The lithosphere

grade 7 lesson about the solid part of the Earth - Lithosphere

1. Layers of the Earth

2. 4. The 6-35 km (4-21 miles) thick lithosphere. Earth's crust. 1. The 1370 km (851 miles) thick inner core, which is in a crystalline state because of the influence of heat and high pressure. 2. The 2000 km (1,250 miles) thick outer core containing such molten heavy metals as nickel and iron. 3. The 2900 km (1.800 miles) thick Mantle layer formed from rapidly flowing magma.

3. Lithosphere The solid part of the earth. It consists of three main layers: crust, mantle and core.

4. The Crust Is the outermost layer of the earth. Has a depth of about 32 to 40 km. The thinnest layer. The uppermost layer is known as the SIAL. It is composed mainly of silicon and aluminum The bottom layer of the crust is called SIMA It is made mostly of silicon and magnesium.

5. Crust are further divided into two major parts: Continental crust It is about 32 kilometers thick, made mainly of granite rocks. The elevated portion of the crust. Oceanic Crust The ocean bed, it is about seven kilometers thick and made mainly of basalt.

6. The Mantle Located just below the crust. It is denser than crust, about 2,900 km thick. It is composed mainly of very hot, solid rocks that flow. The region between the crust and the mantle is called MOHOROVICIC DISCONTINUITY OR MOHO. Scientists have been able to confirm the differences in density between rocks of the crust and those of the mantle by studying the Moho .

7. The Core It is about 4,960 km deep. It is divided into: Outer core It is about 2,270 km thick Composed mainly of nickel and iron melted by intense heat. Inner Core It is composed mainly of solid iron and nickel. The temperature is around 5,000 C to 6,000 C. The temperature ranges from 4,000 C to 5,000 C The pressure is exceedingly high.

8. Materials of the Earth

9. Igneous Rocks

10. (1) Basalt: are dark colored, fine-grained extrusive rocks . The mineral grains are so fine that they are impossible to distinguish with the naked eye or even a magnifying glass. They are the most widespread of all the igneous rocks. Most basalts are volcanic in origin and were formed by the rapid cooling and hardening of the lava flows. Some basalts are intrusive having cooled inside the Earth's interior.

11. (2) Gabbro: is a dark-colored, coarse-grained intrusive igneous rock. Gabbro is very similar to basalt in its mineral make up.

12. (3) Pumice : is a very light colored, frothy volcanic rock. Pumice is formed from lava that is full of gas. The lava is ejected and shot through the air during an eruption. As the lave hurtles through the air it cools and the gases escape leaving the rock full of holes. Pumice is so light that is actually floats on water. Huge pumice blocks have been seen floating on the ocean after large eruptions. Pumice is ground up and used today in soaps, abrasive cleansers, and also in polishes.

13. (3) Pumice : is a very light colored, frothy volcanic rock. Pumice is formed from lava that is full of gas. The lava is ejected and shot through the air during an eruption. As the lave hurtles through the air it cools and the gases escape leaving the rock full of holes. Pumice is so light that is actually floats on water. Huge pumice blocks have been seen floating on the ocean after large eruptions. Some lava blocks are large enough to carry small animals. Pumice is ground up and used today in soaps, abrasive cleansers, and also in polishes.

14. (4) Rhyolite : is very closely related to granite. The differences is rhyolite has much finer crystals. These crystals are so mall that they can not be seen by the naked eye. Rhyolite is an extrusive igneous rock having cooled much more rapidly than granite, giving it a glassy appearance. The minerals that make up rhyolite are quartz, feldspar, mice, and hornblende.

