Earthquakes

Earthquakes

See What’s Shakin’ With Science!

Introduction

An earthquake is a sudden, rapid shaking of the Earth caused by the release of energy stored in the Earth’s crust. “Earthquake” means any seismic event, whether natural (rubbing of tectonic plates) or induced by humans. In this program, we will explore how this happens and some of the effects of earthquakes by making models, building seismographs, and acting out tectonic movement in a game.

Objectives

Students will be able to:

• Create and test hypotheses.
• Discover how earthquakes happen.
• Explore how earthquakes affect structures and how they create so much damage.
• Test which characteristics make for stronger buildings and which are not as ideal.

Background

When we look at the Earth, it appears to have a smooth surface made of one piece. Actually, the surface (outermost layer of the crust and upper mantle) is made up of many large, flat pieces of rock called tectonic plates.

The plate tectonics concept tells us that the Earth's rigid outer shell (lithosphere) is broken into a mosaic of plates that can slide over the uppermost layer of the mantle. The plates are in constant motion, moving at a rate between 2 to 12 cm per year. Heat cycles in the fluid layer beneath the Earth's crust create convection currents that lead to the constant motion of the tectonic plates. There are three common boundaries: convergent (plates crash together), divergent (plates move apart), and transform (plates slide past each other).

At some places the motion of plates isn’t smooth — some parts of plates get stuck against each other while other parts keep moving. When the stress and strain becomes too great, rocks break and the plates move suddenly. The sudden motion and shaking is an earthquake.

Often earthquakes are barely noticeable. However, on occasion they can be strong enough to knock down buildings, break trees in half, and do some other major damage. Earthquakes are commonly measured using the exponential Richter scale. A level 6 earthquake is 10 times as strong as a level 5 which is 10 times as strong as a level 4 and so on.

The largest earthquake ever recorded was magnitude 9.5! This earthquake struck just off the coast of southern Chile on May 22, 1960. It ruptured a segment of fault more than 1,300 km long and caused a tsunami that wreaked destruction around the Pacific Ocean area, including Hawaii and Japan. In this case, the earthquake occurred in an area where the ocean floor is being pushed beneath a continent.

Only a few people will feel a level 1 earthquake. In a level 2 earthquake, a few people who are resting may feel it, especially if they are near the top of a tall building. Nearly everyone will feel a level 5 earthquake, and some dishes and windows will break. Areas with poorly constructed buildings could have major damage. A level 8 can cause damage in areas up to a couple thousand kilometers across!

Earthquakes can occur throughout the world. However, they are most common where 2 (or more) plates meet each other. For example, there are so many earthquakes and volcanoes around the edges of the Pacific Plate that it’s nicknamed “The Ring of Fire.”

What should students do during an earthquake?
(from the Provincial Emergency Program of the Ministry of Public Safety) Drop, Cover and Hold is the most appropriate response to earthquake shaking in British Columbia. Drop under some heavy furniture or into an alcove, cover your head and torso to prevent being hit by falling objects and hold on so that you remain covered.

Entire Lesson

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Other Resources

Science World at TELUS World of Science | Search: The Sara Stern Gallery
Emergency Management BC | Earthquake Information
Natural Resources Canada |  Earthquakes Canada
USGS | Earthquake Hazards Program | Earthquakes for Kids