| Native name:
Mokupuni o Hawai‘i
| |
|---|---|
The Windward Islands of Hawaii
| |
 | |
| Geography | |
| Location | North Pacific Ocean |
| Total islands | 137 |
| Highest point |
|
| Administration | |
United States
| |
| State | Hawaii |
| Unincorporated territory | Midway Atoll |
| Largest settlement | Honolulu |
The Hawaiian Islands (Hawaiian: Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, numerous smaller islets, and seamounts in the North Pacific Ocean, extending some 1,500 miles (2,400 kilometers) 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 that James Cook chose in honor of the then First Lord of the Admiralty John Montagu, 4th Earl of Sandwich. The contemporary name, dating from the 1840s, is derived from the name of the largest island, Hawaiʻi Island. The islands were first known to Europeans after the expedition of Álvaro de Saavedra Cerón in 1527.
Hawaii is the only U.S. state that is not geographically connected to North America. The state of Hawaii occupies the archipelago almost in its entirety (including the mostly uninhabited Northwestern Hawaiian Islands), with the sole exception of Midway Island, which also belongs to the United States, albeit as one of its unincorporated territories within the United States Minor Outlying Islands.
The Hawaiian 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 islands are about 1,860 miles (3,000 km) from the nearest continent.
Islands and reefs
The date of the first settlements of the Hawaiian Islands is a topic of continuing debate. Archaeological evidence seems to indicate a settlement as early as 124 AD.
Captain James Cook visited the islands on January 18, 1778, and named them the "Sandwich Islands" in honor of John Montagu, 4th Earl of Sandwich, who as the First Lord of the Admiralty was one of his sponsors. This name was in use until the 1840s, when the local name "Hawaii" gradually began to take precedence.
The Hawaiian Islands have a total land area of 6,423.4 square miles (16,636.5 km2). Except for Midway, which is an unincorporated territory of the United States, these islands and islets are administered as Hawaii—the 50th state of the United States.
Smaller islands, atolls, reefs
Hawaiian Islands from space.
Smaller islands, atolls, and reefs (all west of Niʻihau are uninhabited except Midway Atoll) form the Northwestern Hawaiian Islands, or Hawaiian Leeward Islands:
- Nihoa (Mokumana)
- Necker (Mokumanamana)
- French Frigate Shoals (Kānemilohaʻi)
- Gardner Pinnacles (Pūhāhonu)
- Maro Reef (Nalukākala)
- Laysan (Kauō)
- Lisianski Island (Papaʻāpoho)
- Pearl and Hermes Atoll (Holoikauaua)
- Midway Atoll (Pihemanu)
- Kure Atoll (Mokupāpapa)
Islets
3-D perspective view of the southeastern Hawaiian Islands, with the white summits of Mauna Loa (4,170 m or 13,680 ft high) and Mauna Kea
(4,206 m or 13,799 ft high). The islands are the tops of massive
volcanoes, the bulk of which lie below the sea surface. Ocean depths are
colored from violet (5,750 m or 18,860 ft deep northeast of Maui)
and indigo to light gray (shallowest). Historical lava flows are shown
in red, erupting from the summits and rift zones of Mauna Loa, Kilauea, and Hualalai volcanoes on Hawaiʻi.
The state of Hawaii counts 137 "islands" in the Hawaiian chain. This number includes all minor islands and islets (very small islands) offshore of the main islands (listed above) and individual islets in each atoll. These are just a few:
- Ford Island (Mokuʻumeʻume)
- Lehua
- Kaʻula
- Kaohikaipu
- Mānana
- Mōkōlea Rock
- Nā Mokulua
- Molokini
- Mokoliʻi
- Moku Manu
- Moku Ola (Coconut Island, Hawaii)
- Moku o Loʻe (Coconut Island, Oahu)
- Sand Island
- Grass Island
A composite satellite image from NASA of the Hawaiian Islands taken from outer space. Click on the image for a larger view that shows the main islands and the extended archipelago.
