Why are there very few volcanoes and earthquakes in Australia?

Answer 1

Australia does experience earthquakes, but not as severely or as commonly as in say Japan, Iran or New Zealand. Meckering WA in 1968 and Newcastle NSW 1989 were two earthquakes which caused severe damage, and loss of life in the case of Newcastle, largely because Australian building codes generally do not take into account earthquakes because their frequency is so low. There were two minor earthquakes off Broome WA and in Gippsland Vic in March 2009.

Essentially, Australia is situated far from tectonic plate margins which are the "hotspots" for severe earthquakes. Stresses can develop away from plate margins, which is why the continent can experience relatively minor earthquakes. Because Australia is centrally located on one of the shields of the earths crust. These are old solid parts of the earth's crust where there is no volcanic activity or movement so there is little in the way of seismic activity.

Answer 2

Australia has no active volcanoes because the majority of volcanoes are formed where two tectonic plates meet. This is due to the pressure built up under the plates, and the lava escapes through volcanoes. Australia is in the middle of a plate, therefore there are no joins underneath it, resulting in a lack of active volcanoes. The Pacific Ring of Fire, which extends around the Pacific Basin and marks the major ring of the world's volcanic and seismic activity, just misses Australia. There are many volcanoes in Australia, or at least the remnants of volcanoes resulting from ancient activity, but none of them are active and most have long been extinct. Mt Gambier in southeast South Australia is one such example. Although declared officially "dormant", seismologists and scientists monitor them, even though there has been no sign of activity since European settlement began in Australia. Australia's only active volcano is found on one of its external territories, that of Heard Island. Big Ben is a volcano which resumed eruptions in about 1993.

There have been a number of earthquakes in Australia, but generally they do not cause major damage. Many of them are simply seismic activity many kilometres underground, which do not translate to ground-shaking events on the surface. Melbourne and southeastern Victoria, and the region around Canberra, for example, are hot-spots for deep seismic activity, but no earthquake in the area has caused death or significant destruction. Although Australia is not on the edge of a plate, the continent experiences earthquakes because the Indo-Australian plate is being pushed north and is colliding with the Eurasian, Philippine and Pacific plates. This causes the build up of stress in the interior of the Indo-Australian plate which is released during earthquakes. The most devastating earthquake in Australia was the one that hit Newcastle on 28 December 1989. It measured 5.6 on the Richter scale, and its effects were felt throughout central-eastern New South Wales. There were reports of damage to buildings in Scone, Gladstone and Sydney, which is 800km away. The shaking was even felt in tall buildings in cities over 5000km away. Thirteen people were killed, and 35,000 homes, 147 schools and 3,000 other structures in the region collapsed. Most of the damage and deaths happened when the walls and floors of the Newcastle Workers Club collapsed. Originally, a US report on the earthquake suggested that the disaster was caused by stress resulting from 200 years of underground coal mining. Australian geoscientists disagreed with this claim, claiming that the Hunter Valley has been prone to minor earthquakes for years. Other evidence suggested that the hypocentre of the earthquake lay too deep underground - 12 kilometres - for it to have been caused by mining. Another earthquake of significance hit Meckering, a small town of some 240 people in the Avon valley region of Western Australia, about 130km east of Perth and 24km west of Cunderdin. In October 1968, the town was hit by an earthquake which registered 6.9 on the Richter scale. There were no deaths, mainly due to the small size of the town and its relative isolation, but the earthquake injured 17 people, and caused about $2.2 million worth of damage, which is the equivalent of around $5 million today. The ground ruptured along a length of 40km, up to 1.5m wide and 2.4m high, and the scar from this rupture can still be seen in the landscape today. On 29 April 1941 the town of Meeberrie, Western Australia felt what is believed to be Australia's biggest onshore earthquake, at magnitude 7.2. Being little more than a homestead, no details were reported, but effects of the earthquake included cracked walls, burst rainwater tanks and ground ruptures. On 19 November 1906 a large magnitude 7.6 earthquake hit the Indian ocean off the coast of Western Australia. It is the largest known quake in Australian Territory