Sunday, January 30, 2011

What are the three types of stress in a rock?

The three types of stress in a rock are tension, compression and shearing.

Tension: Pulls crust, stretching it so that it becomes thinner in the middle. The plates are going opposite directions.

Compression: Squeezes rock until it folds or breaks. The plates are moving against each other.

Shearing: Stress that pushes a mass of rock in two opposite directions.

How does tension change the shape of the Earth’s crust?

Tension pulls the crust in two different directions. This makes it cover more area but become thinner. It’s like a rubber band, if you stretch it, it becomes a lot longer. However, it also becomes a lot thinner and weaker. Tension is caused by two plates moving away from each other.

Compare the way that compression affects the crust to the way that tension affects the crust.

Compression pushes the plates together. This makes the plates take up less space, but take u more volume. Imagine that you had a piece of play dough. Compression would be if you pushed the dough together, creating a fat blob. Tension, however, would be the opposite. Tension is when the plates move away from each other. Using play dough, this would be stretching it out and pulling it from opposite directions. The stretched out dough is going to cover up a lot more space than the fat blob dough, but the fat blob dough is going to be a lot thicker and denser than the stretched out dough.

What is a fault?

A fault is a break in the rock of the crust where rock surfaces slip past each other

Why do faults often occur along plate boundaries?

Most faults occur along the plate boundaries, where the forces of plate motion push or pull the crust so much that the crust breaks.

What type of fault is made when plates diverge, or pull apart? What type of a fault is formed when plates are pushed together?

When compression is occurring, or when plates are pushed together, a reverse fault is formed. In a reverse fault the hanging wall is sliding above the footwall. When tension is occurring, or when plates are pulled apart, a normal fault id formed. In a normal fault the hanging wall is sliding underneath the footwall, and the footwall is above the hanging wall and is sliding upwards.


Name five kinds of landforms caused by plate’s movement.

Types of landforms: Mountains, valleys, volcanoes, plateaus, cliffs, and tsunami.

What are three landforms produced by compression in the crust? What landform is produced by tension?

Compression: mountains, volcanoes, tsunami

Tension: rift valleys, volcanoes, seafloor spreading


Where do the major earthquakes occur?

After analyzing the data below I have found out that the major earthquakes happen mostly in the areas of compression. On the map I found 8 areas of compression, 6 areas of tension, and 3 areas of shearing. The main earthquakes, the 9.5 earthquake in Chile and the 9.2 earthquake in Alaska were also in areas of compression.

6 comments:

  1. Thank you so much for this great explanation! It gave a lot of clarity as I'm preparing to teach about tension to my children in a homeschool geology lesson.

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  2. where did you get the normal reverse and strike slip diagrams, I was looking for a reference

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  3. Thank you very much for the explanation

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  4. Thanks for your help needed it a lot for homework ;)

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  5. Ya this was really great thanks a lot -_-

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