Landslides usually involve the movement of large amounts of either earth, rock, sand or mud or any combination of these.
Landslides can be caused by earthquakes, volcanoes, soil saturation from rainfall or seepage or by human activity (eg. vegetation removal, construction on steep terrain).
The rate of movement of a landslide can vary from exceptionally slow - centimetres per year, to a sudden and total collapse - such as an avalanche of perhaps millions of tonnes of debris.
The distance travelled by landslide debris can also vary greatly, from a few centimetres in 'ground slumps', to many kilometres when large mud flows follow river valleys.
Facts and Figures
Since 1842 there have been hundreds of known landslides in Australia.
Between 1842 and 1997 at least 73 people died in 42 landslides and 15 people died in earthquakes in Australia. A further 49 people have been injured in landslides while 170 people have been injured in earthquakes.
Between 1842 and 1997, more than 150 landslides have caused well over $200 million damage to buildings, roads, railways, pipelines and crops. A total of over 200 buildings are known to have sustained damage due to landslides.
Thredbo (1997) - An Australian Case Study
At about 11:30pm on 30 July 1997, Australia's worst landslide occurred when a large section of steep mountainside below the Alpine Way road collapsed immediately above a section of the Thredbo Ski Village in the NSW Alps.
About 1,000 tonnes of earth, rock and trees slipped rapidly down the steep slope, shearing the Carinya lodge off its foundations and slamming it into the Bimbadeen Lodge.
Both multi-level buildings were completely crushed along with many cars in the 400 metre landslide.
Rescue efforts were hampered by further minor slides, and the extremely unstable mass of earth, rock, shattered lodges, trees and vehicles.
Emergency Services secured broken water, gas and oil lines before undertaking a cautious and painstaking search and rescue operation.
Thermal imaging cameras and seismic listening devices were used in an attempt to locate survivors. 55 hours after the landslide, rescuers located a survivor buried in a void below three huge concrete slabs, 2.5 metres below the rubble.
After a further 10 hours of painstaking tunnelling and shoring, the slightly injured man was successfully rescued. He had endured three nights of 12 degrees below celcius temperatures.
Over 7 days of exhausting searching, rescuers recovered the bodies of 18 people who died in this tragic disaster which also caused damage worth many millions of dollars.
What you should do
You can protect yourself, your family and your property by doing the following:
Before occupying a home or building, check with the local Council and neighbours for the area's history of landslides or instability.
In steep areas, look for the tell-tale signs of ground movement such as trees tilting (down-slope), water seepage and breaks in the ground.
If indoors when a landslide begins, shelter at the least-affected end of the building under a strong table or bench (if possible use a mattress for extra protection). Hold on firmly and stay put until all land movement has ceased.
If outdoors when a landslide begins, always take heed of warning signs, and avoid the tops and bases of cliffs and embankments, especially where there are signs of loose rocks or debris. Never stand or sit on rock overhangs unless you are sure they can bear your weight.
If a landslide threatens, move quickly from its path and keep clear of banks, trees, powerlines and poles.
Further information about landslides
Last updated 18 December 2011