Extrusive volcanism formed the Hawaiian Islands
Scientists have determined that it is the eruptions of lava on the surface, extrusion, which grow Hawaiian volcanoes, rather than internal emplacement of magma, as was previously thought.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Oct 9, 2013
I was always of the impression that internal injection of magma merely formed the high level sill stack magma chamber that formed the bit underlying the summit caldera of the shield. The magma chamber appears also to have an interesting habit of dropping its dense cumulate core out of the base of the crust & top of upper mantle as the volcano sinks & the base flexes. This drop & creation of cavity space filled with new mantle magma from the still warm hotspot is the cause of the late stage alkali basalt & foidite eruptions such as the eruption forming Diamond Head for example well away from the hotspot core.
I regard the dike & high level sill complexes in the rift as part of the extrusive pile due to their individual small volume & generally short lifespan as an active feature, while being merely the subsurface part of an individual extrusive event.
It appears in large part that the article has the same point of view.
For the intrusive complex as a whole merely look @ the Halemaumau crater & its current active pit as an example. It is @ present merely degassing through the pit while transferring the degassed lava down the rift into the current vent @ Puu Oo. The Halemaumau pit is the only part of the eruption revealing an intrusive phase per se (particularly during the formation of the pit.
Incidentally as an aside, Kilauea has had a lot of history after the formation of its last caldera as a smoky hole in the ground, followed by a lava pit topping a small intracaldera overflow shield. This behaviour is likely to be a surface expression of a long term flank rift vent (submarine in that case) similar to the current subaerial event @ Puu Oo.
Keep watching that space.
Have a nice day: Ag
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