Chapter 6 – Plate Tectonics and Earthquakes

Day Activity Homework

1 Notes I, II Gondwanaland Take-Home

Continental Drift*

2 Notes III- V B

Edible Tectonics*

3 Notes V C- VI Article- One Boy’s Experience

Earthquake Data

(Students should begin plotting earthquake data at the

beginning of this unit)

Eye on Earthquakes*

4 Notes VII

Earth’s Interior Egg Lab *

Alternate Activities

1. Edible Tectonics- There are two possible choices for this lab. One with

oranges, and the other with Milky Way candy bars. I have found both to be

successful.

2. Eye on Earthquakes- In this activity students create and present a news

report with each group member playing the role of a geologist, news anchor,

seismologist, historian, geographer, or national disaster rescue official.

NC Goals:

2.02 Analyze the historical development of the theory of plate tectonics.

2.04 Analyze seismic waves including velocity and refraction to:

• Infer Earth’s internal structure

• Locate earthquake epicenters

• Measure earthquake magnitude

• Evaluate the level of seismic activity in North Carolina

Chapter 6 – Plate Tectonics and Earthquakes

If the continents drift, where are we going?

I. Once Upon a One-Land Planet

A. Abraham Ortelius- in 1587 this famous mapmaker noticed that South

America and Africa looked like mirror images. In his book Thesaurus

Geographicus he argues that the continents were once joined.

B. Alfred Wegener- 1912 – the thirty-two year old meteorologist unveiled

his theory of continental drift

1. Wegener theorized that 200 million years ago Earth was one large

continent called Pangaea (meaning “all Earth”)

2. Gradually the continent split into two large landmasses

a. Laurasia in the northern hemisphere

b. Gondwanaland in the southern hemisphere

C. Response from scientists at the time was very negative, but Wegener

persisted

D. About 30 years after Wegener’s death, evidence convinced almost all

scientists that continental drift was an acceptable, useful theory

II. Evidence Supporting Continental Drift

A. Fossils

1. Glossopteris- an extinct plant fossil located in rocks about 250

million years old are found in South Africa, Australia, India, and

Antarctica

a. Seeds of this plant are too large to be carried by wind, too fragile

to be carried by waves

b. This suggests that places the plant fossils are found were once

closer together.

c. Glossopteris fossils found in Antarctica suggest a climate change,

which indicates a position change in the land.

2. Many other reptile fossils support continental drift such as;

Cynognathus, Lystrosaurus, and Mesosaurus

B. Evidence from Rocks

1. Rock formations in Africa match those in South America

2. A folded mountain chain in South Africa matches a folded mountain

chain in Argentina.

3. Coal fields with distinctive layers in Brazil are similar to those in

Africa

4. Glacial deposits are found in South America, Africa, India,

Australia, and Antarctica

5. Rock deposits of coal, salts, and limestone derived from coral reefs

suggest changes in climate caused by continental drift.

C. Evidence from the Ocean Floor

1. New mapping techniques of the 1950’s and 1960’s allowed scientists

a closer look at the ocean floor.

2. Harry Hess, a geologist and Navy submarine commander, proposed

the theory of sea-floor spreading in 1960.

3. Scientists discovered the midocean ridge system, an undersea

mountain range that snakes around the globe.

a. At the midocean ridge, a great deal of volcanic activity causes lava

to erupt from the rift valley.

b. The lava hardens and forms new ocean floor. This is called ocean-

floor spreading, and helps to explain how the continents drift.

c. Old ocean floor that is pushed away from the ridge eventually

moves down deep in the Earth along trenches through a process

called subduction.

Review Questions

1. What scientist developed the theory of continental drift?

2. What evidence was needed to prove the theory of continental drift?

3. Explain how ocean-floor spreading helps prove the theory of continental

drift.

III. Earth’s Moving Plates

A. Lithosphere- contains the crust and the uppermost part of the mantle

and is composed of plates

1. There are 7 major plates named after their associated continents,

or surface features (Ex. North American plate, South American

plate)

2. The Pacific is the largest plate, covering one-fifth of Earth’s

surface.

