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Geography of Hawaii

Information about the geography of Hawaii.

The Hawaiian archipelago is a string of islands and reefs, 3,300 kilometers long, that forms a broad arc in the mid-Pacific. The archipelago begins in the east with the island of Hawaii and ends almost at the international date line with a small speck in the ocean called Kure Atoll (Map 16 : 21K). Only the easternmost 650 kilometers of the state contains islands of any size, as well as almost all of the state's population. It is this portion that is usually considered as the actual "Hawaii."

The eight main islands of Hawaii--Oahu, Hawaii, Maui, Kauai, Lanai, Molokai, Niihau, and Kahoolawe--contain more than 99 percent of the state's land area and all but a handful of its people. The island of Hawaii, at 8,150 square kilometers, comprises nearly two-thirds of the state's total area, and it is often referred to as simply the Big Island. The smallest of the eight, Kahoolawe, is 125 square kilometers and is uninhabited.

Local and Physical 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 31∞C is matched by a record low of only 13∞C.

The latitude of Honolulu, about 20∞N, is the same as Calcutta and Mexico City. As a result, there is little change in the length of daylight or the angle of incidence of the sun's rays from one season to another. This factor, plus the state's maritime position, means that there is little seasonal variation in temperature.

It is variations in precipitation that mark the major changes in season on the islands. During the summer, Hawaii is under the persistent influence of northeast trade winds, which approach the islands over cool waters located to the northeast and create characteristic Hawaiian weather--breezy, sunny with some clouds, warm but not hot. In winter, these trade winds disappear, sometimes for weeks, allowing "invasions" of storms from the north and northwest. Honolulu has received as much as 43 centimeters of rain in a single 24-hour period. Hawaiian weather stations have also recorded 28 centimeters in an hour and 100 centimeters in a day, both of which rank near world records.

The topography of the islands creates extreme variations in precipitation from one location to another. Mount Waialeale, on Kauai, receives 1,234 centimeters annually, making it one of the world's wettest spots, and Waimea, also on Kauai, receives about 50 centimeters annually--yet these two sites are only 25 kilometers apart. Within the metropolitan area of Honolulu, it is possible to live near the beach in a semiarid climate with less than 50 centimeters of rainfall annually or inland near Pali on the margins of a rain forest drenched by 300 centimeters of precipitation a year. Unlike the Pacific Northwest, the greatest precipitation on the higher mountains in Hawaii occurs at fairly low elevations, usually between 600 and 1,200 meters.

Much of the volcanic soil is permeable. This allows water to percolate rapidly, draining beyond the reach of many plants. Thus, many areas of moderate to low precipitation are arid in appearance.

The isolation of the Hawaiian islands, coupled with their generally temperate climate and great environmental variation, has created a plant and bird community of vast diversity. There are several thousand plants native there and found naturally nowhere else; 66 uniquely Hawaiian land birds have also been identified. Interestingly, there were no land mammals on the islands until humans arrived.


Hawaii-Guide "Geology and Geography" Article

General Information About Hawaii

Islands of Hawaii

Destinations in Hawaii

Hawaii for Visitors

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