This page is not intended to scare you, but rather inform you of some of the practicalities of living on a volcano.
Hawaii doesn't just have volcanoes, Hawaii is volcanoes. The Hawaii Islands are the most prominent of a string of about 129 volcanoes (most of which are extinct) that rise from the ocean floor. The chain extends some 3800 miles (6100 kilometers) from the central to the northern Pacific. The volcanoes are created at a "hotspot" on the ocean floor. Continental drift constantly moves the Earth's crust across this hotspot in a northwest direction about 3.5 inches ( 9 cm. ) each year. As islands move from the hotspot area they lose their connection to the molten lava that lies below the crust and their volcanoes become dormant and die. Erosion from wind, rain, and the sea eventually wear the volcano down until it no longer peaks above the ocean's surface.
Our Big Island, at its southeastern position in the string of volcanoes, is the newest volcano complex that has risen above the ocean's surface. A few miles to our southeast a newer volcano, the Loihi Seamount has reached 3,800 feet below the ocean's surface but will not surface for about 200,000 years. The Big Island is actually composed of a cluster of seven volcanoes, two of which do not reach the surface. South Hawaii, as defined here, lies on the southern end of great shield volcano, Mauna Loa.
Mauna Loa is still growing, that is, it still has occasional eruptions. The last eruption was in 1984 when lava flowed north towards Hilo, giving the town quite a scare before the lava stopped flowing only about 4 miles from the city's outskirts. Prior to that, there were flows in 1975 and a rather spectacular eruption in 1950, the remains of which can be seen at about the 93 mile marker on Highway 11. A history of Mauna Loa eruptions in historical times can be seen at: http://hvo.wr.usgs.gov/maunaloa/history/historytable.html
So how does living on a volcano really affect people? Most obviously, there is the threat of an eruption that could take your house. Most people living here do not spend much of their day worrying about that, even though it could happen in many areas. As you drive around South Hawaii you will see places where lava has flowed in historical times and places that have not seen lava in thousands of years. You must weigh in your own mind how you feel about this remote but real possibility.
Mauna Loa is one of the most closely monitored volcanoes in the world. The Hawaiian Volcano Observatory closely watches the shape of the volcano, seismic activity, and other factors. It is comforting to know that the next eruption of Mauna Loa will probably come with plenty of warning.
The island has been divided into different regions based upon likelihood of volcanic lava flows over time. These Lava Hazard Zones have been drawn from estimates historic and prehistoric eruptions. In South Hawaii you will find Lava Zones 2, 3, and 6 in habitable areas. Lower numbers indicate a greater chance that lava will flow in the area in the future. Read about Lava Zones here. Understand that your Lava Zone may limit your ability to obtain home insurance and/or mortgage loans, though presently there are companies servicing in Lava Zone 2. A good lava zone map covering South Hawaii is found here.
Earthquakes come with living on a volcano. Most are so tiny as to go un-noticed by everyone except the Volcano Observatory folks that monitor them with very sensitive equipment. Occasionally though you may feel a significant tremor. Devastating earthquakes are fairly rare here, but the is a 10% chance of "severe shaking" over a 50 year period according to the Volcano Observatory. In 1975 there was a bad quake under Kilauea that caused two deaths from a locally generated tsunami. More recently, on October 15, 2006 a magnitude 6.7 quake and strong aftershocks awoke our island a few minutes after 7 AM. That earthquake was centered off of the northwestern coast of the Big Island. There were no deaths or serious injuries but many homes and other buildings suffered some damage. This event points to the need for all Hawaii residents to pay careful attention to building practices that are earthquake conscious. An interesting discussion is found at:
Consult an architect when building a new home in Hawaii. (You will need architect stamped plans to get a building permit). Ask specific questions about how your home will perform in an earthquake and what can be done to improve that performance.
Note: If you are near the beach and feel a quake, move to higher ground immediately!
Again the HVO website is the best place for information. They have a map that identifies the most recent seismic activity.
Vog is the name given to air pollution that comes from a volcano. The nearly constant eruption of Kilauea on the east side of the island since 1983 currently is the source of vog on the Big Island. Vog is a serious problem in some areas and people with respiratory problems should be aware of its presence. Vog causes acid rain and this can affect your plants and catchment water. Roofs used for catchment should be free of lead bearing materials as acid rain can leach lead into your catchment tank.
A handy daily air quality monitor is online at: http://www.hawaii.gov/doh/air-quality/main.html
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