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Romsey Australia



Volcanoes and Earthquakes.


Daily Earthquake activity Reports latest news feed


Earthquake and Fault Line Maps for Australia.

Is there a risk of a volcanic eruption in Australia ?


Mt. Gambier

Mount Gambier ( Eastern South Australia )  Australia's youngest volcano.
A volcano filled with water.  Erupted 4,500 years ago

"...volcanic activity must be considered a serious environmental hazard and risk for the Australian mainland. "   Source:  The risk of volcanic eruption in mainland Australia  - E. B. Joyce


 
The Western Victorian Volcanic Plains



The Western Victorian Volcanic Plains are the third largest in the world and exceeded only by the Deccan in western India, and the Snake River Plateau in the United States ( Idaho-Nebraska ).

The Victorian Volcanic Plains are located in Western Victoria and covers over 2.3 million ha (10.36% of the State).
It stretches from Portland in the west to Craigieburn in the east and from Clunes in the north to Colac in the south.

Climate and geology.
The Victorian Volcanic Plain bioregion is characterised by vast open areas of fertile plain covered with grasslands and grassy woodlands, and small patches of open woodland.

The bioregion is interspersed with stony rises and numerous extinct volcanic eruption points, denoting old lava flows and numerous scattered large shallow lakes and wetlands.
Few major rivers cross the plain, the most significant of these include the Barwon, Hopkins, Leigh, Maribyrnong, Wannon and Werribee Rivers and Mount Emu Creek and their tributaries.

The basalt plain was formed by extensive volcanic activity mostly from the Upper Cainozoic era (Quaternary) from approximately 6 million years ago to as recently as 7,200 years ago at Mt. Napier.
Several types of lava flows occurred including sheet flows and constricted flows along valleys.
Irregular and chaotic stony rises occupy large areas of the plains.
Numerous volcanic cones dot the landscape with scoria cones being the most common (e.g. Mt Elephant, Mt Napier and Mt Noorat) although some basalt cones are present (e.g. Mt Cottrell).
Soils are generally shallow reddish-brown to black loams and clays (Conn 1993). They are fertile and high in available phosphorous.

Older flows in the Cressy and Hamilton areas have allowed a greater development of deep soils.
Dark saline soils occur around the margins of some lakes.
Amongst the basalt are geological remnants that precede and survive the period of vulcanism that produced the “Plain”.

The majority of the elevation is below 250 m above sea level, however the maximum height does reach 720 m above sea level at two locations, Mount Doran and Mount Egerton, east of Ballarat.

Most of the region receives between 500 and 700 mm of rain per annum (Conn 1993) with rainfall distributed relatively evenly throughout the year except in the higher rainfall areas of the south west which receive a higher proportion of rainfall in winter.
The general pattern of climate is one of gradation rather than fluctuation. Average yearly rainfall generally decreases from southwest to northeast across the region.
Annual average rainfall figures are 840 mm for Portland, 720 for Colac, 680 for Hamilton, 630 at Skipton, 530 at Cressy and 450 at Eynesbury.
The warmest months are January and February with mean maximum temperatures ranging from about 20° to 27°C.
In winter the mean maximum is as low as 10°C with a mean minimum of 3°C.

Area of present vegetation groups.(1)
Major Vegetation Group Area (ha) % total extent
Cleared / modified native vegetation 1,998,844 92.4
Eucalyptus tall open forests 656 0
Eucalyptus open forest 34,392 1.6
Eucalyptus low open forest 40 0
Eucalyptus woodlands 49,616 2.3
Acacia forest and woodlands 180 0
Melaleuca forest and woodlands 4 0
Other forests and woodlands 708 0
Eucalyptus open woodlands 1,020 0
Mallee woodlands and shrublands 1,932 .1
Low closed forest and closed shrublands 4,484 .2
Other Shrublands 852 0
Heath 36 0
Tussock grasslands 4,512 .2
Other grasslands, herblands, sedgelands and rushlands 872 0
Chenopod shrub, samphire shrub and forblands 9,320 .4
Mangroves, tidal mudflat, samphire and bare areas, claypan, sand, rock, salt lakes, lagoons, lakes 54,724 2.5


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Is there a risk of a volcanic eruption ?

