GRADE 7 SCIENCEUNIT 4: THE EARTH’S CRUST11/12Earth’s Crust is constantly changingWeathering and Erosion

Earth’s Structure - Layers of the Earth

Draw a labeled

Diagram

Layers of the Earth Rap’s

https://www.youtube.com/watch?v=Q9j1xGaxYzY

https://www.youtube.com/watch?v=RiHRI_Z2Kgs

Layers Of the Earth

1. Inner Core2. Outer Core3. Mantle4. Crust

Inner Core

Position: In the center of the earth (deepest)

Size: Second smallest

Description: Made of Solid iron and nickel

Outer Core

Position: Between the inner core and mantle

Size: Second thickest layer

Description: Made of liquid iron and nickel

Mantle

Position: Between the crust and outer core

Size: The thickest layer

Description: Partly Molten. Looks “plastic-like” (silly putty)

Crust

Position: On the outside of the earth

Size: The thinnest layer

Description: The Continental (land) crust is thicker than the oceanic (ocean floor) crust

The Crust - In detail

● The crust is broken into pieces (ocean and land crust)!○ These pieces are called Plates.

● The plates are always moving!

Plate Jigsaw activity!

Plate Tectonic Theory

How did we come to understand Earth Science?

Scientists and Technology!

Alfred Wegener

● Saw the continents fit like a puzzle

● He proposed the Theory of Continental Drift

Theory of Continental Drift

● A Theory that:○ the continents move○ There was a lot of evidence to support this

● Problem: There was no mechanism to cause the movement!

Pangea

The supercontinent made when all the continents were together

https://www.youtube.com/watch?v=cQVoSyVu9rk

4 pieces of evidence for continental drift

1. Continental fit: The continents seem to fit together (Africa and South America)

4 pieces of evidence for continental drift

2. Fossils: The same type of fossil are found on different continents (Canada and Europe)

4 pieces of evidence for continental drift

3. Rock layers: The same type of rock layers on different continents

4 pieces of evidence for continental drift

4. Climate: Coal that forms in warmer climate only is found in Antarctica!

Technologies Used in Earth Science

● Sonar● Magnetometers● Deep sea drilling

● Magnetometer paper

activity

Remember!

Although there was a lot of Evidence -

There was no accepted mechanism

(No force that caused the continents to drift)

So… Continental Drift was rejected!

Plate Tectonics

● New technology and data were found!

The theory of continental drift became the Plate Tectonic Theory

Theory of continental Drift to Plate tectonics video

1:22 - 10:15

https://www.youtube.com/watch?v=HrKTuCDierM

Plate Tectonics

Plate: each pieces of the Earth's crust

Plate Boundary: The edges of plates. Where two plates meet

The Driving Force Behind Theory of Plate Tectonics

Convection Currents: the heated rock in the mantle rises then cools and sinks. This moves the plateshttps://www.youtube.com/watch?v=ryrXAGY1dmE

3 Types of Plate Boundaries

1. Divergent

Description: When the plates move away from one another

Force: Pulling apart

Results: Volcanoes and earthquakes

3 Types of Plate Boundaries

2. Convergent:

Description: When the plates move toward each other

Force: Pushing together

Results: Volcanoes, earthquakes and mountains

3 Types of Plate Boundaries

2. Transform:

Description: When the plates move alongside each other

Force: sliding past

Results: Earthquakes

3 plate boundaries video

https://www.youtube.com/watch?v=0mWQs1_L3fA

Canadian Earth Scientists!

J. Tuzo Wilson - proposed the third type of plate movement - Transform boundaries!

Canadian Earth Scientists!

Joseph Tyrrell - discovered dinosaur fossils in Alberta,

● It proved that the local climate was warmer at an earlier time.

Canadian Earth Scientists!

Harold Williams - (Newfoundlander!) highlighted that plate tectonic activity happened on the eastern edge of North America.

Catastrophic Events from plate boundaries!

Earthquakes and Volcanoes!

Discussion questions

1. Do earthquakes and volcanoes occur in NL?

2. Is there evidence that Earthquakes or volcanoes occurred here in the past?

Earthquakes

Definition: The shaking of the earth

Caused by: The release of energy from plate movement in Earth’s crust.

When this energy is released, it travels in waves (seismic waves).

Example: Tsunami that hit burin peninsula

Seismograph

The device used to record earthquakes.

VolcanoesDescription: an opening in the Earth’s crust.

Caused by: Plate movement at boundaries

Example: Mount St. Helen’s in Washington D.C. - in the United States

3 Locations volcanoes form:

1. Convergent plate boundaries2. Divergent plate boundaries3. Hot spots

Volcanoes - 3 locations

1. Convergent plate boundaries

Description: Intense pressure melts rock that later flows to the surface as a volcano

Example: the Pacific Ocean is being subducted under Japan.

Volcanoes - 3 locations

2. Divergent plate boundaries

Description: Molten rock flows up to the surface

Example: The mid-Atlantic Ridge.

Volcanoes - 3 locations

3. Hot spots:

Description: Areas where the crust is thin magma can be forced up through the cracks

Example: The Hawaiian Islands.

Pattern of Earthquakes and VolcanoesOccur mostly along the ‘ring of fire’ (along plate boundaries!)

Past Theories for Volcanoes & Earthquakes

Pele: The Hawaiian goddess who makes the mountains shake and lava flow at Kilauea, Hawaii

Glooscap: Mi’kmaq legend about how Glooscap (the first man) turned a beaver into the Sugarloaf Mountains.

Weathering and Erosion

How could these rock formations occur?

Weathering

The mechanical and/or chemical breakdown of rock.

There are 2 Types:

1. Chemical2. Mechanical

1. Mechanical Weathering

The physical breakdown of rocks into smaller fragments.

Examples:

a. Frost Wedge: Ice breaking apart the rock (most common)

b. Movement by plants/animals: burrowing through rock

2. Chemical Weathering

When chemical reactions break down rocks.

Examples:

a. Acid rain: the acid slowly breaks up the rock

b. Chemicals made by animals: lichens chemicals break down rock

Erosion

The process that loosens and moves weathered rock particles (sediment) over Earth’s surface

Agents of Erosion

1. Water in motion (most powerful)

2. Meteorological processes (rain and wind)

3. geological processes (gravity and glaciers)

Weathering Vs. Erosion - What's the difference?

Weathering Vs. Erosion - What's the difference?

Weathering breaks up the rock

Erosion moves the rock!