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WebQuest: Exploring Earthquakes
http://express.howstuffworks.com/wq-earthquake.htm
Compared to the rest of the planet, the Earth's solid crust is incredibly thin - like the skin of an apple. If you started drilling
in your backyard, you would go through 25-40 miles of this solid rock - which sounds like a lot, except that after that you
would hit 1,800 miles of very hot liquefied metal before reaching the planet's solid core.
So the land we walk on is really just a thin, brittle crust floating on a huge ball of molten goo. Or, more accurately, it's a
bunch of pieces of crust, called plates, sliding around on goo (very slowly), rubbing against each other. Where these
plates meet, you'll find faults -- breaks in the Earth's crust where the blocks of rock on each side are moving in different
directions, in sudden starts and stops. Land along faults will stay stationary for years, even decades at a time, building up
pressure When enough pressure builds, the land will shift abruptly and with great force. The result is an earthquake.
One of the most devastating earthquakes in recent memory struck Bam, Iran, on December 26, 2003. The quake flattened
most of the historic city, including a 2,000-year-old medieval mud fortress (the world's largest). In the end, the city looked
like a sandcastle knocked over by an ocean wave. The quake killed more than 40,000 people, roughly the same number
of people at a sold-out major league baseball game.
Fast Facts
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There are about 8,000 earthquakes a day. That's one every 11 seconds!
Only 1 in 5 earthquakes can be felt by people, and only 1 in 5,000 causes any damage.
The plates on either side of the San Andreas Fault Zone slide past each other at a rate of about 2 to 4 inches per
year. This is about the same rate at which fingernails grow.
Assuming this rate of movement continues, Los Angeles and San Francisco could be right next to each other in
approximately 15 million years.
Between 1975and 1995, there was a significant earthquake in every state except Florida, Iowa, North Dakota, and
Wisconsin.
On average, Alaska has a magnitude 8 or greater earthquake every 14 years. It has had 12 7.0 quakes in the past
30 years alone.
(Source for all fast facts is USGS)
WebQuest Online Exercise
In this journey around the Web, we'll discover what causes earthquakes, how scientists can figure out their exact
location, where they occurred last week and much, much more! Click on the Web site(s) after each question to find
your answer.
1. Around 1912, German meteorologist Alfred Wegener developed a theory called continental drift. He believed that
about 225 million years ago, giant landmasses gradually shifted and broke apart to form the continents as we
know them today. How many original "supercontinents" did Wegener's theory of continental drift assume?
o www.exploratorium.edu/faultline/earthquakescience/pangea.html
2. The Earth's crust is made up of a series twelve interconnected landmasses are called tectonic plates. What are the
major plates that affect the United States?
o www.usatoday.com/graphics/news/gra/quake/frame.htm
o www.bbc.co.uk/science/hottopics/naturaldisasters/earthquakes.shtml
3. Check out this hazard map showing probability for earthquakes. Why do you think California has so many
earthquakes but Florida doesn't? In what hazard zone is your home located?
o www.usatoday.com/graphics/news/gra/earthquakemap/frame.htm
4. What is considered to be the most destructive earthquake in history? When did it occur, where was it, what was its
magnitude and how many people died?
o http://neic.usgs.gov/neis/eqlists/eqsmosde.html
5. What are the three basic types of plate boundaries? Describe each briefly.
o http://www2.nature.nps.gov/geology/usgsnps/pltec/pltec3.html
6. What are tsunamis, what causes them and how fast do they travel?
o www.usatoday.com/weather/tg/wtsunami/wtsunami.htm
7. What are the two types of energy waves created by an earthquake and how do they differ? Which type of wave
travels faster?
o www.thetech.org/exhibits_events/online/quakes/waves/p&s_waves.html
o www.thetech.org/exhibits_events/online/quakes/grams/
8. How much more energy is released by a 7.2 earthquake than by a 6.2 earthquake?
o http://neic.usgs.gov/neis/eqlists/eqstats.html
9. What applications does seismology have besides measuring the magnitude and location of earthquakes?
o www.thetech.org/exhibits_events/online/quakes/app/nuclear.html
o www.thetech.org/exhibits_events/online/quakes/app/xray.html
10. Where did most of the earthquakes happen last week?
o http://earthquake.usgs.gov/recenteqsww/index.html (World map with clickable regions)
o http://earthquake.usgs.gov/recenteqsUS (U.S. map with clickable regions)
11. How do scientists know where an earthquake actually occurred?
o science.howstuffworks.com/earthquake5.htm