The Western Victorian and Eastern South Australia Volcano Map
     Extinct and Dormant Volcanoes.
    Each dot represents where volcanic activity had occurred.
Current active volcanoes in Australian territory are located on Heard and McDonald Islands in the Southern Ocean, about 4100 kms southwest of Western Australia.
Image source courtesy: Distribution of volcanoes and maars in Victoria and South Australia (A; Johnson (1989a)

Volcanoes in eastern Australia that have not erupted in thousands of years still pose a threat and emergency services should be better prepared, an expert told a geology conference today.
But another expert thinks Australia should be more worried about fires, storms and earthquakes than volcanoes.

Bernie Joyce, from the University of Melbourne, presented a paper on volcanic hazards today at the 17th Australian Geological Convention of the Geological Society of Australia held in Hobart, Tasmania (1a).


Volcanoes in Victoria, New South Wales and Queensland could erupt at any time, he told ABC Science Online ahead of the conference.
There has been no volcanic activity in Australia in the past few hundred years, and no major eruption since Mt Gambier, on the border of South Australia and Victoria, 4500 years ago.

But a sudden eruption could still catch emergency authorities unprepared for the floods, mud flows and ash falls that could follow, said Joyce.
He said the kind of eruption Australia could expect was not on the same scale of the Mt Helen's eruption, which wiped out a large area in the U.S. state of Washington in May 1980. Australia could expect a smaller eruption.

According to Joyce, an eruption could either be an explosion like the one at Mt Gambier, creating a big hole in the ground, or a volcanic eruption common in Queensland and Victoria in the past 50,000 years of a different type.
These eruptions have large lava flows followed by a more gaseous eruption where the lava breaks up into small pieces and builds a cone of cinders and sharp rock material.
There is evidence of these cones and crater lakes around Victoria and northern Queensland, Joyce said.

"In either case you wouldn't get much warning and you would be working out what to do when it came," Joyce said.

Eastern Australia had up to 20 volcanoes less than 50,000 years old, said Joyce, who said probability showed these still posed a threat. He warned the consequences of even a small eruption coming into contact with groundwater could include hot, wet ash falls, dangerous gases and ash blown into the air, damage to animals and the environment, and pollution in water systems.


 Map courtesy  (2)

“ There are around 400 volcanoes stretching from the Western District of Victoria into the Western Uplands around Ballarat and to the north of Melbourne around Kyneton and Kilmore, in some parts of the Eastern Uplands such as to the north of Benambra, and across to the South Australian border near Mt Gambier.
A volcanic eruption in the Western Uplands could potentially see lava flows and ash falls impacting on Melbourne.

There is also similar volcano risk present in various provinces in Far North Queensland, stretching from south-west of Townsville to near Cairns and up to Cooktown in the Far North. There are more than 380 volcanoes in total across this part of Queensland.
A future eruption in any of these regions would be unlikely to come from an existing volcano (as the volcanoes there are generally considered to be 'once only’ erupters).
Rather, future eruptions would occur at new sites nearby.
The geological record shows that new volcanoes in these areas have erupted perhaps every 2000 years in the past 40,000 years—and given there has not been a major eruption there for the past 5000 years, a significant eruption seems well overdue. " (3)
Reference  http://www.17thagc.gsa.org.au/


Image Courtesy of Cultural Landscapes of the Volcanic Plains Forum – 30 March 2007

Mt Noorat, near Terang

Many of Victoria's youngest volcanoes are scoria cones. Among them are Mount Elephant near Derrinallum, Mount Noorat near Terang, and Mount Fraser near Beveridge, north of Melbourne.
There are 200 steep-sided scoria volcanoes scattered across Victoria's basalt plain. They were formed when magma interacted explosively with groundwater, blasting molten rock high into the air in spectacular and violent displays.They were true 'fire mountains' when they erupted.

The usual warning signs.
But Dr Wally Johnson, head of the geohazards division at Geoscience Australia told ABC Science Online that Australia's government geological science organisation was more concerned about hazards posed by fires, storms and earthquakes than volcanoes.

"Australians are more likely to face risks from volcanoes when flying to Southeast Asia or the South Pacific and ash from volcanoes getting into the jets and causing problems with aircraft," said Johnson.

While Johnson said that Joyce did a good job raising awareness of the risks posed by volcanoes, he said there were other hazards with higher priorities.

"If Mt Gambier did erupt it would impact on local communities," Johnson said. "But any changes to the state of these volcanoes would be noticed early on, either through earthquakes, or in the case of Mt Gambier an increase in the temperature of the water.

