USGS - science for a changing world

Woods Hole Coastal and Marine Science Center

Skip Navigation

Publications by type, USGS Woods Hole Coastal and Marine Science Center

Scientific Investigations Report by WHCMSC Authors for the year



Pendleton, E.A., Andrews, B.D., Ackerman, S.D., and Twichell, D.C., 2014, Bathymetry of Buzzards Bay and Vineyard Sound: U.S. Geological Survey Scientific Investigations Map 3286 . Online at 10.3133/sim3286
Noble, Marlene A., Rosenberger, Kurt J., Xu, Jingping, Signell, Richard P., and Steele, Alex, 2009, Connections among the spatial and temporal structures in tidal currents, internal bores, and surficial sediment distributions over the shelf off Palos Verdes, California: U.S. Geological Survey Scientific Investigations Report 2008-5094 . Online at http://pubs.usgs.gov/sir/2008/5094/
The topography of the Continental Shelf in the central portion of the Southern California Bight has rapid variations over relatively small spatial scales. The width of the shelf off the Palos Verdes peninsula, just northwest of Los Angeles, California, is only 1 to 3 km. About 7 km southeast of the peninsula, the shelf within San Pedro Bay widens to about 20 km. In 2000, the Los Angeles County Sanitation District began deploying a dense array of moorings in this complex region of the central Southern California Bight to monitor local circulation patterns. Moorings were deployed at 13 sites on the Palos Verdes shelf and within the northwestern portion of San Pedro Bay. At each site, a mooring supported a string of thermistors and an adjacent bottom platform housed an Acoustic Doppler Current Profiler. These instruments collected vertical profiles of current and temperature data continuously for one to two years. The variable bathymetry in the region causes rapid changes in the amplitudes and spatial structures of barotropic tidal currents, internal tidal currents, and in the associated nonlinear baroclinic currents that occur at approximate tidal frequencies. The largest barotropic tidal constituent is M2, the principal semidiurnal tide. The amplitude of this tidal current changes over fairly short along-shelf length scales. Tidal-current amplitudes are largest in the transition region between the two shelves; they increase from about 5 cm/s over the northern San Pedro shelf to nearly 10 cm/s on the southern portion of the Palos Verdes Shelf. Tidal-current amplitudes are then reduced to less than 2 cm/s over the very narrow section of the northern Palos Verdes shelf that lies just 6 km upcoast of the southern sites. Models suggest that the amplitude of the barotropic M2 tidal currents, which propagate toward the northwest primarily as a Kelvin wave, is adjusting to the short topographic length scales in the region. Semidiurnal sea-level oscillations are, as expected, independent of these topographic variations; they have a uniform amplitude and phase structure over the entire region. Because the cross-shelf angle of the seabed over most of the Palos Verdes shelf is 1 to 3 degrees, which is critical for the local generation and/or enhancement of nonlinear characteristics in semidiurnal internal tides, some internal tidal-current events have strong asymmetric current oscillations that are enhanced near the seabed. Near-bottom currents in these events are directed primarily offshore with amplitudes that exceed 30 cm/s. The spatial patterns in these energetic near-bottom currents have fairly short-length scales. They are largest over the inner shelf and in the transition region between the Palos Verdes and San Pedro shelves. This spatial pattern is similar to that found in the barotropic tidal currents. Because these baroclinic currents have an approximate tidal frequency, an asymmetric vertical structure, and a somewhat stable phase, they can produce a non-zero depth-mean flow for periods of a few months. These baroclinic currents can interact with the barotropic tidal current and cause an apparent increase (or decrease) in the estimated barotropic tidal-current amplitude. The apparent amplitude of the barotropic tidal current may change by 30 to 80 percent or more in a current record that is less than three months long. The currents and surficial sediments in this region are in dynamic equilibrium in that the spatial patterns in bottom stresses generated by near-bed currents from surface tides, internal tides, and internal bores partly control the spatial patterns in the local sediments. Coarser sediments are found in the regions with enhanced bottom stresses (that is, over the inner shelf and in the region between the Palos Verdes and San Pedro shelves). Finer sediments are found over the northwestern portion of the Palos Verdes shelf, where near-bottom currents are relatively weak. The nonlinear asymmetries in the internal tidal-period current oscillations cause a net transport of suspended material along and off the shelf, reinforcing the mean flow patterns that also carry sediment either into Santa Monica Bay or offshore and onto the adjacent slope.
