Damon Mcknight
The Bass Strait is a 240km-wide channel that separates Tasmania from mainland Australia. It is believed that the Bass Strait was formed 8,000 years ago by rising sea levels at the end of the last glacial period. The East Australia hotspot, which includes the Cosgrove hotspot track, is a volcanic province in southeast Australia. The Cosgrove hotspot track is a chain of extinct volcanoes that extends 2,000 kilometres from Cape Hillsborough in Queensland to Cosgrove in Victoria. The Australian continent has been moving relatively fast at about 2.7 inches per year, and the formation of the volcanoes in the Cosgrove hotspot track is attributed to the movement of the Australian tectonic plate over a hotspot.
| Characteristics | Values |
|---|---|
| Speed of the Australian plate | 2.7 inches a year |
| Direction of movement | Northward with a slight clockwise rotation |
| Speed of the North American plate | 1 inch a year |
| Speed of the Pacific plate | 3-4 inches a year |
| Distance swum by Tammy van Wisse in the strait in 1996 | 100 km |
| Time taken by Tammy van Wisse | 17 hours and 46 minutes |
| Maximum width of the strait | 150 miles (240 km) |
| Depth of the strait | 180–240 feet (50–70 m) |
| Number of volcanoes in Australia | Nearly 150 |
| Time since volcanic activity in Australia | 4,000 to 5,000 years |
| Time since volcanic activity on the Australian mainland | Since European settlement |
| Time since the most recent eruptions in the East Australia hotspot | 5,600 years ago |
| Length of the Cosgrove hotspot track | More than 2,000 km |
| Length of the Snake River Plain-Yellowstone Caldera | Unknown; the Cosgrove hotspot track is more than three times its length |
| Length of the Yellowstone hotspot tracks | Unknown; the Cosgrove hotspot track is nearly three times its length |
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What You'll Learn
- The Bass Strait is a channel separating Tasmania from mainland Australia
- The Australian plate moves 2.7 inches a year
- The East Australia hotspot has explosive eruptions
- The Cosgrove hotspot track is the world's longest continental volcanic hotspot track
- The Bass Strait is associated with the Great Australian Bight
The Bass Strait is a channel separating Tasmania from mainland Australia
The Bass Strait is a water channel that separates the island state of Tasmania from mainland Australia, specifically the coast of Victoria. The strait is approximately 250 km (160 mi) wide and 500 km (310 mi) long, with an average depth of 60 m (200 ft). The Bass Strait was formed about 8,000 years ago by rising sea levels at the end of the last glacial period, isolating the Aboriginal Tasmanians from the Australian mainland. It was named after English explorer and physician George Bass, who sailed across it with Matthew Flinders in 1798-99.
The Bass Strait provides the most direct waterway between the Great Australian Bight and the Tasman Sea, which is part of the South Pacific Ocean. It is also the only maritime route into the economically significant Port Phillip Bay. The strait has a maximum width of 150 miles (240 km) and a depth of 180-240 feet (50-70 m). King Island and the Indian Ocean are located at its western extremity, while the Furneaux Group is at its eastern end.
The Bass Strait has been the site of several notable incidents, including one of the most famous UFO incidents in Australian history in 1978. It is also a popular route for air and sea travel between Tasmania and the mainland, with major airports in Hobart and Launceston served by airlines such as Jetstar, Virgin Australia, and Qantas. Two passenger ferries also operate daily between Devonport and Melbourne's Station Pier.
The Bass Strait is of geological interest due to its formation and location over a hotspot. The East Australia hotspot, which includes the Bass Strait, is a volcanic province in southeast Australia with both explosive eruptions and pahoehoe lava flows similar to those found in Hawaii. The Australian plate has been moving relatively quickly at about 2.7 inches per year northward with a slight clockwise rotation. This movement has contributed to the formation and characteristics of the Bass Strait over time.
