Schrimpf Road and Davis Road.

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.