California State Waters Map Series—Offshore of Bodega Head, California

Open-File Report 2015-1140
By: , and 
Edited by: Samuel Y. Johnson and Susan A. Cochran

Links

  • Document: Pamphlet (1.7 MB pdf)
  • Sheets:
    • Sheet 1 (21.3 MB pdf) Colored Shaded-Relief Bathymetry, Offshore of Bodega Head Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 2 (23.4 MB pdf) Shaded-Relief Bathymetry, Offshore of Bodega Head Map Area, California By Peter Dartnell and Rikk G. Kvitek
    • Sheet 3 (22.1 MB pdf) Acoustic Backscatter, Offshore of Bodega Head Map Area, California By Peter Dartnell, Mercedes D. Erdey, and Rikk G. Kvitek
    • Sheet 4 (15.7 MB pdf) Data Integration and Visualization, Offshore of Bodega Head Map Area, California By Peter Dartnell
    • Sheet 5 (30.7 MB pdf) Seafloor Character, Offshore of Bodega Head Map Area, California By Mercedes D. Erdey and Guy R. Cochrane
    • Sheet 6 (24.7 MB pdf) Ground-Truth Studies, Offshore of Bodega Head Map Area, California By Nadine E. Golden, Guy R. Cochrane, and Lisa M. Krigsman
    • Sheet 7 (9.5 MB pdf) Potential Marine Benthic Habitats, Offshore of Bodega Head Map Area, California By Bryan E. Dieter, H. Gary Greene, Charles A. Endris, and Erik N . Lowe
    • Sheet 8 (20.2 MB pdf) Seismic-Reflection Profiles, Offshore of Bodega Head Map Area, California by Samuel Y. Johnson, Ray W. Sliter, Stephen R. Hartwell, and John L. Chin
    • Sheet 9 (8.8 MB pdf) Local (Offshore of Bodega Head Map Area) and Regional (Offshore from Salt Point to Drakes Bay) Shallow-Subsurface Geology and Structure, California By Samuel Y. Johnson, Stephen R. Hartwell, Janet T. Watt, and Ray W. Sliter
    • Sheet 10 (17.4 MB pdf) Offshore and Onshore Geology and Geomorphology, Offshore of Bodega Head Map Area, California By Samuel Y. Johnson, Stephen R. Hartwell, and Michael W. Manson
  • Related Works:
  • Dataset: Data Catalog (html) The GIS data layers for this map are accessible from “Data Catalog—Offshore of Bodega Head, California,” which is part of California State Waters Map Series Data Catalog (Data Series 781). Each GIS data file is listed with a brief description, a small image, and links to the metadata files and the downloadable data files.
  • Metadata: Metadata (html)
  • Open Access Version: Publisher Index Page
  • Download citation as: RIS | Dublin Core

Introduction

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow subsurface geology. 

The Offshore of Bodega Head map area is located in northern California, about 70 km north of San Francisco and about 80 km south of Point Arena. The onshore part of the map area is largely undeveloped, used primarily for recreation, farms and ranches, and a few wineries. The small town of Bodega Bay, located on the east side of Bodega Harbor, is the largest cultural center. Bodega Harbor is an important commercial fishing base and, in season, an active sport fishing and recreation harbor. Much of the coastline from Bodega Head north to about 6 km north of the Russian River is part of Sonoma Coast State Park. The Offshore of Bodega Head map area includes two California Marine Protected Areas, the Bodega Head State Marine Reserve and the northern part of the Bodega Head State Marine Conservation Area. Additionally, the inland parts of two large estuaries in the map area, Estero Americano and Estero de San Antonio, have been designated as State Marine Recreational Management Areas.

The map area is cut by the northwest-striking San Andreas Fault, the right-lateral transform boundary between the North American and Pacific plates. This fault juxtaposes rocks of the Jurassic and Cretaceous Franciscan Complex on the northeast with Cretaceous granitic rocks on the southwest, and it has an estimated slip rate of about 17 to 25 mm/yr in this area. The devastating great 1906 California earthquake (M7.8) is thought to have nucleated on the San Andreas Fault offshore of San Francisco, about 80 km south of Bodega Head, with the rupture extending northward through the Offshore of Bodega Head map area and an additional 220 km to the south flank of Cape Mendocino.

North of the mouth of Salmon Creek, the coast and shoreline are rugged and scenic, characterized by flights of uplifted marine terraces, rocky promontories, nearshore sea stacks, kelp-rich coves, and both pocket beaches and longer beach strands, the latter of which include Wrights Beach and Portuguese Beach. The coast has lower relief between the mouth of Salmon Creek and Mussel Point, where South Salmon Creek Beach is backed by a large (about 4 km2) complex of coastal sand dunes. The enormous volume of sand on the beach and in the dune field is derived by southward littoral drift from the Russian River, Salmon Creek, and smaller coastal watersheds. The sediment is trapped by protruding bedrock at Mussel Point, which represents the south end of the Russian River littoral cell. 

