Northwestern Hawaiian Islands

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The Hawaiian island chain Hawaiianislandchain USGS.png
The Hawaiian island chain

The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest (in some cases, far to the northwest) of the islands of Kauai and Niihau. Politically, they are all part of Honolulu County in the U.S. state of Hawaii, except Midway Atoll, which is a territory distinct from Hawaii and grouped as one of the United States Minor Outlying Islands. The United States Census Bureau defines this area, except Midway, as Census Tract 114.98 of Honolulu County. Its total land area is 3.1075 square miles (8.048 km2). All the islands except Nihoa are north of the Tropic of Cancer, making them the only islands in Hawaii that lie outside the tropics.

Island Any piece of sub-continental land that is surrounded by water

An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines.

Atoll Ring-shaped coral reef, generally formed over a subsiding oceanic volcano, with a central lagoon and perhaps islands around the rim

An atoll, sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the volcanic crater or caldera while the higher rim remains above water or at shallow depths that permit the coral to grow and form the reefs. For the atoll to persist, continued erosion or subsidence must be at a rate slow enough to permit reef growth upward and outward to replace the lost height.

Hawaiian Islands An archipelago in the North Pacific Ocean, currently administered by the US state of Hawaii

The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaiʻi in the south to northernmost Kure Atoll. Formerly the group was known to Europeans and Americans as the Sandwich Islands, a name chosen by James Cook in honor of the then First Lord of the Admiralty John Montagu, 4th Earl of Sandwich. The contemporary name is derived from the name of the largest island, Hawaii Island.


The Northwestern or Leeward Hawaiian Islands include:

Nihoa The tallest of ten islands and atolls in the uninhabited Northwestern Hawaiian Islands

Nihoa, also known as Bird Island or Moku Manu, is the tallest of ten islands and atolls in the uninhabited Northwestern Hawaiian Islands (NWHI). The island is located at the southern end of the NWHI chain, 296 km (160 nmi) southeast of Necker Island. Nihoa is the closest NWHI in proximity to the eight main windward Hawaiian Islands at approximately 240 km (130 nmi) northwest of the island of Kauaʻi. The island has two peaks, 272 m (892 ft) Miller's Peak in the west, and 259 m (850 ft) Tanager Peak in the east. Nihoa's area is about 171 acres (0.69 km2) and is surrounded by a 142,000-acre (57,000 ha) coral reef. Its jagged outline gives the island its name, Nihoa, which means "tooth" in the Hawaiian language.

Necker Island (Hawaii) A small island in the Northwestern Hawaiian Islands

Necker Island is a small island in the Northwestern Hawaiian Islands. It is located at 23°34′30″N164°42′01″W in the Pacific Ocean, 155 miles northwest of Nihoa and 8 miles north of the Tropic of Cancer. It contains important prehistoric archaeological sites of the Hawaiian culture and is part of the Hawaiian Islands National Wildlife Refuge within the Northwestern Hawaiian Islands National Monument.

French Frigate Shoals The largest atoll in the Northwestern Hawaiian Islands

The French Frigate Shoals is the largest atoll in the Northwestern Hawaiian Islands. Its name commemorates French explorer Jean-François de La Pérouse, who nearly lost two frigates when attempting to navigate the shoals. It consists of a 20-mile (32 km) long crescent-shaped reef, twelve sandbars, and the 120-foot (37 m) high La Perouse Pinnacle, the only remnant of its volcanic origins. The total land area of the islets is 61.508 acres (24.891 ha). Total coral reef area of the shoals is over 232,000 acres (94,000 ha). Tern Island, with an area of 26.014 acres (10.527 ha), has a landing strip and permanent habitations for a small number of people. It is maintained as a field station in the Hawaiian Islands National Wildlife Refuge by the United States Fish and Wildlife Service. The French Frigate Shoals are about 487 nautical miles northwest of Honolulu.

The islands

The interior of Laysan, showing the hypersaline lake. Laysan Island Interior.jpg
The interior of Laysan, showing the hypersaline lake.
Gardner Pinnacles Two barren rock outcrops surrounded by a reef in the Northwestern Hawaiian Islands

The Gardner Pinnacles are two barren rock outcrops surrounded by a reef and located in the Northwestern Hawaiian Islands at 24°59′56″N167°59′58″W.

Basalt A magnesium- and iron-rich extrusive igneous rock

Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows.

