Volcanoes and Earthquakes. Part 1: Volcanoes

Transcription

1 Volcanoes and Earthquakes Part 1: Volcanoes

2 Introduction Earth s crust is made of cool, solid rock. Yet, most of Earth is made of extremely hot rock in the mantle and liquid metal in the core. Sometimes, this heat escapes to the surface.

3 Volcanoes The Earth s crust is not totally solid. A volcano is a weak spot in the Earth s crust where molten magma, rock fragments and hot gases erupt. A mountain that has been built up from erupted material is also called a volcano. Mount Hood

4 Patterns of Volcanoes Volcanoes occur in distinct belts on Earth. Volcanic belts form along convergent and divergent plate boundaries. At these boundaries, the crust fractures, allowing magma to rise to the surface.

5 Tectonic Plates

6 Volcanoes

7 Ring of Fire The Ring of Fire has 80% of the world s volcanoes. The Ring of Fire is a belt of volcanoes on the edge of the Pacific Ocean. The ring is a series of convergent boundaries, where the Pacific plate subducts below various continental plates. Pacific Continental

8 Ring of Fire

9 Parts of a Volcano rock fragments ash cloud crater vent pipe lava flow magma chamber

10 Volcanic Material Magma and lava are different. Lava is liquid rock at the Earth s surface. Magma is liquid rock below the surface.

11 Lava There are 2 different types of lava: Thick High in silica. Flows very slowly. Explosive eruptions. Infrequent eruptions. e.g. Mt. St. Helens Thin Low in silica. Flows very easily. Weak eruptions. Frequent eruptions. e.g. Mauna Loa

12 Rocks Fragments There are different types of rock fragments. ash Tiny rock fragments < 2 mm in diameter. cinders Medium fragments: larger than rice grains blocks Large fragments: can be huge in size! NOTE: Ash can be carried for 1000s of kilometers!

13 Types of Volcanoes Volcanoes are classified by their activity: active Is erupting or shows signs it may erupt in the near future. Kilauea dormant Not active now but may become active in the future. Vesuvius extinct Has erupted, before, but is unlikely to erupt again. Krakatoa

14 Types of Volcanoes Volcanoes are also classified by shape and size: The type of magma (thick or thin) determines a volcano s shape. There are 3 types of volcanoes: shield volcano cinder cone composite volcano

15 Shield Volcano A shield volcano is a very wide, gently sloping mountain. Built up from many thin layers of runny lava that has hardened over time Eruptions are very frequent, but mild

16 Shield Volcano

17 Cinder Cone A cinder cone is a steep-sided hill made from volcanic rock fragments. Built when eruptions of cinders and fragments pile up around one vent No lava: fragments only Eruptions are frequent and explosive

18 Cinder Cone

19 Composite Volcano A composite volcano is a steep, cone shaped mountain. Built from alternating layers of rock fragments and lava Thick, syrupy lava Eruptions are violent and unpredictable

20 Composite Volcano

21 Review: Types of Volcanoes

22 Predicting Eruptions Vulcanologists closely monitor volcanoes for warning signs of an eruption. The warning signs indicate that magma is rising to the surface. There are several signs: earthquakes ground shift gas release temperatures

23 Any Questions?

24 Volcanoes and Earthquakes Part 2: Effects of Volcanic Eruptions

25 Effects of Eruptions Volcanoes can affect the surrounding environment in number of different ways. Some of these effects include: lava flows pyroclastic flows ash clouds deadly gases land/mudslides tsunami

26 Lava Flow lava flows A lava flows can knock down and burn up anything that s in its path.

27 Pyroclastic Flow pyroclastic flows A pyroclastic flow is a dense cloud of superhot gases & rock fragments that races quickly down the volcano.

28 Pyroclastic Flow

29 Case Study: Mt. Vesuvius On August 24 th 79 A.D., Mt. Vesuvius erupted in Italy. A pyroclastic flow killed thousands.

30 Case Study: Mt. Vesuvius A pyroclastic flow raced down the volcano at 100 km/h, destroying the city of Pompei and suffocating all of its residents.

31 Ash Cloud ash cloud Ash can cause building collapse, block roads, suffocate organisms, and even trigger climate change.

32 Case Study: Mt. Pinatubo In June 1991, Mt. Pinatubo in the Philippines erupted suddenly, sending ash clouds into the atmosphere

33 Case Study: Mt. Pinatubo

34 Gases deadly gases Volcanic gases sometimes contain poisonous compounds.

35 Land and Mudslides Land/Mudslides Volcanic ash and rock mix with water to form landslides.

36 Tsunami Tsunami When large blocks of rock fall into the sea, a tsunami can form.

37 Any Questions?

38 Volcanoes and Earthquakes Part 3: Earthquakes

39 Recall Tectonic plates move & collide with each other. A plate boundary is where the edges of two tectonic plates meet. There are 3 different types: 1. Divergent 2. Convergent 3. Transform

40 1. Divergent Where two plates move apart. 2. Convergent Where two plates push together. 3. Transform Where two plates scrape by each other.

41 Earthquake Huge rock blocks collide at plate boundaries. An earthquake is a shaking of the ground caused by the sudden movement of rock along a plate boundary. The rock that makes up plates is rigid. When the rock breaks and moves suddenly, tremendous energy is released.

42 Focus and Epicenter Epicenter The point on the surface directly above the focus. Focus The point underground where rocks first begin to move.

43 Seismic Waves Quake energy is released as seismic waves. Seismic waves are vibrations caused by earthquakes that carry energy. There are 3 different types of seismic waves: Primary waves Secondary waves Surface waves

44 Seismic Waves Primary (P) Wave Push and pull the ground like an accordion. The fastest seismic wave (5 km/s) Cause the least amount of damage.

45 Seismic Waves Secondary (S) Wave Shake the ground side to side or up and down. Slower than P waves (2.5 km/s) Cause medium amounts of damage.

46 Seismic Waves Primary and Secondary waves move differently. Primary Wave Secondary Wave

47 Seismic Waves Surface Wave Cause the ground to roll up/down and side/side. The slowest seismic wave. Cause the most amount of damage.

48 Measuring Earthquakes Scientists study quakes using seismographs. A seismograph measures ground movement from seismic waves. Seismographs show ground movement as wiggles on a paper or computer screen. This image is called a seismogram.

49 Seismometers horizontal movement vertical movement

50 Seismometers

51 Seismograph

52 Earthquake Magnitude The strength of an earthquake is its magnitude. Magnitude is a number given to an earthquake based on its strength. Geologists use 3 scales: Mercalli scale Richter scale Moment Magnitude scale

53 Magnitude Scales Mercalli Scale Rates earthquakes according to how much damage they cause at a certain location. Richter Scale Rates earthquakes according to the size of their seismic waves. Moment Magnitude Scale Rates earthquakes according to how much total energy is released.

54 0 4 Minor 4 5 Light 5 6 Moderate 6 7 Strong 7 8 Major 8 + Catastrophic Rarely noticed. Slight damage. Moderate damage. Major damage. Large-scale damage. Major to total destruction.

55 Earthquake Damage Earthquakes can cause damage in many ways. ground shaking aftershocks landslides liquefaction tsunami

56 Ground Shaking Ground shaking can crack roads, buildings, dams and other structures.

57 Aftershocks An aftershock is a smaller earthquake that follows a more powerful earthquake.

58 Landslides The shaking from seismic waves can trigger landslides or avalanches.

59 Liquefaction Liquefaction is when the shaking of the ground causes soil to act as a liquid.

60 Tsunami A tsunami is a giant wave produced when earthquakes displace water.

61 Any Questions?