Plate Tectonics Unit: - PowerPoint Presentation

Slide1

Plate Tectonics Unit: Slide2

Composition of the Earth:

Layers of the Earth:

Crust:

5-100km thick. Oceanic crust: thin and more dense, mostly basalt Continental crust: thicker and less dense, made up of more granite than oceanic crust Slide3

Layers, Continued:

mantle:

made of molten (melted rock), very thick, 2,900 km, and likely to have convection currents.

Outer Core: molten iron, 2,200 km thick Inner Core: solid but very hot iron, 1,230 km thick

The core makes up 33% of Earth’s total mass Slide4

Tectonic Plates:

Because of convection currents in the mantle, plates of the earth’s crust move around as they “float” on the mantle. Over many millions of years, the location of the oceans and continents have changed dramatically, and surface features like valleys and mountain ranges are continually created and destroyed. Slide5

Wegener’s Theory of Continental Drift:

In 1910, a German scientist named

Alfred Wegener

proposed that the continents had, in the very distant past, been joined together in one supercontinent he called Pangea, and had since drifted apart into separate continents. He called this theory Continental Drift. Slide6

Wegener’s arguments in support of his theory:

Evidence from landforms:

Continents along the Atlantic Ocean appear to fit together like puzzle pieces.

Mountain ranges in South Africa match up with mountains in South America. Coal deposits in Europe match up with coal deposits in North America. Slide7

2. Evidence from fossils:

Fossils of the same species of land animals and land plants had been found on different continents; they could not have crossed oceans.

Fossils of tropical plants were found on the island of Spitsbergen, which is well north of the Arctic Circle. Wegner proposed that this island had once been close to the equator.

Evidence of glaciers had been found in South Africa, which currently has a subtropical climate. Wegner thought South Africa must have been much farther south millions of years ago. Slide8

Unfortunately, no one believed Wegener at the time. His evidence was not totally convincing, and he could not explain what force could cause whole continents to move. Slide9

Plate Tectonics: Wegener was Right!

Starting in the 1960’s, as scientists started mapping the ocean floor, they discovered that the ocean floor was spreading out along the Mid-Ocean Ridge. This very easily explained how continents could move. Slide10

How Sea-Floor Spreading Works: Slide11

Evidence for Sea-Floor Spreading:

Rock samples from the ocean floor close to the mid-ocean ridge are younger than rock samples farther away.

Magma can actually be observed oozing up from the mid-ocean ridge, and cooling into rock.

Iron samples from the ocean floor alternate their patterns, showing that some parts of the ocean floor were formed at times when the magnetic poles were reversed. Slide12

Subduction

at Deep

O

cean Trenches: Slide13

The Ultimate Cause of Plate Movement? Convection! Slide14

Tectonic Plates of the Earth: Slide15

Homework:

LO: Describe the theory of plate tectonics

SLE: Communicate ideas clearly and articulately

Read p. 108-111 Answer review questions on p. 111 Slide16

Types of Plate Boundaries: Slide17

LO: Describe the theory of plate tectonics

SLE: Meet or exceed NGSS

Checkpoint Quiz on Plate Tectonics:

List the layers of the interior of the earth, starting with the middle and going outwards. How do we know the earth’s core is solid? Give one piece of evidence that the seafloor is spreading.

Give one of Wegener’s arguments in favor of his theory of continental drift.

Describe three types of plate boundaries (OK to draw diagrams). Slide18

LO: Describe the theory of plate tectonics

SLE: Meet or exceed NGSS

Checkpoint Quiz on Plate Tectonics #2:

Describe the process of sea-floor spreading. Give one piece of evidence that the sea floor is spreading.

What causes the formation of most mountain ranges?

Name three types of plate boundaries, and describe the movement of plates along each one (diagrams OK) (2 points) Slide19

The Effects of Tectonic Plate Movement on Earth’s Surface :

Plate movement causes the earth’s surface to

deform (noun: deformation)

: layers of rock bend or break because of the stress placed on them. Slide20

Main Types of Stress:

Compression:

When two plates are squeezed together.

Tension: When two plates are pulled apart.Shearing: when two plates are pulled past one another. Slide21

Folds:

Folding

is the bending of rock layers due to one of these three types of stress.