"We know that volcanoes do provide a fair bit of warning. In most cases this would be months or even years. You might get a volcano way out in western Victoria where you might not notice the warning signs but in most cases you'll get advance warning from geological phenomena," he said.

Advance warnings could include an increase in seismic activity, a change in the temperature of surface soils, or even smoking fumaroles, small eruptions from the side of a volcano that indicate that a major eruption was imminent.

Aborigines witness volcanic eruptions:
Dingo bones and an Aboriginal grinding stone were recovered from beneath tuffs at Tower Hill near Warrnambool in Victoria.
In 1953 Gill observed that “ At Mt Gambier in South Australia, implements and hearths have been found beneath the volcanics, and archaeological dating and radiocarbon dating are possible. "
The eruption at Mount Gambier has now been dated to between 4.3 and 4.6 KYA using plant material embedded in the volcanic deposits (Sutherland, 1995:32). In a number of places in Victoria, too, artefacts have been found beneath volcanic material (Gill 1953).(4)

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Volcanism over the last 60 million years down the east coast of Australia.

Vulcanologists have divided this volcanic activity into lava fields - areas where large amounts of lava flowed from diffuse dykes and pipes over a wide area (shown in red); and central volcanoes - areas where volcanism was produced from either a single central vent or a cluster of vents (shown in orange).
It is now thought that the central volcanoes were produced as the Australian continent moved over a hot spot in the underlying mantle which 'melted' through the plate to form the volcano. As the continent moved northward, the stationary hot spot formed volcanoes further to the south on the continent. Therefore the rocks of central volcanoes down the east coast become younger as you move southward.
Map courtesy.  http://www.ga.gov.au/archive/volcanoes/

  

Distribution of volcanoes in eastern Australia.
Volcanic centres
1 Byrock, 2 El Capitan, 3 Cargelligo, 4 Cosgrove;
Central volcanoes
5 Nadewar, 6 Warrumbungle, 7 Canobolas, 8 Macedon, 9 Ebor,
10 Comboyne;
Lava fields
11 central, 12 Doughboy, 13 Walcha, 14 Barrington, 15 Liverpool Range, 16 Dubbo, 17 Kandos, 18 Sydney 19 Abercrombie 20 Grabben Gullen, 21 Southern Highlands 22 Monaro 23 Snowy Mountains, 24 South Coast, 25
Older Volcanics, 26 Newer Volcanics.
Volcanic centres in Queensland. Compiled from Sutherland (1995) and Johnson and others (1989).

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Hotspot system in our backyard

We have a hotspot system of our very own. Australia's hotspot currently lies under Victoria, Bass Strait, Tasmania, and the floor of the Tasman Sea at a latitude of about 40°S. It's one of more than a hundred systems identified around the world. As far as hotspots go, the one in our backyard is slumbering. Present hotspot activity is possibly confined to the triggering of earthquakes in predicted areas, such as the recent event off the coast of north-west Tasmania, and deep gas discharges under Victoria and Tasmania.

Scientists believe a new Australian volcano is being created.

Geologists suspect an earthquake that originated 50 kilometres from King Island in February 2002 signalled the reawakening of the hot spot, a region in the Earth's crust where the planet expels some of its internal heat.
Australia's hot spot is several hundred kilometres wide and lies under Bass Strait and parts of Victoria and Tasmania.


Wally Johnson, a vulcanologist at Geosciences Australia, said the fact that there were earthquakes taking place in the area "means that geologically, the hot spot has to be regarded as active, even though it hasn't produced volcanic eruptions as such".
He said it could spawn a volcano within 100 years.

One chain of about 13 volcanoes begins in north Queensland.
The largest in this chain is the Tweed Volcano, where Mount Warning represents the main vent. The chain extends south from the Cape Hillsborough Volcano in north Queensland through to the Mount Macedon Volcano in Victoria.
Other volcanoes in the chain include the Glasshouse Mountains, the Warrumbungles and Canobolas near Orange. The volcanoes are quite young. The oldest ones are found in north Queensland, while the youngest are in Victoria - the most northern volcano formed around 33 million years ago.

