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.htm