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H. A. Karl

Publications and source records attributed to H. A. Karl.

5 recordsLinked to original sources
USGS1988

Physiography of the western United States Exclusive Economic Zone

GLORIA (Geologic Long-Range Inclined Asdic) sidescan sonar images were collected over the entire Exclusive Economic Zone (EEZ) west of the conterminous United States. The continuous, overlapping, swath-mapping technique provides, for the first time, a reconnaissance plan view off the entire sea floor from the edge of the continental shelf to 370 km from shore. The mid-ocean ridges, transform faults, seamount provinces, and sediment fans that dominate this region of the EEZ are seen in detail, and many features never before mapped in this region, such as canyons, seamounts, and meandering channels, have been located. Marked differences are apparent in the morphology of the continental slope and in sedimentary features both on the slope and in the deep ocean. Anticlinal ridges and diapirs crossed by large submarine canyon systems are clearly defined on the continental slope north of the Mendocino Fracture Zone. In contrast, the slope south of the fracture zone is incised by a dense network of smaller scale canyons and only a few large canyon systems. The first-order causes of these differences are related to differences in tectonic setting between the subduction-dominated margin north of Cape Mendocino and the strike-slip-dominated margin to the south.

Geology↗
USGS1986

Internal-wave currents as a mechanism to account for large sand waves in Navarinsky Canyon head, Bering Sea

Sand waves are found in the heads of four of five large submarine canyons that incise the northern continental margin of the Bering Sea. The sand waves occur in a restricted depth zone of about 175-490 m. Those in Navarinsky Canyon, the area surveyed in most detail, are best developed in water depths of 300-375 m; they average 5 m in height and about 650 m in wavelength, with crests oriented subparallel to isobaths and almost perpendicular to the axes of the two main branches of the canyon. We speculate that internal-wave currents are responsible for the sand waves. Currents generated by internal waves are a particularly attractive mechanism for at least three reasons: 1) the energy of the internal waves could be amplified in the head of Navarinsky Canyon, especially in the area of the sand wave field; 2) upslope boundary-layer intensification of internal-wave currents might be sufficient to move the sediment composing the sand waves; and 3) the wavelengths of higher-frequency internal waves closely match the spacing of the sand waves. Although we based our assumptions on present-day conditions, we do not know if the sand waves are active. Consequently, we do not discount the possibility that the sand waves could have originated in the Pleistocene when Navarinsky Canyon headed in a shallow embayment that was receiving large quantities of sediment discharged by glacial meltwater streams. These conditions probably caused strong vertical density gradients in the coastal waters, which would have been more favorable than those today for the propagation of high-frequency internal waves.

Journal of Sedimentary Research↗
USGS1980

Variability of currents and sediment transport on continental shelves: Optical and current meter studies of the bottom boundary layer

The Continental Margin Sediment Dynamics program of the U.S. Geological Survey has been using a variety of optical instruments to monitor water turbidity as part of our studies of sediment transport. Although we suspect that optical devices will eventually be supplanted by more direct measures of suspended sediments, results of several field experiments indicate that for now transmissometers and nephelometers offer the best solution to the problem of long term environmental monitoring in the ocean. The Continental Margin Sediment Dynamics (CMSD) program of the U.S. Geological Survey is structured to investigate those oceanographic and geological processes which influence and control the active transport of sediments and other materials over continental margins. The focus of this program is on active sedimentary processes, the mechanisms which create them, and the effects they produce (see Figure 1 for a diagrammatic depiction). Basically, we design our experiments to investigate (1) transport mechanisms of oceanic sediments and other materials as suspended load and bed load, and (2) relationships of erosion and deposition to the dynamical characteristics of oceanic bottom boundary layers. The purpose of this report is to describe briefly those aspects of equipment and experiments that relate to our study of suspended particulate matter and water turbidity. Much of our understanding of the spatial distribution and temporal variability of suspended sediments depends upon measurements from optical instruments. In this report we describe those instruments and give examples of their use and some results of two field experiments.

Proceedings of SPIE↗