What is the first mineral to crystallize basaltic magma?

A Question About Magma?

• Would I be correct in assuming that volcanoes such as Kilauea, which have basaltic lavas, have constant movement of magma into the "pond" that feeds the magma chamber? Since the lava that reaches the surface is basaltic, rich in iron/magnesium ions and low in silicate, am I correct in saying that magmatic differentiation and crystal settling does not occur in the pond because the constant introduction of hotter magma causes convection, interfering with crystal settling? If this is accurate would it also be accurate to say that in volcanoes that have silica rich magma, such as Mt. St. Helens, the pond that feeds the magma chamber receives less magma from the asthenosphere? Without the constant flow of magma into the pond, there is less convection, thus less interference with magmatic differentiation and crystal settling. Therefore the iron/magnesium materials crystallize, leaving the remaining melt rich in silica. Is this correct?

• Answer:

  Would I be correct in assuming that volcanoes such as Kilauea, which have basaltic lavas, have constant movement of magma into the "pond" that feeds the magma chamber? Since the lava that reaches the surface is basaltic, rich in iron/magnesium ions and low in silicate, am I correct in saying that magmatic differentiation and crystal settling does not occur in the pond because the constant introduction of hotter magma causes convection, interfering with crystal settling? No, you are not correct. Volcanoes such as Kilauea are due to hot spots located in the deep mantle or core. As such there is no "pond that feeds the magma chamber". Also, magmatic differentiation and crystal settling do not occur in these situations. If this is accurate would it also be accurate to say that in volcanoes that have silica rich magma, such as Mt. St. Helens, the pond that feeds the magma chamber receives less magma from the asthenosphere? Without the constant flow of magma into the pond, there is less convection, thus less interference with magmatic differentiation and crystal settling. Therefore the iron/magnesium materials crystallize, leaving the remaining melt rich in silica. Is this correct? In the case of the silica rich magmas, instead of saying there is less magma feeding the "pond" from the asthenosphere, I meant to say that the process is much slower than the process that produces basaltic magma. No, again you are not correct. Strato volcanoes such as Mount Saint Helens are due to heat generated from friction between subducted oceanic crust and the overlying continental crust (an oversimplification). Oceanic crust is transformed from basic crust to felsic crust due to interactions with the continent along with additions of sea water and continental siliclastic sediments.