Australia’s Plate Tectonics

Before we knew that Earth was once a “Super Continent” called Pangea, a crazy guy named Alfred Wegener came up with a theory that  the continents were are always moving but very slowly; and that they once use to all be connected. He said this was due to what was called “the continental drift” in which the crust of the earth, also known as the Lithosphere, are separated into plates. It turns out Wegener was right and we now refer to the movement of these plates as plate tectonics.

pangea-continental-drift(httpgeology.compangea.htm)

(The shift of the Continents: Pangaea to Present Day)

As you can see, Australia  use to border India and Antarctica. Over time as the plates shifted (plate tectonics) and as the continents moved (continental drift) Australia eventually ended up in what is now the the India and Pacific Ocean. In relation to the plates, Australia is in the middle of the Australian/Indian plate. Some people may think that since Australia is located in the middle of the plate that its land is stable. This is where people are mistaken. Australia actually recently experience a earthquake with a magnitude of 7.0. according to earthquake.usgs.gov Australia received an earthquake on Saturday, February 09, 2013 at 02:26:39 AM. Some people may ask “how is it possible for Australia to receive a earthquake when its not on a plate boundary? The answer to this question are faults. A fault is a crack in earths crust, it happens from putting so much stress on a rock that it just eventually snaps and breaks.  Australia is a geologically active continent containing moving fault-lines, a long history of mountain making, and has regular seismic activity.

au_faultllines

(fault lines located in Australia)

One well known fault is The Cadell Fault Scarp. According to “Ausralian Govenrment/Geoscience Australia”, “At least five times in the past, the Cadell Fault Scarp has ruptured with an earthquake of Mw1 7.0-7.3.” The Cadell Fault Scarp is located in southern New South Wales on the Riverine Plain. From these five previous earthquakes, the fault has managed to become almost 80km long and up to 15m high.

The type of plate movement that’s causing these earthquakes is called transform interactions. This is when two crusts rub up against each other causing stresses on the crust, which causes them to shake, thus causing an earthquake. There are two other types of plate movement as well, divergent and convergent. Divergent interactions are when two plates are being separated thus causing magma to seep out; this usually happens on the sea floor. Convergent interactions is when two plate collide into each other causing one plate to sub-duct under another which causes the two crust to rise thus creating mountains or volcanoes. Both of these interactions happen in the “Ring of Fire” which is located right on the Australian/Indian plate. Since Europeans have settled on the main land of Australia there have been no volcano eruptions. Yet on the Indian-Australia plate volcanoes have been erupting for the past 33 million years.

Nz1

movement of the plates boundaries
triangles= subvergent
(<— —->) = divergent
(<—-
—–>)=
transformant

If you look at a map that determines the age of the volcanoes you will notice that the volcanoes have been getting younger the more they move south. This determines that there is a hot spot that has been moving along that area for years and its been feeding magma to these volcanoes. A hot spot is an area in the upper mantle, ranging from 100 to 200 kilometers in width, from which magma rises in a plume to form volcanoes. As I said before there have been no recent eruptions on the main land of Australia, but according to “Volcanoes of Australia” the most recent eruptions in Australia were at Mounts Schank and Gambier of the Newer Volcanic Province of Victoria and South Australia.

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