Bothner, Michael H., Reynolds, Richard L., Casso, Michael A., Storlazzi, Curt D., and Field, Michael E., 2008, Sediment mobility along Moloka`i's fringing coral reef; evidence from sediment traps; Chapter 19 of Field, Michael E., Cochran, Susan A., Logan, Joshua B., and Storlazzi, Curt D., eds., The coral reef of south Moloka`i, Hawai`i; portrait of a sediment-threatened fringing reef: U.S. Geological Survey Scientific Investigations Report 2007-5101 . Online at http://pubs.usgs.gov/sir/2007/5101/sir2007-5101_chapter19.pdf
Moloka'i is the fifth youngest island in the long chain of volcanoes and volcanic remnants that compose the Hawaiian archipelago (fig. 1). The archipelago extends from the Island of Hawai'i (the 'Big Island') in the southeast past Midway Island, to Kure Atoll in the northwest, for a total distance of about 2,400 km (1,500 mi). Beyond Kure Atoll, the chain continues as a series of submerged former islands known as the Emperor Seamounts, which extend to the Aleutian Trench off the coast of Alaska. Evolution of the entire Hawai'i-Emperor volcanic chain represents a time span of nearly 80 million years (Clague and Dalrymple, 1989). The volcanic chain is a result of gradual and persistent movement of the Pacific lithospheric plate (the sea-floor crust and rigid uppermost part of Earth's mantle) over a deep fracture (or hot spot) that extends down to the astenosphere, a less rigid part of the mantle (fig. 2). Plumes of molten lava flowed onto the sea floor, repeatedly creating massive shield volcanoes that exceed 10,000 m (33,000 ft) in relief above the surrounding sea floor. The growth of each volcano is a process that takes half a million years or more to construct most of its mass through sequential volcanic phases - submarine, explosive, and subaerial - of shield growth. Once formed, each massive island volcano is carried northwestward on the Pacific tectonic plate at rates of 8.6 to 9.2 cm/yr (Clague and Dalrymple, 1989). The postshield processes of alkalic volcanism, subsidence, landslides, rejuvenated volcanism, weathering, sediment deposition, and reef growth have all markedly influenced each volcano's present-day shape. Subsidence of each island is rapid at first (rates of 2 mm/yr or more; Moore and Campbell, 1987; Moore and Fornari, 1984; Campbell, 1986) in response to the extraordinary weight of large volumes of lava loaded onto the crust. As each island cools and slides northwestward with the sea-floor crust, it continues to subside at decreasing rates, down to the order of 0.02 mm/yr (Detrick and Crough, 1978). The sheer volume of rock that accumulates at each volcano ultimately leads to failure and partial collapse - each island has had spectacular landslides that are amongst the largest on earth (Moore and others, 1989). The large areas of irregular topography on the sea floor around the islands (for example, north of Moloka'i and northwest of O'ahu) attest to the magnitude of these events (fig.1). The normal processes of surface erosion and stream runoff modify volcano slopes early in an island's history. Those processes, along with development of soils, which occurs relatively quickly in humid volcanic terrain, lead to transport and deposition of sediment in alluvial fans, flood plains, and narrow coastal plains. The final process in island shaping is the establishment of coral reefs in shallow waters that are protected from large waves. Corals colonize exposed rock surfaces very quickly (Grigg and Maragos, 1974; Grigg, 1983), and it is likely that they become established early in the evolutionary history of each island. The development of coral reefs - the massive limestone structures capped by a living ecosystem that border many Hawaiian Islands - takes much longer (Grigg, 1987). Each reef is a thick (meters to tens of meters) packet of reefal limestone that likely accumulated over multiple stages of sea-level shifts (Grossman and others, 2006; Grossman and Fletcher, 2004; Sherman and others, 1999). In most locations in Hawai'i, modern coral cover is only a thin living veneer on top of older reef structures that formed during an earlier time under different conditions (Grigg, 1983, 1998).
Field, M.E., Bothner, M.E., Chavez, P.S., Jr., Cochran, S.A., Jokiel, P.L., Ogston, A.S., Presto, M.K., and Storlazzi, C.D., 2008, The effects of a Kona storm on the Moloka`i reef; November and December 2001; Chapter 21 of Field, Michael E., Cochran, Susan A., Logan, Joshua B., and Storlazzi Curt D., eds., The coral reef of south Moloka`i, Hawai`i; portrait of a sediment-threatened fringing reef: U.S. Geological Survey Scientific Investigations Report 2007-5101 . Online at http://pubs.usgs.gov/sir/2007/5101/sir2007-5101_chapter21.pdf
