Structure and Eruptive Cycle of Cinder Cones in the Pinacate Volcanic Field and the Controls of Strombolian Activity

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

“…Although both Vaniman and Crowe (1 98 1) and Bradshaw and Smith (I 994) inferred that pyroclast mounds scattered throughout the lava flow fields (particularly thc SW lava field at Red Cone volcano) are remnants of vents, we favor an interpretation whereby these mounds are comprised of proximal pyroclastic material rafted from thc main cone (see also descriptions of rafted cone material at other small volume basaltic volcanoes; Gutmann, 1979;Holm, 1987;Luhr and Simkin, 1993). Although interpretation of these features is complicated by the degree of post-eruptive surface modification, we argue that this interpretation is consistent with several observations: ( 1)…”

“…It seems likely that this feature is a lava squeeze-up (a rootless dike) from the core of the underlying flow, rather than a true dike related to a separate magmatic (polycyclic) event. Gutmann (1979) describes similar features where lava squeeze ups intrude overlying pyroclastic deposits produced later in the eruption sequence of the same vent in the Pinacate volcanic field.…”

“…The Lathrop Wells volcano was also formed on a southward-sloping surface and exhibits the same relationships of prefcrential rafting with its early, southward-emplaced, lava field (Valentine et al, 2005). Gutmann (Wood, 1980a;Gutmann, 1979) but is an opposite trend to that at Lathrop Wells volcano (Valentine et al, 2005). However, because other features of the three volcanoes are very similar it seems reasonable to postulate that Red and Black Conc volcanoes may have originally had laterally extensive fallout deposits similar to that associated with Lathrop Wells (-0.04 km3; Bechtel SAIC Company, 2004b).…”

“…There are probably many different types of rafts (c.g., see 1979;Holm, 1987;Luhr and Simkin, 1993); Figure 12 shows postemplacement evolution of three different types: (1) raft with intact cone bedding (c.g., Holm, 1987), (2) raft of agglutinate deposits that have partly disintegrated during transport on top of a lava, and (3) raft of initially unconsolidated, loose pyroclastic dcbris blanketed by scoria fallout. These different types of rafts can evolve to mounds with similar appearances that do not on the surface show much of their original character.…”

“…Strong and Wolff (2003) The complex array of eruptive and emplacement mechanisms took place within a framework of monogenetic eruptions, and point to a need for research to determine the controlling factors on changing eruptive processes for basaltic magmas with relatively constant major element compositions. As with other volcanoes, the behavior of these small volume volcanoes must depend upon magma rheology, ascent rate, volatile content, and degassing processes ( e g , Gutmann, 1979;Cervantes and Wallace, 2003;Taddeucci et al, 2004). Given the abundance of small volume basaltic volcanoes in continental 'Volumes calculated by reconstructing a sloping planar paleosurface beneath each volcano (determined by elevation of points around the edge of each volcano, assuming that this is close to the contact between volcanic products and the paleosurface unless noted otherwise), and integrating the digital elevation data above that surface.…”