Types of folds: Anticlines: upward-pointing folds. Synclines: Downward-pointing folds.

Monocline:

A step-like fold in which both ends are horizontal. Slide22

Faults:

Faults

are regions where rock areas break and slide past each other.

When faults are not totally vertical, the upper part is called the hanging wall and the lower part is called the footwall. Slide23

Types of Faults: Slide24

Plate Tectonics and Mountain Formation:

The motion of Earth’s plates causes mountains to form, mostly at plate boundaries.

The type of mountains that are formed depends on what type of plate boundary it is. Slide25

Types of mountains:

Folded Mountains:

When plates are squeezed together and pushed upward. These are usually formed at convergent boundaries.

Fault-Block Mountains: When plates move apart and one section of rock drops down relative to other sections. (These tend to be smaller mountains.) Volcanic Mountains:

Formed by volcanic eruptions, usually near

subduction

zones. Slide26

Homework:

LO: Describe effects of the movement of tectonic plates.

SLE: Articulate ideas clearly and effectively.

Read p. 112-118 Answer review questions on p. 119 Slide27

Earthquakes:

Where earthquakes occur:

Most earthquakes occur at or near plate boundaries. The crust moves more often in these places, and stress is more likely to build up there. Slide28

The cause of earthquakes:

Rock at plate boundaries or along faults will stretch as sections move past one another, but eventually so much pressure builds up that the rock breaks and snaps back (like a rubber band), which releases waves of energy. The sudden snapping back of rock is called

elastic rebound.

http://wn.com/elastic_rebound_and_earthquakes Slide29

Seismic waves:

Seismic waves

are energy waves caused by rock vibrations along a fault. There are 3 kinds of seismic waves:

Primary (P): The first to arrive (the fastest). They compress and expand like a Slinky. Secondary (S)

: They come after primary waves. They move from side to side and up and down. S waves, unlike P waves, can not travel through liquids.

Surface waves:

P or S waves that have reached the surface. These are the waves that cause the most damage, although they are slower than the other two. Slide30
Slide31

How earthquake strength is measured:

Earthquakes are detected, located and their strength measured by a machine called a

seismometer

. They record the movement of the earth using a needle; the more the ground shakes, the more the needle does, too. Slide32

Earthquake measuring scales:

1.

Mercalli

Scale: Developed early in the 20th century, this scale does not measure the energy precisely, but records the amount of damage that has been done.

2. Richter Scale:

Developed in 1930, it measures the strength of an earthquake according to how much motion the nearest seismometer has recorded. This could change depending on how far away from the earthquake the seismometer is.

EaSlide33

3. Moment Magnitude Scale:

This is the scale used today. It measures the total energy produced by the earthquake, not the results of the earthquake. In this scale, each magnitude is ten times larger than the next lowest number. Slide34

Epicenter vs. Focus:

Focus:

The location below ground where the earthquake begins. This can be many Km below the surface.

Epicenter:

The first location on the surface where the earthquake can be felt. Slide35

Homework:

LO: Describe cause and effects of earthquakes.

SLE: Meet or exceed NGSS.

Read p. 130-139 Review questions on p. 139 Slide36

LO: Describe the cause and effects of earthquakes.

SLE: Meet or exceed NGSS

Checkpoint Quiz on Earthquakes:

Draw diagrams of normal, reverse and strike-slip faults. For each type of fault, label the foot wall, hanging wall, and the direction of movement along the fault.

What causes earthquakes?

Where on on Earth are earthquakes most likely to occur?

What device is used to measure the amount of energy produced by earthquakes?

What’s the difference between an epicenter and a focus of an earthquake? Slide37

Earthquake Safety:

The likelihood of experiencing an earthquake depends on where you are. If you live near a plate boundary, your

earthquake

hazard level

is higher. Slide38

Forecasting Earthquakes:

Predicting when and where the next earthquake will occur is very difficult. However, scientists sometimes try the

Gap Hypothesis:

Areas along faults that haven’t had an earthquake in a while are more likely to experience a strong one in the future. Slide39

Earthquake-Proof Building Design Features:

Mass Damper:

A weight placed on the roof to keep the building from swaying.

