Episode 348 - "Hot Juicy Magma"

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

Fun Paper Friday