Sanctuary Integrated Monitoring Network
National Marine Sanctuaries


Geology_ map
Figure 1. Seafloor substrate (hard and soft habitat) within the Monterey Bay, Gulf of the Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
The coastal and seafloor landscapes within the three northern California sanctuaries have been influenced by phenomena including earthquakes, millions of years of wind and water erosion, submarine landslides and changes in sea level.

An area's character can affect both the location and size of habitats for many marine plant and animal species. Therefore, mapping geologic features and understanding the processes that shape them is essential to recognizing and interpreting change.

Each of the three sanctuaries boasts interesting features that have resulted from its geologic history. For example: All three sanctuaries are greatly influenced by their location in the zone where two of the earth's major tectonic plates - the Pacific and North American - meet. The San Andreas Fault system (comprised of several sub-faults) forms the boundary between these two plates. The Pacific Plate is slowly moving northward relative to the North American Plate, but most of this motion occurs in catastrophic bursts of movement - earthquakes - along the fault system.

Movement along these faults helps to shape the surrounding landscape: coastal mountains are thrust upwards, submarine canyons are channeled and underwater landslides are triggered. In the Gulf of the Farallones, the San Andreas Fault zone splits Bolinas Lagoon, Tomales Bay and Bodega Bay; it is responsible for the long, straight, narrow shape of Tomales Bay.

Interesting geology, knobs formed by the differential erosion of sedimentary rock. This is just at the base of the cliff jutting southwest-most at Pillar Point.

Coastal cliffs with arch formed in sandstone.


Research often takes place across the three sanctuaries. Such is the case with the UsSEABED database. This project, spearheaded by the U.S. Geological Survey (USGS), is an ongoing effort to gather diverse geologic data about the continental shelf and organize it through a GIS database.

Of course, many projects are sanctuary-specific as well. For example, researchers have collected and processed high-resolution backscatter and bathymetry data of Cordell Bank and surrounding soft-bottom areas. The data are being used to develop a benthic habitat map of the bank and surrounding region.

In the Monterey Bay region, monitoring efforts focus on three general topics: coastal erosion, the continental shelf and submarine canyons. Some recent studies in each area are noted here.

Coastal Erosion The Continental Shelf Submarine Canyons