Transcript Forces in Earth

Chapter 2
Forces in Earth
By:
Amber
Kim
Kylah
What Causes Earthquakes
• Pressure builds up inside the earth and
stretches rock to its limit it breaks and
causes a vibration that travels through the
earth called an earthquake
Faults
• A Fault is a fracture within Earth where rock
movement occurs
• Normal fault- When rock moves along a fracture
caused by tension forces. Rock above the fault
moves downward in relation to the rock below the
fault surface.
• Reverse fault- When compression force break rock,
the rock above the fault surface moves upward in
relation to the rock below the fault surface
• Strike-slip fault- Shearing forces push on rock in
opposite, but not directly opposite,horizontal
directions
Seismic Waves
• Seismic Waves- earthquake generated waves that travel
through the ground as vibrations
• Focus- the point in Earth’s interior where seismic
waves originate
• Epicenter- the point of earth’s surface directly above
the focus
• Seismograph- an instrument used by scientists to
detect seismic waves as far away as the other side of
the earth
• There are four types of
seismic waves…
Primary & Secondary
waves & 1st & 2nd
surface waves
Speed of Waves
• Surface waves- travel slower than primary
and secondary waves and cause the most
damage
• Primary waves- travel about twice as fast as
secondary waves
• Secondary waves- travel faster than surface
waves but slower than primary waves
Relationship Between
Earthquakes &Volcanoes
• Earth quakes and volcanoes often occur in the
same region
• Volcanic eruptions may trigger some earthquakes
• Pressure is a main cause for both of them
Volcanic Vocabulary
• Magma- Melted rock under earth’s surface
• Lava- Magma that has reached earth’s
surface
• Vent- an opening in earth’s crust were
magma flows through
Volcanic Eruptions
• Magma rises to the surface because lessdense materials (magma) are pushed
upward by denser materials (rock)
• When magma reaches earth’s surface it is
called an eruption
Types of Eruptions
• Some volcanoes erupt with such violent
explosions that the sound is heard thousands
of miles away and the force of the blast
blows away great chunks of the volcano.
• By comparison, some other volcanoes erupt
rather quietly. Melted rock boils out of one
or more openings in earth and flows
outward, until it cools.
Volcano Formations
• There are 3 different types of volcano cones
• Shield Volcano- When hot, thin lava flows without violent explosions
out of one or more vents and then cools and hardens, it builds a gentle
slope.
• Cinder Cone- When volcanic ash and slightly cooled lava are forced
out of a single vent during an explosive eruption, they fall back to
earth. The ash and cooled lava form the steep slope of a cinder cone
around the vent
• Composite Cone- if a volcano throws out flowing lava, hardened lava,
and chunks of ash, a composite cone is formed. Because the layers of
lava cover and protect the layers of loose materials from
erosion,composite cones build into steep-sided towering mountains.
References
• Glencoe Science Interactions Course 2
• Websters Dictionary
• Encyclopedia
Quiz
Chapter 2
Forces in Earth
You may use notes
1.how many different types of
faults are there?
A. 1
B. 3
C. 4
D. 2
2.Where do seismic waves
originate from?
A.
B.
C.
D.
Focus
Epicenter
Seismograph
Primary point
3.What is the fastest seismic
wave?
A.
B.
C.
D.
1st surface
2nd surface
Secondary
Primary
4.True or False? Earthquakes can
make volcanoes erupt.
5.melted rock that has reached
Earth’s surface is called what?
A.
B.
C.
D.
Magma
Lava
Vent
Cinder
6.What has more density?
A. Rock
B. Magma
7. How many types of eruptions
are there?
A.
B.
C.
D.
1
3
2
4
8.How many types of cones are
there?
A.
B.
C.
D.
4
5
3
2
9.What is the steepest cone?
A. Composite
B. Cinder
C. Shield
10.What is the one thing that has
a part in the cause of both
earthquakes and volcanoes?
A.
B.
C.
D.
Heat
Pressure
Vents
Faults
The End!!!