Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the 

U.S. Government

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary between electronic plotters 

and between X and Y directions on the same plotter, and paper may change size due to atmospheric conditions; therefore, scale and 

proportions may not be true on plots of this map.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3261/

Suggested Citation: Phillips, E.L., Erdey, M.D., and Cochrane, G.R., 2013, Seafloor character, Offshore of Carpinteria map area, 

California, sheet 5 in Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Greene, H.G., 

Endris, C.A., Seitz, G.G., Sliter, R.W., Erdey, M.D., Wong, F.L., Gutierrez, C.I., Krigsman, L.M., Draut, A.E., and Hart, P.E. (S.Y. Johnson 

and S.A. Cochran, eds.), California State Waters Map Series—Offshore of Carpinteria, California: U.S. Geological Survey Scientific 

Investigations Map 3261, pamphlet 42 p., 10 sheets, scale 1:24,000, http://pubs.usgs.gov/sim/3261/.

Figure 6. Rugosity (characterization of roughness derived from bathymetry) draped over shaded-relief bathymetry 

(see sheet 2) for same area as figure 4 (Box B on map). Rugosity values are displayed in muted “rainbow” color 

spectrum that ranges from purple (low rugosity) through green (medium rugosity) to red (high rugosity). Areas of 

high slope are indicated by high-rugosity values (red); areas of low slope, by medium- to low-rugosity values (green 

to purple). Interpreted substrate classes from figure 4 included for comparison. 

Fine- to medium-grained 

smooth sediment; 

Depth Zone 2, Slope Class 1

Rock and boulder, rugose; 

Depth Zone 2, Slope Class 1 

Mixed smooth sediment and rock;

Depth Zone 2, Slope Class 1

Figure 5. Acoustic-backscatter image (see sheet 3) draped over shaded-relief bathymetry (see sheet 2) for same 

area as figure 4 (Box B on map). Brighter areas indicate coarse-grained, rough, or hard seafloor; darker areas 

indicate unconsolidated (loosely packed) sediment; small black areas are data-processing artifacts. Interpreted 

substrate classes from figure 4 included for comparison. 

Rock and boulder, rugose; 

Depth Zone 2, Slope Class 1 

Mixed smooth sediment and rock;

Depth Zone 2, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 2, Slope Class 1

Figure 4. Detailed view of substrate classes mapped in area between Rincon Point and Rincon Island (see Box B, 

on map, for location): Depth Zone 2 (intertidal to 30 m), and Slope Class 1 (0°–5°). Fine- to medium-grained smooth 

sediment is shown in shades of green; mixed smooth sediment and rock is shown in shades of tan; and rock is 

shown in shades of pink. 

Rock and boulder, rugose; 

Depth Zone 2, Slope Class 1 

Mixed smooth sediment and rock;

Depth Zone 2, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 2, Slope Class 1

BOX B

Figure 3. Rugosity (characterization of roughness derived from bathymetry) draped over shaded-relief bathymetry 

(see sheet 2) for same area as figure 1 (Box A on map). Rugosity values are displayed in muted “rainbow” color 

spectrum that ranges from purple (low rugosity) through green (medium rugosity) to red (high rugosity). Areas of 

high slope are indicated by high-rugosity values (red); areas of low slope, by medium- to low-rugosity values (green 

to purple). Interpreted substrate classes from figure 1 included for comparison. Bathymetric contour (30 m) added 

for depth reference. 

Rock and boulder, rugose; 

Depth Zone 3, Slope Class 1

Mixed smooth sediment and rock; 

Depth Zone 3, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 3, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 2, Slope Class 1

30 m

Rugged anthropogenic material

(oil-platform structural support); 

Depth Zone 3, Slope Class 1 

Smooth, hard anthropogenic material

(shell hash mound adjacent to platform); 

Depth Zone 3, Slope Class 1 

Rugged anthropogenic material

(oil-platform structural support); 

Depth Zone 2, Slope Class 1 

Smooth, hard anthropogenic material

(shell hash mound adjacent to platform); 

Depth Zone 2, Slope Class 1 

Figure 2. Acoustic-backscatter image (see sheet 3) draped over shaded-relief bathymetry (see sheet 2) for same 

area as figure 1 (Box A on map). Brighter areas indicate coarse-grained, rough, or hard seafloor; darker areas 

indicate unconsolidated (loosely packed) sediment. Interpreted substrate classes from figure 1 included for 

comparison. Bathymetric contour (30 m) added for depth reference. 