B. Plate Boundaries- where two plates meet

1. Divergent boundary- plates move apart (diverge) , ex. Midocean

ridges

2. Convergent boundary- plates come together (converge)

a. creates pressure and friction

b. can cause earthquakes and volcanoes

3. Strike-slip boundary- two plates grind together and slip past one

another horizontally (Ex. San Andreas Fault in California)

C. Plate Motion Hypothesis- convection currents caused by heat deep

within the Earth may be responsible for the movement of continents

1. The layer below the lithosphere is called the asthenosphere and can

flow like a liquid due to the intense heat and pressure in the mantle.

2. Material closer to the core is warm and rises, mantle material closer

to the lithosphere is cooler and sinks

3. The rising and sinking cycle of the mantle material creates a circular

motion that carries the plates of the Earth

Review Questions

1. Why would a divergent boundary at the midocean ridge also be called a

constructive boundary?

2. Explain what allows the plates of the Earth to move and could cause the

continents to drift.

IV. Theory of Plate Tectonics

A. Links together the ideas of continental drift and ocean-floor spreading

B. Explains how the Earth has evolved (changed) over time

C. Helps explain formation, movements, collisions, and destruction of the

Earth’s crust

D. Helps scientists understand the past and helps predict the future

V. Earthquakes

A. Shaking and trembling resulting from movements of Earth’s crust or

plate tectonics

1. Most common cause of earthquakes is faulting- a break in the

Earth’s crust

a. Most faults lie between the surface and a depth of 70 kilometers

b. Focus- point below Earth’s surface where rocks break and move

c. Epicenter- point above Earth’s surface directly above the focus

2. Movement at faults occur due to convection currents

3. Energy is released as the crust moves in the form of seismic waves.

B. Types of Faults ( a break or crack where rocks move)

1. Normal faults- cracks where tension causes one block of rock

(hanging wall) is sliding downward and away from another rock (foot

wall)

a. Hanging wall- block of rock above the fault

b. Foot wall- block of rock below the fault

2. Reverse faults- compression causes one rock (hanging wall) to move

up relative to the other rock (foot wall)

3. Strike-slip faults- shearing forces cause cracks between two plates

to slide past one another

C. Types of Seismic Waves (Earthquake waves)

1. Primary Waves or P waves- travel fastest, travel through solids,

liquids and gases

a. push-pull waves that push rock particles ahead of them

b. speed up when passing through denser material

2. Secondary Waves or S waves- slower than P waves, travel through

solids, but not liquids and gases

a. cause rocks particles to move from side to side

b. speed up when passing through denser material

3. Surface Waves or L waves- slowest-moving seismic waves

a. originate at the epicenter

b. cause most of the damage during an earthquake

c. earth’s surface moves up and down as each L wave passes

D. Measuring Seismic Waves

1. Seismographs- instrument that detects and measures seismic waves

2. Today's high-technology, digital seismographs record ground shaking

over a large band of frequencies and seismic amplitudes.

3. Seismologists determine the strength of an earthquake by studying

the height of waves recorded by seismographs .

a. Richter Scale- an open-ended theoretical scale used to measure the

magnitude of earthquakes (8.9 is largest magnitude assigned to an

earthquake).

i. The scale is logarithmic. Therefore an increase of 1 magnitude

unit represents a factor of ten times in amplitude.

ii. For example, the seismic waves of a magnitude 6 earthquake are

10 times greater in amplitude than those of a magnitude 5

earthquake.

b. Modified Mercalli Scale Measures earthquake intensity. Describes

damage to structures. Ranges from I (felt by only a few) to XII

(total destruction).

Review Questions

1. What is the underground point of origin for an earthquake called?

2. How do S waves and P waves differ?

3. What type of waves cause the most damage during an earthquake?

VI. History of Seismic Activity in North Carolina

A. The first earthquake recorded in NC history was on March 8, 1735 near

Bath, NC.

B. From February 10 to April 17, 1784 there were 75 earthquakes felt in

McDowell County, NC.

C. April 31, 1886 an earthquake with an epicenter in Charleston, SC caused

the most property damage in North Carolina’s history.

