1. Earthquakes and Volcanoes
A Changing Earth
Earthquakes and Volcanoes

2. EARTHQUAKES Plate Tectonics
Lithosphere – the crust and upper part of the earth’s mantle
Inner Core
Outer Core
Mantle
Crust 4 3 1 2

3. EARTHQUAKES Plate Tectonics
Plates – large pieces of the lithosphere
Theory of plate tectonics – the idea that the earth’s crust is made of moving plates
Plate Boundaries – places where the plates meet
Scientists think as the magma in the Earth’s mantle moves, it causes the plate boundaries to collide, separate or slide along each other.

4. EARTHQUAKES Plate Tectonics
Scientists believe the Earth is made up of large plates that float on the partly melted rock of the Earth’s mantle.
Pangaea – a large landmass that some scientists think may have existed at one time
No recorded observations
Genesis 7:11 says “the fountains of the great deep were broken up, and the windows of heaven were opened.”

5. EARTHQUAKES Causes of Earthquakes
Earthquakes often occur when rocks along the plate boundaries shift suddenly and release stored energy.
Construction of large buildings and the movement of molten rock under a volcano can cause earthquakes.

6. EARTHQUAKES Causes of Earthquakes
Faults – breaks in the earth’s surface along which rocks can move
Three kinds of faults – determined by how the rocks move against each other (thrust or reverse fault, normal fault, strike-slip fault)
Reverse fault – rocks push together until a section of rock moves upward

7. EARTHQUAKES Causes of Earthquakes
Three kinds of faults – determined by how the rocks move against each other (thrust or reverse fault, normal fault, strike-slip fault)
Normal fault – rocks moving apart
Strike-slip fault – rocks moving horizontally past each other

8. EARTHQUAKES Earthquake Waves
Earthquakes occur below the surface of the earth.
Focus – beginning point of an earthquake
Seismic waves – vibrations that flow out from the beginning point of an earthquake
Epicenter – the point on the surface of the earth directly above the focus

9. EARTHQUAKES Earthquake Waves
Body waves – seismic waves that occur beneath the surface of the earth
P Waves – primary waves; fastest moving; travel in a straight path by a push and pull motion.
S Waves – secondary waves; move more slowly; move in an up and down zigzag pattern

10. EARTHQUAKES Earthquake Waves
Land Waves – surface waves; the slowest moving and most destructive waves
Love waves – back and forth in a zig zag pattern; fastest moving land waves
Rayleigh waves – move in a circular pattern; rolling motion along the ground

11. EARTHQUAKES Detecting Earthquakes
Seismograph – a machine that detects, times, and measures the movement of the earth
Seismograms – records of the movements of the earth
Seismologists – scientists who study the movement of the earth

12. EARTHQUAKES Measuring Earthquakes
Mercalli scale – based on the amount of destruction caused to man-made structures
Measures observable destruction
Richter scale – measures the magnitude of an earthquake’s seismic waves and assigns it a number
Magnitude – strength of the seismic waves of an earthquake

13. EARTHQUAKES Building for Earthquakes
Features that help structures withstand earthquakes:
Concrete reinforced with steel rods
Foundation laid in rock
Steel framing

14. EARTHQUAKES Related Disasters
Tsunami – giant ocean waves triggered by earthquakes, volcanoes, or landslides
Other catastrophic events associated with earthquakes:
Volcanic eruptions
Landslides

15. VOLCANOES Magma – molten rock under the earth
Volcano – occurs where a crack in the earth’s surface allows magma and gases to come to the surface
Volcanologists – scientists who study volcanoes
Magma chambers – pockets of molten rock in the earth’s lithosphere
Lava – hot molten rock that breaks through the surface of the earth
Vent – opening in the surface of the earth through which lava flows
Crater – the bowl shape at the top of a main vent

16. VOLCANOES Causes of Volcanoes
Volcanic ash – jagged bits of crushed rock
Volcanic cone – funnel-shaped mound 1
Crater
Side Vent
Vent
Lava
Magma Chamber 2 4 3 5

17. VOLCANOES Locations of Volcanoes
Volcanic activity may occur under the ocean, at hot spots, along plate boundaries, and along the Ring of Fire.
Ring of Fire – active volcanoes around the edges of the Pacific Ocean
Under water eruptions (submarine eruptions) are 20x more frequent than eruptions on land
Hot spots – places where a pool of very hot magma rises toward the surface and forms new land

18. VOLCANOES – Classifying By Shape
Shield volcano – large, gradually sloping sides; erupts continuous flowing lava; mild, continuous eruptions
Cinder cone – resembles a hill; has a bowl-like crater; usually has more than one vent; made of cinders
Cinders – bits of ash and lava
Composite cone – steep sides and layers of lava and tephra
Tephra – a mixture of cinders, ash, and rock emitted by a volcano

19. VOLCANOES – Classifying By How Often They Erupt
Volcanoes can have more than one kind of eruption because one eruption can change the conditions inside a volcano, causing it to erupt differently the next time.
Active volcano – one that has erupted at some point during a recorded time period and is expected to erupt again
Dormant volcano – has erupted in the distant past but is currently inactive and not expected to erupt again
Extinct volcano – does not have a recorded eruption and is not expected to erupt in the future
There is NO guarantee that it will remain extinct

20. VOLCANOES – Classifying By The Type of Eruption
Hawaiian eruption – runny lava and little or no cinder, ash or steam; quiet; may continue for long periods of time
Strombolian eruption – fountain of lava that runs down the sides
Vulcanian eruption – violent; causes a loud explosion that sends lava, ash, cinders, and gas into the air
Pelean eruption – produces a pyroclastic flow (avalanche of red-hot dust and gases emitted by a volcano)
Plinian eruption – most powerful; spews lava, blows gases, ash, and debris into the atmosphere
Pyroclastic flow – a high-speed flow of very hot gases and dust

21. VOLCANOES Effects of Volcanoes
Vog – volcanic gases; volcanic fog; pollutes the air and can cause acid rain and respiratory problems
The gases, ash, and dust of volcanoes can cause cooling in the weather.
Dangers of Volcanoes
Debris flow – when part of the mountain collapses and mud and rock fragments surge down the mountain
Products of Volcanoes
Soil rich in nutrients, valuable gems
Igneous rock – formed as magma and lava cool and harden

22. VOLCANOES Effects of Volcanoes
Other thermal eruptions
Hot spring – a heated pool of warmed ground water
Geyser – a hot spring that blows steam and water into the air
Mud pots – a hot spring that contains more mud than water