Rock and boulder, rugose; 

Depth Zone 3, Slope Class 1

Mixed smooth sediment and rock; 

Depth Zone 3, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 3, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 2, Slope Class 1

30 m

Rugged anthropogenic material

(oil-platform structural support); 

Depth Zone 3, Slope Class 1 

Smooth, hard anthropogenic material

(shell hash mound adjacent to platform); 

Depth Zone 3, Slope Class 1 

Rugged anthropogenic material

(oil-platform structural support); 

Depth Zone 2, Slope Class 1 

Smooth, hard anthropogenic material

(shell hash mound adjacent to platform); 

Depth Zone 2, Slope Class 1 

Figure 1. Detailed view of substrate classes mapped in area offshore of Carpinteria (see Box A, on map, for 

location): Depth Zones 2 and 3 (intertidal to 100 m), and Slope Class 1 (0°–5°). Fine- to medium-grained smooth 

sediment is shown in shades of green; mixed smooth sediment and rock is shown in shades of tan; rock is shown 

in shades of pink; and both rugged anthropogenic material (oil-platform structural support) and smooth, hard 

anthropogenic material (shell hash mound adjacent to platform) are shown in shades of purple. Bathymetric 

contour (30 m) added for depth reference. 

Rugged anthropogenic material

(oil-platform structural support); 

Depth Zone 3, Slope Class 1 

Rock and boulder, rugose; 

Depth Zone 3, Slope Class 1

Smooth, hard anthropogenic material

(shell hash mound adjacent to platform); 

Depth Zone 3, Slope Class 1 

Mixed smooth sediment and rock; 

Depth Zone 3, Slope Class 1

Rugged anthropogenic material

(oil-platform structural support); 

Depth Zone 2, Slope Class 1 

Fine- to medium-grained 

smooth sediment; 

Depth Zone 3, Slope Class 1

Fine- to medium-grained 

smooth sediment; 

Depth Zone 2, Slope Class 1

30 m

Smooth, hard anthropogenic material

(shell hash mound adjacent to platform); 

Depth Zone 2, Slope Class 1 

BOX A

0.1 0.1 <0.1 <0.1 0.1 0.1 Anthropogenic

(rugged)

0.4 0.2 Rock and 

boulder, rugose 0.3 0.4 0.1

2.3

<0.1

1.6 Mixed smooth

sediment and rock 0.8 1.2 0.8 1.1

Fine- to mediumgrained smooth

sediment

98.0 139.1 33.1 47.0 64.9 92.1

Total

percent percent of total sq km percent of total sq km

Depth Zone 2

(water depth 0–30 m)

Depth Zone 3

(water depth 30–100 m)

sq km

Anthropogenic

(smooth, hard) <0.1 <0.1 <0.1 <0.1 <0.1 <0.1

Table 1. Coverage of classified seafloor, in square kilometers (sq km) and percent of total area, 

broken into California Marine Life Protection Act Depth Zones 2 and 3.

CALIF.

0 4 8 Nautical Miles

Kilometers 0 5 10

120° 119°40' 119°20' 119°

34°

34°20'

MAP LOCATION

Ventura

Santa Barbara

Anacapa

Island

Santa Cruz Island Santa Rosa Island

Area of Santa Barbara Channel Map

Limit of California’s

State Waters

DESCRIPTION OF MAP UNITS

DEPTH ZONE 2—INTERTIDAL TO 30 METERS WATER DEPTH

SLOPE CLASS 1—0 TO 5 DEGREES

Fine- to medium-grained smooth sediment—Low backscatter, low rugosity; typically mud to 

medium-grained sand; often rippled and (or) burrowed

Mixed smooth sediment and rock—Moderate to very high backscatter, low rugosity; typically 

coarse-grained sand, gravel, cobbles, and bedrock

Rock and boulder, rugose—High backscatter, high rugosity; typically boulders and rugose bedrock 

Rugged anthropogenic material—High backscatter, high rugosity; related to development by humans 

Smooth, hard anthropogenic material—High backscatter, low rugosity; related to development by 

humans

DEPTH ZONE 3—30 TO 100 METERS WATER DEPTH

SLOPE CLASS 1—0 TO 5 DEGREES

Fine- to medium-grained smooth sediment—Low backscatter, low rugosity; typically mud to 

medium-grained sand; often rippled and (or) burrowed

Mixed smooth sediment and rock—Moderate to very high backscatter, low rugosity; typically 

coarse-grained sand, gravel, cobbles, and bedrock

Rock and boulder, rugose—High backscatter, high rugosity; typically boulders and rugose bedrock

