Warmup 11/2/15 Explain what has caused what you’re seeing in this picture. Try to get as specific and detailed as you can. Objective Tonight’s Homework To learn the basics about earthquakes and faults p 126: 2, 5, 6 p 130: 3, 4

Earthquakes and Stress Fractures What is an earthquake? It’s related to plate tectonics. Shown here is the San Andreas fault. These two major plates are trying to slide past each other. But this isn’t smooth. The crack here is full of rough, huge rocks that catch against each other and lock together.

Earthquakes and Stress Fractures Imagine you’re pulling on a door that’s gotten stuck. If this was a normal door, you’d be able to open it slowly and normally and there’d be no danger. But if the door is stuck and you pull hard enough, eventually it will jerk open. The door will move suddenly and you could get hurt in the process.

Earthquakes and Stress Fractures In an earthquake, we’re getting Earth’s plates doing the same thing. They’re trying to move past each other, but they’re getting stuck as rocks grind together. Eventually, the pressure pushing both plates builds up until the rocks can’t take it any more and break. The plates jerk suddenly, moving as much as several feet. This huge jerk causes ripples to spread outward, shaking rock and breaking things as they go.

Earthquakes and Stress Fractures What makes some earthquakes worse than others? Part of it depends on how ductile – or stretchy – the rocks are. Rocks? Stretchy? Seems crazy, but check out these metal bolts to to the right. The bottom one has been stretched by strong machines. Some types of rocks, or rocks at certain temperatures are quite ductile, and just squish under pressure instead of snapping. It’s the rocks that snap that cause worse earthquakes because they build up more force before breaking.

Earthquakes and Stress Fractures So earthquakes happen when plates rub together and rocks break. There are several ways that this break can happen. We call these faults. There are 3 basic kinds of faults. A normal fault is where we have the “underneath” section of land slide upwards, creating a slope or ridge between the two sections.

Earthquakes and Stress Fractures A reverse fault is similar to a normal fault, but in these cases, it’s the other block that lifts. You can tell if you have a reverse fault, because it will create an overhanging ledge instead of a smooth slope. If the slope is really shallow, we call this a thrust fault. In this case, it looks like one section just slides on top of another.

Earthquakes and Stress Fractures A strike-slip fault is different from both of these. Instead of moving up and down, our pieces are moving sideways compared to each other

Faults Models For the rest of class, Mr. C. is going to get you started on an activity where you’ll be making some models of faults. Your job for the rest of today is just to get started on coloring these things. Color each of the numbered regions with a different color or pattern. They represent different rock layers.

Exit Question What kind of fault is being shown here? normal inverted reverse strike-slip twist None of the above