Faults and FoldsBends and Breaks

First, rocks are laid down and organized in

units. Sedimentary rocks are laid down in layers like a cake

by wind and water. This process is called DEPOSTION

Igneous rocks are spread over large areas like maple syrup by VOLCANIC ACTIVITY.

Metamorphic rocks gradually change from one place to the next by extreme geologic events

Rock units and large areas that consist of one kind of rock created by geologic events that happened millions of years ago.

You can walk for miles and miles and just see one kind of rock.

Faults and Folds are what

BEND and BREAK up rock units.Fault Fold

FRACTURE and FLOW

Fracture

Fracture happens when rocks are at the EARTH’S SURFACE and they are COOL.

Fracture is what happens when rocks BREAK!

Fracture = Faults

Flow

Flow happens when rocks are deep UNDERGROUND and they are very HOT.

Fracture is what happens when rocks BEND!

Flow = Folds

Forces in the Earth

Faults and folds happen when masses of rock are colliding, being pulled apart, or sliding next to each other.

Faults and folds happen when there are COMPRESION, TENSION or SHEAR forces. COMPRESSION happens when two plates collide (Are

pressed together)

TENSION happens when two plates SEPARATE (are pulled apart)

SHEAR happens when two plates slide past each other

Let’s see this in action

http://scign.jpl.nasa.gov/learn/plate5.htm

FAULTS

Faults are the result of FRACTURE. They are the result of forces in the earth that BREAK rocks. Fracture happens when rocks are cool.

There are 3 major types of faults:

Normal = Compression

Reverse = Tension

Slip-strike = Sheer

Normal Fault

Normal faults occur when two plates PULL AWAY from one each other.

They are caused by TENSION forces

Reverse Fault

Reverse faults occur when two plates are PUSHED together

Reverse Faults are caused by TENSION forces

Strike-Slip Faults

Strike-Slip faults occur when two plates slide past each other

Strike-Slip faults are caused by SHEAR forces

Let’s see it in action:

http://www.iris.washington.edu/gifs/animations/faults.htm

FoldsFolds are the result of FLOW. They are caused by

the same forces as faults, except they happen deep UNDERGROUND where it is very hot. Because it is hot, the rock bends instead of breaking.

There are two parts to a fold:

The ANTICLINE is the top of the fold (think: ANTHILL)

The SYNCLINE is the bottom of the fold (think: SIN)

ANTICLINES and synclines

Anticlines are at the top (they are the Anthills)

Synclines are at the bottom (sin = hell = bott0m)

Now, go back through your sketches and

label your faults and folds

Ready to test your knowledge?