Mary Ann Kurke
Illinois Geographic Alliance Summer Alaska Tour, 2001

Preview of Main Ideas

The devastating effect of earthquakes has always interested students. This activity is designed to have students briefly learn about earthquakes in general and discover that Alaska has more earthquakes than any other state. The main focus of this lesson is to have students become aware of plate tectonics and the geologic activities that coincide with plate boundaries.

Connection with the Curriculum

This lesson could be used in a geography, social studies, physical science, or geology class.

Teaching Level: Grades 5 – 8

Objectives Classification Outline

Objective # 1: The students will become familiar with earthquakes and plate tectonics in general.

Materials

1. A copy of a map showing the drifting continents (provided)
2. A copy of a "Plate Tectonics Map" (provided)
3. A copy of a map depicting "Tectonic Plate Boundaries" (provided)
4. A copy of facts about earthquakes and plate tectonics – "Shake, Rattle & Roll Alaska, the Earthquake State." (provided)
5. A copy of facts about the "Great 1964 Alaskan Earthquake".(provided)
6. A diagram showing "Major Types of Plate Movement" (provided)
7. Shake, Rattle and Roll Worksheet (provided)

Suggestions for Teaching the Lesson

Opening the Lesson

1. Day 1: Ask students; (1) If they have ever experienced an earthquake?  (2) What causes earthquakes? and (3) What state experiences the most earthquakes?
2. After students have completed discussing the 3 questions, pass out a copy of "Shake, Rattle and Roll - Alaska the Earthquake State". Have students take turns reading the information aloud.
3. Pass out a copy of the "Great 1964 Alaskan Earthquake". Have students again take turns reading the facts.
4. Discuss the readings and answer any questions the students might have.

Developing the Lesson

1. Day 2: Pass out a copy of the map showing drifting continents. Discuss how the continents have moved.
2. Pass out a copy of the map depicting Tectonic Plate Boundaries. Ask students what geologic occurrences are found at plate boundaries? Expected answers - Earthquakes and Volcanoes. Discuss the map and remind students that the plates are moving very slowly (2 to 5 inches per year).
3. Pass out a copy of the map labeled "Plate Tectonics". Have students label the plate names and have them shade in the Earthquake Zone. Ask students what will possibly become of California since part of it is on the Pacific Plate and the rest on the North American Plate. Expected Answer: The Pacific Plate section (from Baja California to San Francisco) will split from the rest of the state and slide in a northwest direction.

Concluding the Lesson

1. Day 3: Pass out the diagram depicting "Major Types of Plate Movements". Discuss, cite examples of where each type of plate movement is occurring. Possible Examples include; Subduction – Alaska, with the heavier Pacific Plate subducting under the lighter North American Plate. Spreading – Mid-Ocean Ridge of the Atlantic Ocean, Sea-floor Spreading. Converging – India pushing into the Eurasian Plate causing the Himalayan Mountains. Faulting – The San Andreas Fault of California
2. Pass out and assign the "Shake, Rattle and Roll" Worksheet.

Extending the Lesson

1. Show a video on earthquakes, or Plate Tectonics
2. Have students do research on earthquakes, volcanoes, The Pacific Ring of Fire, Tsunamis, Continental Drift Theory (plate tectonics), on the Internet and report interesting facts to the class.
3. Have students do research, or create posters depicting famous volcanic eruptions, or devastating earthquakes and report/show them to the class.
4. Have students compare the great 1964 Alaskan earthquake with another recent earthquake.

Assessing Student Learning

1. Quiz students on general facts relating to earthquakes and plate tectonics.
2. Grade the "Shake, Rattle and Roll" worksheet and the Plate Tectonics Map.
3. Have students write a paper summarizing Plate Tectonics and also explain what types of movement occurs at plate boundaries (Subduction, Converging, Faulting Spreading).

Acknowledgments

Baerwald, Thomas J. and Fraser, Celeste. World Geography a Global Perspective. New Jersey: Prentice Hall, 1995.

Christensen, Doug. "Great Prince William Sound Earthquake." Fairbanks: Geophysical Institute of University of Alaska, 2001.

Elliott, Dr. Monty. Geology Lecture on the Great Alaskan Earthquake. Geologist for the Universe Explorer Cruise Ship. 25 July 2001.

