The second Geology field trip at Santa Monica College

Images from the Spring 2008 field trip

to the Carrizo Plain, the Cuyama Valley and the Wheeler Gorge

field trip leader: Dr. Alessandro Grippo, Ph.D.

A natural spring along the Wheeler Gorge
causes deposition of travertine, a form of limestone (CaCO₃).
Edson is pointing up to where the water comes to surface.
Notice the puddle by the road, and the absence of vegetation where travertine is forming.

The Cuyama river does not seem very dangerous, but
Mario and Edson wanted to test their extreme adventure skills by using the rope across the stream.
Once the rope is pulled, people would use it.

Across the Cuyama river Michael is trying not to get wet.

Using the rope actually proved more useful when we climbed the walls
of a narrow slot canyon nearby the Cuyama river valley.

Well, nobody said the first attempt was going to be successful.

Is that a raccoon eating my sandwich down there?

The broad alluvial plain of the Cuyama river
shows gentle meanders and different alluvial bars.

The following morning we woke up to a brisk air and rolling clouds
at the Selby campground in the Carrizo Plain, prelude to an intense day in the field.

This is a picture of Soda Lake in winter, when it is actually a lake.
This picture was taken during my reconnassaince in the winter, when precipitation fills the basin.
When we visited Soda Lake, water had evaporated and only salt was left (see picture below).

Water does not flow out of Soda Lake, so during the warmer season it is left to evaporate in the atmosphere.
When water evaporates, the salts dissolved in it are left behind to form a salt pan.

Notice how, as a consequence of the very low speed with which the water moves through the soil,
the landscape around the lake is still green.

At Santa Monica College we want not only to see from a distance but also BE there:
the students are discussing the salt pan of Soda Lake while being on top of it.

Crossing the San Andreas Fault caused the students to be spread over two different tectonic plates:
the picture was taken from the North American Plate, looking across the San Andreas Fault,
here coinciding with the small stream-incised valley of Wallace Creek, to the Pacific Plate

Putting a foot on the San Andreas Fault at Wallace Creek:
what if an earthquake occurs now?

Wind erosion in sandstones caused the development of tafoni, or honeycomb structures.
Many of these cavities are currently used by birds as a pre-made, protected nest.

Sandstones are made of grains of sand, usually kept together by a cement.
A cement is a chemical precipitate that "glues" the individual grains one to the other.

Sometimes weathering patterns can act differently on different grains
originating what we call differential erosion:
in this case, more easily eroded materials have caused the development of a small arc along the pathway.

One last look across a plate boundary at Wallace Creek:
this time we are on the Pacific Plate, while the mountains in the background belong to the North American plate

The North American plate extends from here all the way to the middle of the Atlantic Ocean, thousands of miles away.

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