Will Kilauea ever explode like Mount St. Helens? Why or why not? Have
there been explosive eruptions of Kilauea? Why did they occur?
Kilauea will not explode like Mount St. Helens. Mount St. Helens magma
is more viscous. Therefore gas cannot escape as readily, resulting in
explosive eruptions. One index of explosivity is volume of eruption.
Since the start of the current Kilauea eruption more than 1,400 million
cubic meters of lava have been erupted. Mount St. Helens erupted 1 cubic
kilometer of ash (about 10 times greater than the current Kilauea
eruption). There have been explosive eruptions at Kilauea. The
Uwekahuna Ash was erupted about 1,500 years ago and may be related to an
older caldera that filled with lava prior to the development of the
present caldera. The Keanakakoi Ash was erupted during weeks or months
of activity in 1790. The early activity was driven by degassing magma
that interacted with groundwater. Later eruptions were driven by steam
explosions. The warriors were killed near the end of the eruption by
what geologists call a
base surge.
Surges are gas-rich and have little volcanic material. This "steam
blast" was not enough to burn their skin but did cause them to
suffocate. The 1924 eruption was caused by a 660 feet (200 m) drop in
the lava lake that allowed groundwater to enter the conduit. The
resulting steam-driven explosions shot rocks weighing several tons as far
as 2,600 feet (800 m). At the end of the eruption Halemaumau was 1,320
feet (400 m deep) (deep enough that that the Empire State building would
fit inside) and had doubled in width from 1,400 to 3,000 feet (430 to 920
m). Note that these explosive eruptions are infrequent.