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Mountain Building…11 Earthquakes…12 Volcanoes…13.

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Presentation on theme: "Mountain Building…11 Earthquakes…12 Volcanoes…13."— Presentation transcript:

1 Mountain Building…11 Earthquakes…12 Volcanoes…13

2 Ch. 11 – Mountain Building A. Stress deformation - the bending, tilting, and breaking of the earth’s crust - isostatic adjustments and plate movements cause stress on the earth’s crust - stress causes strain in the rocks, which can cause bending, tilting, or breaking

3 2. tension - force that pulls rocks apart 3. shearing - forces that pushes rocks in opposite directions past each other three types of stress: 1. compression - occurs when crustal rocks are squeezed together

4 B. The Results of Stress 1. Folding - when rock is permanently deformed by stress without breaking three types of folds: a. anticline - upcurved folds in the layers b. syncline - downcurved folds in the layers c. monocline - gently dipping bends in the layers

5 anticlines

6 synclines

7 monoclines

8 2. Faulting - a break in the rock is called a fracture - when there is movement along a fracture, it is then called a fault four types of faults: a. Normal fault - hanging wall moves down relative to footwall - very steep fault plane - occur along divergent boundaries

9 b. Reverse fault - hanging wall moves up relative to the footwall - very steep fault plane - occurs at convergent boundaries c. Thrust fault - like reverse fault except fault plane is not steep at all d. Strike-slip fault - rock on either side slides past each other horizontally

10 reverse fault

11 normal fault

12 strike-slip fault


14 Ch. 12 – Earthquakes A. Elastic Rebound Theory earthquake - vibrations of the earth’s crust - as the rocks on each side of a fault move slowly, the stress increases and they slowly deform until suddenly they fracture and spring back to their original shape (rebound) - this rebound causes vibrations called seismic waves, and a series of smaller tremors called aftershocks focus - area along the fault (under the surface) where the earthquake begins

15 epicenter - point on surface directly above the focus - the focus can be very deep within the earth, but most earthquakes are shallow-focus earthquakes (0- 70km beneath the surface) B. Major Earthquake Zones - there are three major zones along the earth where earthquakes are the most common (these zones follow plate boundaries - why?) 1. Pacific Ring of Fire 2. Mid-Atlantic Ridge 3. Eurasian-Melanesian Mountain Belt

16 Eurasian-Melanesian mountain belt Mid-Atlantic ridge Pacific Ring of Fire

17 - there are other faults that do not lie within these major zones, but they are usually not as big or as active there is a fault in SE Missouri called the New Madrid Fault which would cause major damage to southern IL and southern IN if a major earthquake occurred (it is supposed to within the next 50-100 years) C. Recording Earthquakes seismograph - instrument used to record earthquake waves - paper is shaken by an earthquake underneath a stationary pen

18 D. Types of Seismic Waves 1. Primary Waves (P waves) - move the fastest, so they are the first waves to be recorded from an earthquake - can travel through solids and liquids, so they can travel through the entire earth - do little damage (only slight vibration) 2. Secondary Waves (S waves) - move slower than P waves, so they are the second waves to be recorded from an e.q. - can only travel through solid material, so they cannot travel through the entire earth - cause rocking back and forth


20 3. Surface Waves or Long Waves (L waves) - slowest-moving waves, so they are last to be recorded from an earthquake - occur as P and S waves reach the earth’s surface - cause an up-and-down motion which is violent and causes the most damage E. Locating an Earthquake - to find the epicenter of an e.q., use time difference b/t P and S waves

21 - must use three different recording stations to locate an e.q. in a technique called triangulation ex.) epicenter

22 F. Earthquake Measurement 1. Richter Scale - scale from 1 to 10 in which each whole number is 32 times as large as the number before it ex.) a 3 earthquake is 32 times larger in magnitude than a 2 earthquake a 4 earthquake is 1024 times larger in magnitude than a 2 earthquake - earthquakes below 2.5 are called microquakes and are not felt by anyone - not used anymore by scientists (only useful for a handful of earthquakes)

23 2. Moment Magnitude - similar to Richter scale, but takes into account more factors to actually calculate energy (magnitude) of eq

24 3. Mercalli Scale - expresses the intensity of the earthquake, or the amount of damage an earthquake does - uses Roman Numerals from I to XII, with each numeral having a description of the damage it would cause to structures, etc. ex.) II = Felt by only a few persons at rest, especially on upper floors of buildings; delicately suspended objects may swing slightly X = Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked; rails bent; landslides considerable from riverbanks and steep slopes; shifted sand and mud; water splashed over banks