Microsoft Encarta Encyclopedia, 99 ed. "Earthquakes."

Microsoft Encarta Encyclopedia, 99 ed. "Tsunami."

Tarbuck, Edward J. and Lutgens, Frederick K. Earth an Introduction to Physical Geology. New Jersey: Prentice Hall, 1999.

US Department of Commerce Report. "1964 Alaskan Earthquake." Alaska: 1964.

USGS National Earthquake Information Center. "Alaska Earthquakes, Active Faults, and Rupture Zones." Denver: World Data Center for Seismology, 2001.

USGS National Earthquake Information Center. "Earthquake History of Alaska." Denver: World Data Center for Seismology, 2001.

USGS National Earthquake Information Center. "Largest Earthquakes in the United States." Denver: World Data Center for Seismology, April 5, 2001

"Walker, Bryce. Planet Earth Earthquake. Alexandria: Time-Life Books, 1982.

World Book Encyclopedia, 1975 ed. "Earthquakes."

When most people think of earthquakes the state of California comes to mind. However, Alaska is the "Earthquake State" having more tremors than any other region in North America and is by far the most active of the 50 states. Alaska has 11% of the World’s earthquakes and 52% of all earthquakes in the U.S. The state averages over 5,000 earthquakes yearly, 350 – 500 monthly, 70 – 120 weekly, and 10 – 20 daily. Alaska averages one earthquake of a magnitude of 8 or greater every 10 years. The state accounted for three of the six largest earthquakes in recorded history, and seven of the ten largest earthquakes in the U.S.

Earthquakes are vibrations of the earth produced by the rapid release of energy from rocks that break because they have been subjected to stress beyond their limit. The movements that cause most earthquakes occur along large fractures, called faults that are usually associated with plate boundaries. Along a fault, rocks store energy as they are bent. As the rocks move the strain is so great that the breaking point is reached and the rock will spring back to its original shape. The energy released radiates out in all directions from the focus (its source) in the form of shock waves that we call an earthquake.

The earth’s crust is not one solid piece of rock. Instead the crust and upper mantle is broken into a number of large moving plates. These plates are not stationary, but move very slowly over a hot and pliable layer of the mantle. The earth’s continents and oceans ride atop these plates as they move in different directions (see diagram of drifting continents). It is along the boundaries where plates meet that most earthquakes and other geologic events occur. Look at the map of Tectonic Plate Boundaries. Notice the incidence of earthquakes and volcanoes along the plate boundaries.

Where plates meet at their boundaries, one of three different reactions will occur when there is movement. (See Major Types of Plate Movement Diagram.) 1. They pull away from each other, known as diverging or Spreading. Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges and movement of the crust away from the mid-ocean ridges. 2. They grind past each other, known as Faulting. The sliding plates cause an area of high earthquake activity and often a fault line may be seen. 3. They move toward each other, causing Subduction or Converging. Subduction occurs when a heavier plate dives under a lighter plate. Volcanic Mountain building and earthquakes may occur, as well as a deep trench. Converging occurs when plates of equal weight collide. They meet head on causing mountain building and of course earthquakes.

The Great 1964 Alaskan Earthquake

On March 27, 1964 one of the most violent earthquakes ever recorded occurred in Alaska at 5:36 P.M. Good Friday. The quake had a magnitude of 8.5 to 8.6 on the Richter Scale. This was later revised to 9.2 on the Moment Magnitude (an entirely different scale adopted in 1976). The death toll of 131 was extremely small for a quake of this size, due to low population density, and the time of occurrence. Since the trembler occurred on a holiday, schools were closed and business areas uncrowded. It also occurred at a time when most people were out of office buildings and on their way home from work, and the tides were low, helping to prevent the death toll from surpassing 131. Total damage from the earthquake was between $400 and $500 million. Some interesting facts about this strong earthquake can be found below.

