Mass Wasting on Highway 33 EarthCache

This location can be viewed from a large pullout on the west side of Highway 33.

The relatively steep sides of the valley are composed of Matilija Sandstone. The Matilija Sandstone was deposited in the Eocene (46 to 48.5 million years ago) in a marine environment. This coarse grained formation is a series of deep-ocean turbidites (see Point Mugu Turbidites) that likely formed off a tectonically active coast that creates steep mountains near the shore along with steep off-shore ocean bottoms.

Even though this rock formation is quite strong, it is still affected by mass wasting. Mass wasting is the movement of soil and rock under the influence of gravity. Gravity by nature pulls material down hill. While there are many ways to classify mass wasting, they are often categorized into one of the following categories

• Creep - slow, nearly continuous downslope movement;
• Slides - sudden downhill movement;
• Flows- dense, fluid mixtures;
• Falls – airborne or nearly airborne movement.

Mass wasting events may have characteristics of each of these categories, but they are named based on the predominant form of movement. Other terms are sometimes used to describe gradations between the categories above. A mass wasting event is further categorized into broad groups that give the impression of the type or size of material in motion. For example:

• Rock – any particle larger than a pebble
• Land/Earth – particles smaller than a pebble
• Mud – small particles with a significant component of water
• Debris – a mixture of soil, vegetation, and other material

Putting these two elements together creates the matrix for naming mass wasting events:

Not all of these combinations are used and other combinations that more accurately describe an event can be created. Additionally, some combinations don’t normally occur since the material involved would not create a slope required for that type of mass wasting event. For example, mud would not be found on a vertical slope required for a fall so a mud fall would not be found. In other cases, such as creep, the type of material is often not included.

Logging requirements:
Send me a note with :

1. The text "GC1RHZP Mass Wasting on Highway 33" on the first line
2. The number of people in your group.
3. Using the naming methodology above classify the mass wasting event that occurred on the mountain side to across HWY 33 to the north. Note: there is absolutely no need to cross the highway.

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