Heard Island and McDonald Islands-CIA WFB Map

The McDonald Islands () are an uninhabited

archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands. Examples of archipelagos include: the Indonesian Arc ...

in the southern

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

in the vicinity of

Heard Island The Territory of Heard Island and McDonald Islands (HIMI) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size ...

(). Together with Heard Island, they make up the Australian external

Territory of Heard Island and McDonald Islands The Territory of Heard Island and McDonald Islands (HIMI) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size ...

. The McDonald Islands are the emergent peaks of submarine volcanoes and are Australian

external territory A dependent territory, dependent area, or dependency (sometimes referred as an external territory) is a territory that does not possess full political independence or sovereignty as a sovereign state, yet remains politically outside the controlli ...

. Prior to 1992, there had not been an eruption in the previous 75,000 years.

Morphology

The McDonald Islands comprise three islands: McDonald Island, Flat Island (which later merged with McDonald Island) and Meyer Rock. The islands are mostly composed of

phonolitic Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous ...

low-silica

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...

dike Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes ...

s and lava domes, and sit atop a submarine plateau, the

Kerguelen Plateau The Kerguelen Plateau (, ), also known as the Kerguelen–Heard Plateau, is an oceanic plateau and a large igneous province (LIP) located on the Antarctic Plate, in the southern Indian Ocean. It is about to the southwest of Australia and is ...

. They are located about 75 km from

. McDonald Island is the largest of the islands, at around in area. It has been the main focus of volcanic activity in recent times. Prior to 1996, McDonald Island had been a flat green island whose pumice beaches provided a great nesting area for penguin breeding. The island now has two main peaks, Maxwell Hill and Samarang Hill – the highest is Maxwell Hill at .

Eruptions

Prior to 1992, no eruptions had taken place at the McDonald Islands volcano for 75,000 years. A series of eruptions started in 1992.

1992 eruption

The first recorded eruption from the McDonalds was from a submarine vent (a small VEI-0 eruption) in December 1992. The eruption was probably the cause of pumice that washed up on the shore of

1996–1997 eruption

Fresh eruptions were reported in December 1996 when a vapour plume was noticed by an aeroplane pilot. The plume was thought to have originated from Heard Island's Big Ben cone. However, on 18 March 1997 the crew of a passing ship heading for Heard Island reported that steam rose vigorously from a fissure on McDonald Island's steep north face; steam also vented from the island's north summit. Steam vented from a rubble-covered slope, indicating that a lava flow or

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...

had occurred. On 2 April 1997, the crew of another ship noted that steam continued to vent from the fissure, rising from the summit and flanks of the island. That crew also observed lava flows travelling down gullies; the lava flows covered a significant area of the north part of the island. Sulphur deposits were also discovered and fresh pumice washed up on Heard Island. The eruption is estimated to have ended sometime in January–March 1997.

2001 eruption

Another eruption started at McDonald Island in 2001. The eruption was first sighted from a ship passing by the islands. Material was being ejected from the flanks of the island and also in the north and northwest of the island, and steam was issuing from near the summit crater. Work suggested that prior to the ship's visit, the volcano had been erupting, covering the island in dark, smooth material. Many features had been filled in, such as Williams Bay. The eruptions had also joined Flat Island to McDonald Island as of land had been added to windward point. A new volcanic cone had also been created. An observation made in November 2002 noted two new lava domes had been formed; their date of formation is unknown.

2005 eruption

Analysis of satellite imagery noted that an eruption took place on 12 July 2005 on the northwest shore of the island. The eruption may have added a small portion to the area of the island.

Heritage

In 2002 the Heard Island and McDonald Islands were declared a

marine reserve A marine reserve is a type of marine protected area (MPA). An MPA is a section of the ocean where a government has placed limits on human activity. A marine reserve is a marine protected area in which removing or destroying natural or cultural ...

; this was expanded in 2014. The islands are also recognised as a

World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...

.World heritage
Australian Antarctic Division. 28 February 2005.

Notes

References

Global Volcanism Program

Official Heard Island and McDonald Islands page

External links

Photo of the McDonald Islands in 2002 on Panoramio.com
{{Authority control Volcanoes of Heard Island and McDonald Islands Active volcanoes Complex volcanoes