Distribution of Cenozoic volcanism on the Australian plate. a, White arrows show location of s-shaped bends in the Tasmantid and Lord Howe seamount tracks. Hotspot-derived central volcanoes are shaded black; non-hotspot mafic lava fields are grey, and seamount tracks are outlined in white. White circles show predicted present-day hotspot locations. The oldest total-fusion 40Ar–39Ar ages for Tasmantid seamounts are shown in black to the left of the chain; calculated ages are shown in white to the right of the two tracks at 5-Myr intervals. b, Locations of silicic rocks (shown in red) from the central volcanoes (outlined in blue and dashed where approximate) sampled for 40Ar–39Ar geochronology.
".....our evidence for a brief period of altered plate motion between 26–23 Myr rests on the assumption that central volcanoes in eastern Australia are generated over a relatively stationary hotspot."
Source and image courtesy of: Rapid change in drift of the Australian plate records collision with Ontong Java plateau. Kurt M. Knesel, Benjamin E. Cohen, Paulo M. Vasconcelos & David S. Thiede   Earth Sciences, The University of Queensland, St Lucia, Queensland, 4072, Australia - Nature Vol 454 7 August 2008



Another chain of hotspot volcanoes extends along the floor of the Tasman Sea and includes the Gascoyne seamount.

  

Simplified geological fault line map of Tasmania.
Source: Burrett and Martin, 1989.
 
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Seafloor Imaging - Topography of South East Australia.

Sea floor Tasmania

SEAMOUNTS
A seamount is an underwater mountain, often of volcanic origin, defined as a steep geologic feature rising from the seafloor reaching a minimum height of 1,000 meters and with a limited extent across its summit. The definition, however, is not strictly adhered to and any steep undersea mountain is often referred to as a seamount, regardless of its size.


Water depth in Bass strait measured in metres.


Glacial sea level declination.

During glacial sea level declination Tasmania was connected to the Australian mainland, with the existing islands forming hills in the Bassian Plain.
People could have easily walked to Tasmania from what is now the State of Victoria.
South-western Tasmania was occupied by 30,000 BP, suggesting that Tasmania was initially colonised during the low sea level phase of 29,000 to 37,000 years BP (Cosgrove, et al., 1990).

Sea levels rose and flooded the Bassian Rise connecting Victoria to Flinders Island and north-eastern Tasmania between 12,000 and 13,500 years BP (Jennings, 1971; Chappell and Thom, 1977).

The Tasmanians apparently did not have adequate watercraft to cross Bass Strait, or reach the major islands within it, so with high sea levels came isolation. The precise date of the first human occupation of Australia is not known, estimates range from 30,000 to 60,000 years ago. The Aboriginal people are thought to have crossed to Australia from south-east Asia.

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Active Australian Volcanoes.
Heard Island and McDonald Islands is a subantarctic island group located in the Southern Ocean, about 4100 kms southwest of Western Australia.
The islands and surrounding waters teem with wildlife and other natural wonders that make it a special place.
Heard Island consists of 2 volcanic cones, Big Ben and Mt. Dixon, joined by a narrow isthmus. Both cones are young, but only Big Ben has been observed to erupt.
Big Ben is a large, glacier-covered, composite cone 20-25 km in diameter at sea-level, consisting mainly of basaltic lavas and lesser ash and scoria. Its summit region consists of a SW-facing semi-circular ridge 5-6 km in diameter, 2200-2400 m above sea-level.


Night-time view of Big Ben erupting on 3 February 2001,
viewed from Atlas Cove. Photo Stu Fitch  
Courtesy Australian Antarctic Division © Commonwealth of Australia 2006

  

Heard Island Volcano Eruptions   53.106 S,   73.513 E

2008, 2007, 2006, 2003-04, 2000-01, 1993, 1992, 1985-87, 1954, 1953, 1950-52, 1910, 1881?  

McDonald Island began erupting in 1992, after lying dormant for 75,000 years. It has erupted several times since with satellite pictures in 2001 showing that the island had doubled in size. The initial evidence came in the form of abundant pumice washing up on beaches north and south of The Spit at the eastern extremity of Heard Island, directly to the east of McDonald island.  This is Australia's second currently active volcano.

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Earthquake and Fault Line Maps for Australia.

The first reported earthquake in Australia was felt at Port Jackson (Sydney) in June 1788, when Governor Phillip reported:
"The 22nd of this month we had a slight shock of an earthquake; it did not last more than 2 or 3 seconds. I felt the ground shake under me and heard a noise that came from the southward, which I at first took for the report of guns fired at a great distance."
Similar earthquakes were felt in the early days of Adelaide (1837), Melbourne (1841), Hobart (1827) and Perth (1849).