Maro Reef A largely submerged coral atoll in the Northwestern Hawaiian Islands

Maro Reef is a largely submerged coral atoll located in the Northwestern Hawaiian Islands. It was discovered in 1820 by Captain Joseph Allen of the ship Maro, after whose ship the reef was named. With a total area of 747 square miles (1,935 km2), it is the largest coral reef in the Northwestern Hawaiian Islands. It contains 37 species of stony coral. Unlike most atolls, the coral extends out from the center like spokes on a wheel. Located about 850 miles northwest of Honolulu, Hawaii, Maro Reef contains about 1 acre (4,000 m2) of dry land which itself can be submerged depending on the tides. Some scientists believe that it "may be on the verge of drowning" because the reefs are detached and are vulnerable to strong storm waves.


The Northwestern Hawaiian Islands were formed, approximately 7 to 30 million years ago, as shield volcanoes over the same volcanic hotspot that formed the Emperor Seamounts to the north and the Main Hawaiian Islands to the south. [2] As the Pacific Plate moved north and later northwest over the hot spot, volcanic eruptions built up islands in a linear chain. The isolated land masses gradually eroded and subsided, evolving from high islands in the south, much like the Main Islands of Hawaii, to atolls (or seamounts) north of the Darwin Point . Each of the NWHI are in various stages of erosion. Nihoa, Necker, and Gardner Pinnacles are rocky, basalt islands that have not eroded enough to form an atoll, or lack a substantial coral reef. Laysan and Lisianski are low, sandy islands that have been eroded longer. French Frigate Shoals, Pearl and Hermes, Midway, and Kure are atolls.

Shield volcano Low profile volcano usually formed almost entirely of fluid lava flows

A shield volcano is a type of volcano usually composed almost entirely of fluid lava flows. It is named for its low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid lava erupted, which travels farther than lava erupted from a stratovolcano, and results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.

Hotspot (geology) Volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.

Pacific Plate An oceanic tectonic plate under the Pacific Ocean

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres (40,000,000 sq mi), it is the largest tectonic plate.

North of Darwin Point, the coral reef grows more slowly than the island's subsidence, and as the Pacific Plate moves northwest, the island becomes a seamount when it crosses this line. Kure Atoll straddles Darwin Point, and will sink beneath the ocean when its coral reef cannot keep up with the rate of subsidence, a destiny that awaits every Hawaiian island. [3]

Kure Atoll An atoll in the Pacific Ocean in the Northwestern Hawaiian Islands

Kure Atoll or Ocean Island is an atoll in the Pacific Ocean 48 nautical miles beyond Midway Atoll in the Northwestern Hawaiian Islands at 28°25′N178°20′W. The only land of significant size is called Green Island and is a habitat for hundreds of thousands of seabirds. A short, unused and unmaintained runway and a portion of one building, both from a former United States Coast Guard LORAN station, are located on the island. Politically it is part of Hawaii, although separated from the rest of the state by Midway, which is a separate unorganized territory. Green Island, in addition to being the nesting grounds of tens of thousands of seabirds, has recorded several vagrant terrestrial birds including snow bunting, eyebrowed thrush, brambling, olive-backed pipit, black kite, Steller's sea eagle and Chinese sparrowhawk.

Biodiversity and endemism

The Nihoa finch Telespiza ultima.gif
The Nihoa finch

The Hawaiian Islands are about 2,500 miles (4,000 km) from North America and 3,800 miles (6,100 km) from Asia, and it is because of this isolation that the Hawaiian Islands have extraordinary numbers of unique species. [4] Only a species that could fly or swim immense distances could reach the archipelago. But whereas Polynesians, and later, Europeans, have largely altered the ecosystem of the Main Hawaiian islands by introducing alien species, the ecosystems of the NWHI remain, for the most part, intact. The extensive coral reefs found in Papahānaumokuākea are home to over 7,000 marine species. [5] Of the many species that live here, over 1,700 species of organisms are endemic to the Hawaiian Islands (i.e., they are found nowhere else). For this reason, the region has been dubbed "America's Galápagos".

Endemism Ecological state of being unique to a defined geographic location or habitat

Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. The extreme opposite of endemism is cosmopolitan distribution. An alternative term for a species that is endemic is precinctive, which applies to species that are restricted to a defined geographical area.

Though not subject to nearly as much extinction as the main islands, the Leeward Islands have had their share of abuse. From the late 19th to the early 20th centuries, fishermen, guano miners, and feather hunters killed most of the birds and sea life living in the NWHI. Rabbits were introduced to Laysan and Lisianksi, where they multiplied and devoured most of the vegetation, permanently extinguishing several species. However, most of the damage was reversed, and the islands were restored largely to their pre-exploitation state.

