Chapter 2Forces 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 less-dense 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. 1B. 3C. 4D. 2

2.Where do seismic waves originate from?

A. Focus

B. Epicenter

C. Seismograph

D. Primary point

3.What is the fastest seismic wave?

A. 1st surface

B. 2nd surface

C. Secondary

D. Primary

4.True or False? Earthquakes can make volcanoes erupt.

5.melted rock that has reached Earth’s surface is called what?

A. Magma

B. Lava

C. Vent

D. Cinder

6.What has more density?

A. Rock

B. Magma

7. How many types of eruptions are there?

A. 1

B. 3

C. 2

D. 4

8.How many types of cones are there?

A. 4

B. 5

C. 3

D. 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. Heat

B. Pressure

C. Vents

D. Faults

The End!!!