The Mono-Inyo Craters erupt in complex spatial and temporal patterns. Understanding, modeling and predicting these patterns requires detailed knowledge of the individual volcanoes and their associated deposits. For an exercise in deciphering the patterns, the chain can be broken into major subsections of the Red Cones-Mammoth Mountain, Inyo Craters, Mono Craters and islands of Mono Lake. Tephra stratigraphy in the Red Cones-Mammoth Mountain area records a relatively brief, sparse history of eruptions. The Red Cones, two small scoria cones of basaltic andesite, located 10 km southwest of Mammoth Lakes in eastern California, represent the second youngest mafic eruption in the Mono-Inyo Craters chain. The eruption occurred within an apparent hiatus of rhyolitic eruptions of the Mono-Inyo Craters. Charcoal recovered from beneath the Red Cones tephra at two separate locations suggests that the eruption most likely occurred somewhat more recently than 8490 ± 90 C-14 yr B.P. Effusive and mildly explosive activity produced a lava flow covering c. 6 km2 (volume 3.1 × 106 m3), a tephra layer elongated to the northeast covering 46 km2, as well as the scoria cones (total tephra volume 3.7 × 106 m3). Sedimentological analysis of the tephra deposit, including thickness and grain size, shows that the eruption was probably a small Strombolian event. The only other known Holocene volcanic activity in Red Cones-Mammoth Mountain formed the Mammoth Mountain Craters (MMC). The five craters describe a 2.5 km-long WNW alignment of vents near northern foot of the mountain. The craters are small explosion pits with highly localized deposits of massive, very poorly sorted throw-out debris, and were formed by low-volume phreatic events. Where they occur, the crater deposits directly underlie both the North Mono tephra of c. 650 yr B.P., and the Inyo tephra of c. 550 yr B.P., consistent with previous radiocarbon results. There is no indication of soil formation or reworking between the crater debris and the North Mono tephra. Compared to activity in the rest of the Mono-Inyo Craters, that at Red Cones-Mammoth Mountain is low in volume and infrequent. In addition, its connection to tectonism is much less obvious than in the sections of the chain to the north.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- 8455 Tephrochronology (1145);
- 8486 Field relationships (1090;