Geology
This chain of islands, or archipelago, developed as the Pacific Plate slowly moved northwestward over a hotspot in the Earth's mantle
at a rate of approximately 32 miles (51 km) per million years. Thus,
the southeast island is volcanically active, whereas the islands on the
northwest end of the archipelago are older and typically smaller, due to
longer exposure to erosion. The age of the archipelago has been estimated using potassium-argon dating methods. From this study and others, it is estimated that the northwesternmost island, Kure Atoll, is the oldest at approximately 28 million years (Ma); while the southeasternmost island, Hawaiʻi,
is approximately 0.4 Ma (400,000 years). The only active volcanism in
the last 200 years has been on the southeastern island, Hawaiʻi, and on
the submerged but growing volcano to the extreme southeast, Loʻihi. The Hawaiian Volcano Observatory of the USGS documents recent volcanic activity and provides images and interpretations of the volcanism. Kīlauea had been erupting nearly continuously since 1983 when it stopped August 2018.
Almost all of the magma of the hotspot has the composition of basalt, and so the Hawaiian volcanoes are composed almost entirely of this igneous rock. There is very little coarser-grained gabbro and diabase. Nephelinite is exposed on the islands but is extremely rare. The majority of eruptions in Hawaiʻi 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.
Eruptions from the Hawaii hotspot left a trail of underwater mountains across the Pacific over millions of years, called the Emperor Seamounts
Hawaiʻi island (the Big Island) is the biggest and youngest island in the chain, built from five volcanoes. Mauna Loa, taking up over half of the Big Island, is the largest shield volcano
on the Earth. The measurement from sea level to summit is more than 2.5
miles (4 km), from sea level to sea floor about 3.1 miles (5 km).
Earthquakes
The Hawaiian Islands have many earthquakes, generally caused by volcanic activity. Most of the early earthquake monitoring took place in Hilo, by missionaries Titus Coan, Sarah J. Lyman and her family. Between 1833 and 1896, approximately 4 or 5 earthquakes were reported per year.
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 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 150 miles (240 km) from the epicenter.
Power outages lasted for several hours to days. Several water mains
ruptured. No deaths or life-threatening injuries were reported.
On May 4, 2018 there was a 6.9 earthquake in the zone of volcanic activity from Kīlauea.
Earthquakes are monitored by the Hawaiian Volcano Observatory run by the USGS.
Tsunamis
Aftermath of the 1960 Chilean tsunami in Hilo, Hawaiʻi, where the tsunami left 61 people dead and 282 seriously injured. The waves reached 35 feet (11 m) high.
The Hawaiian Islands are subject to tsunamis, great waves that strike the shore. Tsunamis are most often caused by earthquakes
somewhere in the Pacific. The waves produced by the earthquakes travel
at speeds of 400–500 miles per hour (600–800 km/h) and can affect
coastal regions thousands of miles (kilometers) away.
Tsunamis may also originate from the Hawaiian Islands. Explosive volcanic activity can cause tsunamis. The island of Molokaʻi 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 Hawaiʻi 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. The
Governor declared it a "good drill" for the next major event.
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 $30.1 million in damages.
Ecology
The islands are home to a multitude of endemic species. Since human settlement, first by Polynesians,
non native trees, plants, and animals were introduced. These included
species such as rats and pigs, that have preyed on native birds and
invertebrates that initially evolved in the absence of such predators.
The growing population of humans has also led to deforestation, forest degradation,
treeless grasslands, and environmental degradation. As a result, many
species which depended on forest habitats and food became extinct—with
many current species facing extinction. As humans cleared land for
farming, monocultural crop production replaced multi-species systems.
The arrival of the Europeans
had a more 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 many
more species to the list of extinct animals of the Hawaiian Islands. As of 2009, many of the remaining endemic species are considered endangered.
National Monument
On June 15, 2006, President George W. Bush issued a public proclamation creating Papahānaumokuākea Marine National Monument under the Antiquities Act of 1906. The Monument encompasses the northwestern Hawaiian Islands and surrounding waters, forming the largest marine wildlife reserve in the world. In August 2010, UNESCO's World Heritage Committee added Papahānaumokuākea to its list of World Heritage Sites. On August 26, 2016, President Barack Obama greatly expanded Papahānaumokuākea, quadrupling it from its original size.
Climate
The climate of the Hawaiian Islands is tropical but it experiences many different climates, depending on altitude and weather. The islands receive most rainfall from the trade winds on their north and east flanks (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.
In general, the lowlands of Hawaiian Islands receive most of their precipitation during the winter months (October to April). Drier conditions generally prevail from May to September. The tropical storms, and occasional hurricanes, tend to occur from July through November.
During the summer months the average temperature is about 84 °F
(29 °C), in the winter months it is approximately 78,8 °F (26°C). As the
temperature is relatively constant over the year the probability of
dangerous thunderstorms is approximately low.
