The results of paleomagnetic, petrographic, and radiometric studies of the Eastern Caroline Islands in the western Pacific indicate that the islands were formed by a hot spot located near the paleoequator between 1 and 11 Ma. The islands show a linear progression of mean ages from 1 Ma in the east (Kusaie) to 11 Ma in the west (Truk). The results of volumetric measurements and geochemical studies suggest that the hot spot source is waning and perhaps was slowly dying during the time Truk, Ponape, and Kusaie were being formed. The dominant shield‐building magmas in the Caroline Islands are part of a differentiated alkalic series. The posterosional lavas are highly silica undersaturated and trace element enriched nephelinites. The latter were erupted subsequent to the cessation of the main shield phase of volcanism. The petrography and geochemical evolution of Truk are strongly reminiscent of that of the Hawaiian chain; however, the shield‐building lavas are compositionally similar to the alkalic lavas that typically form only thin, late‐stage caps on many Hawaiian volcanos. No tholeiitic rocks were found despite sampling deep within the eroded volcanic structure of the islands. This absence of tholeiitic lavas and dominance of alkalic lavas stand in contrast with Hawaii, where tholeiitic volcanism dominates and alkalic lavas form only a minor component of the exposed lavas. The absence of tholeiitic lavas in the main shield‐building phase of construction, however, is not unique to the Caroline Islands. Dominant alkalic volcanism appears characteristic of other seamounts in the Pacific, including the Samoan, Austral‐Cook, and Line Islands.

The topography of the marine geoid (and corresponding sea surface) contains characteristic local features caused by seamounts. These features can be successfully detected and located using matched filters to process single tracks of satellite altimeter data. Comparison of detected seamount features with the SYNBAPS and Scripps bathymetric data bases can reveal uncharted seamounts. This technique has been applied to 33 Seasat tracks in a region of the western Pacific bounded by 0 to 15 degrees North and 160 to 165 degrees East. From this analysis, we find three uncharted seamounts in this region. In all three cases, a detailed examination of the bathymetry shows no known bathymetric feature consistent with the detected signature. The method used to estimate the size and location of these uncharted seamounts is discussed.

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The ATS 6 satellite, during an orbital maneuver in September 1976, passed within a few hundred kilometers of the geosynchronous satellite 1976-059A. Analysis of the 30-to 80-keV electron data from the University of California at San Diego (UCSD) electrostatic analyzers on ATS 6 and the 30-to 300-ke_V electron data from the Los Alamos Scientific Laboratory instrument on 1976-059A during this period reveals good agreement between the two instruments even when the separation is ñ7 ø . The low-energy UCSD ion data from ATS 6 allow a simultaneous determination of the potential difference between ATS 6 and the ambient medium. Use of the 1976-059A electron data to approximate the ambient plasma electron density and temperature during these charging periods indicates sufficient information exists in order to estimate the maximum potentials to which ATS 6 charges in sualight and eclipse. As data from 1976-059A and similar satellites are potentially available in real time, the information therefore exists to create a satellite charging index for the geosynchronous regime that would be valid within at least ñ7 ø longitude of the position of each measurement.

The degree of seamount compensation can be estimated from satellite radar altimetry and bathymetry data. Seamount signatures in the sea‐surface topography are detected, located and extracted from Seasat radar altimetry data using a matched filtering algorithm. We have developed an efficient method for determining the two‐dimensional undulation signature of any axi‐symmetric seamount with an arbitrary degree of compensation. Given the seamount dimensions as determined from bathymetry, we vary its degree of compensation until the model signature matches the signature extracted from Seasat data. We use this technique to map the relative degrees of local seamount compensation within a region. We have applied this technique to 14 of the Musicians Seamounts. Two of these seamounts have been analyzed using two crossing tracks each and confirm the repeatability of the technique. The results suggest the existence of a chain of low compensation seamounts within the highly compensated Musicians. Independent verification is needed from other geophysical and geochemical analyses to support this hypothesis.

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