Name | Hawaiian Islands |
---|---|
Nickname | Mokupuni o Hawai‘i |
Image name | Hawaje-NoRedLine.jpg |
Image caption | True colour satellite image of the Hawaiian Islands |
Locator map | Hawaiianislandchain USGS.png |
Locator caption | Map of the Hawaiian Islands, a chain of islands that stretches in a northwesterly direction from the southern tip of the island of Hawaii. |
Location | North Pacific Ocean |
Highest mount | Mauna Kea |
The islands are the exposed peaks of a great undersea mountain range known as the Hawaiian-Emperor seamount chain, formed by volcanic activity over a hotspot in the Earth's mantle. The Hawaiian islands are about from the nearest continent.
The Hawaiian Islands have a total land area of . Except for Midway, which is an unincorporated territory of the United States, these islands and islets are administered as the state of Hawaii — the 50th state of the United States of America.
The eight main Hawaiian islands (also known as the Hawaiian Windward Islands) are listed here from east to west. All except Kahoolawe are inhabited.
The state of Hawaii counts 137 "islands" in the Hawaiian chain, and the Midway Islands. This number includes all minor islands and islets offshore of the main islands (listed above) and individual islets in each atoll. These are just a few: Ford Island (Mokuumeume)
Almost all magma created in the hotspot has the composition of basalt, and so the Hawaiian volcanoes are constructed almost entirely of this igneous rock and its coarse-grained equivalents, gabbro and diabase. A few igneous rock types with compositions unlike basalt, such as nephelinite, do occur on these islands but are extremely rare. The majority of eruptions in Hawaii are Hawaiian-type eruptions because basaltic magma is relatively fluid compared with magmas typically involved in more explosive eruptions, such as the andesitic magmas that produce some of the spectacular and dangerous eruptions around the margins of the Pacific basin.
Hawaii island (the Big Island) is the largest and youngest island in the chain, built from five volcanoes. Mauna Loa, comprising over half of the Big Island, is the largest shield volcano on the Earth. The measurement from sea level to summit is more than , from sea level to sea floor about .
Hawaii accounted for 7.3% of the United States' reported earthquakes with a magnitude 3.5 or greater from 1974 to 2003, with a total 1533 earthquakes. Hawaii ranked as the state with the third most earthquakes over this time period, after Alaska and California.
On Sunday, October 15, 2006, there was an earthquake with a magnitude of 6.7 off the northwest coast of the island of Hawaii, near the Kona area of the big island. The initial earthquake was followed approximately five minutes later by a magnitude 5.7 aftershock. Minor-to-moderate damage was reported on most of the Big Island. Several major roadways became impassable from rock slides, and effects were felt as far away as Honolulu, Oahu, nearly from the epicenter. Power outages lasted for several hours to whole days. Several water mains ruptured. No deaths or life-threatening injuries were reported.
Earthquakes are monitored by the Hawaiian Volcano Observatory run by the USGS.
Tsunamis may also initiate in the Hawaiian Islands. Explosive volcanic activity can cause tsunamis. The island of Molokai had a catastrophic collapse or debris avalanche over a million years ago; this underwater landslide likely caused tsunamis. The Hilina Slump on the island of Hawaii is another potential place for a large landslide and resulting tsunami.
The city of Hilo on the Big Island has been most affected by tsunamis, where the in-rushing water is accentuated by the shape of Hilo Bay. Coastal cities have tsunami warning sirens.
A tsunami resulting from an earthquake in Chile hit the islands on February 27, 2010. It was relatively minor, but local emergency management officials utilized the latest technology and ordered evacuations in preparation for a possible major event. It was declared a "good drill" for the next major event by the Governor.
A tsunami resulting from an earthquake in Japan hit the islands on March 11, 2011. It was relatively minor, but local officials ordered evacuations in preparation for a possible major event. The tsunami caused about $1 million in damages, almost all limited to the Kona coast of the Big Island.
The endemic plant and animal species of the Hawaiian Islands developed in nearly complete isolation over about 70 million years. Prior to the human arrival, the only native mammal was the Hawaiian hoary bat.
Human contact, first by Polynesians, introduced new trees, plants and animals. These included voracious species such as rats and pigs, who took a heavy toll on native birds and invertebrates that evolved in the absence of such predators. The growing population also brought deforestation, forest degradation, treeless grasslands, and environmental degradation. As a result, many species which depended on forest habitats and food went extinct. As humans cleared land for farming, monocultural crop production replaced multi-species systems.
The arrival of the Europeans had a significant impact, with the promotion of large-scale single-species export agriculture and livestock grazing. This led to increased clearing of forests, and the development of towns, adding more species to list of extinct animals of the Hawaiian Islands. As of 2009, many of the remaining endemic species are considered endangered.
In general, the Hawaiian Islands receive most of their precipitation during the winter months (October to April). Drier conditions generally prevail from May to September, but the warmer temperatures increase the risk of hurricanes.
Temperatures at sea level generally range from highs of 85-90 °F (29-32 °C) during the summer months to 79-83 °F (26-28 °C) during the winter months. Rarely does the temperature rise above 90 °F (32 °C) or drop below 60 °F (16 °C) at lower elevations. Temperatures are lower at higher altitudes; in fact, the three highest mountains of Mauna Kea, Mauna Loa, and Haleakala often receive snowfall during the winter.
