Don't Panic Geocast

Episode 348 - "Hot Juicy Magma"

November 6th, 2022
  • Forms in fractures of rocks already in place, so it an INTRUSIVE feature
  • Form at right angles to the direction of extension in the area - nature’s frac jobs
  • Can be super thin or super thick, but generally are self-consistent
  • Can have multiple periods of injection or even multiple compositions of injection over time
  • Can get en echelon patterns, rings, and cones (last two common with caldera volcanism)
  • Magmatic are the most well known and form when magma flows into a crack and cools into a sheet.
  • The igneous rock is generally more weathering resistant so we get cool weathering features
  • Can be rhyolitic, but mostly basaltic
  • Rate of cooling determines grainsize (slow = big) and big near the center
  • Can have columnar jointing
  • Big phenocrysts orient with flow direction - cool! AMS studies show this.
  • These are awesome when you get them radially around a volcano!
  • Horizontal dikes are called sills
  • Clastic dikes are formed by sediments episode 177
  • Can be formed with fluid pressure
  • Cracks in permafrost that fill in

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