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Montebello Islands facts for kids

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Montebello Islands is located in Western Australia
Montebello Islands
Montebello Islands
Location in Western Australia
Montebello Islands
Map of the Montebellos and Barrow Island
Op hurricane
The mushroom cloud resulting from Trimouille Island's Operation Hurricane detonation

The Montebello Islands, also known as the Monte Bello Islands, are an archipelago of around 174 small islands (about 92 of which are named) lying 20 km (12 mi) north of Barrow Island and 130 km (81 mi) off the Pilbara coast of north-western Australia. The islands form a marine conservation reserve of 58,331 ha (144,139 acres) administered by the Western Australian Department of Environment and Conservation. The islands were the site of three British atmospheric nuclear weapons tests in 1952 and 1956.


The islands of the archipelago have a collective land area of about 22 km2. The largest islands, Hermite (or Hermit) and Trimouille have areas of 1022 ha and 522 ha respectively. They consist of limestone rock and sand. The rocky parts are dominated by Triodia hummock grassland with scattered shrubs, while the sandy areas support grasses, sedges and shrubs, mainly Acacia. Patches of mangroves grow in sheltered bays and channels of the archipelago, especially at Hermite Island. The climate is hot and arid with an annual average rainfall of about 320 mm.


The islands have been identified by BirdLife International as an Important Bird Area (IBA) because they support over 1% of the world populations of fairy and roseate terns, and of sooty oystercatchers. Greater crested terns breed there irregularly, sometimes in large numbers. Other birds breeding on the islands include ospreys, white-bellied sea eagles, pied oystercatchers, Caspian terns and bridled terns. The islands support 12–15 breeding pairs of beach stone-curlews. Yellow white-eyes have been recorded.


Invasive feral cats and black rats have been eradicated from the islands, allowing endangered rufous hare-wallabies and Shark Bay mice to be translocated to the islands under the conservation management strategy for these threatened species. They are now common on many of the larger islands.


It is believed that the islands were occupied by indigenous Australians until about 5,000 BCE, when a period of global warming and rising sea levels caused the Montebellos to become more distant from the mainland, and forced abandonment.

The first Europeans known to have seen the islands were the crews of a French Navy exploration expedition, led by Nicolas Baudin, in 1801. Baudin named Hermite Island after Admiral Jean-Marthe-Adrien L'Hermite and Trimouille Island after a French aristocratic family. There are inconsistencies in the naming of the islands in the accounts of the early explorers, and it has been suggested that later explorers mixed up the names of Lowendal and Hermite Islands.

An early reference to the islands is in 1622, when the English ship Tryall was wrecked just west of them. For years afterwards their approximate position was recorded on charts as the Tryal Rocks.

The islands were economically significant for pearl fishing from the end of the 19th century until the outbreak of the Second World War.

British nuclear weapons tests

The Montebello islands were the site of three nuclear weapons tests by the British military: one in 1952, and two in 1956.

A bay on Trimouille Island was the site of Operation Hurricane, the first ever atomic weapon tested by the United Kingdom, on 3 October 1952.

While most subsequent British tests were conducted at sites on mainland Australia, in 1956 there were two further tests, on Alpha and Trimouille Islands respectively. The second of these, codenamed "G2", included the largest nuclear explosion in Australia, with a yield of 98 kilotons.

Fallout from the Montebello tests is reported to have contaminated areas of mainland Australia as far away as the Queensland towns of Mount Isa, Julia Creek, Longreach and Rockhampton.


Further information: List of named islands in the Montebello Islands archipelago

Of the smaller islands, the largest are:

  • North-West Island
  • Primrose Island
  • Bluebell Island
  • Alpha Island
  • Crocus Island
  • Campbell Island
  • Delta Island
  • Renewal Island
  • Ah Chong Island

There are also 10 named groups of small islets, whose individual islands have not yet been named:

  • Corkwood Islands
  • Fig Islands
  • Hakea Islands
  • Jarrah Islands
  • Jasmine Islands
  • Karri Islands
  • Marri Islands
  • Minnieritchie Islands
  • Mulga Islands
  • Quandong Islands
Montebello Islands-NASA
NASA World Wind satellite image of main Montebello Island group

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