Map of Australia where earthquakes have occured. 1788 to 2008.

Map of Australia where historic earthquakes have occured.
Enhanced Image courtesy of Claire Payne
Environmental Systems & Services Seismology Research Centre(7)

(Grey/White markers) ES&S Historic Earthquake Catalogue.1788 to 2008.
(Red markers) Events recorded by ES&S network from Jan 01 – Dec 31 2009 in Australian Region.
Earthquake locations presented on this map are computed primarily from data from ES&S operated seismic recorders with additional data contributed by Geoscience Australia, PIRSA and the A.S.C. Image thanks to Google Earth. (7)


Earthquakes 1800 to 2003

The map shows earthquakes with Richter magnitudes greater than 3.5 and suggests the higher seismicity and hazard regions are along eastern Australia (in bands running from Melbourne to Newcastle, Brisbane to Gladstone, and Mackay to Cairns), in the Adelaide geosyncline, and in parts of Western Australia. Less seismographs and lower population density during the last century in Queensland relative to eastern NSW and Victoria means that the true seismicity in Queensland compared to eastern NSW and Victoria may be higher than it appears on the map.

Among Australian cities, Adelaide share with Perth the dubious distinction of being the most dangerous place seismically, although on a world scale the risk is slight and the estimated recurrence period of a 1954-sized earthquake is about 100 years.

 
Fault line and Earthquake map of Adelaide South Australia.

Earthquakes from 1980 to 2001.
Image courtesy Office of Mineral Resources  - minerals pir sa gov au

The largest known South Australian earthquake occurred at an epicentre near Beachport in the South-East on 10 May 1897. It has been assigned an intensity of 9 and a magnitude of 6.5.
On 19 September 1902 an earthquake of somewhat smaller magnitude occurred at Warooka on southern Yorke Peninsula. Both the Beachport and Warooka shocks were clearly felt in Adelaide.
South Australian earthquake epicentres occur in two main seismic zones. The major zone, within the Adelaide Geosyncline, extends from Kangaroo Island through the Mount Lofty Ranges and Flinders Ranges to Leigh Creek.
The second seismic zone is on Eyre Peninsula where some epicentres may be associated with the Lincoln Fault. There are two other zones, one near Kingston SE, and the other in the Simpson Desert in the far north - possibly the most active seismic zone on the Australian continent.
Source:  "Atlas of South Australia | Natural Hazards"   http://www.atlas.sa.gov.au/

Earthquake hazard map of Australia.


 Greater than 0.10   Between 0.05 and 0.10   Less than 0.05 
High
Medium
Low

The numbers, e.g., "greater than 0.10”, refer to the ground acceleration (measured as a fraction of the Earth’s gravitational acceleration, g, i.e., 1.0 g = 9.8 m/s2) with a 10% probability of being exceeded in 50 years.



Distribution of Intraplate faults (5)

Earthquakes occur in Australia even though the nation does not sit on a tectonic plate boundary.
The nearest boundary passed through Papua New Guinea to the north, into the Pacific Ocean and south to New Zealand.
Australia experiences "intraplate earthquakes" along fault lines dating back millions of years when parts of the country were on or near plate boundaries.
The greatest earthquake risk in Queensland is in Central Queensland.
A fault line just 30 kilometres west of Bundaberg ( the origin of a quake at least 5.4 in magnitude in 1935 ) has the potential for another large earthquake.  Source: Central Queensland Seismology Research Group  April 24, 2009

"There are probably lots of active faults that could generate earthquakes in places that haven't had earthquakes yet."  Source:  Professor Paul Somerville, Macquarie University.

 Major Geological Fault Lines located in south eastern Australia.

Map of South Eastern Australia showing Major Earthquake Fault Lines
 
Image courtesy of (6)  Source: Gray_et _al : Victoria,Paleozoic rocks.
 
 

Geological Fault Lines in the vicinity of Melbourne and surrounding towns.


  Fault Line and Mineral Resources Map of Victoria click here to enlarge.

Some of the fault lines around Melbourne are:
Selwyn's Fault and the parallel Tyabb Fault - Mornington Peninsula.
Beaumaris Monocline transected by the perpendicular Melbourne Warp under the south-eastern suburbs.
Multiple fault lines running from Gippsland to the eastern aspect of Westernport Bay.
Rowsley Fault - north-west of Geelong running northwards to Bacchus Marsh.
Barrabool Fault - running west from Geelong to Colac
Bellarine Peninsula fault, parallel to Selwyn's Fault.
Torquay Fault - running along coastline.


