Chapter 10: Plate Tectonics Grade 6 Earth Science

Mr. Norton

Chapter 10: Plate Tectonics Section 1: Continental Drift

Section 1: Continental Drift Objectives

What is Continental Drift?

A hypothesis that the continents have moved slowly to their current locations

Where did it come from?

Section 1: Continental Drift

The hypothesis was the work of a German scientist named Alfred Wegener

Wegener said that all the continents were once connected as one large landmass now called Pangaea

The land mass broke apart, and the continents drifted to their present positions.

Section 1: Continental Drift

Is there evidence for Wegener’s Continental Drift hypothesis?

Yes!

The puzzle-like fit of the continents

Similar fossils have been found on different continents.

Remains of warm-weather plants in Arctic areas and glacial deposits in tropical areas suggest that the continents have moved.

Similar rock structures are found on different continents.

Section 1: Continental Drift

At first continental drift was not accepted because nobody could explain how or why continents had moved.

Section 1: Continental Drift

Why is the fact that similar fossils have been found on different continents considered evidence for continental drift?

If fossils of similar plants and animals are found on widely separated continents, it is more likely that the continents had once been joined than that the plants and animals migrated.

Section 1: Continental Drift Discussion Question

Chapter 10: Plate Tectonics Section 2: Seafloor Spreading

Section 2: Seafloor Spreading Objectives

Plate Tectonics Section 2: Seafloor Spreading

Plate Tectonics Section 2: Seafloor Spreading

Using sound waves, scientists discovered a system of underwater mountain ranges called the mid-ocean ridges in many oceans.

In the 1960s, Harry Hess suggested a theory of Seafloor Spreading to explain the ridges

Section 2: Seafloor Spreading

The Seafloor Spreading theory of Harry Hess said:

Hot, less dense material below Earth’s crust rises upward to the surface at the mid-ocean ridges.

Then, it flows sideways, carrying the seafloor away from the ridge.

As the seafloor spreads apart, magma moves up from the cracks, cools, and forms.

Section 2: Seafloor Spreading

Evidence for Seafloor Spreading:

Youngest rocks are located at mid-ocean ridges.

Reversals of Earth’s magnetic field are recorded by rocks in strips parallel to ridges.

Section 2: Seafloor Spreading

How could seafloor spreading be related to continental drift?

If the seafloor is constantly spreading apart and moving, it will affect and move the continents as well.

Section 2: Seafloor Spreading Discussion Question

Chapter 10: Plate Tectonics Section 3: Theory of Plate Tectonics

Section 3: Theory of Plate Tectonics Objectives

http://www.extremetech.com/wp-content/uploads/2012/10/earthcut.jpg

Section 3: Theory of Plate Tectonics Plate Movements

Earth’s crust and upper mantle are broken into sections.

The sections are called plates that move on the plasticlike layer of the mantle.

The plates and upper mantle form the lithosphere.

The plasticlike layer below the lithosphere is called the asthenosphere

Section 3: Theory of Plate Tectonics Plate Movements

http://www.physicalgeography.net/fundamentals/images/lithosphere.gif

Section 3: Theory of Plate Tectonics Plate Movements

1 km = .6 miles

1 mile = 1.6 km

You do the math!

Section 3: Theory of Plate Tectonics Converting km to miles

Plates moving apart – divergent boundaries

Plates moving together – convergent boundaries Denser plates sink under less dense plates

Newly formed hot magma forced upward forms volcanic mountains

Plates collide Plates crumple up to form mountain ranges

Earthquakes are common

Plates slide past – called transform boundaries Their sudden movement can cause earthquakes

Section 3: Theory of Plate Tectonics Plate Boundaries

https://www.youtube.com/watch?v=dkELENdZukI&index=3&list=PLRot3FlJRMWm8Azy4oIvK9sVs77wDMPam

Section 3: Theory of Plate Tectonics Plate Boundaries

Convection inside earth is thought to be the force behind plate tectonics

The cycle of heating, rising, cooling, and sinking of material inside the earth produces that force

Section 3: Theory of Plate Tectonics Convection

Faults and rift valleys.

Mountains and volcanoes

Strike-slip faults – cause of earthquakes!

Section 3: Theory of Plate Tectonics Features Cause by Plate Tectonics

Faults and rift valleys. http://mvsdperiod6.wikispaces.com/file/view/c02244.jpg/45490523/c02244.jpg

Section 3: Theory of Plate Tectonics Features Cause by Plate Tectonics

Mountains and volcanoes http://www.mountainprofessor.com/images/osorno-volcano-Chile2.jpg

Section 3: Theory of Plate Tectonics Features Cause by Plate Tectonics

Strike-slip faults http://earthquake.usgs.gov/learn/animations/animation.php?flash_title=Strike-slip+Fault+Flash+Animation&flash_file=strikeslip&flash_width=240&flash_height=310

Section 3: Theory of Plate Tectonics Features Cause by Plate Tectonics

Scientists use tools to measure plate movements

These movements can be as little as 1cm per year!

http://oceanlink.island.net/SOLE/tectonics/WCDA.html

Section 3: Theory of Plate Tectonics Testing for Plate Tectonics

What will happen if a continental plate collides with an oceanic plate? A continental plate with a continental plate? Why?

The denser plate will always subduct, or bend under, the less dense plate. Oceanic plates are denser than continental plates, so the oceanic plate will sink under it. When two continental plates collide, neither will subduct because they are both less dense than the asthenosphere beneath them. Instead, they will crumple up and form mountain ranges.

Section 3: Theory of Plate Tectonics Discussion Question

Chapter 10: Plate Tectonics Oreo Lab

Grade 6 Earth Science

Mr. Norton

Your final outcome should be:

http://www.redcross.ca/blogImages/en-CA/2010/04/quakevolcano.jpg