![]() We give each sense of motion its own name: Right-Lateral or Left-Lateral. On the other hand, the circle with the X inscribed is what you’d see if an arrow was moving away from you (the X represents the tail feathers).Īs you could imagine, there are two ways strike-slip faults can move. You can remember which is which by thinking of archery: the circle with a dot in the center is the view you’d have if an arrow was coming toward you. These symbols are commonly used to represent motion in or out of the board, page, screen, etc. ![]() In the diagram below, the left side of the fault is coming out of the screen (denoted by the circle with a dot in the center), and the right side of the fault is moving in to the screen (denoted by the circle with the X in the center). They occur in regions where the two sides of the fault move past one another. Strike-slip faults are almost always nearly vertical ( dip of 90 degrees). For normal faults, the hanging wall moves DOWN relative to the foot wall. Normal faults typically have a dip of about 60 degrees (similar to reverse faults). Normal faults occur in regions of extension (areas where the rocks are pulling apart, or extending). For thrust and reverse faults, the hanging wall moves UP relative to the foot wall. **Remember a blind fault is one that doesn’t reach the surface or have any surface expression. The angle (from the horizontal) at which a fault occurs is called the dip. Below, you can see the difference between the angle of thrust and reverse faults. Thrust faults and reverse faults are the same, except thrust faults occur at shallow angles (~30 degrees from horizontal) and reverse faults occur at steeper angles (~60 degrees from horizontal). 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.
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |