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Showing posts with label Snake River Plain. Show all posts
Showing posts with label Snake River Plain. Show all posts

Wednesday, June 15, 2016

Larger Super-Eruptions at Yellowstone National Park 8 to 12 Million Years Ago

    A smaller number of giant super-eruptions between 8 and 12 million years ago that could be larger than the colossal eruptions known to have taken place at Yellowstone have been identified in the United States through research led by the University of Leicester.




     The international research team suggests that while the number of volcanic eruptions thought to have originated from the central Snake River Plain in Idaho, USA, is less than previously believed, the 12 recorded giant eruptions were likely 'significantly larger' than research has previously suggested.






     Dr. Tom Knott, Professor Mike Branney and Dr. Marc Reichow, from the University of Leicester's Department of Geology's Volcanology Group, conducted the research with a team of international collaborators from the U. of California, Santa Cruz, the U. of Copenhagen, Denmark and Idaho State University.

     "Using a multi-technique approach, including whole-rock and mineral chemistries, palaeomagnetic data, and radio-isotopic dates, the team has been able to 'fingerprint' individual eruption deposits and correlate these over vast regions (thousands of square kilometers)."




    In establishing widespread correlations, the team drastically reduced the number of eruptions previously thought to have originated from the central Snake River Plain by more than half.



     "The researchers have reported that one of the super-eruptions from the Yellowstone hotspot-track, defined as the Castleford Crossing eruption, occurred about 8.1 million years ago and estimate the eruption volume to have exceeded 1,900 cubic kilometers. 

     "The single volcanic sheet covers an area over 14,000 square kilometers in southern Idaho, and is more than 1.3 kilometers thick in the caldera of the super-volcano."




     "This is just one of 12 giant eruptions reported from the area by the Leicester researchers who show that intense hotspot magmatism caused major crustal subsidence, forming the 100 kilometer-wide Snake River Basin. The team also demonstrates that these eruptions were in fact significantly larger than previously thought and may rival those better known at Yellowstone."

     Dr. Knott said "While it is well-known that Yellowstone has erupted catastrophically in recent times perhaps less widely appreciated is that these were just the latest in a protracted history of numerous catastrophic super-eruptions that have burned a track along the Snake River eastwards from Oregon to Yellowstone from 16 million years ago to present.




    "The size and magnitude of this newly defined eruption is as large, if not larger, than better known eruptions at Yellowstone, and it is just the first in an emerging record of newly discovered super-eruptions during a period of intense magmatic activity between 8 and 12 million years ago."

Ever been to the Snake River Plain or Yellowstone? Ash me no questions. . .
Steph

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