Rugged anthropogenic material—High backscatter, high rugosity; related to development by humans

Smooth, hard anthropogenic material—High backscatter, low rugosity; related to development by 

humans

EXPLANATION OF MAP SYMBOLS

Area of “no data”— Areas near shoreline not mapped owing to insufficient high-resolution seafloor 

mapping data; areas beyond 3-nautical-mile limit of California’s State Waters were not mapped as 

part of California Seafloor Mapping Program

3-nautical-mile limit of California’s State Waters

DISCUSSION

This seafloor-character map of the Offshore of Carpinteria map area in southern California was produced using 

video-supervised, maximum-likelihood classification of the bathymetry and backscatter (intensity of return) signals 

from sonar systems (a summary of the video data collected for the purpose of supervising the classification is shown 

on sheet 6). Rugosity (a GIS-derived characterization of roughness) and backscatter intensity were used as variants 

in the classification. The interpreted classifications were then draped over shaded-relief bathymetry (see sheet 2). 

The substrate classes mapped in this area have been divided into the following California Marine Life Protection Act depth zones: Depth Zone 2 (intertidal to 30 m), and Depth Zone 3 (30 to 100 m). In addition, the following 

slope class is represented on this map (Coastal and Marine Ecological Classification Standard slope zone is shown in 

parentheses): Slope Class 1, 0° to 5° (flat). Depth Zone 1 (intertidal), Depth Zones 4 and 5 (greater than 100 m), and 

Slope Classes 2 to 4, greater than 5° (sloping to vertical) are not present in this map area.

Fine- to medium-grained smooth sediment (sand and mud) makes up 98.0 percent of the map area (139.1 km2): 

47.0 km2 is in Depth Zone 2, and 92.1 km2 is in Depth Zone 3. Mixed smooth sediment (sand and gravel) and rock 

(sediment typically forming a veneer over bedrock, or rock outcrops having little to no relief) make up 1.6 percent of 

the area mapped (2.3 km2): 1.2 km2 is in Depth Zone 2, and 1.1 km2 is in Depth Zone 3. Rock and boulder, rugose 

(rock and boulder outcrops having high surficial complexity) makes up 0.3 percent of the map area (0.4 km2): 0.4 

km2 is in Depth Zone 2, and less than 0.1 km2 is in Depth Zone 3. Rugged anthropogenic material (oil-platform 

structural support) makes up 0.1 percent of the map area (0.1 km2): less than 0.1 km2 is in Depth Zone 2, and 0.1 

km2 is in Depth Zone 3. Smooth, hard anthropogenic material (shell hash mound adjacent to platform) makes up less 

than 0.1 percent of the map area (<0.1 km2): less than 0.1 km2 is in Depth Zone 2, and less than 0.1 km2 is in Depth 

Zone 3 (table 1).

Seafloor Character, Offshore of Carpinteria Map Area, California

By

Eleyne L. Phillips, Mercedes D. Erdey, and Guy R. Cochrane

2013

ONE MILE = 0.869 NAUTICAL MILES

1 .5 0 1 KILOMETER

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 1/2 0 1 MILE

SCALE 1:24 000

APPROXIMATE MEAN

DECLINATION, 2013

MAGNETIC NORTH

12 / ° 1 2

TRUE NORTH

Onshore elevation data from NOAA Coastal Services 

Center (data collected by EarthData International in 

2002-2003) and from U.S. Army Corps of Engineers (data 

collected by Fugro Pelagos, in 2009). Offshore 

shaded-relief bathymetry from map on sheet 2, this 

report. California's State Waters limit from NOAA Office 

of Coast Survey

Universal Transverse Mercator projection, Zone 11N

NOT INTENDED FOR NAVIGATIONAL USE

Seafloor character mapped by Eleyne L. Phillips and 

Guy R. Cochrane, 2011 

GIS database and digital cartography by Eleyne L. 

Phillips and Mercedes D. Erdey

Edited by Taryn A. Lindquist

Manuscript approved for publication June 13, 2013

Carpinteria

Rincon Point

Rincon Island

Summerland

119°30'

119°30'

119°35'

119°35'

34°25'

34°25'

34°20'

34°20'

BOX A 

BOX B

Scientific Investigations Map 3261

Sheet 5 of 10

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey