Agenda: Wed Opening Activity- basic review of plate tectonics Finish volcano PPT Earthquakes Bill Nye video Assignment- time to work on tomorrow and Friday in LAB 222

Earthquakes

Tell me what you know about earthquakes...

Some Facts... The largest recorded earthquake occurred on May 22nd, 1960 in Chile. It measured 9.5 on the Richter Scale. Approximately 500,000 earthquakes occur worldwide every year. Approximately 100,000 can be felt and 100 cause damage. The California area has about 10,000 earthquakes every year. Earthquakes on one side of the Earth can shake the other side of the Earth. In 2004, a tsunami occurred in the Indian Ocean. Earthquakes were felt as a result in California. The deadliest earthquake ever occurred on January 23rd, 1556 in Shansi, China. 830,000 are estimated to have died.

What is an Earthquake? Some definitions: The result of a sudden release of energy in the Earth's crust that creates seismic waves Or in simple terms: THE EARTH SHAKING! An earthquake can cause significant damage to buildings and other structures. The amount of damage is determined by factors such as the length of the earthquake and the magnitude.

Where do earthquakes occur? What do we notice about the location of many of these earthquakes?

Where do earthquakes occur? Earthquakes usually occur along the boundaries of the Earth’s tectonic plates

How do we know an earthquake is occurring? We don’t always know an earthquake is happening! It depends on the intensity of the earthquake. The most obvious sign is when the ground and everything around us is shaking Sometimes we may only see items around us swaying gently (e.g. hanging plants waving back and forth, items wobbling on a shelf) You may hear a low rumbling noise

Why do earthquakes occur? Driven by the heat of the Earth’s mantle, plates grind against each other along the boundaries of the Earth’s tectonic plates. These are called “faults”. When the plates get stuck, stress builds up and the fault gives way. Energy then releases and travels within the Earth and along its surface. These are called seismic waves

Hypocentre The hypocentre of an earthquake is where the earthquake begins to occur (where the fault begins to rupture)

Epicentre The epicentre of an earthquake is the point on the Earth’s surface directly above where the earthquake occurs (where the fault begins to rupture) In most cases, the epicentre is where the most damage occurs.

How do we measure earthquakes? A tool called the “Richter Scale” is used to determine the magnitude (extent or intensity) of an earthquake. The Richter Scale was invented in 1935 by Charles Francis Richter. He invented it to compare the size of different earthquakes. It measures the ground motion using multiples of 10. A magnitude 2.0 earthquake has 10 times the amount of ground motion as a magnitude 1.0 earthquake. A magnitude 3.0 earthquake has 10 times the amount of ground motion as a magnitude 2.0 earthquake and so on.

Average earthquake effects Frequency of Occurrence (average) Magnitude Average earthquake effects Frequency of Occurrence (average) Less than 2.0 “Microearthquakes” -- not felt at all. Only recorded by seismographs. Continual/several million per year 2.0–2.9 Felt slightly by few people. No damage to buildings. Over one million per year 3.0–3.9 Often felt by at least some people, but very rarely causes damage. Shaking of indoor objects can be noticeable. Over 100,000 per year 4.0–4.9 Noticeable shaking of indoor objects and rattling noises. Most people feel the earthquake. Generally causes no damage to slight damage. Moderate to significant damage very unlikely. Some falling of objects. 10,000 to 15,000 per year 5.0–5.9 Can cause moderate to major damage to poorly constructed buildings. At most, no damage to slight damage to all other buildings. Felt by everyone. Deaths can depend on the effects. 1,000 to 1,500 per year Magnitudes

6.0–6.9 Can be damaging/destructive in populated areas in regions of any size. Damage to many buildings. Poorly-designed structures receive moderate to severe damage. Felt in wider areas; likely to be hundreds of miles/kilometers from the epicenter. Can be damaging of any level further from the epicenter. Strong to violent shaking in epicentral area. Death toll between none and 25,000. 100 to 150 per year 7.0–7.9 Causes damage to many to all buildings over areas. Some buildings partially or completely collapse or receive severe damage. Well- designed structures are likely to receive damage. Felt in enormous areas. Death toll is usually between none and 250,000. 10 to 20 per year 8.0–8.9 Major damage to poorly-designed buildings and most structures, likely to be destroyed. Will cause moderate to heavy damage to normal and earthquake-resistant buildings. Damaging in big areas. Possible total destruction. Definitely felt in unusually large regions. Death toll is usually between 100 and one million; however some earthquakes this magnitude have killed none. One per year (rarely none, two, or over two per year) 9.0–9.9 Severe damage to all or most buildings with massive destruction. Damage and shaking extends to distant locations. Ground changes. Death toll usually between 1,000 and several million. One per 5 to 50 years Magnitudes

Interesting Fact Two plates, the Pacific and the North American, meet in California. The Pacific Plate is moving north, creating a transform fault (called the San Andreas Fault) Over the last 20 million years the Pacific Plate has slid about 200 miles north. If it keeps moving as predicted, San Francisco will become neighbors with Seattle in 20 million years!

Tsunamis Giant waves occur when the epicentre of an earthquake occurs in water If this earthquake occurs close enough to land, the nearest coast is in danger of a tsunami – the large waves hitting land and flooding everything in its path These waves get larger and faster as they approach land. They only slow down when they hit really shallow waters. Video of 2010 Japan Tsunami: http://www.youtube.com/watch?v=w3AdFjklR50

How to stay safe from earthquakes If an earthquake occurs while you are indoors, it is best to remain indoors. The safest places to be are away from any potential falling objects. Under a strong desk or table is strongly recommended or under the structural strong points of a room. If you are cooking, turn off the stove or oven. If you are outdoors, get to the most open area you can find – away from trees, powerlines and buildings. This is important to know because earthquakes can and have happened in Ottawa! (http://www.youtube.com/watch?v=EKKAEkybanQ)

Some videos: Buildings swaying following a 9.0 magnitude earthquake in Japan: http://www.youtube.com/watch?v=Sn4t13uxJFQ Footage from 2010 Japan Earthquake: http://www.youtube.com/watch?v=jBdvvXyS-r4 Bill Nye the Science Guy – Earthquakes: http://www.youtube.com/watch?v=IqBZUqEg5fQ