Western continental shelves of Australia

Geologically, the Sahul Shelf () is a part of the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

of the Australian continent, lying off the northwest coast of

mainland Australia Mainland Australia is the main landmass of the Australia (continent), Australian continent, excluding the Aru Islands Regency, Aru Islands, New Guinea, Tasmania, and other list of islands of Australia, Australian offshore islands. The landmass ...

Etymology

The name "Sahull" or "Sahoel" appeared on 17th century Dutch maps applied to a submerged sandbank between

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and

Timor Timor (, , ) is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is Indonesia–Timor-Leste border, divided between the sovereign states of Timor-Leste in the eastern part and Indonesia in the ...

. On his 1803 map,

Matthew Flinders Captain (Royal Navy), Captain Matthew Flinders (16 March 1774 – 19 July 1814) was a British Royal Navy officer, navigator and cartographer who led the first littoral zone, inshore circumnavigate, circumnavigation of mainland Australia, then ...

noted the "Great Sahul Shoal" where

Indonesians Indonesians (Indonesian language, Indonesian: ''orang Indonesia'') are citizens or people who are identified with the country of Indonesia, regardless of their ethnic or religious background. There are more than Ethnic groups in Indonesia, 1,300 ...

came from

Makassar Makassar ( ), formerly Ujung Pandang ( ), is the capital of the Indonesian Provinces of Indonesia, province of South Sulawesi. It is the largest city in the region of Eastern Indonesia and the country's fifth-largest urban center after Jakarta, ...

to fish for ''trepang'' (

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

). The name Sahul Shelf () was coined in 1919 by G.A.F. Molengraaff, an authority on the geology of the then

Dutch East Indies The Dutch East Indies, also known as the Netherlands East Indies (; ), was a Dutch Empire, Dutch colony with territory mostly comprising the modern state of Indonesia, which Proclamation of Indonesian Independence, declared independence on 17 Au ...

Geography

The Sahul Shelf proper stretches northwest from Australia much of the way under the

Timor Sea The Timor Sea (, , or ) is a relatively shallow sea in the Indian Ocean bounded to the north by the island of Timor with Timor-Leste to the north, Indonesia to the northwest, Arafura Sea to the east, and to the south by Australia. The Sunda Tr ...

towards Timor, ending where the seabed begins descending into the Timor Trough. To the northeast, the Sahul Shelf merges into the Arafura Shelf, which runs from the northern coast of Australia under the

Arafura Sea The Arafura Sea (or Arafuru Sea) lies west of the Pacific Ocean, overlying the continental shelf between Australia and Western New Guinea (also called Papua), which is the Indonesian part of the Island of New Guinea. Geography The Arafura Sea is ...

north to

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

. The Aru Islands rise from the Arafura Shelf. The Sahul Shelf is sometimes taken to also include the Rowley Shelf to the southwest of Cape Leveque, girding the north coast of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

as far as North West Cape. The existence of an extensive Sahul Shelf was suggested in 1845 by George Windsor Earl who called it the "Great Australian Bank" and noted that macropods (kangaroos) were found on Australia, New Guinea, and the Aru Islands. Earl also suggested the existence of the

Sunda Shelf Geology, Geologically, the Sunda Shelf () is a south-eastern extension of the continental shelf of Mainland Southeast Asia. Major landmasses on the shelf include the Indonesia, Indonesian islands of Bali, Borneo, Java, Madura Island, Madura, an ...

(which he called the "Great Asiatic Bank") covering the western

Malay Archipelago The Malay Archipelago is the archipelago between Mainland Southeast Asia and Australia, and is also called Insulindia or the Indo-Australian Archipelago. The name was taken from the 19th-century European concept of a Malay race, later based ...

and the

Malay Peninsula The Malay Peninsula is located in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The area contains Peninsular Malaysia, Southern Tha ...

. In the 1970s, biogeographers coined "

Sundaland Sundaland (also called Sundaica or the Sundaic region) is a biogeographical region of Southeast Asia corresponding to a larger landmass that was exposed throughout the last 2.6 million years during periods when sea levels were lower. It inc ...

" and " Sahul" as contrastive names for the continental regions extending from the adjacent shelves.

Geology

When sea levels fell during the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

, including the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent between 26,000 and 20,000 years ago. Ice sheets covered m ...

about 18,000 years ago, the Sahul Shelf was exposed as dry land. Evidence of the shoreline of this time has been identified in locations which now lie 100 to 140 metres below sea level. A Flash-based interactive timeline of sea level changes was developed by Monash University in the 2000s.

Ecology

The Arafura Shelf formed a

land bridge In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea le ...

between Australia, New Guinea, and the Aru Islands, and these lands share many

Marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

mammals, land birds, and freshwater fish as a result. Lydekker's Line, a biogeographical line, runs along the northwestern edge of the Sahul Shelf where it drops off into the deep waters of the

Wallacea Wallacea is a biogeography, biogeographical designation for a group of mainly list of islands of Indonesia, Indonesian islands separated by deep-water straits from the Asian and Australia (continent), Australian continental shelf, continental ...

biogeographical area. Wallacea sits in a gap between the Sahul Shelf and the

, part of the continental shelf of Southeast Asia. The land bridge enabled early human migrations to Australia.

References

{{Submerged landmasses Continental shelves Geology of the Pacific Ocean Landforms of Oceania Landforms of Southeast Asia Landforms of the Pacific Ocean Landforms of Indonesia Landforms of Papua New Guinea Landforms of Western New Guinea Coastline of the Northern Territory Coastline of Western Australia

Etymology

Geography

Geology

Ecology

See also

References