Hawaii - Setting
Hawaii is near the middle of the Pacific Ocean. Honolulu, the state capital, is 3,850 kilometers west of San Francisco, California, 6,500 kilometers east of Tokyo, Japan, and roughly 7,300 kilometers northeast of the Australian coast. This might be viewed as a case of extreme isolation, and until the last few centuries this was probably true. But as countries around the Pacific Basin began to communicate more with one another and to use the ocean's resources, these islands became an important center of interaction.
The Hawaiian chain is merely the visible portion of a series of massive volcanoes. The ocean floor in this area is 4,000 to 5,000 meters below sea level. Hence, for a volcano to break the water's surface requires a mountain already approaching 5 kilometers in height.
The kind of volcanic activity that created the islands and that continues there today has, for the most part, not been of the explosive type in which large pieces of material are thrown great distances. Volcanic cones resulting from explosive eruptions do exist on the islands. Diamond Head, the Honolulu landmark, is the largest at about 240 meters. More common, however, are features formed from a gradual buildup of material as a sequence of lava flows piled one layer on top of another. The usual shape of volcanic mountains formed in this way is domelike, with the main feature being undulating slopes instead of steep cliffs.
Several of the volcanos on the Big Island remain active. Mauna Loa pours out lava on the average of once every four years, and volcanic activity poses a constant threat to Hilo, the island's largest town. A 1950 eruption covered some 100 square kilometers. Another volcano, Kiluea, is usually active, but lava actually flows from it about once in every seven years. A 1960 flow from Kiluea covered 10 square kilometers, adding some 260 hectares to the island's size.
Hawaii is a state of rugged slopes and abrupt changes in elevation. This is the result of the erosion of the volcanic surfaces by moving water. Sea cliffs cut by waves form a spectacular edge to parts of the islands. Such cliffs on the northeast side of Molokai stand as much as 1,150 meters above the water and are among the world's highest; others on Kauai exceed 600 meters. Some small streams on the northeast side of the Big Island drop over such cliffs directly into the sea.
Stream erosion has heavily dissected many of the lava surfaces. Canyons lace many of the domes. The floor of Waimea Canyon, on Kauai, is more than 800 meters below the surface of the surrounding land. Waterfalls several hundred meters high are common on the islands. The Pali, on Oahu, is a line of cliffs where the headwaters of streams eroding from opposite sides of the island meet. Those flowing east have eroded the ridges separating them to cut a broad lowland; the westward-facing valleys are higher and remain separated by ridges.
One important result of this intense erosive action is a limited amount of level land on the islands. Kauai is particularly rugged, with the only lowlands formed as a thin coastal fringe. Maui has a flat, narrow central portion separating mountainous extremities. Molokai is reasonably flat on its western end. Oahu has a broad central valley plus some sizable coastal lowlands. The island of Hawaii has only some limited coastal lava plains.
Hawaii's oceanic location obviously has a substantial impact on its climate. It is the ocean that fills the winds with the water that brush the islands' mountains. The ocean also moderates the islands' temperature extremes--Honolulu's record high of 31C is matched by a record low of only 13C.
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