"...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
Select an article on this page.
Volcanoes.
1: The Western Victorian Volcanic Plains.
2: Is there a risk of a volcanic eruption ?
3: Australian Volcanism over the last 60 million years.
4: Australia's hotspot and the creation of a new volcano.
5: Seafloor Imaging - Topography of South East Australia.
6: Active Australian Volcanoes.
Earthquakes.
7: Earthquake and Fault Line Maps for Australia..
8: Fault Line Map for Port Phillip and Burnley Tunnel.
9: Fault line and Earthquake map of Adelaide South Australia.
10: The big earthquake still building in South East Australia.
11: Tectonic plates and Fault Line Map for Asia - Pacific region.
12: Earthquake could hit Australia's capital cities.
Other related articles.
Human Induced Earthquakes - Seismic activity.
Why does the Mt.Gambier Blue Lake change colour ?
View all Alerts and News Feeds
Daily Australian Earthquake activity Reports
Daily Earthquake activity Reports latest news feed
View Local and World Earthquake Monitor and Maps
Fault Line and Gold fields
Map of Victoria.
Recent Volcano Observatory Activity Reports
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.
| 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 |
Is there a risk of a volcanic eruption ?
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/
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)
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).
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
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.
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.
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.
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.
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).
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.
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/
| Greater than 0.10 | Between 0.05 and 0.10 | Less than 0.05 |
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.
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.
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.
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.
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).
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
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.
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
• 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.
(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
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?
