Earth’s Crust

Earth’s Crust

Inside Earth Chapter 2.1Pages 54-61

in Motion

Stress(ed)?

• Stress is the measure of the amount of force applied to a given area.

Effect on Rocks• Stress is the force that acts on a rock to change

its shape or volume• Adds energy to the rock.

Deformation• Deformation: Any change in the shape or

volume of Earth’s crust (caused by stress)

• Crust deforms from the force of plates colliding– Transform boundaries.

Where is the Deformation?

Relieving Stress• Over time, stress builds up in the plates

• Eventually, the stress is released…

Earthquakes• The shaking and trembling that results from the

movement of rock beneath Earth’s surface.• Releases MASSIVE amounts of energy• Generates seismic waves

Compression• Definition: Squeezing• Effect on Rock:• Makes rock layers thicker and shorter

• Associated Fault Type: – Reverse Fault

• Associated Plate Boundary:– Convergent Boundary

Tension• Definition: Pulling apart• Effect on Rock:– Stretches making rocks longer and thinner

• Associated Fault Type: – Normal Fault

• Associated Plate Boundary:– Divergent Boundary

Shear• Definition: Moving in opposite directions– Think of shears or scissors

• Effect on Rock:– Stress distorts the shapes of rocks.

• Associated Fault Type: – Strike-Slip

• Associated Plate Boundary:– Transform

• A fault is a break in the lithosphere

• Usually occur along plate boundaries, where the motions of plates compress, pull or shear the crust so much that the crust breaks.

• 3 Types of Faults– Strike Slip Fault– Normal Fault– Reverse Fault

Faults

• Above the fault plane.

Hanging Wall

Hanging (head) Wall

Foot Wall

• Below the fault plane

Hanging (head) Wall

Foot Wall

Foot Wall

• Hanging Wall– Lantern

• Foot Wall– Path

Which Wall’s Which?

• How rocks move determines how much friction there is between opposite sides of the fault

• Friction: a force that opposes the motion of one surface as it moves across another

What about the surfaces causes friction?– It exist because surfaces are not perfectly smooth.

Friction along Faults

Normal Fault

• Force: Tension (diverging)

• Hanging wall: Moves down (with gravity)

Reverse Fault

• Force: Compression (converging)

• Hanging wall: Moves up (against gravity)

Strike-Slip Fault

• Force: Shear (transform)• Rocks on both sides of the

fault slide past each other

Landforms• Topography: determined by

its elevation, relief and landform

• All landforms have elevation and relief

• A landform region is an area where the topography is similar.

Elevation• The height above sea-level

on Earth’s surface.

Relief• The difference between

the highest point of elevation and the lowest parts of an area– have high relief– low relief.– Mountains – Plains

Plateaus

• Have high elevation and relief– Perfectly smooth on top

• May be really thick (1,500m), streams or rivers can cut through.

Plains• Flat or gently rolling land

with low relief and varying elevation.

• Depends on location…– Coastal Plains have low

elevation at or near sea level along the coast.

– Interior Plains are away from the coast, causing varied elevation.

Mountains

• A landform with high elevation and relief

• Mountain Ranges are groups of mountains that are closely related in shape, structure and age.

Moraine Lake, CO Rockies

HIMALAYAN MOUNTAINS, INDIA

Mountains formed From Faulting

• Normal Faults uplift blocks of rock and the hanging wall drops.

Mountains formed From Folding

• When continental plates collide, stress can cause rock layers to fold.

• Creates bends in the rock layers– Himalayas Mts. – Appalachian Mountains

Anticline

• A term used to describe folds in rocks• An arching fold in the rock layers or “apex”

WorldArchways of the

Syncline

• A downward pointing fold or “slump”

Anticline/Syncline

Anticline/Syncline

What to Work On

• Read Section 2.1 (pages 54-61)• Answer section review questions

(page 61, #1-4)