Kauai History and Hotspot Theory

At one time or another we have all heard the theory of plate tectonics, in which the Earth’s surface consists of about a dozen rigid slabs or plates, each averaging at least 50 miles thick. These plates move relative to one another at average speeds of a few inches per year. The great majority of the world’s earthquakes and active volcanoes occur near the boundaries of the Earth’s shifting plates.

Why then are the Hawaiian volcanoes located near the middle of the Pacific Plate more than 2,000 miles from the nearest plate boundary?

Enter the ‘hotspot theory’. According to the hotspot theory, the Hawaiian Island chain resulted from the Pacific Plate moving over a deep, stationary hotspot in the mantle, located beneath the present-day position of the Big Island. Heat from this hotspot is producing a persistent source of magma by partly melting the overriding Pacific Plate. The magma then rises through the mantle and crust to erupt onto the sea floor, forming an active seamount. Over time, countless eruptions cause the seamount to grow until it finally emerges above sea level to form an island volcano. As the plate movement carries the island beyond the hotspot, the magma source is cutoff, leaving one island volcano extinct, and another waiting to develop over the hotspot. This trail of volcanic islands and seamounts can be seen across the Pacific Ocean floor.

The State of Hawaii is composed of 132 islands, reefs and shoals that extend for over 1500 miles across the central North Pacific Ocean from the Big Island to Midway and Kure Atolls. Included in this chain are some of the Earth’s largest mountains, rising 18,000 feet from the ocean bottom to a height above sea level of nearly 14,000 feet. Mauna Kea and Mauna Loa on the Big Island are volcanic mountains with a total elevation of nearly 32,000 feet.

next – Kauai History and Volcano Islands