Download Appendix #5: Volcanoes on Hawaiian Islands

Appendix #5: Volcanoes on Hawaiian Islands
The Hawaiian Islands show evidence of an interesting tectonic event. Stretching to the west and to the north of the
big island of Hawaii is a string of smaller islands and submerged volcanoes, “seamounts”, 3,700 miles long.
There is convincing evidence that every one of these islands and seamounts has been formed in the exact
place where Hawaii now stands. What is the nature of the forces at work here?
Geologists believe that a huge column of upwelling lava, known as a “plume,” lies at a fixed position under
the Pacific Plate. (It never moves.) As the ocean floor moves over this “hot spot” at about five inches a year, the
upwelling lava creates a steady succession of new volcanoes that migrate along with the plate - a veritable
conveyor belt of volcanic islands.
Hawaii itself consists of five connected volcanic mountains that were built by this lava plume rising from the
mantle. Kilauea, the world’s largest active volcano, is still rumbling because the island has yet to move
completely off the hot spot. The farther the other islands in the chain are from Hawaii, the greater their age.
About 150 miles to the northwest is Oahu, which burst out of the sea about 3.5 million years ago. Midway Island,
one of the oldest islands in the chain, was formed between 15 and 25 million years ago.
Source: http://www.platetectonics.com/book/page_17.asp Image: http://www.soest.hawaii.edu/pibhmc/pibhmc_nwhi.htm
A NEW HAWAIIAN ISLAND??
If the hot-spot theory is correct, the next volcano in the
Hawaiian chain should form east or south of the Island of
Hawai'i. Abundant evidence indicates that such a new
volcano exists at Lö'ihi, a seamount (or submarine peak)
located about 20 miles off the south coast. Lö'ihi rises
10,100 feet above the ocean floor to within 3,100 feet
of the water surface.
Scientists wonder when the still-growing Lö'ihi will
emerge above the surface of the Pacific to become
Hawai'i's newest volcano island. It will almost certainly
take several tens of thousands of years, if the growth
rate for Lö'ihi is comparable to that of other Hawaiian
volcanoes (about 0.1 foot per year averaged over
geologic time). It is also possible that Lö'ihi will never
emerge above sea level and that the next link in the
island chain has not yet begun to form.
Images Source: http://hvo.wr.usgs.gov/volcanoes/
The lighter shaded “Big Island” of Hawaii
is shown in the background, shaded
green. In the foreground is the undersea
mount Loihi.
Image Source:
http://www.soest.hawaii.edu/pibhmc/pibhmc_nwhi.ht
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