D. February 21, 1916 Asheville, NC - the most intense earthquake in NC

history, measuring a 6 on the Mercalli scale.

E. June 5, 1998 an earthquake in Moorseville, NC measured 3.2 on the

Richter scale, but there was no reported damage.

VII. Use of Seismic Waves in Developing a Model of Earth’s Structure

A. Solid Inner Core

1. When analyzing the activity of seismic waves through the Earth,

scientists found that P waves began to speed up at 5150 kilometers.

This indicates the waves were passing through solid material,

proving the solid composition of the inner core.

2. Scientists theorize the inner core is composed of iron and nickel

which under great pressure become solid.

B. Liquid Outer Core

1. Scientists found that S waves terminated at a depth of 2900

kilometers. This indicates the outer core is liquid.

2. P waves also slow down as they pass through liquids to support this

conclusion.

3. Scientists also theorize the outer core is composed of iron and

nickel, but in liquid form.

C. Mantle- directly above the outer core

1. Plasticity is the property of a solid with the ability to flow like a

liquid at very, very slow rates.

a. High temperature and pressure allow the rock to flow like a liquid

b. This also allows the plates of Earth (lithosphere) to move on the

mantle.

2. The mantle is composed of silicon, oxygen, iron and magnesium.

3. Moho- boundary between the crust and the mantle

a. Change in the speed of seismic waves moving through the Earth led

to its discovery

b. Discovered in 1909 by a Yugoslav scientist, Andrija Mohorovicic

D. Crust- thin outermost layer

1. Oceanic crust – (less than 10 kilometers thick), made mostly of

silicon, oxygen, iron and magnesium

2. Continental crust- (average thickness of 32 kilometers) made mostly

of silicon, oxygen, aluminum, calcium, sodium and potassium

Review Questions

1. Is North Carolina considered a high risk area for earthquakes?

Why or why not?

2. List the layers of the Earth beginning with the crust.

3. How does the property of plasticity help explain the theory of plate

tectonics?

Plate Tectonics

is thought to be driven by describes is a theory supported by convection currents in the mantle movement of plates data and observations where plates slip by plates diverge plates converge each other San Andreas at at at divergent boundaries producing convergent boundaries transform boundaries that include Continental rifts mid-ocean ridge continental- oceanic- oceanic-continental continental oceanic Mid-Atlantic Ridge creating make where trenches large mountain belts one plate moves under another Word Bank Himilayas convection currents subductionsubduction divergent theory trenches San Andreas Himilayas

Created by: CIESE Real Time Data Projects

http://www.k12science.org/curriculum/musicalplates3/en/studentactivities.shtml

Activity 1 Student Worksheet: Plot Current Earthquake Data

Materials

You will need either a small world map to plot the earthquakes individually or in a small group OR a

large world map to plot the earthquakes as a class. If you do not have a map, you can download a

map from the National Geographic Xpeditions web site.

Instructions:

1. Click on one of the web sites listed below to see all of the earthquakes that have occurred

over the last few days which were larger than 2.5 on the Richter Scale. Note that in the first

two columns you will see the time and date for each earthquake. Note that in the second two

columns you will see the latitude and longitude coordinates for the epicenter of the

earthquake.

o TEXT-BASED (Recommend)

USGS Earthquake Bulletin

http://earthquakes.usgs.gov/recenteqsww/Quakes/quakes_all.html

NOTE: Magnitude Greater Than 2.5 Earthquakes From Around the World

IRIS List of Earthquakes (last 30 days)

http://www.iris.edu/seismon/last30days.phtml

NOTE: a latitude of + corresponds to degrees North and a latitude of -

corresponds to degrees South

a longitude of + corresponds to degrees East and a longitude of - corresponds

to degrees West

o INTERACTIVE MAPS

USGS

Recent earthquakes with tectonic plate boundaries (last 7 days)

http://neic.usgs.gov/neis/bulletin/

Recent earthquakes (last 7 days)

http://earthquakes.usgs.gov/recenteqsww/

IRIS Seismic Monitor

http://iris.edu/seismon/

2. Use the latitude and longitude coordinates to plot a dot on your world map which represents

the epicenter of the earthquake.

