The cohesive Naranjo debris-flow deposit (10 km 3):
Mass movement processes on volcanic terrains such as landslides and debris avalanches can cause the obstruction of main drainages producing the formation of temporary dams. A good example of this occurred 18.5 ka ago when the eastern flank of the Nevado de Colima Volcano collapsed producing a debris-avalanche deposit that was previously described as one of the largest in the world. The deposit extended from the volcanic summit as far as the Pacific coast, 120 km away. New stratigraphic, sedimentological, and componentry data suggest that the volcanic collapse of Nevado de Colima resulted in a debris avalanche that traveled 20 km southeast to the Naranjo River. There it crashed against a topographic barrier consisting of Cretaceous limestones (Cerro la Carbonera) and the flow direction was diverted to the south down the Naranjo River channel for another 25 km before the avalanche came to a halt. The obstruction of the drainage produced a temporary dam that stored ca. 1 km3 of water and deposited fluvial and slack-water sediments. Some time after the damming, the accumulated water-sediment load was able to overtop the obstructing material and to release a breakout flow with a calculated initial flow discharge of 3.5 million m3/s. The resulting flood (cohesive debris flow) followed the channel of the Naranjo River and, due to the high erodibility of the channel and introduction of substrate material, the debris flow progressively increased its volume up to 10 km3, six times its initial volume. This study highlights the relevance of evaluating the potential remobilization of debris-avalanche deposits to initiate large magnitude cohesive debris flows. Therefore, the hazard and risk analysis of future potential events of this nature must consider the pre-eruption conditions and the topography surrounding a volcano. 7 2002 Elsevier Science B.V. All rights reserved.
Volcán Tancítaro, Michoacán, Mexico, 40Ar/39Ar constraints on its history of sector collapse
Abstract Volcan Tancitaro is a 97 ± 3 km3 stratovolcano located in the Michoacan Guanajuato volcanic field (MGVF), part of the Trans Mexican Volcanic Belt. Prior to this study, there was only one K–Ar date (530 ± 60 ka; [Ban, M., Hasenaka, T., Delgado-Granados, H., Takaoka, N., 1992. K–Ar ages of lavas from shield volcanoes in the Michoacan–Guanajuato volcanic field, Mexico. Geofisica Internacional 31 (4), 467–473.] and one sector-collapse event reported for this volcano in the literature [Garduno-Monroy V.H., Corona-Chavez, P., Israde-Alcantara, I., Mennella, L., Arreygue, E., Bigioggero, B., Chiesa, S., 1999. Carta Geologica de Michoacan, scale 1:250,000. Universidad Michoacana de San Nicolas de Hidalgo.; Capra, L., Macias, J.L., Scott, K.M., Abrams, M., Garduno-Monroy, V.H., 2002. Debris avalanches and debris flows transformed from collapses in the Trans-Mexican Volcanic Belt, Mexico — Behavior, and implications for hazard assessment. Journal of Volcanology and Geothermal Research 113, 81–110.]. Twenty-six new 40Ar/39Ar ages indicate that Volcan Tancitaro became active ≥ 793 ± 22 ka and that the most recent effusive activity occurred at 237 ± 34 ka. Two catastrophic sector-collapse events are identified and dated; the first one occurred on the west side between 694 and 571 ka, whereas the second one occurred on the east side between 261 and 238 ka. The older collapse produced a 2.3–3.4 km3 debris-avalanche and laharic deposit spread over ∼ 567 km2, whereas the more recent collapse left a 3-km wide, horseshoe-shaped scar on the eastern flank and produced a 3.6–7.0 km3 debris-avalanche and laharic deposit that covers ∼ 654 km2. Reconstruction of the main edifice of Volcan Tancitaro using ArcGIS software and digital elevation models indicates that the volume removed during the eastern sector collapse was ∼ 4.7 km3.
On the ontology of particle mass and energy in special relativity
Einstein claimed that the fundamental dynamical insight of special relativity was the equivalence of mass and energy. I disagree. Not only are mass and energy not equivalent (whatever exactly that means) but talk of such equivalence obscures the real dynamical insight of special relativity, which concerns the nature of 4-forces and interactions more generally. In this paper I present and defend a new ontology of special relativistic particle dynamics that makes this insight perspicuous and I explain how alleged cases of mass–energy conversion can be accommodated within that ontology.