Picrites are dark, heavy rocks rather similar to peridotite.
Both form deep in the Earth's mantle, and both are rich in
dark green olivine and brown augite. But while peridotite is
often carried up into large intrusive masses, along with
gabbro, norite and
pyroxenite, picrite tends to be
found in sills and intrusive
sheets. Although picrite
magma forms only under
extreme pressures deep in the
mantle, it is the one
ultramafic rock that normally
erupts on the surface as lava,
as it did in the 1959 eruption
of Kilauea in Hawaii. In this
eruption, gigantic fire fountains
shot out picrite lavas containing as
much as 30 per cent olivine. Yet for
picrite to erupt as lava like this,
temperatures must be very high incleed -
which is why it is often linked to hotspot
volcanoes such as those in Hawaii.
Picrites are dark, heavy rocks rather similar to peridotite. Both form deep in the Earth's mantle, and both are rich in dark green olivine and brown augite. But while peridotite is often carried up into large intrusive masses, along with gabbro, norite and pyroxenite, picrite tends to be found in sills and intrusive sheets. Although picrite magma forms only under extreme pressures deep in the mantle, it is the one ultramafic rock that normally erupts on the surface as lava, as it did in the 1959 eruption of Kilauea in Hawaii. In this eruption, gigantic fire fountains shot out picrite lavas containing as much as 30 per cent olivine. Yet for picrite to erupt as lava like this, temperatures must be very high incleed - which is why it is often linked to hotspot volcanoes such as those in Hawaii.
การแปล กรุณารอสักครู่..
