Small-volume basaltic volcanoes: Eruptive products and processes, and posteruptive geomorphic evolution in Crater Flat (Pleistocene), southern Nevada

Abstract

Five Pleistocene basaltic volcanoes in Crater Flat (southern Nevada) demonstrate thc complexity of eruption processes associated with small-volume basalts and the cffccts of initial emplacement characteristics on post-eruptive geomorphic evolution of thc volcanic surfaces. The volcanoes record eruptive processes in their pyroclastic facies ranging from "classical" Strombolian mechanisms to, potentially, violent Strombolian mechanisms. Cone growth was accompanied, and sometimes disrupted, by effusion of lavas from the bases of cones. Pyroclastic cones were built upon a gently southwardsloping surface and were prone to failure of their down-slope (southern) flanks. Early lavas flowed primarily southward and, at Red and Black Cone volcanoes, carricd abundant rafts of cone material on the tops of the flows. These resulting early lava ficlds eventually built platforms such that later flows erupted from the eastern (at Rcd Cone) and northern (at Black Cone) bases of the cones. Three major surface features -scoria cones, lava fields with abundant rafts of pyroclastic material, and lava fields with littlc or no pyroclastic material -experienced different post-eruptive surficial processcs. 1Contrary to previous interpretations, we argue that the Pleistocene Crater Flat volcanoes are monogenetic, each having formed in a single eruptive episode lasting months to a few years, and with all eruptive products having emanated from the area of the volcanocs' main cones rather than from scattered vents. Geochemical variations within thc volcanoes must be interpreted within a monogenetic framework, which implies preservation of magma source heterogeneities through ascent and eruption of thc magmas.

Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

“…During their short-lived eruption usually small magma volumes are involved producing small-scale volcanic landforms [38,40]. In spite of this simple model, current research showed numerous evidences that volcanoes considered earlier as monogenetic, including maar-diatremes, can be complex both from a volcanic edifice and chemical point of view [103,109]. This paradox can be solved through the introduction of an intermediary type in volcano classification where complex monogenetic volcanoes are somehow distinguished from sensu stricto monogenetic and purely polygenetic volcanic landforms [109].…”

“…In spite of this simple model, current research showed numerous evidences that volcanoes considered earlier as monogenetic, including maar-diatremes, can be complex both from a volcanic edifice and chemical point of view [103,109]. This paradox can be solved through the introduction of an intermediary type in volcano classification where complex monogenetic volcanoes are somehow distinguished from sensu stricto monogenetic and purely polygenetic volcanic landforms [109]. This problem is critical while interpreting large maar-diatreme volcanoes that evidently represent complex volcanic features which cannot be explained to have been formed in a single eruptive episode [109].…”

“…In general, the Strombolian-style magma fragmentation occurs at shallow depth (upper part of the magma column), when the over-pressurized and segregated gas-bubbles break and burst out from the rising, mostly mafic, magmas [38,[103][104][105]. In spite of this general trend of scoria cone eruption and growth, scoria cones are far more complex volcanoes [98], and evolve through various eruption styles from Hawaiian lava fountaining [106], violent Strombolian [107] to intermittent phreatomagmatic eruptions such as maar-forming [104,108] can take place during their relatively short lived (days to years) eruption period [109]. As a result, the shape of the scoria cone will depend on these variations of the eruption style.…”

“…In addition, scoria cones can be active over years [38,[109][110][111], commonly forming fissure-controlled chains of cones [112,113], and producing relatively large-volume complex volcanic edifices that clearly document polycyclic, or even polymagmatic eruptive nature [38].…”

Evaluating Igneous Activity at Yucca Mountain

“…During the period from about 9 to 11 million years ago, this felsic volcanism transitioned to basaltic magmatism with four recognized pulses, including the 80,000-year-old Lathrop Wells event and several 1-million-year-old events in Crater Flat adjacent to Yucca Mountain. General agreement is that future igneous activity is likely to be a small-volume, single-episode basaltic event similar to the Lathrop Wells volcano [Valentine et al, 2006] with comparable power, duration, type of erupted products, spatial relationship to the topographic surface, geochemical characteristics of the magma, and feeder igneous dike characteristics.…”