UC Davis Natural Reserve System
Stebbins Cold Canyon Reserve

UC Davis NRS Reserves

Stebbins Links:

	Hiking Information
	Directions
	Guide Program
	Use Applications

Natural History

	Land Use
	Geology
	Invertebrates    Insects    Mollusks    Spiders
	Vertebrates    Reptiles and    amphibians    Birds    Mammals
	Vegetation    Mushrooms

Research

Site Map

Technical Information

	Species Lists
	Site Information
	Maps
	Bibliography

McLaughlin External Links:

NRS Systemwide Homepage

Systemwide 
UC Davis NRS Sites

The Geology of Cold Canyon

Like the entire surface of the Earth, the landscape of Cold Canyon is constantly changing. Geologic processes are continually reshaping the rocks and sediments that make up the landforms on the surface of the planet. Less than one million years ago, Cold Canyon was merely a shallow trough, not the deep canyon present today. Millions of years before that, the rock that would later form Cold Canyon was located far beneath the surface of the sea. The present landforms of Cold Canyon are the products of three slow but very active geologic processes: deposition of sediments, continental uplift, and erosion. Over many millions of years these geologic processes have created, uplifted, and eroded vast amounts of rock to create Cold Canyon. Evidence of all three processes can be seen today at the mouth of the canyon. Sedimentary layers bent skyward by uplift surround Monticello Dam, while nearby, Cold Creek erodes material from the canyon walls and deposits it on the banks of Putah Creek.

Sediment Deposition.  Millions of years ago, off the western coast of the ancient continent, the land that would later become Cold Canyon was being deposited as river delta sediment. As rivers flow into the sea, they lose velocity, and thus lose their ability to carry sediment. Larger, heavier particles carried by the river, such as sand, are deposited close to shore, while finer grained particles, such as silt and clay, are carried farther offshore by the diminishing current. Some sediment is carried all the way to the continental shelf, the edge of the continent where it falls away steeply into the sea. Here, sediments accumulate on the steep slope, and over time become unstable. These sediments can then slide under their own weight, similar to a landslide or avalanche. These ‘undersea landslides’ are called turbidites, and can occur quite regularly. As the muddy turbidite slides down the continental slope, the larger, heavier particles, such as sand, are the first to settle onto the slope, followed by lighter, finer particles, such as silt and clay. In the end, the muddy sediments have been sifted into layers, with silts and clays generally overlaying sands.

Over several million years, as new depositional layers are built upon old layers, the weight of the upper layers creates great pressure on the lower layers, causing a transformation from muddy sediment to solid rock. The coarse sediments form sandstones, while the finer particles form mudstones.

Continental Uplift.  As this deposition was

California’s Coast Range was formed by the actions of a convergent plate boundary. A collision of the oceanic plate with the continental plate forced the coastal sediments up above sea level. Further pressures from this collision bowed these horizontal sedimentary layers into a near vertical orientation. This vertical layering is visible around Monticello Dam, near the mouth of Cold Canyon. After uplift, the motion along the plate boundary changed from convergence to lateral sliding, as attested by the motion of the San Andreas Fault today. 

The Cold Canyon region may still be tectonically active.  To the north of Putah Creek, a number of mineral springs lie scattered on a line extending southward towards Cold Canyon. The presence of certain minerals and the linear pattern of springs on the landscape indicate the presence of  a fault in this area. A similar spring is located within Cold Canyon. Although the evidence is not conclusive, the presence of this spring suggests that an active fault runs through the canyon, and within a quarter mile of Monticello Dam.

Weathering and Erosion.  Cold Canyon was formed by the weathering and erosion of these vertical layers by wind and water. Weathering is the breakdown of rock into small particles and can occur through chemical or physical mechanisms. Erosion is the transport of these particles by running water or landslides. Running water will typically seek the path of least resistance, cutting through softer, finer grained rock layers, while avoiding more resistant layers. This is evidenced by the fact that the floor of Cold Canyon lies in the midst of a fine grained mudstone layer, while the canyon walls consist of more resistant sandstone layers. 

The erosion that created Cold Canyon continues today both on a small scale, through the chemical breakdown of rock by air and rain, and on a larger scale by physical mechanisms such as landslides. Landslides are common on the steep walls of Cold Canyon. In 1995, a large landslide came down the eastern wall, toppling trees and piling soil and rocks along the streambank. The evidence of this slide can easily be seen along the trail, near the mouth of the canyon. More gradual erosive processes are also currently taking place. The creek actively erodes its channel, especially during winter floods, and Cold Canyon gets slightly deeper every day. The rounded boulders in the creek bed, smoothed by the scouring action of sediments transported by the stream, attest to this on-going erosion.

The powerful geologic processes which formed Cold Canyon continue today. The sediments currently being eroded from the walls of Cold Canyon are being deposited downstream, forming new sedimentary layers. The process of creation is an on going one; Cold Canyon is not the endpoint. One can only speculate how geology will continue to shape Cold Canyon in the future.

For more information see a technical report of the surface and bedrock geology in the Cold Creek watershed. To view a Geological Topo Map click here. 

Last Updated 03/09/06