Plate Tectonics

Plate Tectonics

Learning Objectives

• Define plate tectonics theory and identify the lithosphere.

• Explain how mantle convection currents move plates.

• Compare oceanic crust and continental crust differences.

• Describe the three main types of plate boundaries.

• Plate tectonics: Earth's outer shell (lithosphere) is broken into moving plates.

• The lithosphere includes the crust and the top part of the mantle.

• These plates move slowly and constantly, like puzzle pieces on Earth's surface.

• "Tectonic" relates to Earth's crust and the major processes that shape it.

What is Plate Tectonics?

Multiple Choice

According to the theory of plate tectonics, what part of Earth is broken into moving plates?

• The inner core

• The entire mantle

• The lithosphere (crust and upper mantle)

• Only the crust

• Tectonic plates move due to mantle convection currents below them.

• Convection: Hotter material rises, cooler material sinks in a cycle.

• The mantle's solid rock flows very slowly in these currents.

• These currents slowly move plates across Earth over millions of years.

Convection Currents: The Driving Force

Multiple Choice

What process within the mantle is responsible for moving Earth's tectonic plates?

• Conduction

• Radiation

• Subduction

• Convection currents

• Earth's plates have oceanic or continental crust.

• Oceanic crust is under oceans, dense, and thin.

• Continental crust forms land, less dense, and thick.

• Density difference controls how plates interact when meeting.

Oceanic vs. Continental Crust

Multiple Choice

Which type of crust is typically denser and thinner?

• Continental crust

• Oceanic crust

• Mantle crust

• Lithospheric crust

• Plates move very slowly, only 1-10 cm per year – like fingernails!

• We use GPS technology to measure this tiny movement accurately.

• Over millions of years, this reshapes continents and oceans. Think Pangaea!

• Pangaea broke apart 200 million years ago, forming today's continents.

How Fast Do Plates Move?

Multiple Choice

Approximately how fast do tectonic plates move per year?

• 1-10 meters

• 1-10 kilometers

• 1-10 centimeters

• 1-10 millimeters

• Plates meet at boundaries, causing big geological changes.

• Most earthquakes and volcanoes happen at these boundaries.

• Big landforms like mountains and ocean trenches often form here.

• The 'Ring of Fire' around the Pacific has many earthquakes and volcanoes.

Plate Boundaries and the Ring of Fire

Multiple Choice

The 'Ring of Fire' is an area around the Pacific Ocean known for frequent:

• Hurricanes and tornadoes

• Blizzards and ice storms

• Earthquakes and volcanic eruptions

• Floods and droughts

• Divergent boundaries are where two tectonic plates move away from each other.

• This creates mid-ocean ridges underwater and rift valleys on land.

• Magma rises from the mantle, cools, and forms new crust.

• The Mid-Atlantic Ridge and Iceland's rift valleys are examples.

Divergent Boundaries: Plates Moving Apart

Multiple Choice

What geological feature is typically formed at a divergent boundary where oceanic plates move apart?

• Mountain range

• Deep-ocean trench

• Mid-ocean ridge

• Transform fault

• Convergent boundary: Two tectonic plates move toward each other and collide.

• Continents collide: Crust folds and buckles, pushing up huge mountains like the Himalayas.

• Subduction: Denser plate sinks under the less dense plate when they collide.

• Subduction creates deep ocean trenches and magma, forming volcanoes on land or sea.

Convergent Boundaries: Coming Together

Multiple Choice

What happens when an oceanic plate collides with a continental plate at a convergent boundary?

• Both plates stop moving.

• The continental plate subducts beneath the oceanic plate.

• The oceanic plate subducts beneath the continental plate.

• The plates slide past each other horizontally.

• Plates slide horizontally past each other.

• Movement isn't smooth; stress builds up, causing earthquakes.

• They often leave visible offsets in roads or streams.

• The San Andreas Fault in California is one example.

Transform Boundaries: Plates Sliding By

Multiple Choice

What type of geological event is most commonly associated with transform boundaries?

• Volcanic eruptions

• Mountain formation

• Seafloor spreading

• Earthquakes

​Correction

• Plates = lithosphere sections carrying continents AND oceans.

• Plate movement is very slow (cm/year), seen over millions of years.

• Most quakes and volcanoes occur along plate boundaries.

• Both continental and oceanic parts of the plates move.
  

​Misconception

Common Misconceptions

• Plates are continents floating on water.

• Plate movement is very fast and happens daily.

• Earthquakes and volcanoes can happen anywhere randomly.

• Only continents move, not ocean floors.
  

Summary

• Earth's lithosphere (crust, upper mantle) is broken into plates.

• Mantle convection currents slowly move these plates each year.

• Plates interact at divergent, convergent, and transform boundaries.

• Plate boundaries cause earthquakes, volcanoes, and mountain building.

Open Ended

What process in the mantle drives the movement of tectonic plates?

Poll

Which type of plate boundary is associated with plates sliding past each other horizontally?

• Convergent

• Divergent

• Transform

• Subduction

Open Ended

Name one feature created at a divergent boundary.

Poll

On a scale of 1-4, how well do you feel you understand the different types of plate boundaries and their effects? (1=Not well, 4=Very well)

• 1

• 2

• 3

• 4

Open Ended

What concept from today's lesson on plate tectonics would you like to review further?