Moloka'i is the fifth youngest island in the long chain of volcanoes and volcanic remnants that compose the Hawaiian archipelago (fig. 1). The archipelago extends from the Island of Hawai'i (the 'Big Island') in the southeast past Midway Island, to Kure Atoll in the northwest, for a total distance of about 2,400 km (1,500 mi). Beyond Kure Atoll, the chain continues as a series of submerged former islands known as the Emperor Seamounts, which extend to the Aleutian Trench off the coast of Alaska. Evolution of the entire Hawai'i-Emperor volcanic chain represents a time span of nearly 80 million years (Clague and Dalrymple, 1989). The volcanic chain is a result of gradual and persistent movement of the Pacific lithospheric plate (the sea-floor crust and rigid uppermost part of Earth's mantle) over a deep fracture (or hot spot) that extends down to the astenosphere, a less rigid part of the mantle (fig. 2). Plumes of molten lava flowed onto the sea floor, repeatedly creating massive shield volcanoes that exceed 10,000 m (33,000 ft) in relief above the surrounding sea floor. The growth of each volcano is a process that takes half a million years or more to construct most of its mass through sequential volcanic phases - submarine, explosive, and subaerial - of shield growth. Once formed, each massive island volcano is carried northwestward on the Pacific tectonic plate at rates of 8.6 to 9.2 cm/yr (Clague and Dalrymple, 1989). The postshield processes of alkalic volcanism, subsidence, landslides, rejuvenated volcanism, weathering, sediment deposition, and reef growth have all markedly influenced each volcano's present-day shape. Subsidence of each island is rapid at first (rates of 2 mm/yr or more; Moore and Campbell, 1987; Moore and Fornari, 1984; Campbell, 1986) in response to the extraordinary weight of large volumes of lava loaded onto the crust. As each island cools and slides northwestward with the sea-floor crust, it continues to subside at decreasing rates, down to the order of 0.02 mm/yr (Detrick and Crough, 1978). The sheer volume of rock that accumulates at each volcano ultimately leads to failure and partial collapse - each island has had spectacular landslides that are amongst the largest on earth (Moore and others, 1989). The large areas of irregular topography on the sea floor around the islands (for example, north of Moloka'i and northwest of O'ahu) attest to the magnitude of these events (fig.1). The normal processes of surface erosion and stream runoff modify volcano slopes early in an island's history. Those processes, along with development of soils, which occurs relatively quickly in humid volcanic terrain, lead to transport and deposition of sediment in alluvial fans, flood plains, and narrow coastal plains. The final process in island shaping is the establishment of coral reefs in shallow waters that are protected from large waves. Corals colonize exposed rock surfaces very quickly (Grigg and Maragos, 1974; Grigg, 1983), and it is likely that they become established early in the evolutionary history of each island. The development of coral reefs - the massive limestone structures capped by a living ecosystem that border many Hawaiian Islands - takes much longer (Grigg, 1987). Each reef is a thick (meters to tens of meters) packet of reefal limestone that likely accumulated over multiple stages of sea-level shifts (Grossman and others, 2006; Grossman and Fletcher, 2004; Sherman and others, 1999). In most locations in Hawai'i, modern coral cover is only a thin living veneer on top of older reef structures that formed during an earlier time under different conditions (Grigg, 1983, 1998).
Riggs, Stanley R., and Ames, Dorothea V., 2007, Effect of storms on barrier island dynamics, Core Banks, Cape Lookout National Seashore, North Carolina, 1960–2001: U.S. Geological Survey Scientific Investigations Report 2006-5309, Web Only
Hutchinson, D., Hart, P., and Pilger, 0, Regional stratigraphic framework of gas hydrates in the central Gulf of Mexico: U.S. Geological Survey Scientific Investigations Report
Riggs, S.R., 0, Geologic Evolution of the Lower Roanoke River and Albemarle Sound Drainage System in Response to Climate Change and Sea-Level Rise: U.S. Geological Survey Scientific Investigations Report
Riggs, S.R. and Ames, D.V., 0, Barrier Island Evolution: A Model for Development of the Geomorphic Framework, North Carolina Outer Banks: U.S. Geological Survey Scientific Investigations Report
Ames, D.V., Riggs, S.R., and Thieler, R., , Geomorphic framework of the North Carolina Outer Banks:
Hemphill-Haley, Kelsey, Graehl, Casso, Caldwell, Loofbourrow, Robinson, Vemeer, Southwick, , Evidence for Earthquakes, Tsunamis, or Storms Recorded at Five Coastal Sites in Northern California, USA.: U.S. Geological Survey Scientific Investigations Report
Valentine, P.C., Cross, V.A., , Seabed maps showing topography, ruggedness, backscatter intensity, sediment mobility, and the distribution of geologic substrates in quadrangle 5 of the Stellwagen Bank National Marine Sanctuary region offshore of Boston, Massachusetts: U.S. Geological Survey Scientific Investigations Map
Skip USGS links group

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USAGov logo U.S. Department of the Interior | U.S. Geological Survey
End of USGS links group
URL: http://woodshole.er.usgs.gov/pubsearch/pub_list.php
Page Contact Information: WHSC Webmaster
Script last modified Friday, 05th May, 2017 @ 06:00pm