Koolau Range (''koolau'' means "

windward In geography and seamanship, windward () and leeward () are directions relative to the wind. Windward is ''upwind'' from the point of reference, i.e., towards the direction from which the wind is coming; leeward is ''downwind'' from the point ...

" in Hawaiian) is the dormant fragmented remnant of the eastern or windward

shield volcano A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...

of the Hawaiian island of

Oahu Oahu (, , sometimes written Oahu) is the third-largest and most populated island of the Hawaiian Islands and of the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. The island of Oahu and the uninhabited Northwe ...

. It was designated a

National Natural Landmark The National Natural Landmarks (NNL) Program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only national natural areas program that identifies and recognizes the best e ...

in 1972.

Geology

It is not a

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have aris ...

in the proper sense, because it was formed as a single mountain called Koolau Volcano. What remains of Koolau is the western half of the original volcano that was destroyed in prehistoric times when the entire eastern half—including much of the summit

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

—slid cataclysmically into the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

. Remains of this ancient volcano lie as massive fragments strewn nearly over the ocean floor to the northeast of Oahu. Kāneʻohe Bay is what remains of the ancient volcano's summit caldera after the slide. The modern Koolau mountain forms Oahu's windward coast and rises behind the leeward coast city of

Honolulu Honolulu ( ; ) is the List of capitals in the United States, capital and most populous city of the U.S. state of Hawaii, located in the Pacific Ocean. It is the county seat of the Consolidated city-county, consolidated City and County of Honol ...

— on its leeward slopes and valleys are located most of Honolulu's residential neighborhoods. The volcano is thought to have first erupted on the ocean floor more than 2.5 million years ago. It eventually reached

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

and continued to grow in elevation until about 1.7 million years ago, when the volcano became dormant. The volcano remained dormant for hundreds of thousands of years, during which time

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

ate away at the initially smooth slopes of the shield-shaped mountain; and the entire body subsided considerably. The highest elevation perhaps exceeded ; today, the summit of the tallest peak, Puu Kōnāhuanui is only .

Honolulu Volcanics

After hundreds of thousands of years of dormancy, Koolau volcano began to erupt again. Some thirty eruptions over the past 500,000 years or so have created many of the landmarks around eastern Oahu, such as Diamond Head, Koko Head ( Hanauma Bay), Koko Crater, Punchbowl Crater, Tantalus, and Āliapaakai, and are collectively known as the Honolulu Volcanic Series, or simply Honolulu Volcanics. According to the US Geological Survey, the most recent eruptions in this series of activity occurred between about 70,000 to 100,000 years ago. There is a possibility that Koolau volcano could erupt again; however, the chance of such an eruption occurring in "our lifetimes, or even those of many future generations" is remote.

History

In 1795, the newly-formed

Hawaiian Kingdom The Hawaiian Kingdom, also known as the Kingdom of Hawaiʻi ( Hawaiian: ɛ ɐwˈpuni həˈvɐjʔi, was an archipelagic country from 1795 to 1893, which eventually encompassed all of the inhabited Hawaiian Islands. It was established in 1795 w ...

conducted a battle resulting in the triumphant conquest of O'ahu on the range within part of the Nu‘uanu Pali Lookout, under the command of Kamehameha the Great, as his troops forced all of the warriors up the valley to fall to their deaths below the cliffs. The Ko‘olau Range was designated in 1972 as a

Transportation

There are three roads that tunnel through the southern part of the Koolau Range, connecting Honolulu to the Windward Coast. From leeward to windward: * Hawaii Route 61 (Pali Highway) * Hawaii Route 63 (Likelike Highway) * Interstate H-3

Gallery

File:Koolau Range 02.JPG, View of Koolau Range with Koko Crater and Maunalua (Hawaii Kai) visible. File:Oahu Landscape.jpg, Nuʻuanu Pali, a section of the Koolau Range. Olomana is visible on the right side of the image. File:Sunset from Awawaloa.jpg, Sunset from Awawaloa File:View of Konahuanui from near summit of Awawaloa.jpg, View of Konahuanui from near the summit of Awawaloa

Notes

References

External links

* {{DEFAULTSORT:Koolau Range Volcanoes of Oahu Extinct volcanoes of the United States Mountains of Hawaii National Natural Landmarks in Hawaii Polygenetic shield volcanoes Pliocene shield volcanoes Pleistocene shield volcanoes Neogene Oceania Pleistocene Oceania Cenozoic Hawaii