25 E. Earthquake Damage 1. Destruction to Buildings and Property - buildings not usually built to withstand swaying or shaking - tall buildings can fall on others nearby - fires can occur because of broken gas lines - loose soil or rock underneath a structure can vibrate and become like a liquid - landslides can be triggered by vibrations

26 - freeway destruction near Los Angeles, 1994

27 - Building damage from EQ in Kobe, Japan, 1995

28 - Building damage from EQ in Washington, 2001

29 - Freeway destruction in Kobe, Japan, 1995 - Homes destroyed in western India, 2001

30 - Roads and land deformed in Japan, 2004

31 - EQ in Japan, 1999

32 - Rail damage from EQ in Turkey - Fence displaced by EQ near San Francisco, 1906 gional/states/events/

33 - magnitude 9.2 EQ in Anchorage, Alaska, 1964 photos/videopop3.jsp?Alaska_Summer_AK_CH_Feature_1964_EarthquakeFLV100001.flv,Alask a_Summer_AK_CH_Feature_1964_EarthquakeFLV300001.flv

34 2. Tsunamis - major earthquakes that occur on the ocean floor can trigger giant waves called tsunamis - tsunamis seem to begin small because most of the wave is underwater, but as the wave moves towards shore, the wave (still the same height) sticks out of the water more as it is pushed up by the upward slope of the seafloor near the shore tsunami earthquake

35 h/nova/tsunami/anatomy.html

36 - tsunamis caused by the Good Friday Earthquake drove a 2x6 plank through this 10-ply truck tire at Whittier, Alaska

37 EQ video that caused the tsunami near Banda Aceh, Indonesia

38 Tsunami video from Indonesia


40 Tsunami video from Sri Lanka

41 Tsunami video from Banda Aceh, Indonesia

42 F. Earthquake Warnings and Predictions 1. Use paleoseismology, or the study of past earthquakes to predict when future ones will occur 2. Use seismic gaps to determine where the rock is locked and has not been moving 3. Use precursors, or small tremors right before an earthquake, to give a short-term warning 4. Use the slow down of other P waves to predict whether an earthquake will occur Long- term predictions Short- term predictions

43 Ch. 13 – Volcanoes A. Volcanism volcanism – the movement of magma toward or onto the surface of the earth

44 B. Volcanic Features

45 C. Major Volcanic Zones 1. Subduction Zones - convergent boundaries - continental coasts or island arcs ex.) Pacific Ring of Fire 2. Mid-Ocean Ridges - divergent boundaries - rifts along ocean floor (occasionally through dry land) ex.) Iceland (Mid-Atlantic Ridge) 3. Hot Spots - volcanism outside of plate boundaries - as plate moves, old volcanoes move on and new ones form over hot spot ex.) Hawaiian Islands


47 D. Volcanic Eruptions 1. Kinds of lava a. mafic (basaltic) lava – dark colored when hardened, rich in magnesium and iron, usually from oceanic crust - very little gas and water vapor - quiet eruptions with more lava and very little tephra b. felsic (granitic) lava – light colored when hardened, rich in silica, usually from continental crust (more gas and water vapor) dry magma wet magma

48 - more gas and water vapor (and, thus, more pressure built up) - violent eruptions with more tephra and less lava c. Lava textures - thin, mafic lava usually hardens slowly with a wrinkled surface  pahoehoe

49 - if lava cools quickly, it forms large, jagged chunks  aa - if lava cools underwater, it cools rapidly, usually in a round shape  pillow lava

50 E. Volcanic Rock Fragments 1. tephra - rock fragments ejected from a volcano - also called pyroclastic material a. ash - less than 2 mm b. dust - less than 2.5 mm c. lapilli - less than 64 mm d. bombs - large, round clots of lava that partially solidify in the air e. blocks - very large solid rock blasted out of the volcano

51 F. Volcanic cones 1. Shield cones - broad, gently sloping - formed from quiet lava eruptions 2. Cinder cones - short, steep slopes - formed from explosive tephra eruptions (aka: pyroclastic flows) 3. Composite cones - tall, varying slopes - alternating kinds of eruptions

52 What kind of cone? cinder cone composite cone shield cone

53 cinder cone composite cone cinder cone shield cone

54 cinder cone composite cone

55 G. Predicting Volcanic Eruptions 1. small earthquakes before an eruption 2. bulging of the surface of the volcano 3. changes in composition of gases given off by the volcano 4. volcano’s past behavior

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