Earthquakes and Volcanoes

1. Earthquakes and Volcanoes

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

3. EARTHQUAKESPlate 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. EARTHQUAKESPlate 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

5. EARTHQUAKESCauses 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 also cause earthquakes.

6. EARTHQUAKESCauses 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. EARTHQUAKESCauses 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. EARTHQUAKESEarthquake Waves • Earthquake is vibration or shaking of the earth’s crust. • What causes earthquakes: Plates move pass each other, pressure builds up enough that rock break, and the plates move suddenly. • Focus (A) – beginning point of an earthquake • Seismic waves – vibrations that flow out from the beginning point of an earthquake • Epicenter (B) – the point on the surface of the earth directly above the focus

9. A= FocusB= Epicenter

10. EARTHQUAKESEarthquake 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; these waves move back and forth • S Waves – secondary waves; move more slowly; move in an up and down zigzag pattern; causes the particles in the rock to vibrate to the direction in which the wave is moving

11. EARTHQUAKESEarthquake Waves • Surface Waves: the slowest moving and most destructive waves • Can move back and forth in a zig zag pattern; fastest moving land waves • Can move in a circular pattern; rolling motion along the ground

12. EARTHQUAKESDetecting 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

13. EARTHQUAKESMeasuring 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, this is how much energy is released.

14. EARTHQUAKESBuilding for Earthquakes • Features that help structures withstand earthquakes: • Concrete reinforced with steel rods • Foundation laid in rock • Steel framing

15. EARTHQUAKESRelated Disasters • Tsunami – giant ocean waves triggered by earthquakes, volcanoes, or landslides • Other catastrophic events associated with earthquakes: • Volcanic eruptions • Landslides

16. VOLCANOES • Magma – molten rock under the earth • Volcano – are a form of a mountain, they occur when 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

17. VOLCANOESCauses of Volcanoes • Volcanic ash – jagged bits of crushed rock • Volcanic cone – funnel-shaped mound • Draw this Diagram in your notes. • Side Vent • Vent • Lava • Magma Chamber 1 2 4 3 5

18. VOLCANOESLocations 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

19. VOLCANOES – ClassifyingBy 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

20. VOLCANOES – ClassifyingBy 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

21. VOLCANOES – ClassifyingBy 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

22. VOLCANOESEffects 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

23. VOLCANOESEffects 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 • Mudpots – a hot spring that contains more mud than water

24. Review for CFA #11 Earthquakes & Volcanoes • Earthquakes occur along breaks in the earth surface, these breaks are called___________. List and Describe the 3 types. • The _________is the beginning part of an earthquake & the ____________is the point on the surface of the earth directly above the focus. • ________ ________ are the vibrations that flow out of the beginning point of an earthquake. List and Describe the 3 types. • What are the 2 scales used to measure the strength of an earthquake? How do they differ? • What is magnitude? • What is a volcano? • Where can volcanic activity occur? • What is the ring of fire? • What are some of the effects of a volcanic eruption? • What types of geological events occur at plate boundaries?