Can volcanoes actually "explode"? Like if the top is really tightly
plugged?
Pheonix Rose
Hi Pheonix Rose,
In some cases, the answer is yes, they do explode. The only difference is
that the "explosion" often lasts for hours or even days. However, the
original blast often happens as the strength of the volcano's top is
overcome by the pressure of the magma below. On volcanoes where the magma
is viscous there can also be explosions even after the top of the volcano
has collapsed inward to form a caldera. In these cases it is the high
viscosity of the lava (or perhaps of a lava dome) that provides the "cap"
to keep the pressure in. Eventually the strength and weight of the dome
is no longer sufficient to hold in the pressure and you get an explosive
eruption.
In Hawai'i the magma/lava is so fluid that it just flows out of the way
and doesn't allow pressures to build up. However, if fluid lava comes
into contact with water (a lake, the ocean, or ground water), then you can
have very strong steam explosions. These are called "phreatomagmatic"
explosions. They are impressive and dangerous, but pretty small compared
to the purely magmatic explosions that I mentioned earlier.
Sincerely,
Scott Rowland
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