Geological cross-section along the Burnley Tunnel of the Melbourne City Link.
Source:  Gondwana break-up and its aftermath.   M. L. Cupper and S. White (Coordinators) and J. L. Neilson
 
Tectonic plates

Tectonic plates

The Earth’s surface consists of interlocking plates. Most plates comprise both continents and ocean floors. The original concept of continental drift emphasised continents because that was where the rocks were mapped and the connections drawn. However, we now use the term ‘plate tectonics’ because it is the plates that are moving, and the continents are being carried upon them. The main plates are named in the figure.

Two major, modern mountain belts have formed at convergent margins: the Himalaya and the Andes. The Indo-Australian plate carries two continental masses (Australia and India) and three smaller masses (Papua New Guinea and the north island and the western side of the south island of New Zealand).
To the south of Australia the ocean floor is spreading as the Indo- Australian plate moves away from Antarctica. To the north, the plate is converging with Asia. The plate motion shown is as measured at Darwin: 67 mm/yr in the direction 35° east of north.


Tectonic blocks and Fault lines of the Asia - Pacific Region.

Tectonic plates

Tonga in regard to the large tectonic blocks of the new global tectonics.
Heavy lines are island arcs or arc-like features.
Tensional (divergent arrows) and compressional (convergent arrows) indicate relative movements at margins of blocks;
length of arrows is roughly proportional to rate of relative movements. Some historically active volcanoes are indicated by X.
Open circles represent earthquakes that generated tsunamis (seismic sea waves) detected at distances of 1,000 or more kilometres from their source. The six major tectonic blocks are shown Modified from Isacks, Oliver, and Sykes (1968).

 
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Experts warn a major earthquake could hit Australia's capital cities.

According to Seismologist Dr Kevin McCue of Central Queensland University in Rockhampton, the Australian continent is hit by a magnitude 6 earthquake every five to six years and currently, one is overdue, " so we're just waiting to see what will happen in Victoria ", and he thinks that it is just luck we haven't had an earthquakes under Melbourne and Sydney.
Earthquakes frequently occur close to plate boundaries, where the plates that make up the earth's crust push and slide against each other.
Despite sitting in the middle of a tectonic plate, scientists say Australia is subjected to the stresses and strains from movements at the edges of plate boundaries. "Compared to Canada, US, South Africa, central Africa and India, Australia is more active,"

US seismologist Professor Paul Somerville, deputy director of Risk Frontiers, based at Macquarie University in Sydney, says Australia is under "quite high tectonic stress". "As is the case in other stable regions, the earthquake activity appears to be generally higher around the margins (edges) of the continent than in its interior," he says. "Since Australia's population is more concentrated on its coasts than other stable regions, this by itself presents a higher hazard level."

Australians are "complacent" to the risks posed by earthquakes and that one could strike a major city, say earthquake experts.
The warning comes after two moderate-sized earthquakes recently struck the Gippsland town of Korumburra in southeast Victoria. 06/03/2009
Both were felt 120 kilometres away in the city of Melbourne.
The earthquakes registered magnitude 4.6 on the Richter scale, with another small earthquake felt in the area in January 2009.
Both struck 15 kilometres below ground and were associated with uplift of the Strzelecki Ranges.
Source:  Australians 'complacent' to earthquakes  ABC Science  Friday, 27 March 2009

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The big earthquake still building South East Australia


Epicentres of Australian earthquakes in the period 1859 to 1992 with magnitudes of ML4 or greater.(Illustration courtesy AGSO)

Two separate geological studies have concluded that an area from Adelaide to south-east Victoria is seismically active and the next
'big one' could endanger lives and infrastructure.

Contrary to the popular notion that Australia is an ancient continent that has for millions of years been geologically comatose, University of Melbourne geologists have uncovered evidence that parts of South-eastern Australia recently stirred from their geological slumber and are in an active mountain building phase. These mountains are being shaped by earthquakes, some reaching greater than 6 on the Richter scale.

"When these big quakes reoccur, they have the potential to cause catastrophic damage to cities such as Melbourne, Adelaide, and the La Trobe Valley area, which straddle some of these major faults lines," says Professor Mike Sandiford, who conducted one of the studies.

