South east coast Savai'i island - Samoa 2009

The Samoan archipelago is a chain of 16 islands and numerous seamounts covering in the central

South Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

, south of the equator, about halfway between

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

, forming part of

Polynesia Polynesia () "many" and νῆσος () "island"), to, Polinisia; mi, Porinihia; haw, Polenekia; fj, Polinisia; sm, Polenisia; rar, Porinetia; ty, Pōrīnetia; tvl, Polenisia; tkl, Polenihia (, ) is a subregion of Oceania, made up of ...

and of the wider region of

Oceania Oceania (, , ) is a geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern and Western hemispheres, Oceania is estimated to have a land area of and a population of around 44.5 million ...

. The islands are Savaiʻi,

Upolu Upolu is an island in Samoa, formed by a massive basaltic shield volcano which rises from the seafloor of the western Pacific Ocean. The island is long and in area, making it the second largest of the Samoan Islands by area. With approxi ...

, Tutuila, ’Uvea, Taʻū, Ofu, Olosega, Apolima, Manono,

Nuʻutele Nuutele is an island that consists of a volcanic tuff ring. It lies 1.3 km off the eastern end of Upolu island, Samoa. It is the largest of the four Aleipata Islands, with an area of . Nuutele, together with Nuulua, a smaller island in th ...

, Niulakita, Nuʻulua, Namua, Fanuatapu,

Rose Atoll Rose Atoll, sometimes called Rose Island or Motu O Manu ("Bird Island") by people of the nearby Manu'a Islands, is an oceanic atoll within the U.S. territory of American Samoa. An uninhabited wildlife refuge, it is the southernmost point belo ...

, Nu'ulopa, as well as the submerged

Vailuluʻu Vailuluu is a volcanic seamount discovered in 1975. It rises from the sea floor to a depth of and is located between Tau and Rose islands at the eastern end of the Samoa hotspot chain. The basaltic seamount is considered to mark the current loc ...

Pasco banks {{short description, Long ridge-like seamount in the south Pacific The Pasco Banks refers to a naturally occurring geological and marine formation in the south Pacific Ocean. The Pasco Banks is a long ridge-like seamount that rises from about 200& ...

, and

Alexa Bank Alexa Bank is a seamount in Samoa, northwest of Rotuma. The seamount reaches a depth of below sea level and has the appearance of an atoll with a flat top and steep slopes. Some active coral growth takes place at its top, but if it ever was an ...

Tectonics

The Samoan archipelago has many features that are consistent with a plume-driven hotspot model, including the currently active submarine volcano

that anchors the eastern extremity. However, the chain's proximity to the northern end of the Tonga trench, and the presence of voluminous young volcanism on what should be the oldest (~5 my) western island Savaiʻi has induced controversy regarding a simple plume/hotspot model. The Samoan archipelago was most likely created by the Pacific Tectonic Plate traveling over a fixed hotspot. The Samoa hotspot trail is in part coincident with a large group of islands and seamounts long, which were probably formed by the same hotspot, but also intersect with older seamounts along the hotspot highway left by the Macdonald,

Rurutu Rūrutu is the northernmost island in the Austral archipelago of French Polynesia, and the name of a commune consisting solely of that island. It is situated south of Tahiti. Its land area is .Rarotonga Rarotonga is the largest and most populous of the Cook Islands. The island is volcanic, with an area of , and is home to almost 75% of the country's population, with 13,007 of a total population of 17,434. The Cook Islands' Parliament buildings a ...

hotspots and feature substantial postshield volcanism, probably owing to tectonic phenomena triggered by the subduction of the Pacific Plate under the

Australian Plate The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India brok ...

at the nearby Tonga Trench.

is a

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plat ...

seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise a ...

discovered in 1975. It rises from the sea floor to a depth of and is located between Tau and

Rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...

islands at the eastern end of the Samoa hotspot chain. The

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than ...

seamount is considered to mark the current location of the Samoa hotspot. The summit of Vailuluu contains a wide, deep oval-shaped

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

. Two principal rift zones extend east and west from the summit, parallel to the trend of the Samoan hotspot. A third less prominent rift extends southeast of the summit.

and Malulu seamount are likely remnants of where the path of either the Macdonald or

Rarotonga Rarotonga is the largest and most populous of the Cook Islands. The island is volcanic, with an area of , and is home to almost 75% of the country's population, with 13,007 of a total population of 17,434. The Cook Islands' Parliament buildings a ...

hotspots crossed the path of the Samoa hotspot. Some seamounts in western

Samoa Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands ( Savai'i and Upolu); two smaller, inhabited islands ( Manono and Apolima); ...

("Samoan Seamounts"), which were emplaced together with Tuvalu between 63 and 42 million years ago are likely remnants of the

Rurutu hotspot Arago hotspot is a hotspot in the Pacific Ocean, presently located below the Arago seamount close to the island of Rurutu, French Polynesia. Arago is part of a family of hotspots in the southern Pacific, which include the Society hotspot and th ...

. These are also known as the "interloper seamounts". Other undated seamounts in Samoa have been linked to the Rurutu hotspot on the basis of geochemical evidence.

Islands of the Samoan archipelago

Climate

Due to its positioning in the South

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

, the Samoan archipelago is frequently hit by tropical cyclones between November and April.Samoa has an equatorial climate, with an average annual temperature of 26.5 °C (79.7 °F) and a main rainy season from November to April, although heavy rain may fall in any month.

Terrain

The terrain of the larger islands consists of a narrow coastal plains with volcanic, rocky, rugged mountains in the interior. The Natural resources include hardwood forests, fish, and hydropower. The smaller islands are remnants of eroded

tuff rings, some are just a coral reef atop the eroded cone of a defunct volcano. Rose Atoll is the easternmost point of the archipelago and the southernmost point of the United States. American Samoa is home to the National Park of American Samoa. The highest mountains are: Mt Silisili ( Savaiʻi) at , Mount Fito (

) at , Lata Mountain ( Taʻū), ;

Matafao Peak Matafao Peak (Samoan: Fa’asi’usi’uga o Matafao) is a mountain in American Samoa, on the island of Tutuila. With an elevation of 653 meters (2,142 ft), it is the highest peak on Tutuila Island. The mountain, like Rainmaker Mountain acr ...

( Tutuila) at , Piumafua ( Olosega) at , and Tumutumu ( Ofu) at .

Mount Pioa Rainmaker Mountain (also known as Mount Pioa) is the name of a mountain located near Pago Pago, American Samoa on Tutuila Island. Rainmaker Mountain traps rain clouds and gives Pago Pago the highest annual rainfall of any harbor. The average annu ...

( Tutuila), nicknamed the Rainmaker, is . American Samoa is also home to some of the world's highest sea cliffs at .Harris, Ann G. and Esther Tuttle (2004). ''Geology of National Parks''. Kendall Hunt. p. 603. .

References

Sources