# Geography of Samoa

The Samoan archipelago is a chain of 16 islands and numerous seamounts covering 3,123 km$^2$ (1,206 sq mi) in the central South Pacific, south of the equator, about halfway between Hawaii and New Zealand, forming part of Polynesia and of the wider region of Oceania. The islands are Savaiʻi, Upolu, Tutuila, ’Uvea, Taʻū, Ofu, Olosega, Apolima, Manono, Nuʻutele, Niulakita, Nuʻulua, Namua, Fanuatapu, Rose Atoll, Nu'ulopa, as well as the submerged Vailuluʻu, Pasco banks, and Alexa Bank.

## Tectonics

The Samoan archipelago has many features that are consistent with a plume-driven hotspot model, including the currently active submarine volcano Vailuluʻu 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 1,700 km (1,056 mi) long, which were probably formed by the same hotspot, but also intersect with older seamounts along the hotspot highway left by the Macdonald, Rurutu, and Rarotonga hotspots and feature substantial postshield volcanism, probably owing to tectonic phenomena triggered by the subduction of the Pacific Plate under the Australian Plate at the nearby Tonga Trench.
Vailuluʻu is a volcanic seamount discovered in 1975. It rises from the sea floor to a depth of 593 m (1,946 ft) and is located between Taʻu and Rose islands at the eastern end of the Samoa hotspot chain. The basaltic seamount is considered to mark the current location of the Samoa hotspot. The summit of Vailuluʻu contains a 2,000 m (6,600 ft) wide, 400 m (1,300 ft) deep oval-shaped caldera. 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.
Rose Atoll and Malulu seamount are likely remnants of where the path of either the Macdonald or Rarotonga hotspots crossed the path of the Samoa hotspot. Some seamounts in western Samoa ("Samoan Seamounts"), which were emplaced together with Tuvalu between 63 and 42 million years ago are likely remnants of the Rurutu hotspot. 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

| Island | Area | Coastline | Population | Highest Point | Last Volcanic Eruption | Country/Territory |
| Savaiʻi | 1,694 | 195 | 43,142 | 1,858 | 1911 CE | Samoa |
| Upolu | 1,125 | 197 | 143,418 | 1,113 | Unknown | Samoa |
| Tutuila | 142.3 | 135 | 55,876 | 653 | 440 CE | American Samoa |
| ’Uvea | 96 | 43 | 8,333 | 131 | Unknown | Wallis and Futuna |
| Taʻū | 47.02 | 32 | 790 | 931 | Unknown | American Samoa |
| Ofu | 7.215 | 11.47 | 176 | 491 | 1866 CE | American Samoa |
| Olosega | 5.163 | 13.38 | 172 | 629 | 1866 CE | American Samoa |
| Apolima | 4.1 | 4.19 | 75 | 165 | Unknown | Samoa |
| Manono | 3 | 7.5 | 889 | 37 | Unknown | Samoa |
| Nuʻutele | 1.15 | 5.04 | 0 | 180 | Unknown | Samoa |
| Niulakita | 0.4 | 2.2 | 34 | 4.6 | Cretaceous | Tuvalu |
| Nuʻulua | 0.23 | 2.78 | 0 | 96 | Unknown | Samoa |
| Namua | 0.18 | 2.08 | 0 | 91 | Unknown | Samoa |
| Fanuatapu | 0.06 | 1.81 | 0 | 31 | Unknown | Samoa |
| Rose Atoll | 0.05 | 0.75 | 0 | 3.5 | 10,000 ya | American Samoa |
| Nu'ulopa | 0.01 | 0.45 | 0 | 37 | Unknown | Samoa |
| Total | 3,126 | 654 | 252,905 |

## Climate

Due to its positioning in the South Pacific Ocean, the Samoan archipelago is frequently hit by tropical cyclones between November and April. Samoa has a trade-wind tropical rainforest climate (Köppen Af), with an average annual temperature of 26.5 °C or 79.7 °F. The wettest period occurs from November to April, although heavy rain may fall in any month.
Climate data for Apia, Upolu :
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Mean daily maximum °C (°F) | 30.4 (86.7) | 30.6 (87.1) | 30.6 (87.1) | 30.7 (87.3) | 30.4 (86.7) | 30.0 (86.0) | 29.5 (85.1) | 29.6 (85.3) | 29.9 (85.8) | 30.1 (86.2) | 30.3 (86.5) | 30.5 (86.9) | 30.2 (86.4) |
| Mean daily minimum °C (°F) | 23.9 (75.0) | 24.2 (75.6) | 24.0 (75.2) | 23.8 (74.8) | 23.4 (74.1) | 23.2 (73.8) | 22.6 (72.7) | 22.8 (73.0) | 23.1 (73.6) | 23.4 (74.1) | 23.6 (74.5) | 23.8 (74.8) | 23.5 (74.3) |
| Average rainfall mm (inches) | 489.0 (19.25) | 368.0 (14.49) | 352.1 (13.86) | 211.2 (8.31) | 192.6 (7.58) | 120.8 (4.76) | 120.7 (4.75) | 113.2 (4.46) | 153.9 (6.06) | 224.3 (8.83) | 261.7 (10.30) | 357.5 (14.07) | 2,965 (116.72) |
| Source: World Meteorological Organization (UN) ||||||||||||||

## 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 volcanic 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 1,858 m (6,096 ft), Mount Fito (Upolu) at 1,113 m (3,652 ft), Lata Mountain (Taʻū), 3,170 ft (970 m); Matafao Peak (Tutuila) at 2,141 ft (653 m), Piumafua (Olosega) at 2,095 ft (639 m), and Tumutumu (Ofu) at 1,621 ft (494 m). Mount Pioa (Tutuila), nicknamed the Rainmaker, is 1,718 ft (524 m). $^{:3}$ American Samoa is also home to some of the world's highest sea cliffs at 3,000 ft (910 m).