In some cases, a local earthquake or undersea landslide close to shore can initiate a tsunami that strikes almost without warning.  In 1998, a 7.0 magnitude undersea earthquake near Papua, New Guinea, triggered a massive submarine landslide that started a 50-ft. tsunami close to shore.  The wave hit the shoreline within minutes and wiped out several villages along the New Guinea coast, stripping the land almost bare.  2200 people died.

However, most major tsunamis are started by undersea earthquakes in deep water.  In the Pacific Ocean, a quake will be picked up by seismometers, pressure sensors, and tidal gauges at the reporting stations of the Pacific Tsunami Warning System operated by 26 nations bordering the Pacific Basin.  The collected data registers on the instruments at the Pacific Tsunami Warning Center in Ewa Beach, Hawaii.  If readings indicate the disturbance may have started a tsunami, warnings are issued immediately to the areas in danger with approximate arrival time of the first wave.

As part of the international tsunami warning network, the United States has recently completed its own U.S. Tsunami Warning System that takes in the Pacific Tsunami Warning System, the West Coast & Alaska Tsunami Warning System, and the Atlantic Tsunami Warning System.  The U.S. system is composed of 39 DART (Deep Ocean Assessment and Reporting of Tsunami) and DART II stations.  Five stations are located in the Atlantic, Caribbean, and Gulf of Mexico, and the remaining 34 in the Pacific.  The DART system is made up of a pressure sensor resting on the ocean bottom that transmits continuous data by acoustic telemetry (sound waves) to a surface buoy anchored near the pressure sensor.  The buoy is equipped with a satellite link that relays the real time information to tsunami warning centers around the world.  Certain fluctuations in ocean bottom pressure can indicate the presence of a tsunami.

Shield volcanoes fueled by hotspots are different from the stratovolcanoes of the Pacific Rim. The magma pouring into shield volcanoes is mainly basalt, lighter and less viscous than the silica-based magma fueling the Pacific Rim volcanoes produced by the collision of tectonic plates.

The hotspot theory might well be demonstrated by the way in which the Hawaiian Islands were formed. The theory suggests that there is an area in the mid-Pacific hundreds of miles below the ocean floor in the earth’s mantle called The Hawaiian Hotspot. The hotspot size is estimated at 50 miles in diameter. The temperature in the hotspot is higher than that of the surrounding mantle. This intense heat melts the material from the lower part of the overriding tectonic plate and converts it into magma. The hotspot magma is lighter than the material in the rest of the mantle and rises to the earth’s crust in a narrow stream called a mantle plume. The mantle plume brings magma up to the ocean floor, and a volcanic cone begins to build. Over time, repeated eruptions produce more and more lava that continue to build the cone higher and higher, until it finally emerges above the surface of the ocean as an island many thousands of years later.

The tectonic plate on which the Hawaiian Islands sit is called the Pacific Plate. The Pacific Plate moves in a northwesterly direction at about 1 inch per year. Moving at that rate, it takes several million years for the island to pass over and clear the stationary Hawaiian Hotspot. Island building progresses during this long period of time, and large islands with tall volcanic mountains are created, as is the case with the island of Maui with its 10,000 ft. Haleakala volcano, and the Big Island of Hawaii with its chain of volcanoes in 13,700 ft. Mauna Kea, 13,600 ft. Mauna Loa, and currently active Kilauea.

Once the moving plate carries an island away from the hotspot plume, the volcanoes on that island go dormant and start to erode, and the plume proceeds to build the next island. Niihau and Kauai, the easternmost islands of the Hawaiian chain, were the first to be built up from the hotspot activity. The Pacific Plate continued its northwesterly movement over the hotspot and the islands of Oahu, Molokai, Lanai, and Maui were created in succession. The last island over the hotspot is the still volcanically active Big Island of Hawaii.

Just a few miles off the Big Island, a new island is starting to build. It is called Loihi, and has pushed up two miles from the ocean floor, but is still a mile beneath the surface of the ocean. It is estimated that Loihi will appear above the ocean surface in 220,000 years.

One source suggests there are 50 active hotspots throughout the world. Some, such as the Hawaiian Hotspot, lie under oceanic plates, and others under continental plates. Among the volcanic islands created by oceanic hotspots are Iceland, the Azores, the Galapagos, Samoa, the Marquesas Islands, the Society Islands, and Reunion.

The best example of continental plate hotspot activity is Yellowstone National Park. The heart of the park is an active caldera that powers hot springs, fumaroles, mud pots, and geysers such as Old Faithful. The thermal energy derives from a large hotspot underlying the caldera. This same hotspot has produced many other caldera and lava bed areas throughout the western states, as the North American Plate moves southwesterly. The Yellowstone caldera was created by a massive volcanic eruption 600,000 years ago.

In recent years, a number of scientists have challenged the idea of a stationary hotspot and of a mantle plume being the source of hotspot magma. Several other explanations have been put forth. Since hotspots are located deep in the earth’s mantle, no one has ever seen one. Their existence and the way they work can only be assumed.

The Atlantic threat most talked about is the Cumbre Vieja volcano in the Canary Islands, 3000 miles from Boston and 3700 miles from Miami.  In 1949, a flank of the volcano split off, creating a 3-ft. rift, the flank sliding down 3 feet toward the ocean before it stabilized.  Earthquakes and a buildup of pressure inside the volcano were associated with the event.  The concern is that another earthquake or eruption could dislodge the entire flank and send as much as 300 cubic miles of debris plunging into the ocean.  One school of thought suggests that such a monster landslide would start a tsunami capable of reaching the eastern seaboard of the United States 5 or 6 hours later.

However, many geologists dispute the notion that such an event would send a killer tsunami smashing into the East Coast of the U.S.  The height of the initial wave would be enormous, and destructive to the local area, but the length between waves would be relatively short, meaning its ability to maintain its energy while travelling long distances would be minimized.

A tsunami, a threat sure to quicken pulses and heighten blood pressure, is headed for the coast of Southern California.  Gordon Gumpertz takes us on this thrilling journey of seismography and volcanology and of parallel lives that unexpectedly intersect.  From sabotage to smuggling as well as a little romance, it’s all included in this contemporary page turner. Kate Greenwood, armchair interviews

I loved this book.  If you want to be entertained, intrigued, and enthralled by the dual plot of nature versus man and greed versus the good of man then you will love it too.  Stepanie Boyd, TCM Reviews

It takes a special writing skill to bring these types of events to life on the written page, and author Gordon Gumpertz does a fantastic job, and made me feel as though I am right in the thick of things, right from the beginning.  I really enjoyed Tsunami — this book is fantastic.  bookshipper.blogspot.com

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