Transcript Earthquakes: Chapter 19

EARTHQUAKES
Year 1 Science
EQ: WHAT 3 STRESSES LEAD TO EARTHQUAKES?
EARTHQUAKES
EARTHQUAKES ARE…
Natural vibrations of crust that
are caused by stress from plate
tectonics
3 TYPES OF STRESSES
Compression:
The squeezing of rock together until it
folds or breaks
3 TYPES OF STRESSES
Tension:
The pulling of the crust until
materials thin and break
3 TYPES OF STRESSES
Shear
Pushing rocks into 2 opposite
directions
EARTHQUAKE WAVES
Vibrations of the ground during an earthquake are
called seismic waves.
 3 Types of Seismic Waves:
Primary Waves: waves that cause rock
particles to move back and forth
Secondary Waves: cause rocks to move at
right angles in relation to the wave
Surface Waves: waves that cause particles to
move in two directions: up and down, side to
side
Epicenter
The point on Earth’s surface directly
above the focus
Focus
The point below ground where the
earthquake originates
MEASURING
EARTHQUAKES
SEISMOMETERS
Scientists use seismometers to measure
ground movement caused by seismic waves
The strength of an earthquake = magnitude (a
# given to an earthquake based on its strength)
RICHTER SCALE MEASUREMENTS
Scale
0-4
4-5
5-6
6-7
7-8
8+
Damage
Minor
Light
Moderate
Strong
Major
Catastrophic
NOTE REVIEW
-Highlight the following headings:
-3 Types of Stresses
-3 Types of Seismic Waves
-Measuring Earthquakes
-Circle the following terms in BLUE:
-Earthquake, Tension, Compression, Shearing, PWaves, S-Waves, Surface Waves, Epicenter,
Focus, Seismometer, Magnitude
-Underline the definitions for the circled terms from
above in GREEN