Bodega Head is underlain by Cretaceous granitic rocks, and its shoreline is variously characterized by relatively low-lying terraces, steep and high bluffs, and a few pocket beaches. East of Bodega Head, Doran Beach (part of Doran Regional Park) is a 1.7-km-long sand spit that forms the north boundary of Bodega Bay and the south boundary of Bodega Harbor. The coast south of Doran Beach on the east flank of Bodega Bay is composed of rocky bluffs, hummocky marine terraces, and a few small pocket beaches. The bluffs are underlain by sheared rocks of the Franciscan Complex and are highly susceptible to landslides. This section of coast includes two prominent watersheds, Estero Americano and Estero de San Antonio, which drain westward into Bodega Bay.

The offshore part of the Offshore of Bodega Head map area is characterized by an extensive, rugged and rocky shelf underlain by Cretaceous granitic rocks. This rocky terrain, centered offshore of Bodega Head, extends northwestward for about 15 km, from the south edge of the map area (where it forms the west boundary of Bodega Bay) to the northern-central part of the map area offshore of the mouth of Salmon Creek. This rocky seafloor reaches water depths of 40 to 80 m and is overlain by young sediment. 

Circulation over the shelf and seafloor in the map area (and in the broader central California region) is dominated by the southward-flowing California Current, the eastern boundary current of the North Pacific Gyre. Associated upwelling brings cool, nutrient-rich waters to the surface, resulting in high biological productivity. Persistent northwest winds are sometimes weak or absent during the fall and winter, causing the California Current to move farther offshore so that the shelf is affected by the Davidson Current, a weaker northward-flowing countercurrent. As a result, net flow over the continental shelf is commonly southeastward during the spring and summer and northwestward during the fall and winter. 

Throughout the year, this part of the northern California coast is exposed to four wave climate regimes: the north Pacific swell, the southern swell, northwest wind waves, and local wind waves. The north Pacific swell dominates in winter months (typically November through March). During summer months, the largest waves come from the southern swell, generated by storms in the south Pacific and offshore of Central America. Northwest wind waves affect the coast throughout the year, whereas local wind waves are most common from October to April.

Potential marine benthic habitats in the Offshore of Bodega Head map area include unconsolidated continental-shelf sediments, mixed continental-shelf substrate, and hard continental-shelf substrate. Rocky-shelf outcrops and rubble are considered to be promising potential habitats for rockfish and lingcod, both of which are recreationally and commercially important species.

Suggested Citation

Johnson, S.Y., Dartnell, P., Golden, N.E., Hartwell, S.R., Erdey, M.D., Greene, H.G., Cochrane, G.R., Kvitek, R.G., Manson, M.W., Endris, C.A., Dieter, B.E., Watt, J.T., Krigsman, L.M., Sliter, R.W., Lowe, E.N., and Chin, J.L. (S.Y. Johnson and S.A. Cochran, eds.), 2015, California State Waters Map Series—Offshore of Bodega Head, California: U.S. Geological Survey Open-File Report 2015–1140, pamphlet 39 p., 10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/ofr20151140.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Chapter 1. Introduction
  • Chapter 2. Bathymetry and Backscatter-Intensity Maps of the Offshore of Bodega Head Map Area
  • Chapter 3. Data Integration and Visualization for the Offshore of Bodega Head Map Area
  • Chapter 4. Seafloor-Character Map of the Offshore of Bodega Head Map Area
  • Chapter 5. Ground-Truth Studies for the Offshore of Bodega Head Map Area 
  • Chapter 6. Potential Marine Benthic Habitats of the Offshore of Bodega Head Map Area
  • Chapter 7. Subsurface Geology and Structure of the Offshore of Bodega Head Map Area and the Salt Point to Drakes Bay Region 
  • Chapter 8. Geologic and Geomorphic Map of the Offshore of Bodega Head Map Area

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title California State Waters Map Series—Offshore of Bodega Head, California
Series title Open-File Report
Series number 2015-1140
DOI 10.3133/ofr20151140
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pacific Coastal and Marine Science Center
Description Report: iv, 39 p.; 10 Plates: 46.0 x 36.0 inches or smaller; Metadata; Data Catalog
Country United States
State California
Other Geospatial Bodega Bay
Online Only (Y/N) Y
Additional Online Files (Y/N) Y