4.1 EarthQuakes
LESSON #1: Introduction to Earthquakes
1. Workbook Earthquakes- Open in Notability to complete
2. Current Earthquakes: USGS MAPS
3. California Quake: San Francisco and Oakland 1989
Japan Now Closer to North America!
4. Interactive site.
- GO to "Explore Section" on right
- Click Bottom image with title: Earthquakes and Plates.
LESSON #2: EARTHQUAKES: WHY THEY HAPPEN
The earth's crust is moving at different rates, at different places, and at different times.
When we feel it move, we experience an earthquake.
The forces that move the crust is not visible to us. The molten rock (magma) in the mantle
is responsible for moving large pieces of the crust against, side by side, or away from each other.
Convection currents of heated magma rise from the core to the underside of the crust;
pulling or pushing it as it comes into contact with it.
Pieces of crust are called Tectonic Plates.
TECTONIC PLATES
There are 8 major ones (we will worry about)
7 of the major plates are called CONTINENTAL PLATES as they have large land masses on them.
The 8th major plate is called Oceania (or Pacific Plate) it only has very small islands so is not refereed
to as a continental plate.
Plate boundaries are where the plates meet each other (their edges). They are major seismic zones.
Earthquakes occur at Fault Lines (cracks in the earth's crust) and not just at Plate Boundaries.
Plate boundaries are not the only cracks in the earth's crust.
There are minor cracks WITHIN the major Plates.
Ottawa has fault lines that run right down town.
From the Gatineau Hills to Dow's Lake there is an old fault line.
Major earthquakes tend to happen at or near plate boundaries, but earthquakes occur regularly
everyday around the world.
Canada experiences around 4000 earthquakes every year. Many near Ottawa.
Interactive GIf Site
The earth's crust is floating on the mantle. The heated magma rises from the core to the
underside of the crust, pushing it around.
Folded Mountains occur at compressional fault lines and are one type of Convergent Boundary
LESSON #3: TECTONIC FORCES
¨From time to time earthquake shocks indicate sudden shifts or fractures in the crust, as forces
within the crust raise up mountains and plateaus or sink.
¨Tectonic forces are the stresses and strains within the earth that bring about fracture
(breaks) and movement of the crust and cause magma to flow.
LESSON #2: TYPES OF EARTHQUAKES
Damage in Alaska
TYPES OF EARTHQUAKES:
THREE TYPES OF PLATE BOUNDARIES
Divergent: Two plates move apart
Convergent: Two plates move together
Transform: Two plates slide side by each
Depending on the direction each plate moves in at it boundary or
or along a fault line it will have a different name. Think of two object
moving beside each other. Essentially they will move towards each other,
away from each other, or grind in different directions beside each other.
Each one of the "forces" causes something to happen to the nearby crust
along that "fault" line.
1- Divergent Fault Line: Tensional forces caused by expansion (stretching apart) ß à
2- Convergent Fault Line: Compression forces caused by contraction, compression or folding
(squeezing together) à ß
A compression fault is when the plates put equal pressure causing the crust to rise and create folded mountains.
( Rockies and Himalayas are examples)
A Subduction fault is when one plate slips below the other (Japan)
3- Transform Fault: Boundary where the plates strike/slip past each other
Movement of the Crust at Plate Boundaries
Movement of the Crust at Plate Boundaries
● The earth Crust is made up of moving pieces of crust we call tectonic plates (think giant jigsaw puzzle).
● There are seven major continental plates
● Earthquakes occur at plate boundaries (edges) where there are fracture (breaks) in the crust we call fault lines.
● Magma under the crust is moving (called convection currents) and pushing the plates in many directions
● When the plates move the rub against each other creating stress forces (pressure) towards the fault or away from it.
¨ Basically the continents are floating around like giant pieces of a puzzle, some moving
apart and others colliding/sliding past each other.
¨ In some parts of Africa, like the the Great Rift Valley, the Plates are moving apart at
the rate of 30 centimeters per year.
¨ The St. Lawrence Valley is another example of a rift valley, example of a
Divergent Boundary.
¨ The Rocky Mountains in Canada, and the Himalayan Mountains in India were
created when the 2 plates collided and caused buckling (think of a car accident).
This is an example of a Convergent Boundary.
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LESSON #3: ENRICHMENT ACTIVITIES
1. WEBQUEST: Causes and Effects
- Go to this Earthquake webpage and complete the worksheet
- Work sheet provided for you.
2. ARTICLE:
3 . Think you got it?
- Go here to check your knowledge of earthquakes
CL
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