3. Use a blue star if the earthquake occurred near the surface (less than 100 km) and use a red

star if it occurred deep (greater than 100 km) in the earth (you will see the depth

measurements in the table.)

4. NOTE: You can use the links that appear in the last column of the table to assist you in finding

the locations of the earthquakes if using the latitude and longitude coordinates is too

difficult.

5. Do this for a period of one or two weeks.

Activity 2 Student Worksheet: Look for Patterns

1. Instructions:

Your teacher will tell you to record your answers in your 'Musical Plates' journal/notebook OR on this worksheet.

1. At the end of the one or two week period, study the map that you have produced displaying the recent earthquake events. See if you can answer these questions:

a. Do the earthquakes appear to occur all over the earth's surface or only in isolated regions?

b. Is there a recognizable pattern to where earthquakes seem to occur?

c. If such a pattern does exist, could you use it to determine where high risk earthquakes zones are located?

d. Name several high risk zones that the President might want to know about.

2. Now, compare your world map from Activity 1 which has the earthquakes plotted on it to this tectonic plate map below. See if you can answer these questions:

a. Do you see any relationship between the map you created and the map above showing tectonic plates?

b. Do you think that there might be a correlation between tectonic plates and earthquakes?

c. What do you think this correlation is?

d. What do you think is happening in the places where two plates are touching each other?

e. When two plates rub against each what might the results be? Why? How might this relate to earthquakes?

3. If you distinguished between shallow and deep earthquakes when you plotted the data, examine this plate boundary map that shows the types of boundaries (i.e. convergent, divergent, transform) that exist between certain plates. See if you can answer the following questions:

a. Do deep earthquakes seem to correlate to any particular type of plate boundary? If so, what type of boundary?

b. Do shallow earthquakes seem to correlate to any particular type of plate boundary? If so, what type of boundary?

c. If there is a correlation, can you explain it?

Activity 3 Student Worksheet: Where will your home be in a million years?

Instructions:

1. Locate the station HILO in Hawaii on the GPS Time Series Global Velocities Map below:

2. Use the scaling arrow at the bottom of the left-side of Global Velocities map to determine the speed at which station HILO is moving ("5 cm/yr --->"). See if you can answer these questions:

a. How fast is it moving in one year?

b. How far will it move in 10 years? 100 years? 1,000 years? 100,000 years? a million years?

Don't forget to include the units (cm, m, km, etc.)

Year(s) Years 1 - ___________________ 1,000 - ___________________ 10 - ___________________ 100,000 - ___________________ 100 - ___________________ 1 million - ___________________

3. Determine the plate on which station HILO is located. What plates are touching it?

4. Use the "direction arrow" for station HILO to determine the direction that that station will move in. Assuming that station HILO remains moving in that direction, use the scale on your map to determine where station HILO will be in for each of the time periods above.

Don't forget to include the units (cm, m, km, etc.)

Year(s) Years 1 - ___________________ 1,000 - ___________________ 10 - ___________________ 100,000 - ___________________ 100 - ___________________ 1 million - ___________________

5. Do the same activity for station AUCK in Auckland, New Zealand.

Don't forget to include the units (cm, m, km, etc.)

Year(s) Years 1 - ___________________ 1,000 - ___________________ 10 - ___________________ 100,000 - ___________________ 100 - ___________________ 1 million - ___________________

6. See if you can answer these questions: a. How would the movement of either station affect the climate that plants and

animals located on the land mass would experience?

b. How might this change in climate affect the habitat on the land mass?

c. How might this habitat affect the animals?

d. What animals living in the region might become extinct and which might be able to survive?

7. Based on the map of plate movements, where will North Carolina be in 100 years? 1000 years?

EXTENSION

1. Scroll down past the Global Velocities Map, http://slideshow.jpl.nasa.gov/mbh/series.html 2. Click on the station you would like to view 3. You can access the geodetic position measurements from that station from 1990 to the

present day to determine its direction and movement for the last 10 years.

GPS Time Series Global Velocities Map