Some of the endemic species of the NWHI include the Nihoa and Laysan finch, the Laysan duck (the "rarest native waterfowl in the United States"), [6] and the Nihoa fan palm. Other notable species are the Laysan albatross, the highly endangered Hawaiian monk seal, and the green sea turtle. The only native trapdoor spiders in the Hawaiian archipelago (Nihoa spp.), recently discovered, are found only here. Most endemic species are highly vulnerable to extinction as one major catastrophic event could wipe out all of the vegetation on each small island. Additionally, seventy percent of all coral reefs in the United States are found here.


The reserve sign on Lisianski Lisianski Island Reserve Sign.jpg
The reserve sign on Lisianski

It is known that the Ancient Hawaiians ventured from the main islands as far as Mokumanamana (Necker), but they might have gone further to French Frigate Shoals. However, they must have been gone by the 18th century, when Europeans discovered the islands, because the islands were deserted upon discovery. Many agricultural terraces have been found on Nihoa, proving that Hawaiians lived there long-term, but Mokumanamana, much barer of vegetation, was probably not able to support many people for long. It is thought that the early Hawaiians only came to Mokumanamana for religious purposes.

The first of the Leeward Isles to be discovered by Europeans was Nihoa. James Colnett discovered it in 1786, although historically the credit has gone to William Douglas. Later that year, La Pérouse discovered Necker, and named it for Jacques Necker, the French Minister of Finance. La Pérouse then went on to discover French Frigate Shoals. The last of the NWHI to be discovered was Midway Atoll, which was found by N.C. Middlebrooks in 1859. In 1925, the Tanager Expedition travelled to many of the NWHI. The islands were mapped, new species were discovered and described, and the archeological sites on Nihoa and Necker were found.

Naming system

Most of the islands have two names; one in English and one in Hawaiian (indicated in parentheses above). The majority of the Hawaiian names used as alternative to the English ones were created in modern times, the original names that ancient Hawaiians gave to all of these islands that they encountered prior to Western contact are found in various oli (chants) and moʻolelo (stories).

National Monument

On June 15, 2006, American President George W. Bush issued a public proclamation creating Papahānaumokuākea Marine National Monument under the Antiquities Act of 1906. The Monument encompasses the islands and surrounding waters, forming the largest marine wildlife reserve in the world. President Theodore Roosevelt had declared the Northwestern Hawaiian chain a bird sanctuary in 1909 and the islands had been protected since 2000 with a designation as an 'ecosystem reserve' by President Bill Clinton, but increasing it to national monument status provides unprecedented control. 139,000 square miles (360,000 km2) of ocean was at that time set aside for protection, about the size of the U.S. state of California.

In August 2016, President Barack Obama expanded the area of the monument by roughly four times. The expanded monument was at that time the world's largest marine protected area. [7] [8]

Entry to the Monument is limited through a permit system, jointly administered by the state of Hawaii, NOAA, and FWS. Anyone who comes to the islands must follow stringent procedures designed to prevent any stray species from entering and disrupting the ecosystem. All clothes must be bought new, and kept wrapped until before arrival. In fact, all "soft" items (camera strap, blanket) must be bought new, and all "hard" items (camera, binoculars) must be cleaned thoroughly. Then, every item must be frozen for 48 hours. A new set of equipment must be prepared for each island one is going to, to prevent inter-island species introduction. However, French Frigate Shoals and Midway Atoll are exempted from these rules, as they are deemed too altered by humans already to worry about introducing new species.

See also


  1. Rauzon, 100
  2. Clague, D. A. and Dalrymple, G. B. (1989) Tectonics, geochronology, and origin of the Hawaiian-Emperor Chain in Winterer, E. L. et al. (editors) (1989) The Eastern Pacific Ocean and Hawaii, Boulder, Geological Society of America.
  3. Rauzon, 3
  4. Rauzon, 4
  5. "Papahānaumokuākea Marine National Monument". official web site, National Oceanic and Atmospheric Administration . Retrieved 2009-07-28.
  6. FWS (2009). "Laysan Duck - Midway Atoll National Wildlife Refuge". U.S. Fish & Wildlife Service.
  7. Eagle, Nathan (August 26, 2016). "Obama To Create World's Largest Protected Marine Area Off Hawaii" . Retrieved August 26, 2016.
  8. "Fact Sheet: President Obama to Create the World's Largest Marine Protected Area". August 26, 2016. Retrieved September 3, 2016.

