BLOG # 1 - Newer Volcanic Providence of Victoria, Australia

Australia sits directly on top of the Indo-Australia plate, which is currently moving north at a rate of 7.5cm/year by subducting, or sinking, underneath the Pacific and Indo-Asian plates (Volcano World).

The black arrows indicate the Indian-Australian plate is moving north, and underneath the Pacific plate. While the opposing arrows at the bottom of the image indicate the divergence between the Antartica plate and the southern edge of the Indian-Australian plate.  The northern movement of the Indian-Australian plate is relevant to the volcanic development along the eastern coast of the Australian island.

Photo Credit: http://volcano.oregonstate.edu/vwdocs/volc_images/australia/volc_australia.html

 A hotspot is a stationary location where magma rises up from the mantle through weaker spots in the earth’s crust causing exterior volcanic activity.   Volcanologists have identified a solitary hotspot that created the Newer Volcanic Providence in Southeastern Australia. 

Photo Credit: http://en.wikipedia.org/wiki/East_Australia_hotspot
Text cropped into corner of image credited to: Julia Johns

The physical markings of plate movement are demonstrated by the linear development of volcanic regions from northern Australia, with the youngest volcanoes on the southern coast of Australia and even younger volcanoes on the island of Tasmania. The two images below demonstrate the northern movement of the Australian plate to create the linear volcanic development from north to south, due to the stationary hotspot as the continent travelled for millions of years over the hotspot.

http://volcano.oregonstate.edu/vwdocs/volc_images/australia/volc_australia.html

As the plate moves over the hotspot of rising magma, a chain of volcanoes is formed

Photo Credit: http://en.wikipedia.org/wiki/File:Hotspot(geology)-1.svg

Mount Shank is the youngest volcano on the southern coast of Australia because it was the last volcano to erupt on the island around 5,000-7,500 years ago.  All the volcanoes along the Newer Volcanic Providence are considered to be dormant.

http://www.seismicity.see.uwa.edu.au/welcome/seismicity_in_australia/volcanoes_and_earthquakes_in_southeastern_australia


"Mount Schank's cinder cone-shaped landform is a rare South Australian example of volcanic activity in recent geological time" (DENR, Australia)


http://www.environment.sa.gov.au/Heritage/Heritage_places_and_areas/State_heritage_areas/Mount_Schank




In geological timeline, all of the volcanic and tectonic plate development described above happened relatively recently, but spans eons of human history.  Since the hotspot is no longer underneath Victoria, Australia, the threat of volcanic activity threatening urban life is non-existant. 
The final image of Mount Shank even depicts agricultural and irrigation development across the cone, which is protected geological/historical land under the Victorian providencial government Department of Environment and Natural Resources. 


It is still debatable whether the Newer Volcanic Providence should be considered "dormant" or "extinct" because there is no foreseeable threat to human life but scientists cannot prove without a doubt that the volcanic chain will never be active again.

Works Cited

Australia, D. o. (n.d.). Mount Schank State Heritage Area. Retrieved from http://www.environment.sa.gov.au/Heritage/Heritage_places_and_areas/State_heritage_areas/Mount_Schank

Volcano World. (n.d.). Retrieved from Oregon State Volcanology: http://volcano.oregonstate.edu/vwdocs/volc_images/australia/volc_australia.html

Geography Comic

This is purely for amusement - and not intended to be part of the first blog assignment due this Tuesday 2/14/12.


photo credit: Bizarro. Dan Piraro.

According to www.marianatrench.com, the Mariana Trench measures at 11,033 meters or 36,201 feet.

Works Cited:

http://www.marianatrench.com/mariana_trench-oceanography.htm

BLOG # 2 - Twelve Apostles

The southern coast of Australia is layers of limestone sedimentary rock which you can see as the lighter and darker layers in the first image below.  Sedimentary rocks contain joints at the different layers because each layer has different levels of hardness, allowing weathering forces to take advantage of the weaknesses of the rock.  These joints are responsible for the development of the Twelve Apostles along the Great Ocean Road in southern Australia.

Photo Credit: Janet Julia Kennedy

Ten to twenty-five million years ago, the coastline of Australia was where the stacks exist in the middle of the ocean, and has since eroded from the relentless power of the Southern Ocean waves crashing into the limestone. The erosion is a form of chemical weathering called dissolution which the rock is  completely dissolved by water. The distance between the stacks and the mainland is how far the ocean has eroded the coastline of Australia. With each subsequent wave, the softer rock is broken down and washed away into the Southern Ocean.   Over millions of years, the waves eroded the base enough to create caves, which you can see in the image below.

Photo Credit: Janet Julia Kennedy, photo of informational sign at Port Campbell National Park: tourist viewing area of the Twelve Apostles

Photo Credit: Dr. Casey Allen's February 16, 2012 class lecture, edited for accuracy

As the caves grow, the denser parts of the limestone are left behind creating arches between the pillars/stacks and the mainland. As the arches thin, they will ultimately collapse into the Ocean. When the arches collapse they leave behind only stacks of rock that are, as of today, about 450 feet tall.  

As discussed in the video, new stacks are constantly being formed because wave erosion is creating arches from the existing stacks.  You can see the waves breaking through one of the stacks about one minute into the video.  Eventually the arch in the picture below will collapse, creating two stacks out of one.  Over the next couple million years, all of the current stacks will collapse, but new ones will form out of the mainland.

Photo Credit: Janet Julia Kennedy

The Twelve Apostles have been an incredible tourist attraction for Victoria, Australia, making up a substantial portion of the $800 million tourist revenue that the Great Ocean Road provides annually.

http://articles.cnn.com/2005-07-04/world/australia.apostles_1_australian-state-stacks-sea?_s=PM:WORLD

http://www.vnc.qld.edu.au/enviro/landform/landf-su.htm