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The Hawaiian Islands is an archipelago of numerous islands and atolls trending northwest by southeast in the North Pacific Ocean between latitudes 19° N and 29° N. The archipelago takes its name from the largest island in the group and extends some 1500 miles (2400 km) from the Island of Hawai‘i in the south to northernmost Kure Atoll. The archipelago represents the exposed peaks of a great undersea mountain range formed by volcanic activity over a hotspot in the earth's mantle. At about 3,000 km (1,860 miles) from the nearest continent, the Hawaiian Island archipelago is the most isolated grouping of islands on Earth (Macdonald, Abbott, and Peterson, 1984).
Islands and reefs of the Hawaiian archipelago
The eight main Hawaiian islands (all inhabited except for Kaho‘olawe) are, listed here from south to north:
- Hawai‘i (also known as the Big Island)
- Kaho‘olawe (uninhabited; temporary residential facilities)
Smaller islands, atolls, and reefs (beyond Ni‘ihau and all uninhabited); called the Northwestern Hawaiian Islands:
- French Frigate Shoals
- Gardner Pinnacles
- Maro Reef
- Pearl and Hermes Reef
- Midway (temporary residential facilities)
Visitor information on Hawai‘i will often state that there are 137 islands in the Hawaiian chain. This number includes minor islands offshore of the main islands, and individual islets in each atoll. (See Hawai‘i state government .pdf file, Table 05.09: ).
The chain of islands or archipelago formed as the Pacific plate moves slowly northwestward over a hotspot in the earth's crust. Hence the islands in the northwest of the archipelago are older and typically smaller (have been eroding far longer).
Hawai‘i (the Big Island) is the largest and youngest island in the chain, built from seven different volcanoes. Mauna Kea, comprising over half of the Big Island, is the largest shield volcano on the planet. The measurement from the base locally depressing the sea floor to its peak is abut 56,000 feet (17 km; USGS)
See also: List of Hawaii rivers
The Hawaiian Islands are home to a large number of endemic species. The plant and animal life of the Hawaiian Islands developed in nearly complete isolation over about 70 million years. Human contact, first by Polynesians and later by Europeans, had a significant impact, driving many species to extinction. Today, many of the remaining endemic species are considered endangered.
See also: Endemism in the Hawaiian Islands
The islands receive most rainfall from the trade winds on their north and east flanks (called the windward side) as a result of orographic precipitation. Coastal areas in general and especially the south and west flanks or leeward sides, tend to be drier. Because of the frequent build-up of Tradewind clouds and potential showers, most tourist areas have been built on the leeward coasts of the islands.
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 (see below).
Temperatures at sea level generally range from high temperatures of 85-90°F (29-32°C) during the summer months to low temperatures of 65-70°F (18-21°C) during the winter months. Very 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 sometimes receive snowfall during the winter.
The hurricane season in the Hawaiian Islands is roughly from June through November, when hurricanes and tropical storms are most probable in the North Pacific. These storms tend to originate off the coast of Mexico (particularly the Baja California peninsula) and track west or northwest towards the islands. Hawai‘i is protected by the vastness of the Pacific (i.e. the improbability of a direct hit); as storms cross the Pacific they tend to lose strength if they bear northward and encounter cooler water. It is thought that the topography of the highest islands (Haleakalā on Maui, Mauna Kea and Mauna Loa on the Big Island) may protect these islands, and certainly Kaua‘i has been hit more often in the last 50 years than the others.
The Hawaiian islands can be affected by tsunamis, great waves that strike the shore typically but not exclusively from the north. Tsunamis are movements of the surface layer of the ocean most often caused by earthquakes somewhere in the Pacific. The city of Hilo on the Big Island has historically been most impacted by tsunamis, where the inrushing water is accentuated by the shape of the bay in front of the town.
- Macdonald, G. A., A. T. Abbott, and F. L. Peterson. 1984. Volcanoes in the Sea. The Geology of Hawaii, 2nd edition. University of Hawaii Press, Honolulu. 517 pp.
- The Ocean Atlas of Hawai‘i - SOEST at University of Hawai‘i
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