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Tuesday, January 26, 2016

{Geologic!} Hotspot in Eastern Australia, Bass Strait, and Tasmania

         Hotspots within continental plates are not just for Wi-Fi ;-) or for the famous Snake River Plain-Yellowstone Caldera any more. . .



      The ages of the volcanic eruptions in the northwest U.S. range from 16.1 million years on the west end (dark green) to 0.6--2.1 million years at the east end (yellow) in Yellowstone. The continental plate records the location of the underlying hotspot and possible mantle plume as the continental plate moves generally westward.






      As reported in the September, 2015, issue of "Nature", the eastern Australia south-southwestern series of extinct volcanos extends from Queensland 





at the north end of Australia 2000 kilometers through the eastern middle of the continent toward Cosgrove volcano and southward into the Bass Strait and possibly into the island of Tasmania.




     The northernmost volcanoes are 33 million years old and the Cosgrove volcano to the south is 9 million years old. The Australian plate 





      is moving north-northeastward at a very high rate of 7 centimeters per year. Currently, the Australian plate is one of the fastest moving tectonic plates as evidenced by a span of 24 million years from north to south over a distance of 2000 kilometers.
      The "Cosgrove Track," extending the entire length of Australia is more than three times the length of the Snake River Plain-Yellowstone Caldera. That Australian plate is smoking!

       The East Australia hotspot has both explosive eruptions, as well as the pahoehoe lava flows similar to the Hawaii hotspot (located within an oceanic plate). The hotspot is explosive because basaltic magma interacts with groundwater in aquifers below the surface producing violent magmatic eruptions.



     What puzzles me most is that it took so long to connect the northern and southern Australian volcano dots. . .

Your thoughts?
Steph


37 comments:

  1. So, if the southernmost part of the continental crust passed over the presumed magma plume 9 million years ago, why isn't there a string of younger volcanic islands south of Tasmania today?

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    1. I wondered the same thing. . .I believe researchers are looking. . .

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    2. "The researchers are now trying to determine if the lack of a volcano at the plume's current location is caused by the thickness of the lithosphere there."

      "There is some seismicity in this region, there's been some earthquakes around that location recently which does hint that something is going on there, but we haven't been able to find any seamounts or volcanic regions at present," Dr. Davies said."

      The lack of volcanoes in the 700 km between the north and south parts of the chain is hypothesized to be due to a thicker lithosphere in that area. . .

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  2. Steph,
    I cannot open the "dots..." link (?) at the end of your text.

    "Magmatic" is a wonderful word. If you pull the "rug" out from the middle and put it at the end, you get another name for the vehicle in this song.

    Regarding: "That Australian plate is smoking!" It must be smoking Chesterfields.

    LegoMagmanimous

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    Replies
    1. No, it's not a link, Lego. I was trying to highlight the "dots. . ." to look like volcanoes along the hotspot. . .and to echo the ellipsis theme. Yes, I can get a little carried away with that punctuation mark . . .

      Lava your links, btw!

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    2. ". . ." is "S" in Morse Code; maybe that's why I like it, Lego ;-).

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  3. Thanks for all the info! My favorite hotspot will always be Hawai'i, though!

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    1. Yes, I'd agree for a hotspot under an oceanic plate! I especially enjoy the older vegetation on Kaua'i.

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  4. Can the presence of a magma plume be confirmed seismically, the way I can order a CT or MRI on a patient with a suspected mass?

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    1. We typically didn't go that deep in the oil biz and we were mostly looking at sedimentary layers. . .But, theoretically it should be possible if there's a strong delineation between the mantle plume and the surrounding material. Having seismic reach that deep would be the confining factor. . .

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    2. Maybe Australia could open up the outback to North Korea, India, and Pakistan for nuclear testing, generate some nice big seismic waves?

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    3. Ha! Perfect, jan!

      I did find this study of the Tasmantid seamounts (not Tasmanian) east of Australia. The researchers used SONAR BEAMS to map the seamounts along their 2000 kilometer length.

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    4. Too bad RV Southern Surveyor was decommissioned the following year; it might have been useful in the search for MH370.

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    5. True. Some of those photos in the link above under SONAR BEAMS are pretty cool. . .

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  5. "Scientists recently realized that separate chains of volcanic activity in Australia were actually caused by a single hotsput (sic) lurking under the Earth's lithosphere:" from this article in Live Science.

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  6. There's more than one kind of hot spot. We've discussed boudinage before, and this just came over the AP wire. The last line reminds me of Andrei Codrescu talking about "gas food" on NPR.

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    Replies
    1. Open to serendipity here; glad we live in the Boudin Age of "gas foods."

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  7. Replies
    1. Was it wrong to eradicate the smallpox and rinderpest viruses? Even the name Anopheles means "useless"! I'd take my chances, but I don't like our odds. They'll almost certainly outlast us.

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    2. ... And this in spite of the fact that it's NJ's official state bird!

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    3. I go along with getting rid of them.

      You might be bugging ornithologists though with that bird comment. . .

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    4. After what West Nile virus did to some bird populations, they might give me a pass as long as I favor exterminating skeeters.

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  8. Replies
    1. I've found more than one meaning for "phatic". Is there a relation to "emphatic"? Which can be anagrammed to "empathic"? (But not to any Middle Eastern countries or cities, as fas as I know.)

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    2. 'Sup?

      Merriam Webster says "You may also have spotted a similarity to "emphatic," but that turns out to be purely coincidence; "emphatic" traces back to a different Greek verb which means "to show.""

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    3. 'Sup?

      Merriam Webster says "You may also have spotted a similarity to "emphatic," but that turns out to be purely coincidence; "emphatic" traces back to a different Greek verb which means "to show.""

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    4. Oh, Auntie Em, if I only had the courage to be emphatic! Or the heart to be empathic! (Or a brain!)

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  9. That was one freaked-out black bird!

    We are quite white-blanketed here; 14 inches in my backyard.

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  10. Replies
    1. I guess Australia and environs really is quite the hotspot these days.

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  11. I am deep into a post on zebrafish this week but this research from Brown U about deep earthquakes at subduction zones is quite timely: Deep Earthquakes in Subduction Zones, Lawsonite, and Dehydration Embrittlement

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  12. New post titled "A Zebrafish Will Develop Its Nervous System in The Time You Are Awake Today (!)" is up. How has your past 17 hours been?!

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