Landforms, Rocks, and Minerals

Chapter 7

What Makes the Crust Move?

• Earth’s crust is constantly moving, if not in one place then in another. Sometimes it moves quickly enough to be seen and felt (such as an earthquake).

Earthquake

• Earthquakes are related to cracks in the crust called faults. The faults may have formed from earlier earthquakes. Sometimes they form while the earthquake happens.

Earth’s Vibrations

• During an earthquake vibrations travel through the crust. The farther away people are from the earthquake, the harder it is for them to feel the vibrations.

• The vibrations that move through the Earth’s layersare called seismic waves.

• These vibrations are measuredon a machine called a seismograph.

Fault

Seismograph

• A seismograph, or seismometer, is an instrument used to detect and record earthquakes. Generally, it consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not.

Not all motion happens along faults. Often, layers of the crust bend. Bending, like motion along a fault, may happen gradually over time.

To measure crust movement, surveyors measure elevation—how high a place is above sea level.

They leave plaques called bench marks that tell the exact location and elevation of a place. When some bench marks are remeasured, they are found to have risen or sunk.

• Geologists are scientists who study the Earth.

Tools of the Trade

Geologist Estwing Rock Hammer

Geologist Brunton Pocket Transit

Geologist Outfit

Earth’s Layers The Earth is composed of four

different layers. 1. Crust – Earth’s outermost layer

that is thinnest under the oceans and thickest through the mountains.2. Mantle – largest layer of Earth’s interior that lies above the outer core and is solid yet flows slowly.3. Outer core – layer of Earth that lies above the inner core and is thought to be composed mostly of molten metal.4. Inner core – solid, innermost layer of Earth’s interior that is the hottest part of the Earth and experiences the greatest amount of pressure.

Clues to Earth’s Interior

Scientist or geologist use indirect observations to gather clues about what the Earth’s interior is made of and how it is structured. Geologist studies:

1. Waves 2. Rock Clues

Earth’s Plates

• The rigid, upper part of Earth’s mantle and the crust is called the lithosphere.

Plates – The moving pieces of the relatively rigid outer layer of the Earth (the lithosphere), made up of the crust and upper mantle, which contain the continents and ocean floors.

Plate Boundaries (3 types):Plate boundaries – the places where the edges of different plates meet.

1. Mountains – landforms that extends above the surrounding terrain.2. Rift valleys – elongated depressions.3. Faults – large fracture in rocks along which movement occurs. (Fracture – a break in a rock formation due to structural

stresses.)

• The movements of the plates are fairly slow, often taking more than a year to creep a few centimeters.

Plates Slow Creep

Plates That Move Apart

• Subduction – a type of plate movement that occurs when one plate sinks beneath another plate.

Three Types of Convergent Plate Boundaries

1. Continental-continental collisions

2. Continental-oceanic collisions

3. Oceanic-oceanic collisions

Uplift of Earth’s Crust

There are four main types of mountains: 1. Fault-block 2. Folded 3. Upwarped 4. Volcanic

http://pirate.shu.edu/~schoenma/mountains.htm

Fault-Block Mountains• Fault-block mountains form from pulling forces. They

are sharp jagged mountains made of huge, tilted blocks of rock that are separated from surrounding rock by faults and form because of pulling forces. (Fault – large fracture in rock along which movement occurs.)

Folded Mountains• Folded mountains are mountains formed

by the folding of rock layers caused by compression forces.

Upwarped Mountains• Upwarped mountains form when forces

inside Earth push up the crust.

Volcanic Mountains• Volcanic mountains are mountains that

forms when magma is forced upward and flows onto Earth’s surface.

http://www.arenal.net/photo/latest/2005-september/

Parts Of A Volcano

What type of mountains make up the Hawaiian Islands?

Volcanic Mountains

Other Types Of Uplift

• According to the principal of isostasy, the crust and lithosphere are able to float on the mantle.

• The principle of isostasy relates to the buoyancy of rocks. (Buoyancy is the tendency of a body to float or rise when submerged in a fluid.)

The End

Does all of this drive you apes?