1.
Earthquakes

2. Describe the three types of Volcanos
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Describe the three types of Volcanos

3. Earthquakes are natural vibrations of the ground caused by movement along fractures in Earth’s crust, or sometimes, by volcanic eruptions.
Fractures form when stress exceeds the strength of the rocks involved.
Stress is the forces per unit area acting on a material.

4. Strain is the deformation of materials in response to stress.
There are three kinds of stress that act on Earth’s rocks:
Compression is stress that decreases the volume of a material.
Tension is stress that pulls a material apart.
Shear is stress that causes a material to twist.
Strain is the deformation of materials in response to stress.

5. A fault is the fracture or system of fractures along which movement occurs.
The surface along which the movement takes places is called the fault plane.

6. There are three basic types of faults:
Reverse faults are fractures that form as a result of horizontal compression.
Normal faults are fractures caused by horizontal tension.
Strike-slip faults are fractures caused by horizontal shear.

7. Most earthquakes are caused by movements along faults.
Irregular surfaces in rocks can snag and lock, causing stress to build in the rocks.
When the rocks reach their elastic limit they break, and this produces an earthquake.

8. Every earthquake generates three types of seismic waves.
The vibrations of the ground during an earthquake are called seismic waves.
Every earthquake generates three types of seismic waves.
Primary waves, or P-waves, are the first waves detected and travel to the center of the earth

9. Types of Seismic Waves
Secondary waves, or S-waves, are the second waves detected and also travel to the center of the Earth
Surface waves travel along Earth’s surface with little detection in the lithosphere

10. Types of Seismic Waves
The focus of an earthquake is the point of failure of rocks at the depth where an earthquake originates.
The epicenter of an earthquake is the point on Earth’s surface directly above the focus.

11. Seismographs or Seismometers are sensitive instruments that detect and record the vibrations sent out by earthquakes.
A seismogram is the record produced by a seismometer.

12. Travel-Time Curves
Seismologists have been able to construct travel-time curves for P-waves and S-waves of an earthquake
For any distance from the epicenter, the P-waves always arrive first at a seismic facility
The time separation between the curves for the P-waves and S- waves increases with travel distance
From this separation, the distance of a quake to the seismic facility can be determined

14. We know about Earth’s Interior because of seismic waves which change speed and direction when they hit different materials.
When waves hit the mantle they travel in direct paths which shows its liquid. Waves bend when they hit the core which shows it is solid.

15. Magnitude is the measurement of the amount of energy released during an earthquake.

16. Richter Scale- measures the largest seismic waves generated by an Earthquake- each a factor of ten on a scale of 1-10
Moment Magnitude Scale- measures the size of the fault and amount of movement
Modified Mercalli Scale- Rates the damage using Roman Numerals I- XII

18. An Epicentral distance tells the distance of the epicenter to a seismic station
It takes three seismic stations to find the epicenter because you must find where the epicentral distances meet 18