Unit 6 Part 3: Plate Boundaries and Faults

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Plate Boundaries and Faults

Multiple Choice

Which theory describes the motion of and force driving Earth's plates?

• The First law of Motion

• The Third Law of Motion

• Continental Drift

• Plate Tectonics

Multiple Choice

Where does Subduction Occur?

• Along the middle of some Ocean Floors

• Down the middle of Mountain Ranges

• On Continents

• At Deep-Ocean trenches

Multiple Choice

Which process adds more crust to the ocean floor

• Suction

• Sea-floor Spreading

• Subduction

• Magnetic Stripe

Lesson Objectives

• Summarize the characteristics of divergent, convergent, and transform plate boundaries

• Describe how the crust is shaped by plate movement

Introduction

• Tectonic plates meet at plate boundaries

• Many types of geologic activities occur at these boundaries

  • Earthquakes

  • Mountain Building

  • Volcanoes

• Three types of plate boundaries exist

  • Divergent

  • Convergent

  • Transform

​Divergent Boundaries

• Plates are pulled apart from each other

• Magma from the Earth's mantle erupts to the surface

• When Plates move away, they can create massive cracks in the crust

  • When underwater, mid-ocean ridges form

  • When on land a deep rift valley forms​

​Convergent Boundaries

• Plates collide together

  • the denser plate sinks while the less dense plate rises​

    • Oceanic crust more dense and it sinks to the mantle

    • Continental crust raises up and forms mountains

  • When plates with the same density collide, the crust squeezes into high mountains

​Transform Boundaries

• Plates slide past each other in opposite directions

  • two jagged edges can get "caught" on each other and lock in place together

  • eventually enough force will break the two plates apart

• Crust is neither created or destroyed

• Mainly where Earthquakes occur​

  • The San Andreas Fault​

Multiple Choice

Type of plate boundary that causes the lithospheric plates to be pulled apart

• Divergent

• Convergent

• Transform

Multiple Choice

Type of plate boundary that causes the lithospheric plates to move horizontally past each other

• Divergent

• Transform

• Compression

• Convergent

Multiple Choice

Type of plate boundary that causes the lithospheric plates to move towards each other

• Divergent

• Transform

• Convergent

How Does Stress change the Earth's Crust?

• The movement of Earth's plates creates forces that can bend and fold rocks

• Stress: a force that acts on rock to change its shape or volume​

  • Increases with Force

  • Adds Energy to Rock, which is stored until the Rock breaks

• Three types of stress in the Earth change the shape of rock over millions of years

Tension

• Stress force that pulls the crust of the Earth and thins Rock in the middle

• Occurs when two plates pull apart​

Compression

• Stress force that squeezes rock until it folds or breaks

  • Occurs when two plates come together​ and push into each other

Shearing

• Stress force that pushes a mass of Rock in two opposite directions

• Can cause Rocks to break or slip apart

• changes the shape of the rock

• Occurs when two plates slide against each other​

Match

Match the following types of stress with how they move

• Tension

• Compression

• Shearing

Two Plates Pulling Apart

Two Plates Coming Together

Two Plates Slide against Each Other

• Two Plates Pulling Apart

• Two Plates Coming Together

• Two Plates Slide against Each Other

How do Faults Form?

• Most Faults occur along plate boundaries where the forces of plate motion push/pull the crust so much it breaks

  • When enough stress builds up inside a rock​, it will break & create a fault

• Three types of Faults

  • Normal

  • Reverse

  • Strike-slip

Normal Faults

• The Fault cuts through rock at an angle so one block of rock sits over the fault & the other sits under the fault

  • Hanging Wall: the rock over the fault in a normal fault

  • Foot Wall: The Rock that lies under the fault​

• ​When movement occurs the hanging wall slips downwards

• Occur where tension pulls rock apart​

Reverse Faults

• Has the same structure as a normal fault, but moves in the opposite directions

  • Hang wall Moves up, Foot wall moves down

• Form in areas of compression in the crust

Strike-Slip Faults

• Formed by Shearing

• Rocks slide past each other sideways, with little up or down motion

• When forms the boundary between two plates, it is called a Transform Boundary​

Multiple Choice

When two plates move away from each other ________________ faults are created.

• Normal

• Reverse

• Strike-Slip

Multiple Choice

Stress is a(n) ____________   that acts on rock to change its shape or volume.

• Force

• Power

• Scale

• Epicenter

Match

Match the faults to their descriptions

• Normal Fault

• Reverse Faults

• Slip-Strike Fault

Hanging Wall Slides down when tension pulls rocks apart

Hanging Wall Slides up when plates push against each other

Rocks on either side of a fault slid against each other

• Hanging Wall Slides down when tension pulls rocks apart

• Hanging Wall Slides up when plates push against each other

• Rocks on either side of a fault slid against each other

Multiple Choice

The Stress Force that pulls on the crust and thins the rock in the middle is

• Shearing

• Compression

• Tension

• Uplifting

Multiple Choice

The Stress Force that squeezes a rock until it folds or breaks is

• Shearing

• Compression

• Tension

• Uplifting

Multiple Choice

A fault in which the rocks on either side of the fault move sideways past each other is a __________

• Slip-Strike Fault

• Normal Fault

• Hanging Fault

• Reverse Fault

​How Does Plate Movement Create New Landforms

• Changes in the crust occur extremely slowly and are not easy to observe

• Over millions of years, the forces of plate movement can change a flat plain into different features

  • anticlines

  • synclines

  • folded mountains

  • fault-block mountains

  • plateaus

​Folding of the Earth's Crust

• Folds: bends in rock that form when compression shortens and thickens Earth's Crust

  • When the crusts fold, rocks bend without breaking

  • a fold can vary in width

​Anticlines and Synclines

• Anticline: an upward bend in a rock

• Syncline: A downward bend in a rock

• Both Form in areas of compression in the crust

  • anticlines and synclines form when rocks fold over from compression

​Stretching the Earth's Crust

• Tension can stretch the Crust and leave Valleys surrounded by high elevations

  • Fault-Block Mountains: Mountains f​ormed by tension

​Uplifting the Earth's Crust

• Plateaus: a large area of flat land elevated high above sea level

  • has many different flat layers

  • Occur when forces in the crust push up large flat pieces of Rock​

Multiple Choice

Tension can cause the formation of Mountains and ________

• Plateaus

• Valleys

• Anticlines

• Sinclines

Multiple Choice

Normal faults occur when two plates ________

• Come together

• Pull Apart

• Slide Against Each Other

Multiple Select

Mark all Correct Answers: Compression Causes the Formation of

• Anticlines

• Synclines

• Plateaus

• Valleys

Multiple Choice

A large Flat area of Land elevated High above Sea level is a(n)

• Anticlines

• Synclines

• Plateaus

• Valleys