Possibly, the most dramatic indication of this geological stirring, which the studies estimate began suddenly about ten million years ago, can be found in the landscape of the Mount Lofty Ranges near Adelaide.

"Some faults around Adelaide have moved slabs of the continent up to 30 metres in the last one million years," says Sandiford.

"A typical earthquake of magnitude 6.0 might produce a displacement of about one metre. Thirty metres is equivalent to 30-50 big earthquakes in the last million years," he says.

Other areas of intense mountain building have been around Victoria's Otway Ranges, Mornington Peninsula and Strzeleckis. In some of these areas, similar uplift and erosion over the last 10 million years have thrust chunks of Australia upwards in the order of one kilometre.

Tectonic movements have pushed the Otways 250 metres higher in the last three million years, and The Selwyn fault, which runs from Mt Martha, on Victoria's Mornington Peninsula, east to the Dandenong Ranges has possibly produced six metres of uplift in the last 100,000 years.

"This is potentially six big earthquakes," says Sandiford.

"We are still trying to determine the slip rates along these fault lines, but our evidence so far suggests that we should expect, on any one of the major faults, a large earthquake every 10-20,000 years. The estimated return period of a quake greater than 6.0 in south-east Australia is about 30 years, but none have been recorded in the last 100 years," he says.

"Most earthquakes experienced by this region are less than three on the Richter scale and occur several times a year. It is unusually quiet at the moment with nothing over 1.5 for the last few months."

Sandiford's evidence for the mountain building comes from extensive airborne geophysical data that measure radioactivity and magnetic field of the soil and rock. Rocks of different ages and types display different levels of radioactivity and magnetic properties. Faults and uplift which bring older rocks to the surface or bury younger strata can be detected through such measurement.

A second study led by the University's Dr Malcolm Wallace investigated sediments and seismic data from petroleum surveys to determine the long-term history of earthquakes and seismic activity in South East Australia.

Evidence of faulting, buckling and uplift can be clearly seen in the young sediment record from this region. The team obtained an age for the various faults and folds by using a combination of fossils and radioactive isotope dating methods.

The findings confirm that the young mountain building and earthquake activity began around 10 million years ago and continues to the present day.

"This young faulting and folding has had very important economic effects for Australia. The giant oil and gas fields of the Gippsland Basin are largely trapped in young geological deformations produced by the seismic activity. Faulting, however, can also rupture the reservoirs and cause leakage.

"In the La Trobe Valley it is this tectonic activity that has made the thick sequences of brown coal that Victoria relies on for its power generation economically accessible," says Wallace.

In the Murray Basin, the same activity was largely responsible for the heavy mineral deposits such as titanium and rare earths. It also caused the damming of the Murray River only 60,000 years ago forming the Barmah Swamp near Echuca, Victoria.

"While this is still nothing compared to the activity along the plate margins of, for example, New Zealand and California, it defies the notion that Australia is an inactive continent."

Dr Wallace's research team is Julie Dickinson (PhD student) and Dr Guy Holdgate, all from the University's Department of Earth Sciences.

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Other Articles
Drought and Bush Fires in Victoria 1851 Black Thursday
Chronology of Australian Major Bush fires
Chronology of Australian Major Droughts
Archaeological site at Mount William Stone Hatchets.
Megafauna bones found at Lancefield - Giant Kangaroo.


