Web Services--Offshore of Aptos

Citation

Golden, N.E., compiler, 2015, California State Waters Map Series Data Catalog: U.S. Geological Survey Data Series 781, https://pubs.usgs.gov/ds/781/.

Summary

The map area offshore of Aptos, California, which is referred to herein as the “Offshore of Aptos” map area, is located on the Pacific Coast, on the north side of Monterey Bay, 88 kilometers (55 miles) south of San Francisco. The largest incorporated city in the map area, Capitola (and numerous unincorporated towns including Aptos) lie on uplifted marine terraces between the shore and the northern-trending Santa Cruz Mountains, part of the northwest trending Coast Ranges that run roughly parallel to the San Andreas Fault Zone (SAFZ) (California Geological Survey, 2002). As of 2013 the U.S. Census Bureau estimated populations of Aptos and Capitola were approximately 6000 and 10,000 respectively. Aptos is one of the few remaining Ohlone [...]

Summary

The map area offshore of Aptos, California, which is referred to herein as the “Offshore of Aptos” map area, is located on the Pacific Coast, on the north side of Monterey Bay, 88 kilometers (55 miles) south of San Francisco. The largest incorporated city in the map area, Capitola (and numerous unincorporated towns including Aptos) lie on uplifted marine terraces between the shore and the northern-trending Santa Cruz Mountains, part of the northwest trending Coast Ranges that run roughly parallel to the San Andreas Fault Zone (SAFZ) (California Geological Survey, 2002). As of 2013 the U.S. Census Bureau estimated populations of Aptos and Capitola were approximately 6000 and 10,000 respectively. Aptos is one of the few remaining Ohlone Indian named places. There are no harbor facilities in the Offshore of Aptos map area. The economy in the Offshore of Aptos map area is based primarily on tourism, and retail business. Capitola is the oldest recorded beach resort on the US west coast. All of the State waters in the map area are part of the Monterey Bay National Marine Sanctuary. In the southern map area the Soquel Canyon State Marine Conservation Area extends from the State waters boundary to the east across Soquel Canyon. The western margin of North America is the only continental margin in the world delineated largely by transform faults such as the San Andreas. The Santa Cruz Mountains lie between the SAFZ and the San Gregorio Fault Zone (SGFZ). The coastal geomorphology is controlled by late Pleistocene and Holocene slip in the SGFZ. A westward bend in the SAFZ to the north and right-lateral movement along the SGFZ has caused regional folding and uplift. The SAFZ and SGFZ lie outside State waters in the vicinity of the Offshore of Aptos map area. The shelf in the map area is cut by numerous steeply dipping to vertical faults. The map area contains highly irregular and low rocky cliffs and sparse small pocket beaches backed by low, terraced hills associated with uplifted areas in the northeast and continuous sandy beaches on lowlands associated with the low standing lands and waters of the Monterey Bay and Canyon. The uplifted northern edge of Monterey Bay provides protection for the beaches in the map area by sheltering them from the dominantly northwesterly waves. Coastal sediment transport in the Offshore of Aptos map area is characterized by north-to-south littoral transport of sediment that is derived mainly from ephemeral streams, and local coastal erosion. Sediment transport occurs within the Santa Cruz littoral cell which terminates in Monterey Submarine Canyon. At the southern edge of the map area the head of Soquel Canyon incises the slope. This canyon is disconnected from the onshore watershed by changing sea level which has risen about 125 m since the low-stand associated with the last glacial maximum (LGM) about 20,000 to 18,000 years ago. Map area beach processes are strongly related to the Santa Cruz harbor jetty where the maximum long term beach accretion rate is seen to the west and the maximum long term erosion rate is seen to the east of the harbor. Harbor dredge spoils have been used to nourish beaches to the east of the Santa Cruz harbor and beach nourishment has been used to maintain Capitola Beach. The Offshore of Aptos map area consists of relatively flat and shallow continental shelf. The shelf dips gently seaward (less than 1°), so that water depths in California’s State Waters are predominantly less than 80 m. Depths greater than 130 m in Soquel Canyon at the southern edge of the map area where state waters have been extended beyond 3 nautical miles across Monterey Bay. Distance to the shelf break is approximately 7 to 10 km. To the west of the map area where the shelf break is not on the edge of a canyon the shelf breaks at water depths of about 150 m. This part of Central California is exposed to large North Pacific swells from the northwest throughout the year. North Pacific swell heights range from 2 to 10 meters, with larger swells occurring from October to May. During El Nino Southern Oscillation (ENSO) events winter storms track further south than normal years, impacting the map area more frequently with waves of larger height. Bedrock exposed along the coast consists of erosion-resistant sedimentary rocks, and significant erosion events are primarily due to storm wave activity that erodes the overlying unconsolidated terrace sediments. The shelf is underlain by variable amounts (0 to 30 m) of upper Quaternary shelf, estuarine, and fluvial sediments deposited as sea level fluctuated in the late Pleistocene. The thickest deposits occupy paleo-channels that formed during the previous sea level minimum and extended shoreward from Soquel Canyon. These paleo-stream channels were filled by local sediment eroded during the most recent sea level transgression.

Contacts

Point of Contact :: PCMSC Science Data Coordinator
Originator :: Nadine Golden
Metadata Contact :: PCMSC Science Data Coordinator
Publisher :: U.S. Geological Survey
USGS Mission Area :: Natural Hazards
SDC Data Owner :: Pacific Coastal and Marine Science Center

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Aptos_webservices_metadata.xml Original FGDC Metadata	View	23.13 KB	application/fgdc+xml

Extension: OffshoreAptos_WebServices.zip
thumbnail.png		11.8 KB
OffshoreAptos_WebServices.sd		622.98 MB

Related External Resources

Type: Publication that references this resource

Cochrane, G.R., and others, (G.R. Cochrane and S.A. Cochran, eds.), 2016, California State Waters Map Series—Offshore of Aptos, California: U.S. Geological Survey Open-File Report 2016–1025, 43 p., 10 sheets, scale 1:24,000, https://doi.org/10.3133/ofr20161025.	https://doi.org/10.3133/ofr20161025

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