Download Science Chapter 8 What Causes Earthquakes

Science Chapter 8
What Causes Earthquakes, and How Can They Be Compared? Slides 1-15 notes
Earthquake is a vibration of Earth, caused by release of energy that has been stored along a fault.
Most occur along tectonic plate boundaries
What do you think happens when an earthquake occurs? Plates interact…they slide, collide or
separate.
What kind of damage could these events cause? Buildings fall, people and animals are in danger,
loss of crops, streets break…
Examples of earthquakes:

Guatemala, 1976 23,000 people killed

Mexico , 1985 9,000 people killed
Earthquakes happen on faults.
What is the name of the fault line that runs along the length of California?
San Andreas Fault and it is 720 miles long
Aftershock- is a shock that occurs after the first shock of the earthquake.
Richter Scale- Are numbers ranging from 1 to 10 that describes the magnitude, or strength, of an
earthquake.

Named after American scientist Charles Richter

Minor earthquakes are under 4

Major earthquakes are over 5
Magnitude- is the amount of energy released by the quake.
Focus- the point at which an earthquake begins
Epicenter- the point on Earth’s surface directly above the focus of an earthquake
What do you call a scientist that studies earthquakes?
Seismologists
How have we been predicting Earthquakes? Seismologist have found that there are changes in
the earth before earthquakes happen. So, they watch instruments that measure and record
these changes.
Lesson 1 review
1. Where do earthquakes occur?
2. What is an earthquake?
3. What is the smaller earthquake like activity the happens after the first earthquake?
4. Who studies earthquakes?
5. How can you predict an earthquake?
Lesson 1 review
1. Where do earthquakes occur?
2. What is an earthquake?
3. What is the smaller earthquake like activity the happens after the first earthquake?
4. Who studies earthquakes?
5. How can you predict an earthquake?
Science Ch. 8 Slides 15-33
What Happens To Earth’s crust During an Earthquake?
How are Earthquakes Located and Measured?
How do scientists measure the strength of an earthquake, and how can they predict future
earthquakes?
Seismometer and seismographs
Seismograph - Seismic waves are recorded by this instrument
Pendulum seismograph-measures side to side movements.
Spring seismograph- measures up and down movements
Chinese created the first earthquake detectors known as Chang Heng’s seismoscope in AD132.
Tsunamis- Is a seismic sea wave forms when earthquakes hit the ocean floor.
Tsunamis are also known as DESTUCTIVE WALLS OF WATER
Causes of Tsunamis are:
1. Earthquakes on the sea floor
2. Landslides on the ocean floor
3. Volcanic eruptions
Tsunami Facts are:
1. Can begin at 3ft and can reach a height of 46ft when it strikes land.
2. Travels at 500 mph
Tsunamis can cause damage like:
1. Loss of land
2. Loss of grass/trees
Predicting Tsunamis:
1946 the Tsunami Warning System was established to warn people.
Two warning centers in the USA near Anchorage, Alaska and near Honolulu, Hawaii.
Tsunami sensors that rest of the ocean floor. These sensors are very sensitive and can detect
a change in sea level of less than millimeter.
Chapter 8 Review
Vocabulary
Aftershock
Earthquake
Fault
Richter Scale
Seismograph
Seismologist
Tsunami
Magnitude
Epicenter
focus
Short Answer Questions:
1. What kind of damage could these events cause?
2. How do scientists measure the strength of an earthquake, and how can they predict future
earthquakes
3. What three things Happen to Earth’s crust during an Earthquake?
Test Questions:
1. What is an earthquake?
2. Where do earthquakes occur?
3. What is the smaller earthquake like activity the happens after the first earthquake?
4. Who studies earthquakes?
5. How can you predict an earthquake?
6. What causes a tsunami?
7. What are the two kinds of seismographs and what kind of movements does each measure?