One distinctive feature of Hawaii’s climate is the small annual variation in temperature range. This is because there is only a slight variation in length of night and day from one part of Hawaii to another because all its islands lie within a narrow latitude band. The small variations in the length of the daylight period, together with the smaller annual variations in the altitude of the sun above the horizon, result in relatively small variations in the amount of incoming solar energy from one time of the year to another. The surface waters of the open ocean around Hawaii range from between late February and early April, to a maximum of in late September or early October. With water temperatures this mild for hundreds of miles around, the air that reaches Hawaii is neither very hot nor very cold. Temperatures of and above are quite uncommon (with the exception of dry, leeward areas). In the leeward areas, temperatures may reach into the low 90’s several days during the year, but temperatures higher than these are unusual.
The other reason for the small variation in air temperature is the nearly constant flow of fresh ocean air across the islands. Just as the temperature of the ocean surface varies comparatively little from season to season, so also does the temperature of air that has moved great distances across the ocean; the air brings with it to the land the mild temperature regime characteristic of the surrounding ocean. In the central North Pacific, the trade winds represent the outflow of air from the great region of high pressure, the North Pacific High, typically located well north and east of the Hawaiian Islands. The Pacific High, and with it the trade-wind zone, moves north and south with changing angle of the sun, so that it reaches its northernmost position in the summer. This brings trade winds during the period of May through September, when they are prevalent 80 to 95 percent of the time. From October through April, the heart of the trade winds moves south of Hawaii; however, the winds still blow much of the time. They provide a system of natural year-long ventilation throughout the islands and bring mild temperatures characteristic of air that has moved great distances across tropical waters.
Major storms occur most frequently in October through March. There may be as many as six or seven major storm events in a year. Such storms bring heavy rains and can be accompanied by strong local winds. The storms may be associated with the passage of a cold front , the leading edge of a mass of relatively cool air that is moving from west to east or from northwest to southeast.
Kona storms are features of the winter season. The name come from winds out of the "kona" or usually leeward direction. Rainfall in a well-developed Kona storm is widespread and more prolonged than in the usual cold-front storm. Kona storm rains are usually most intense in an arc, extending from south to east of the storm and well in advance of its center. Kona rains last from several hours to several days. The rains may continue steadily, but the longer lasting ones are characteristically interrupted by intervals of lighter rain or partial clearing, as well as by intense showers superimposed on the more moderate continuous, steady rain. An entire winter may pass without a single well-developed Kona storm. More often there are one or two such storms a year; sometimes four or five. Three harbors provide some protection from Kona storms: Kahului Harbor (used mostly for commercial vessels), Lahaina and Maalaea Harbors (used primarily) for sailing craft.
True hurricanes are very rare in Hawaii; only four have affected the islands during 63 years. Tropical storms are more frequent. These have more modest winds, below . Because tropical storms resemble Kona storms, and because early records do not distinguish clearly between them, it has been difficult to estimate the average frequency of tropical storms. Every year or two a tropical storm will affect the weather in some part of the islands. Unlike cold fronts and Kona storms, hurricanes and tropical storms are most likely to occur during the last half of the year, from July through December.
As storms cross the Pacific, they tend to lose strength if they bear northward and encounter cooler water. The topography of the highest islands (Haleakalā on Maui, Mauna Kea and Mauna Loa on the Big Island) may protect these islands, because Kauai has been hit more often in the last 50 years than the others.
Hawaii's high mountains present a substantial obstacle to the trade winds. The elevated topography blocks the airflow, effectively splitting the trade winds in two. This split causes a zone of weak winds, called a "wind wake", on the leeward side of the islands.
Aerodynamic theory indicates that an island wind wake effect should dissipate within a few hundred kilometers and not be felt in the western Pacific. However, the wind wake caused by the Hawaiian Islands extends , roughly 10 times longer than any other wake. The long wake testifies to the strong interaction between the atmosphere and ocean, which has strong implications for global climate research. It is also important for understanding natural climate variations, like El Niño.
There are number of reasons why this has only been observed in Hawaii. First, the ocean reacts slowly to fast-changing winds; winds must be steady to exert force on the ocean, such as the trade winds. Second, the high mountain topography provides a significant disturbance to the winds. Third, the Hawaiian Islands are large in horizontal scale, extending over four degrees in latitude. It is this active interaction between wind, ocean current, and temperature that creates this uniquely long wake west of Hawaii.
The wind wake drives an eastward "counter current" that brings warm water from the Asian coast. This warm water drives further changes in wind, allowing the island effect to extend far into the western Pacific. The counter current had been observed by oceanographers near the Hawaiian Islands years before the long wake was discovered, but they did not know what caused it.
Category:Hawaii * Hawaiian Islands Category:Geology of Hawaii Category:Hudson's Bay Company trading posts
ast:Archipiélagu de Ḥawai az:Havay adaları be:Гавайскія астравы be-x-old:Гавайскія астравы bg:Хавайски острови ca:Illes Hawaii cs:Havajské ostrovy cy:Ynysoedd Hawaii da:Hawaii-øerne et:Hawaii saared es:Archipiélago de Hawái fr:Archipel d'Hawaï gl:Arquipélago de Hawai ko:하와이 제도 haw:Mokupuni o Hawai‘i id:Kepulauan Hawaii ia:Insulas Hawai lt:Havajai (salynas) ms:Kepulauan Hawaii nl:Hawaïaanse eilanden ja:ハワイ諸島 no:Hawaiiøyene pl:Hawaje (archipelag) pt:Arquipélago do Havaí ro:Insulele Hawaii ru:Гавайские острова simple:Hawaiian Islands sk:Havajské ostrovy ckb:دوورگەکانی ھاوایی sv:Hawaiiöarna tl:Kapuluang Hawayano uk:Гавайські острови vi:Quần đảo Hawaii zh:夏威夷群島This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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