Thread by @sandramcgeo

It’s #FridayFault time again and I’ve rediscovered our collection of fabulous wooden block fault models 🤩 a mini thread of videos for teaching intro #geology 👇 1/11

Faults are described by both orientation (dip and strike of the fault plane itself) and displacement (amount and sense of movement) In this model the fault plane dips ~45 degrees .. 2/11

If the movement (slip) is all in the direction of the strike, it’s called a strike-slip fault .. 3/11 #StrikeSlipFault

If the movement (slip) is all in the direction of the dip, it’s a dip-slip fault. If the movement is up dip along the fault plane, this is a reverse fault (if a reverse fault dips shallowly <30 degrees, we can further term it a thrust fault) .. 4/11 #ReverseFault

If the movement (slip) is downwards on the fault plane in the direction of the dip, it’s a normal fault .. #NormalFault If a normal fault dips shallowly <30 degrees, it’s a detachment fault .. 5/11

Of course, there could be movement (slip) in *both* the direction of the strike *and* the direction of the dip, this is oblique slip and can be normal (down-dip) .. 6/11

Or reverse (up-dip) .. 7/11

Other fault terms we use include the hangingwall (for the block of rock above the fault plane) and footwall (for the block of rock below the fault plane)

In normal faults the hanging wall moves downdip, in reverse faults the hangingwall moves updip .. 8/11

Faults are often associated with the formation of crushed rock (breccia or gouge) and slickensides, which are small scratches on the fault surface, that can help us work out the fault movement direction if we can’t see marker beds on either side .. 9/11

The direction of movement of the fault often reflects the stress regime, so we use faults to interpret regional and local stresses and from there, larger scale tectonics! 🌏 .. 10/11

Faults are cool 😎 #FridayFault .. 11/11