Introduction to Volcanoes

Volcanoes or volcanism as stated in our textbook, is closely related to plate tectonics with most volcanoes being located near active plate boundaries.

There are 5 different types of volcanoes:

1. Stratovolcano  
2. Lava Dome
3. Shield Volcano
4. Cinder Cone
5. Continental calderas

All Volcano eruptions are measured by the Volcanic Explosion Index (VEI). Which is a relative scale that measures different eruptions and can be compared based on quantitative and qualitative observations of explosivity. The scale ranges from 0-8 zero being the lowest. The scale is logarithmic based, which means each interval is a 10x increase in volume of ejected materials. 

Australia is home to the world's longest chain of continental volcanoes which has been discovered stretching for more than 2,000 kilometers along eastern Australia. This volcanic chain was created over the past 33 million years, as Australia moved north-northeast over a mantle plume hotspot. 

Volcanoes in Australia: 

 Active volcanoes generally occur close to the major tectonic plate boundaries. They are rare in Australia because there are no plate boundaries on this continent. Nonetheless, there are two active volcanoes located 4000 kilometers south west of Perth in the Australian Antarctic Territory: Heard Island and the nearby McDonald Islands.

Other active volcanoes nearest Australia are in Papua New Guinea, New Zealand, Indonesia and the Philippines. Composite volcanoes and calderas are the most common varieties in the region. These types of volcanoes severely threaten lives, property, agricultural lands and lifelines throughout south east Asia and the Australian region.

Predicting Eruptions:

• A volcano's eruptive history can provide some clues. Because only a small number of the world's volcanoes have a known history it is extremely difficult to predict future eruptions
• Earthquake activity around a volcano can provide valuable information. An eruption can be preceded by hundreds of small earthquakes know as earthquake swarms.
• Small changes in the shape of a volcano such as bulging may indicate that magma is rising.
• Gases emitted at, or near a volcano may show that a magma chamber is refilling or that a new type of magma is rising from depth.

Mantle Plume hotspot recently discovered.

This image shows the seismic activity around Australia, and possibilities of volcanic eruptions 

Sources:

http://www.ga.gov.au/scientific-topics/hazards/volcano/basics 

http://volcano.oregonstate.edu/oldroot/volcanoes/volc_images/australia/volc_australia.html

Natural Hazards 4th edition Keller/Devecchio, Chapter