|
What
are my risks?
Oahu Volcanoes
Oahu
has been formed from two principle volcanoes: Waianae
and Koolau. Waianae is about 2.2-3.8 million years old
and Koolau is about 1.8-2.6 million years old. Both volcanoes
are now considered extinct.
The
island is also riddled in spots by smaller volcanic features
such as Diamond Head, Punchbowl, Salt Lake Crater, Koko
Head and Koko Crater. These smaller volcanoes formed in
more recent times, although the age determinations on
them are not very good. In general, these "post-erosional"
volcanoes are believed to be between 70,000 and 500,000
years old.
Is
there a threat of a volcano erupting on Oahu again?
It
is always possible, but the odds are extremely slim. Vulcanologists
(people who study volcanoes) predict volcanic activity
for places such as Oahu by looking at the area's historical
record. Although data is limited, it suggests Oahu's post-erosional
volcanoes erupted every couple of 10,000 years or so.
Since it has been longer than that since the last eruption,
it indicates volcanic activity has finished for Oahu.
Dr.
Ken Rubin, Assistant Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu, HI 96822
Vog
and Laze Hazards on Oahu
Although
volcanoes on Oahu are extinct, volcanic hazards do affect
the island. Volcanoes spew noxious plumes of acidic gases.
The resulting vog and laze effect many communities across
the State, including Oahu.
When
a volcanic erupts, sulfur dioxide within the molten rock
is converted to sulfuric acid. The resulting plume is
known as vog (volcanic fog).
Gases
are also produced at the ocean. When the lava enters the
ocean, hydochloric acid is produced - called laze
(lava haze). Both of these gases can contain particulate
matter, such as volcanic glass or trace metals.
Vog
and laze are carried by winds across the county. The impacts
include:
- obscured
views;
- lower agricultural
yields for certain crops;
- adverse
health effects for people with respiratory or heart
conditions; and
- acidified
rainwater catchment tanks (which, in turn, produces
a secondary hazard of leached lead in local water supplies).
|
