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[en] We report on a joint gravimetric and ground deformation study on Montserrat, with the aim of quantifying mass and/or density changes beneath the island related to the volcanic activity at Soufrire Hills Volcano (SHV). Our observations coupled with 3-D data inversion indicate the existence of a previously unrecognised NNW-SSE trending zone of structural weakness (i.e. fault) that is located at shallow depths beneath the Centre Hills of Montserrat, along which active fluid migration is coupled to magmatic stressing at SHV.
[en] Images characteristic of geographic regions other than the northeastern part of the United States are presented for interpretation. Pre- and post-eruption imagery of Mt. St. Helens volcano serves to demonstrate the advantages of thermal infrared sensing, and the potential for developing a timely, decision oriented thematic map to be used in solving drought-related problems in Upper Volta is examined to show the applicability of satellite remote sensing in all geographic areas
[en] I first stepped through the doorway of the Hawaiian Volcano Observatory in 1976, and I was impressed by what I saw: A dozen people working out of a stone-and-metal building perched at the edge of a high cliff with a spectacular view of a vast volcanic plain. Their primary purpose was to monitor the island's two active volcanoes, Kilauea and Mauna Loa. I joined them, working for six weeks as a volunteer and then, years later, as a staff scientist. That gave me several chances to ask how the observatory had started.
[en] La Peligrosa Caldera is located at Sierra Colorada (470 15'S, 710 40' W) in the Chon-Aike silicic LIP. It represents an unique window to understand the eruptive mechanisms that prevailed throughout the ignimbritic flare-up in Southern Patagonia during middle to late Jurassic times. Key pieces of lithologic and structural evidences are taken into account to reconstruct the volcanic structure.
[en] Complete text of publication follows. The multi-specimen differential pTRM paleo-intensity method (Dekkers and Boehnel, 2006, EPSL 248, 507-516) presently lacks a constraint for the selection of the pTRM acquisition temperature. For reliable results (of any paleo-intensity (PI) method) no or very little changes in magnetic state should occur during the experiment. The occurrence of such changes is directly related to the pTRM acquisition temperature (also referred to as set-point temperature) at which the experiment is carried out. It is therefore important to constrain this temperature. This would yield an indication for the reliability of the outcome of the PI experiment independent of the actual result in technical terms. Detecting changes in magnetic state as function of temperature along with thermo-chemical alteration has shown to be not trivial. Various ways have been proposed, including measurement of changes in low-field susceptibility or magnetization as function of temperature, and measurement of the susceptibility or hysteresis properties before and after the PI experiment. While insightful in some ways, these methods gave equivocal results when applying them on a sample set from historic (20th century) lavas from mount Etna, Italy: no alterations were detected after heating at 160 deg C, while the multi-specimen method yielded an underestimate of the PI of about 25% compared to the IGRF. This indicates that very subtle changes in magnetic state, that go undetected by the aforementioned magnetic measurements, do have a large influence on the outcome of the PI method. Here we explore the suitability of ARM acquisition curves to diagnose subtle changes in magnetic state. As is well known, specific ARM intensity varies strongly with magnetic grain size, particularly in the SD grain-size realm. By using the automated SQUID magnetometer with in-line rock magnetic facilities available in the Utrecht paleomagnetic laboratory, high-resolution ARM acquisition curves (47 steps) were taken from samples annealed at various temperatures. The results, although very preliminary at this stage, indicate that ARM acquisition might be an important addition to the aforementioned magnetic measurements to detect changes in magnetic state with temperature. Therefore it would provide an a priori constraint on the set-point temperature for the multi-specimen pTRM paleo-intensity protocol.
[en] Current ideas about the moon appear to be mistaken on two fundamental points. First, at least within certain large classes of lunar craters, internal origin (i.e., some form of volcanism) predominates over impact; this result raises questions about the reality of the era of violent bombardment. Second, the origin of tektites by meteoritic impact on the earth cannot be reconciled with physical principles and is to be abandoned. The only viable alternative is origin by lunar volcanism, which implies the following: continuance of (rare) explosive lunar volcanism to the present time; existence of silicic lunar volcanism and of small patches of silicic rock at the lunar surface; a body of rock in the lunar interior, probably at great depth, which is closely similar to the earth's mantle and which contains billions of tons of volatiles, probably including hydrogen; and origin of the moon from the earth after the formation of the earth's core. 42 references