Thrust (or Reverse) faults occur in regions of compression (areas where the rocks are squeezing together, or being compressed). The miner could hang his lantern on the hanging wall and stand on the foot wall. The terms hanging wall and foot wall come from ore mining days where many mines were along faults. This top side is called the hanging wall and the lower side is called the foot wall. Since normal faults and reverse faults are typically at steep angles (~60 degrees from the horizontal), one side of the fault lies atop the other side. To help distinguish between an normal fault and a reverse or thrust fault, we give names to each side of the fault and talk about how they move relative to one another. If you cut a slice into the cake and remove the piece, you can all of a sudden see the cake in cross-section (and perhaps that you have a 7-layered chocolate cake on your hands that must be eaten immediately).Ībove, I’ve drawn a fault in cross-section showing the two sides of the fault and its surface expression (the black line between the trees). If you just look down from above, you can only see the icing on top.

In Earth Science, we often want to look at or illustrate things in cross-section because it allows us to look at layers and features below the surface. Here’s a cartoon version of what a fault might look like in cross-section. Before the activity, we’ll start off with the components that make up a fault. While it may seem juvenile, it’s an activity I’ve done in university classrooms. Hopefully they were useful in describing the 3 different types of faults. First off, apologies for the very short videos. Be sure to catch #1 and #2!Īfter the last post on faults, I got some great questions and thought I’d address them here.

Strike slip fault hanging wall footwall