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Here, sporadic mafic and felsic eruptions, representing at least five major and several smaller pulses of effusive and explosive volcanic products that range in age from 25.5 Ma to 68.3 ka, crop out within the Jemez volcanic field and the surrounding areas in north central New Mexico.
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Data supporting idea that terrestrial volcano- tectonic depressions resembling Moon craters exist, noting Mogollon plateau in New Mexico
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Side-looking radar imagery superiority over aerial photography of geological faults and patterns in St. Francis Mountains, Missouri
The chemical, mineralogical, and oxygen-isotopic changes accompanying K-metasomatism are described. The similarities with diagenetic reactions in both deep marine and alkaline, saline-lake environments are noted. The common occurrence of K-metasomatism in upper-plate rocks of detachment terranes indicates that the early stage of severe regional extension causes crustal downwarping and, in arid to semi-arid regions, development of closed hydrographic basins.
In the present investigation, it is shown that a one-to-one correspondence exists on Io between hot spots and features with normal albedos less than or equal to 0.3 (in the Voyager orange filter). It is pointed out that the hot spots are a manifestation of the prolific volcanic activity and heat flow of Io, widely believed to be due to dissipation of tidal energy resulting from the forward eccentricity of Io's orbit and the tides raised by Jupiter. All of the hot spots identified by the Voyager 1 infrared interferometric spectrometer (IRIS) correspond to relatively low-albedo features. An approach has been developed to identify hot spots not included in the IRIS inventory and to model their temperatures. The spectral reflectivities of the low-albedo features, extracted from the multispectral mosaics produced by Soderblom et al. (1985), are also presented, and compared to the laboratory spectra of a variety of candidate materials.
Reports of shock-deformed phenocrysts from the Toba ignimbrite deposits, Sumatra, have prompted considerable debate over whether shock-deformation products are clear evidence of a meteorite impact origin for the K/T boundary deposits as well as terresrial 'cryptoexplosion' structures. Evidence presented in favor of volcanically induced shock at Toba includes kinked biotites and rare occurrences of single set of lamellae in quartz grains but rests most heavily upon occurrences of mosaic extinction patterns in plagioclase phenocrysts. The present analysis of several of the same Toba samples reveals that these mosaic patterns ae related to distinct compositional zoning and cannot be attributed to deformation of the crystal lattice that shock would produce. Additionally, in more than 200 quartz grains examined, no occurrences of microdeformation features or mosaic textures similar to those associated with known impact structures and the K/T boundary are detected. It is concluded that evidence of shock deformation in the Toba deposits has not been demonstrated.
The results using interferometric synthetic aperture radar(SAR) to measure the co-seismic displacement from the June 28, 1992 Landers earthquake suggest that this technique may be applicable to other problems in crustal deformation.
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Presented by NETL at AGU Fall Conference, 12/16