Shear wall: braces in walls to prevent them from tearing in half. Active tendon system: Shock absorbers built into the frame of the building.

Base isolators:

Felxible

layers of material built into the foundation of the building.

Pilings:

In soft soil

, long

posts underground attached to the bedrock below the surface.

Cross braces:

To keep the building

f

rom shaking apart.

Flexible pipes:

To prevent fires from gas leaks. Slide40

What to do during an earthquake:

Drop, cover and hold

Wait 100 seconds in case of immediate aftershocks

Quickly and calmly exit the building Gather in an open area and await instructions from trusted adults. Slide41

Homework:

LO: Identify and describe earthquake-resistant design features

SLE: Work independently

Read p. 140-145 Review questions p. 145 Slide42

LO: Identify and describe earthquake-proof design features.

SLE: Work collaboratively.

Design and build an earthquake-proof building.

Materials: 100 3 x 5 cards, 1m masking tape, 10 straws.

Rules:

You may only use the materials provided.

Building must be at least 50cm tall and 20cm wide.

Building must be free-standing.

Building must have 4 or more earthquake design features.

Must be able to withstand shaking for 30 seconds. Slide43

Volcanoes:

A

volcano

is a crack or weak point in the earth’s crust through which magma comes near or onto the surface. (Once magma reaches the surface, it’s called

lava

.)

Magma:

below ground

Lava:

above ground Slide44

Types of volcanic eruptions:

Explosive:

Non-explosive: Slide45

Structure of a volcano: Slide46

Products of Volcanic Eruptions:

Lava:

the thickness of lava is determined by the amount of the mineral silica- the more silica, the thicker the lava.

Volcanic ash: dust and small bits of rock from explosive eruptionsBombs: large rocksLapilli:

small rocks

Gas:

mostly CO2

, but also toxic gases

Pyroclastic flow:

an avalanche of hot gas, ash and dust that flows down the side of the volcano at very high speeds. Slide47

LO: Model effects of pressure on volcanic eruptions.

SLE: Work Collaboratively

Problem:

What effect does increased pressure have on the force of volcanic eruptions? Hypothesis:

Procedure:

Place 50ml of vinegar in the bottom of a flask with a wider opening.

Add 2-3

tsp

of baking soda, and observe what happens.

Repeat steps 1-2 with a flask with a narrow opening

Compare observations.

Data:

Using words or pictures, describe what happens with each “volcano.” (qualitative data)

Conclusion: Slide48

Types of Volcanic Landforms:

A

volcanic landform

is a feature of the earth’s surface that is created by volcanic eruptions. These include:

Shield volcanoes

Cinder cone volcanoes

Composite volcanoes

Lava plateaus

CalderasSlide49

Shield Volcanoes:

Shield volcanoes

are created by many layers of non-explosive (lava-only) eruptions. They have very gentle slopes, and can even be flat, but some of them are enormous. (The tallest mountain on earth is a shield volcano.)Slide50

Cinder Cone Volcanoes:

Cinder cone volcanoes

result from small to medium –sized explosive eruptions, and are made almost entirely of ash and dust (pyroclastic material). They tend to be small, but have very steep sides full of loose material. Slide51

Composite Volcanoes:

Composite volcanoes

are formed by alternating explosive and non-explosive eruptions. Inside, they have alternating layers of ash and lava. They are often dormant for thousands of years, but can also produce extremely large, destructive explosive eruptions. (All four of WA’s volcanoes are composite volcanoes.) Slide52

Lava Plateaus:

Lava plateaus

are formed when thin lava flows out from one or more long cracks in an area. Over many thousands or millions of years, many layers of lava form a high flat area (plateau). Some lava plateaus are gigantic: the Columbia Plateau in WA is a lava plateau. Slide53

Caldera:

Sometimes, explosive eruptions are so large and violent that the entire magma chamber beneath a volcano empties out all at once. With nothing below to support the weight of an entire mountain, it collapses in on itself and forms a gigantic hole in the ground called a

caldera. Slide54

Homework:

LO: Identify and describe volcanic landforms.

SLE: Articulate ideas clearly and effectively.

Write a 7-sentence (more is OK) paragraph that describes each major type of volcanic landform. Include a description of how each one is formed and what it looks like.