Source for cited articles and reference material:
Reference:  Bernie Joyce School of Earth Sciences The University of Melbourne   http://web.earthsci.unimelb.edu.au/Joyce/joyce.html
(1) Source: Australian Natural Resources Atlas  http://www.environment.gov.au/index.htm
(1a) Source: 17th Australian Geological Convention  4 February 2004
(2) Source: Australian Natural Resources Atlas  http://www.environment.gov.au/index.htm
(3) Source: Science Alert  http://www.sciencealert.com.au/news/20092109-19788.html
  Accessed 24th Sep 2009
(4) Source: Humans and Volcanoes in Australia and New Guinea.  Peter Bindon and Jean-Paul Raynal
(5) Reference: Geoscience Australia http://www.ga.gov.au/
(6) Source: Gray et al Chapter 2  Structure, metamorphism, geochronology and tectonics of Palaeozoic rocks. ftp://129.78.124.227/.../Gray_etal_Victoria_Paleozoic_rocks_GeolVic.pdf
(7) Source: Seismic Network Report 2009 Compiled by Claire Payne Environmental Systems & Services Seismology Research Centre  http://www.aees.org.au/Articles/Payne_ESS-SNR_2009.pdf
• Reference:  ABC Science Online  http://www.abc.net.au/science/news/
• Reference:  Geoscience Australia  http://www.ga.gov.au/
• Reference:  Australian Antarctic Division  http://www-new.aad.gov.au/default.asp?casid=2099
• Reference:  Australian Antarctic Division  http://www-new.aad.gov.au/default.asp
• Reference:  Global Volcanism Network's
  http://users.bendnet.com/bjensen/volcano/indian/indian-heard.html
• Reference:   Volcanoes & Earthquakes in SE Australia  http://www.seismicity.segs.uwa.edu.au/welcome
• Photograph of South Australian Volcano
Courtesy.  Office of Minerals & Energy Resources, South Australia.
• Images from poster by B. Joyce (University of Melbourne), Cities on Volcanoes Conference, Auckland, N.Z. Feb 2001
• Map courtesy.  http://www.ga.gov.au/archive/volcanoes/
• Map Tasmania fault lines courtesy. The Lake Edgar Fault:  ANNALS OF GEOPHYSICS, VOL. 46, N. 5, Oct 2003
• Reference:  Sutherland, L., 1995, The Volcanic Earth: Sydney, University of New South Wales Press, 248 p.
• Reference:  Johnson, R. W. (ed) 1989a. Intraplate alkaline volcanism in eastern Australia and New Zealand. Cambridge University Press, Sydney, 408pp.
Source: http://halshs.archives-ouvertes.fr/docs/00/03/40/67/PDF/Australie_volcans.pdf
Source: ABC Science Online http://www.abc.net.au/science/news/stories/s1042020.htm
Image:  Seafloor Imaging  Courtesy Geoscience Australia  http://www.ga.gov.au/
Source: Gill, E.D., 1955. Radiocarbon dates for Australian archaeological and geological samples. Aust. Jour. Sci. 18:49-52.
Source: Sutherland, L., 1995. The Volcanic Earth. (University of New South Wales Press, Sydney)
References and further reading.
United Nations - Asian and Pacific Training Centre for Information and Communication Technology for Development.
United Nations - ICT for Disaster Management: Real life examples © IDD-ESCAP, 2011
Download: United Nations - ICT for Disaster Management: Real life examples © IDD-ESCAP, 2011
•  Ashley, P. M., Duncan, R. A., Feebrey, C. A., 1995. Ebor Volcano and Crescnet Complex, northeastern New South Wales: age and geological development. Australian Journal of Earth Sciences 42, 471-480.
• Ernst, R. E., Buchan, K. L., Campbell, I. H., 2005, Frontiers in large igneous province research. Lithos 79,
• Ferrett, R. R. 2005. Australia’s volcanoes. New Holland Publishers (Australia), Sydney, 160pp.
• Johnson, D., 2004. The geology of Australia. Cambridge University Press, Cambridge, 276 pp.
• Johnson, R. W. (ed) 1989a. Intraplate alkaline volcanism in eastern Australia and New Zealand. Cambridge University Press, Sydney, 408pp.
• Johnson, R. W. 1989b. Volcano distribution and classification. In: Johnson, R. W. (ed), Intraplate alkaline volcanism in eastern Australia and New Zealand. Cambridge University Press, Sydney, 7-11.
• Johnson, R. W., Taylor, S. R., 1989. Introduction to intraplate volcanism – preview. In: Johnson, R. W. (ed), Intraplate alkaline volcanism in eastern Australia and New Zealand. Cambridge University Press, Sydney.
• Lewis, G. B., Mattox, S. R, Duggan, M., McCue K. 1998. Australian volcanoes educational slide set. Australian Geological Survey Organisation, Canberra
• Sutherland, F. L. 1998. Origin of north Queensland Cenozoic volcanism: relationships to long lava flow basaltic fields, Australia. Journal of Geophysical Research 103, 27347-27358.
•  The Volcanism Blog:  Australia ‘overdue’ for volcanic eruption?




Volcanoes and Earthquakes.  (30 pages)

by Romsey Australia
is licensed under a Creative Commons Attribution 2.5 Australia License.


     

Updated and Revised 10-07-2012