ISSN:
1432-0819
Schlagwort(e):
Key words Littoral cones
;
Mauna Loa
;
Volumetric flow rate
;
Lava tubes
;
Lava
;
water interaction
;
Lava delta
;
Bench collapse
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Geologie und Paläontologie
Notizen:
Abstract Pyroclastic cones along the southwest coast of Mauna Loa volcano, Hawai`i, have a common structure: (a) an early formed circular outer rim 200–400 m in diameter composed mostly of scoria and lapilli, and (b) one or more later-formed inner rims composed almost exclusively of dense spatter. The spatter activity locally fed short lava flows that ponded within the outer rims. Based on various lines of evidence, these cones are littoral in origin: relationships between the cones and associated flows; the degassed nature of the pyroclasts; and (although not unequivocal) the position of the cones relative to known eruptive vent locations on Mauna Loa. Additional support for the littoral interpretation comes from their similarity to (smaller) littoral cones that have been observed forming during the ongoing Ki¯lauea eruption. The structure of these Mauna Loa cones, however, contrasts with that of "standard" Hawaiian littoral cones in that there is (or once was) a complete circle of pyroclastic deposits. Furthermore, they are large even though associated with tube-fed pāhoehoe flows instead of `a`ā. The following origin is proposed: An initial flow of tube-fed pāhoehoe into the ocean built a lava delta with a base of hyaloclastite. Collapse of an inland portion of the active tube into the underlying wet hyaloclastites or a water-filled void allowed sufficient mixing of water and liquid lava to generate strong explosions. These explosions broke through the top of the flow and built up the outer scoria/lapilli rims on the solid carapace of the lava delta. Eventually, the supply of water diminished, the explosions declined in intensity to spattering, and the initial rim was filled with spatter and lava.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00304433
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