Hawaii History - Volcanoes And Creation

Why are the Hawaiian Islands located in the middle of the Pacific Ocean more than 2,000 miles from any major land masses?

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 active volcanoes occur near the boundaries of the Earth’s shifting plates. But not Hawaii.

According to the 'hotspot' theory, the Hawaiian Island chain resulted from the Pacific Plate moving over a deep, stationary hotspot in the Earth's mantle, located beneath the present-day position of the Big Island. Heat from this hotspot is melting the Pacific Plate, and the magma is rising through the mantle and erupting onto the sea floor, forming an active seamount. After millions of years, and millions of eruptions the seamount grows until it finally emerges above sea level to form an island volcano. Meanwhile, the plate movement carries the island beyond the hotspot, cutting off the source of magma, and leaving one island volcano extinct, and another waiting to develop over the hotspot.

This trail of volcanic islands, east to west, lies across the Pacific Ocean floor, as the State of Hawaii extends for over 1500 miles from the Big Island to Midway and Kure Atolls, and is composed of 132 islands, reefs, and shoals. 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.

These volcanoes of the Hawaiian chain moved along this ‘geological conveyor belt’ and got progressively older and more eroded the farther west they traveled beyond the hotspot. The youngest volcanic rocks are found on the island of Hawaii, and the oldest volcanic rocks are on Kauai. Part of the Big Island still sits over the hot spot and still remains active.

The other Hawaiian islands moved northwest beyond the hot spot and are no longer volcanically active. This progressive drift of the islands from their point of origin over the hot spot can by confirmed by the ages of the principal lava flows on the various Hawaiian Islands from southeast to northwest. Hawaii is 0.5 million years old, Maui is 1 million, Molokai 1.5, Oahu 3, Kauai 5 million years old, and the Midway and Kure Atolls at the northwest end of the chain are 28 million years old.

Following this line of progression, the next volcano in the Hawaiian chain should form southeast of the Big Island. And evidence shows that a new volcano exists at Loihi, a seamount located about 20 miles off the south coast of the Big Island. Loihi currently rises 10,100 feet above the ocean floor to within 3,100 feet of the water surface. Underwater eruptions at Loihi will eventually break the ocean’s surface to form the next Hawaiian island.

Present-day Kauai shows a dramatic history of eruptions, landslides and erosion.  Eons of wind and rain have been creating knife-edged cliffs and steep valleys while pounding surf and currents are carving bays and points.  Kauai is geologically the most mature of the main Hawaiian Islands with extensive development of broad, lush erosional valleys and coastal features such as fringing coral reefs and sandy beaches. The Na Pali coast, on the northwest coast of Kauai, is simply one of the most spectacular wild places left on earth.  All along the coast, huge cliffs covered by tenacious greenery form knife-edge ridges with deep canyons graced by waterfall cascades hundreds of feet high.

But remember, these islands are isolated in the middle of the North Pacific Ocean some 2400 miles from the nearest land mass.  There are three ways to fill the islands with life... wind, wing, and wave.

Wind... this is one of the ways life came to the Hawaiian Islands.  A spore from a plant somewhere far, far away is released into the wind and carried by a rising current high into the jet stream.  Eventually it drifts down and settles on a barren lava field.

Wing... imagine migrating birds carrying seeds either in their digestive tracts or stuck to their feathers.  After visiting a distant island in the South Pacific, the bird heads back to the north and lets go a seed in the form of a dropping.  If it hits an island, and if it lands in a suitable area, in the right type of soil, in the right climate, at the right elevation, maybe it will grow.

Wave... ocean currents transporting salt-resistant seeds, rafted plants, or insects on floating debris.  Picture a seed with its own built-in flotation device, bobbing along for miles and miles until it is washed up on shore in hopes that it will take root.

Of the millions of organisms that embarked on this chance voyage, very few arrived here, and then actually survived here. Owing to its isolation, the Hawaiian Islands are biologically unique, and the percentage of endemic species (species found nowhere in the world except Hawaii) is very high.  Plants and animals colonizing Hawaii gradually changed with time, evolving into new forms that were better adapted to island life. With the absence of predators and competitors found in their former homelands, their survival no longer depended on elaborate defense mechanisms.  Those qualities that once protected them proved unnecessary and were eventually lost.

The island’s 100 endemic land birds evolved from as few as 20 original ancestors.  One thousand kinds of flowering plants evolved from 280 original plants.  And about 10,000 insect and spider species evolved from about 400 colonists.  The astounding diversity of life that flourished on these isolated, and once barren islands bears witness to the force of evolution and the tenacity of life.

Hawaii boasts an astounding degree of biodiversity containing 21 of the world’s 22 climatic zones - from deserts, to tropical rainforests, to alpine, to snow-capped summits.  The tropical climate of the Hawaiian Islands is quite hospitable, making the area particularly rich in flora.

The Hawaiian honeycreepers are the most spectacular example of adaptation anywhere in the world.  Through diversity, bill variation, feather coloring, foraging patterns, and diet, the honeycreeper boasts twenty-three different variations all evolving from a single ancestor.  Nectar-feeding honeycreepers evolved long, curved bills designed for probing flowers.  Insectivorous honeycreepers developed thin, warbler-like bills for picking insects from the foliage.  Bark-picking honeycreepers relied on their bills to pick, pry, peck, and probe.  Seed-eaters developed stouter, stronger bills for cracking tough husks.  And some multi-tasking honeycreepers developed mis-matched upper and lower beaks, each with a specific purpose.  Some of these amazing birds even developed tubular tongues to better sip the floral nectar.

Kauai has the largest number of native bird species in Hawaii.  Amphibians, reptiles, freshwater fish, and most mammals were unable to cross the vast expanse of ocean, but the monk seal and hoary bat succeeded.  The hoary bat lives in Kokee State Park while the Hawaiian monk seal occasionally hauls out of the ocean and suns itself on some of the island’s more isolated beaches.

The Hawaiian animals and plants began to evolve in nearly complete isolation, while others were never able to successfully make the journey here.  Instead, this was partially offset by biological diversity through evolution.  Some animal and plant groups reached Kauai more slowly than others, leaving much opportunity for the early arrivals to evolve.  Seeds adapted to different soil conditions, plants adapted to different climate zones, and birds adapted to available food sources.  Beginning with only a single colonizing species, certain animal and plant groups underwent a sequence of events that produced large numbers of related species living in a wide range of habitats and playing a variety of ecological roles.

It took millions of years for the black lava flows of Kauai to become a lush, green landscape.  The current ongoing eruptions on the Big Island have added many square miles of new land to the island, and the modern day process of plant colonization over freshly-cooled lava flows gives us a glimpse at the cycle of destruction and creation.  Millions of years ago, fire erupted deep in the heart of the Pacific Ocean and rose higher and higher to create Kauai.  It is believed that from destruction comes serenity and beauty, and Kauai is a true example of this.

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Comments 2 comments

dustin 3 years ago

neat


dustin 3 years ago

awsome

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