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Midway Atoll One of the United States Minor Outlying Islands in the Hawaiian archipelago

Midway Atoll is a 2.4-square-mile (6.2 km2) atoll in the North Pacific Ocean at 28°12′N177°21′W. Midway is roughly equidistant between North America and Asia. Midway Atoll is an unorganized, unincorporated territory of the United States. Midway continues to be the only island in the Hawaiian archipelago that is not part of the state of Hawaii. Unlike the other Hawaiian islands, Midway observes Samoa Time, which is one hour behind the time in the state of Hawaii. For statistical purposes, Midway is grouped as one of the United States Minor Outlying Islands. The Midway Atoll National Wildlife Refuge, encompassing 590,991.50 acres (239,165.77 ha) of land and water in the surrounding area, is administered by the United States Fish and Wildlife Service (FWS). The refuge and most of its surrounding area are part of the larger Papahānaumokuākea Marine National Monument.

Pearl and Hermes Atoll Part of the Northwestern Hawaiian Islands

The Pearl and Hermes Atoll is part of the Northwestern Hawaiian Islands, a group of small islands and atolls that form the farthest northwest portion of the Hawaiian island chain. The atoll consists of a variable number of flat and sandy islets, typically between five and seven. More were noted in historical sources but have since been lost to erosion and rising sea levels.

Laysan One of the Northwestern Hawaiian Islands

Laysan, located 808 nautical miles northwest of Honolulu at N25° 42' 14" W171° 44' 04", is one of the Northwestern Hawaiian Islands. It comprises one land mass of 1,016 acres (4.11 km2), about 1 by 1 12 miles in size. It is an atoll of sorts, although the land completely surrounds a shallow central lake some 8 feet (2.4 m) above sea level that has a salinity approximately three times greater than the ocean. Laysan's Hawaiian name of Kauō means egg, referring to its shape and how much life springs from the island.

Lisianski Island One of the Northwestern Hawaiian Islands

Lisianski Island is one of the Northwestern Hawaiian Islands, with a land area of 384.425 acres (155.571 ha) and a maximum elevation of 40 feet (12 m) above sea level. It is a low, flat sand and coral island about 905 nautical miles (1,676 km) northwest of Honolulu. The island is surrounded by reefs and shoals, including the extensive Neva Shoals. Access to the island is limited by helicopter or by boat to a narrow sandy inlet on the southeastern side of the island.

Papahānaumokuākea Marine National Monument national monument in the United States

The Papahānaumokuākea Marine National Monument is a World Heritage listed U.S. National Monument encompassing 583,000 square miles (1,510,000 km2) of ocean waters, including ten islands and atolls of the Northwestern Hawaiian Islands. Created in June 2006 with 140,000 square miles (360,000 km2), it was expanded in August 2016 by moving its border to the limit of the exclusive economic zone, making it one of the world's largest protected areas. It is internationally known for its cultural and natural values as follows:

"The area has deep cosmological and traditional significance for living Native Hawaiian culture, as an ancestral environment, as an embodiment of the Hawaiian concept of kinship between people and the natural world, and as the place where it is believed that life originates and to where the spirits return after death. On two of the islands, Nihoa and Makumanamana, there are archaeological remains relating to pre-European settlement and use. Much of the monument is made up of pelagic and deepwater habitats, with notable features such as seamounts and submerged banks, extensive coral reefs and lagoons."

<i>Amaranthus brownii</i> species of plant

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Bonin petrel species of bird

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Tanager Expedition a series of five biological surveys of the Northwestern Hawaiian Islands

The TanagerExpedition was a series of five biological surveys of the Northwestern Hawaiian Islands conducted in partnership between the Bureau of Biological Survey and the Bishop Museum, with the assistance of the U.S. Navy. Four expeditions occurred from April to August 1923, and a fifth in July 1924. Led by Lieutenant Commander Samuel Wilder King on the minesweeper USS Tanager (AM-5), and Alexander Wetmore directing the team of scientists, the expedition studied the plant animal life, and geology of the central Pacific islands. Noted members of the team include archaeologist Kenneth Emory and herpetologist Chapman Grant.

<i>Montipora dilatata</i> species of cnidarian

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Hurricane Neki Category 3 Pacific hurricane in 2009

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