Unit 6 Part 3: Plate Boundaries and Faults

​Science Root of the Day:

DO NOW: Write what you think the example words mean in your lab manual.

Extra Credit: Find three additional words that use this root and write them and their definition in your lab manual (6 Points Max)

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