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The Australian plate moves 2.7 inches a year
The Australian plate, which includes the continent of Australia, portions of New Guinea, New Zealand, and the Indian Ocean basin, is moving about 2.7 inches a year in a northward direction with a small clockwise rotation. This movement is significantly faster than that of other plates, such as the North American plate, which moves at roughly one inch per year. In contrast, the Pacific plate moves at a quicker pace of three to four inches annually.
The Australian plate's northward movement and rotation are relative to other tectonic plates. For instance, in relation to India, Australia is moving northward at 1.2 inches per year. This movement is consistent with a zone of deformation between the two plates. The Australian plate is also colliding with the Sunda plate, previously part of the Eurasian plate, with a maximum convergence velocity of 2.9 inches per year at the Java Trench.
The Australian plate's interaction with the Pacific plate, another major plate, is particularly notable. There is oblique convergence between the two plates near eastern Papua New Guinea, resulting in complex shear stresses. This interaction has led to the formation of multiple microplates and a convergence velocity ranging from 0.79 to 18.90 inches per year in the New Britain subduction zone. To the south, the Australian plate starts subducting under the Pacific plate at the Puysegur Trench, with a rate of 1.4 inches per year.
The movement of the Australian plate has implications for navigation technology, such as the Global Positioning System (GPS). As the continent shifts, the GPS coordinates need to be updated to ensure smooth functioning. The last adjustment to Australia's GPS coordinates was made in 1994, and since then, the continent has shifted by 4.9 feet.
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The East Australia hotspot has explosive eruptions
The East Australia hotspot is a volcanic province in southeast Australia, which includes the Peak Range in central Queensland, the Main Range on the Queensland-New South Wales border, and the Newer Volcanics Province (NVP) in Victoria and South Australia. The hotspot has had explosive eruptions, similar to the runny lava flows of the Hawaii, Iceland, and Réunion hotspots. These eruptions are caused by the interaction of basaltic magma with groundwater in aquifers below the surface, resulting in violent phreatomagmatic eruptions. The last volcanic eruptions in this region occurred around 4,000 to 5,000 years ago, with the most recent being about 5,600 years ago. These eruptions formed the volcanoes Mount Schank and Mount Gambier in the NVP, and their memories are preserved in Aboriginal folklore.
The East Australia hotspot, also known as the Cosgrove Track, extends the entire length of Australia and is believed to be much longer than the Snake River Plain-Yellowstone Caldera. The hotspot's existence is attributed to the movement of the Australian continent over a "hotspot" or fixed heat anomaly within the Earth's mantle. This movement results in volcanic eruptions on the surface. The cause of volcanism in the area is a subject of debate, with theories such as the mantle plume theory and plate theory being proposed. The mantle plume theory suggests that deep mantle plumes forced magma through weaknesses in the Indo-Australian Plate as it moved northward. However, the lack of clear age progression and the orientation of the NVP contradict this theory.
The plate theory, on the other hand, attributes volcanic activity to changes in plate boundary configurations, resulting in lithospheric thinning and decompression melting of the asthenosphere. Some models combine both plume and plate-tectonic processes. Additionally, the strength of the hotspot and magma supply play crucial roles in determining the explosiveness of eruptions. A stronger hotspot and a more direct supply of magma result in larger and longer-lasting volcanoes, while a weaker hotspot and a reduced magma supply lead to more explosive eruptions as the magma encounters multiple chambers on its way to the surface.
The East Australia hotspot is now believed to represent multiple hotspots, including a southwestern Cosgrove hotspot. The Cosgrove hotspot has been linked to the formation of the Central Volcanoes, which exhibit definite linear age progression. The Newer Volcanics Province (NVP), a part of the East Australia hotspot, is characterised by a lack of clear age progression and an orientation that contradicts the plate motion expected in a single plume model. This suggests that the NVP may be influenced by additional geological processes beyond a single mantle plume.