• The great Alaskan earthquake of 64 was the largest earthquake in North America and the second largest ever recorded (the largest occurred in Chile in 1960 – 9.5 magnitude).
• The epicenter was in the Northern Prince William Sound about 75 miles east of Anchorage, or about 55 miles west of Valdez – Latitude 61.04 N, Longitude 147.73 W.
• The depth, or focus point was about 14 miles within the earth’s crust.
• The strong ground motion reported in the Anchorage area lasted about 4-5 minutes (the average shaking from most quakes is 30 seconds). It was reported that it was impossible to stand up in Anchorage.
• The 4-5 minute shaking triggered many landslides and avalanches.
• Thousands of aftershocks were recorded in the months following the main shock. In the first day 11 of these aftershocks had a magnitude greater than 6.0 on the Richter scale; in the next 3 weeks there were 9 more. Smaller aftershocks continued for more than a year.
• This earthquake generated a seismic sea wave (tsunami) that devastated towns along the Gulf of Alaska and left serious damage along the west coast of the United States, and in Hawaii. The tsunami traveled 400 mph and the largest wave height was near Valdez Inlet (221 feet).
• The earthquake caused at least 5 local slide generated tsunamis within minutes of the earthquake. In Seward, a city about 90 miles from Anchorage, a section of the waterfront slid into Resurrection Bay. This created a local tsunami causing much damage and the spreading of oil which was on fire and floating on the water. About 20 minutes after this occurred the first wave of the main tsunami arrived.
• Kodiak Island was hit with 10 sea waves, 17 feet above normal water level
• Anchorage sustained the most severe damage to property. About 30 blocks of dwellings and commercial buildings were damaged or destroyed in the downtown area.
• Landslides in Anchorage caused heavy damage. Huge slides occurred in the downtown business section. In Turnagain Heights an area of 130 acres was devastated by displacements that broke the ground into many deranged blocks that were collapsed and tilted at all angles. This slide destroyed about 75 private homes. Water mains, gas, sewer, telephone, and electrical systems were destroyed throughout the area.
• ¼ of the State’s highways suffered damage, and ½ of all the bridges had to be rebuilt.
• 75% of the state’s commerce and industry was in ruins.
• The earthquake caused as much as 33 feet of uplift near the epicenter. Kodiak Island dropped 5 feet, and sections of downtown Anchorage dropped 30 feet.
• A 6 foot drop, near the city of Portage, allowed salt water from the Turnagain Arm to filter into land killing the Spruce trees and creating a ghost forest that still stands today.
• There was vertical displacement of land over an area of 170,000 to 200,000 square miles
• The main shock and its aftershocks occurred on a fault, which is part of the boundary between the Pacific and North American Plate.
• The cause of earthquakes in this area is the northwestward motion of the Pacific plate at about 5 to 7 cm per year. This causes the crust of southern Alaska to be compressed and warped. After a period of many years, this compression is relieved by the southeastward motion of portions of coastal Alaska as they move back over the subducting Pacific Plate.

Name __________________
Date ___________________
Period __________________

1. List the number of earthquakes the state of Alaska has on an average.

Yearly

Monthly

Weekly

Daily

2. True or False Alaska averages an earthquake of a magnitude of 8 or greater every year.
   
   
3. What is an earthquake?
   
   
   
4. A large fracture or crack in the earth’s surface associated with a plate boundary is called a ______________.
   
   
5. True or False During an earthquake the rocks will spring back to their original shape.
   
   
6. The source of an earthquake that shock waves radiate out from is called its _______.
   
   
7. True or False The crust and upper mantle are broken into a number of large moving plates.
   
   
8. True or False These plates move very rapidly causing earthquakes.
   
   
9. Look at the map of the "Drifting Continents". When all the continents were together the super-continent was called ____________.
   
   
10. Name two continents that were at one time connected.
    
    
11. Look at the map "Tectonic Plate Boundaries". List the names of 9 tectonic plates.

_______________ _______________ _______________

_______________ _______________ _______________

_______________ _______________ _______________

 

12. What is the name of the plate that the United States is on?
    
    
13. What two geologic events occur frequently at plate boundaries?

_______________ _______________



14. True or False The earth’s continents and oceans ride atop these plates as they move in different directions.
    
    
15. Look at the diagram depicting "Major Types of Plate Movement". Are Subducting Plates moving toward or away from each other?
    
    
16. Are Spreading Plates moving toward or away from each other?
    
    
17. Are Converging Plates moving toward or away from each other?
    
    
18. Faulting Plates do not move toward or away from each other. How do they move?
    
    
19. What is the difference between a Subducting and Converging Plate?

 

 

20. Name an area of the world that exemplifies one of the plate movements.
    
    
    Movement Type - _______________ Region of the world - _______________

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