Hawaii Volcanoes National Park
|Hawaii Volcanoes National Park (courtesy, Hawaiian Tourism)|
Many millions of years ago, a hot spot developed in the mantle of the earth that underlies the crust. Because magma is more buoyant than solid rock, the magma rose through fissures, and surfaced on the ocean floor as lava. As repeated eruptions continued, a massive submarine volcano was built and eventually rose above the surface of the sea. Thus the Hawaiian Islands were born.
The island of Hawaii is the largest of the islands in the main group, over twice as large as all the rest of the Hawaiian Islands put together. It is composed of five separate volcanoes: Kohala, Mauna Kea, Hualalai, Mauna Loa, and Kilauea. The Pacific Plate, according to the theory of plate tectonics, is moving in a northwestward direction a few inches per year, carrying the islands along with it. The more or less stationary hot spot is the site of fitful activity, and so the islands vary in size, as well as in distance from one another. Because of the movement of the Plate, the islands become increasingly older as we travel northwest along the Hawaiian Archipelago. The island of Hawaii, which is currently over the hot spot, is less than a million years old and still growing, while Kaua'i is approximately 6 million years old. Kure, an atoll 1,500 miles to the northwest of Hawaii Island, is the last outpost of the Hawaiian Chain, and is about 35 million years old.
Three of the volcanoes, Hualalai, Mauna Loa, and Kilauea are active. Kilauea and Mauna Loa, two of the world's most active volcanoes, are still adding land to the island of Hawaii.
Mauna Loa is the most massive mountain on the earth, occupying an area of 10,000 cubic miles. Measured from its base on the sea floor, it rises 30,000 feet, more than a thousand feet higher than Mount Everest. In contrast to the explosive continental volcanoes, the more fluid and less gaseous eruptions of Kilauea and Mauna Loa produce fiery fountains and rivers of molten lava. These flows, added layer upon layer, produced a barren volcanic landscape that served as a foundation for life. Hundreds of species of plants and animals found their way across the vast Pacific on wind, water, and the wings of birds. A few survived, adapted, and prospered during this time of isolation. The arrival of humans, first Polynesians, then Europeans, and the plants and animals they bought with them drastically altered this evolutionary showcase, this grand natural experiment.
Today Hawaii Volcanoes National Park displays the results of 70 million years of volcanism, migration, and evolutionprocesses that thrust a bare land from the sea and clothed it with complex and unique ecosystems and a distinct human culture. Created to preserve the natural setting of Kilauea and Mauna Loa, the park is also a refuge for the island's native plants and animals and a link to its human past. Park managers work to protect the resources and promote understanding and appreciation of the park by visitors. Research by scientists at the Hawaiian Volcano Observatory has made Kilauea one of the best understood volcanoes in the world, shedding light on the birth of the Hawaiian Islands and the beginning of planet Earth.
The Kilauea Caldera
The summit of Kilauea Volcano is crowned by a caldera. A caldera is formed when the magma reservoir inside the mountain shrinks in size, leaving the surface of the ground unsupported. The top of the mountain then caves in, leaving a basin shaped depression at the summit. The caldera may, during the course of hundreds of years, fill up, overflow, and then collapse again, as the magma reservoir goes through cycles of swelling and shrinking. Kilauea Caldera is about 3 miles across and 400 feet deep.
The Caldera Floor
Once on the caldera floor, you are nearly 500' below the clifftop of Ka'auea and inside the crater of one of the world's most active volcanoes. The volvano was once much deeper, but during the last few hundred years has been nearly filled by eruptions at Halema'uma'u as well as from fissures on the caldera floor. The caldera is bounded by arc-shaped faults formed during different episodes of collapse of the summit. The path to the floor from the Volcano House goes through an area where blocks did not quite make it to the main floor of the caldera. The terraces that are found at locations around the summit are also places where large fault blocks partially fell into the pit.
A magnitude 6.7 earthquake in November 1983 caused numerous rockfalls on the caldera walls, destroyed sections of trail and severely damaged roads in the park. Evidence of the destruction can be seen along the path to the caldera floor.
Details mentioned in this article were accurate at the time of publication