The study of the East Australia hotspot and its volcanic chain provides valuable insights into the life cycle of hotspots and how they influence the evolution of volcanoes. The absence of active volcanoes on the Australian mainland today indicates that the hotspot may have diminished over time. However, the continent's movement over the hotspot has resulted in a diverse range of volcanic structures and eruptions throughout its geological history.
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The Cosgrove hotspot track is the world's longest continental volcanic hotspot track
The Cosgrove hotspot track consists of two parts in the north and south, with a centre section where the lithosphere is too thick for melt to form. The northern section, in Queensland, produces basaltic volcanism due to the thinner lithosphere beneath it, while the southern section, in New South Wales and Victoria, consists of low-volume leucitite lavas due to the intermediate thickness of the lithosphere. The track was formed over the past 33 million years as the Australian continent moved north-northeast over a mantle plume hotspot, which is now believed to be located in the Bass Strait between King Island and Tasmania or possibly further northwest of Tasmania.
The mantle plume theory and the plate theory are the two main theories proposed to explain the volcanism in the area. The mantle plume theory suggests that the region is underlain by one or more deep mantle plumes that force magma up through weaknesses in the Indo-Australian Plate as it moves northward. On the other hand, the plate theory suggests that the hotspot is created by the movement of the tectonic plate over the hotspot, resulting in a chain of volcanoes.
The discovery of the Cosgrove hotspot track provides valuable insights into the composition of volcanic rock and how it evolves over time. By studying this track, scientists hope to gain a better understanding of volcanism on other continents and during earlier periods in Earth's history. Additionally, the research provides direct evidence that lithospheric thickness influences the volume and chemical composition of hotspot-derived volcanic rock.
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The Bass Strait is associated with the Great Australian Bight
The Bass Strait is a strait that separates Tasmania from mainland Australia (specifically, the coast of Victoria). The strait was formed 8,000 years ago by rising sea levels at the end of the last glacial period. It was named after English explorer and physician George Bass.
The International Hydrographic Organization (IHO) defines the eastern limit of the Great Australian Bight as a line from Cape Otway, Australia, to King Island, and then to Cape Grim, the northwest extreme of Tasmania. The IHO's definition of the Great Australian Bight includes the Bass Strait, designating the Bight as 62 and the Bass Strait as 62-A.
The Australian Hydrographic Service (AHS) does not consider the Bass Strait to be part of its expanded definition of the Southern Ocean, but rather states that it lies within the Tasman Sea. The AHS defines the Great Australian Bight as having the following limits: On the north, the south coast of the Australian mainland; on the south, a line joining West Cape Howe, Australia, to South West Cape, Tasmania; and on the east.
The Bass Strait is also associated with the Great Australian Bight in terms of their shared geological history. The Bass Strait was formed 8,000 years ago at the end of the last glacial period, during which Aboriginal Tasmanians arrived in Tasmania via a land bridge called the Bassian Plain. The Great Australian Bight was formed around 50 million years ago when the supercontinent Gondwana broke apart, separating Antarctica from Australia.
In addition, both the Bass Strait and the Great Australian Bight have been explored and studied by European and British explorers and navigators such as Abel Tasman, James Cook, George Bass, and Matthew Flinders. The Bass Strait and the Great Australian Bight also face strong currents from the waters of the Indian and Pacific Oceans, and both have been sites of oil and gas exploration.
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Frequently asked questions
The East Australia hotspot is a volcanic province in southeast Australia, which includes the Peak Range in central Queensland, the Main Range on the Queensland-New South Wales border, Tweed Volcano in New South Wales, and the Newer Volcanics Province (NVP) in Victoria and South Australia.
The Cosgrove hotspot track is a chain of extinct volcanoes that extends southward across eastern Australia. It is believed to be the world's longest continental volcanic hotspot track, stretching over 2,000 kilometres.
The Australian plate has been moving relatively fast at about 2.7 inches per year, in a northward direction with a slight clockwise rotation.