15. (5) Granite : is an igneous rock that is composed of four minerals. These minerals are quartz, feldspar, mica, and usually hornblende. Granite forms as magma cools far under the Earth's surface. Because it hardens deep underground, it cools very slowly. This allows crystals of the four minerals to grow large enough to be easily by the naked eye. Granite is an excellent material for building bridges and buildings because it can withstand thousands of pounds of pressure. It is also used for monuments because it weathers slowly. Engraving in granite can be read for hundreds of years, making the rock more valuable. Granite is quarried in many places in the World including the United States. The state of Hew Hampshire has the nickname "Granite State" because of the amount of granite in the mountains of that beautiful state. The Canadian Shield of North American contains huge outcroppings (surface rocks) of granite.

16. (6) Obsidian : is a very shiny natural volcanic glass. When obsidian breaks its fractures with a distinct conchoidal fracture. Obsidian is produced when lava cools very quickly. The lave cools so quickly that no crystals can form. When people make glass they melt silica rocks like sand and quartz then cool it rapidly by placing it in water. Obsidian in produced in nature in a similar way. Obsidian is usually black or a very dark green, but it can also be found in an almost clear form. Ancient people throughout the World have used obsidian for arrowheads, knives, spearheads, and cutting tools of all kinds. Today obsidian is used as a scalpel by doctors in very sensitive eye operations.

17. Metamorphic Rock: (1) White Marble : is a metamorphosed limestone or dolomite. both limestone and dolomite have a large concentration of calcium carbonate (CaCO 3 ). Marble has many different sizes of crystals. Marble has many color variances due to the impurities present at formation. Some of the different colors of marble are white, red, black, mottled and banded, gray, pink, and green. Marble is much harder than its parent rock. This allows it to take a polish which makes it a good material for use as a building material, making sink tops, bathtubs, and a carving stone for artists. Today, headstones are made from marble and granite because both of these rocks weather very slowly and carve well with sharp edges. Marble is quarried in Vermont, Tennessee, Missouri, Georgia, and Alabama.

18. ( 2) Slate : is a fine-grained metamorphic rock with perfect cleavage that allows it to split into thin sheets. Slate usually has a light to dark brown streak. Slate is produced by low grade metamorphism, which is caused by relatively low temperatures and pressures. Slate has been used by man in a variety of ways over the years. One use for slate was in the making of headstones and grave markers. Slate is not very hard and can be engraved easily. The problem with the slate though is its perfect cleavage. The slate headstones would crack and split along these cleavage planes. This in not a desirable attribute for a headstone. Slate was also used for chalk boards. The black color was good as a background and the rock cleaned easily with water. Today it is not very advantageous to use this rock because of its weight and the splitting and cracking over time.

19. (3) Schist : is a medium grade metamorphic rock. This means that is has been subjected to more heat and pressure than slate, which is a low grade metamorphic rock. The individual grains of minerals can be seen by the naked eye. Many of the original minerals have been altered into flakes. Because it has been squeezed harder than slate it is often found folded and crumpled. Schists are usually named by the main mineral from which they are formed. Bitotite mica schist, hornblende schist, garnet mica schist, and talc schist are some examples of this.

20. ( 4) Gneiss : is a high grade metamorphic rock. This means that gneiss has been subjected to more heat and pressure than schist. Gneiss is coarser than schist and has distinct banding. This banding has alternating layers that are composed of different minerals. The minerals that compose gneiss are the same as granite. Feldspar is the most important mineral that makes up gneiss along with mica and quartz. Gneiss can be formed from a sedimentary rock such as sandstone or shale, or it can be formed from the metamorphism of the igneous rock granite. Gneiss can be used by man as paving and building stone.

21. (5) Quartzite : is composed of sandstone that has been metamorphosed. Quartzite is much harder than the parent rock, sandstone. It forms from sandstone that has come into contact with deeply buried magmas. Quartzite looks familiar to its parent rock. The best way to tell quartzite from sandstone is to break the rocks. Sandstone will shatter into many individual grains of sand while quartzite will break across the grains.

22. (6) Anthracite Coal : is organic sedimentary rocks formed from the build up and decay of plant and animal material. This usually forms in swamp regions in which there is an abundant supply of growing vegetation and low amounts of oxygen. The vegetation builds so quickly that new layers of vegetation bury the dead and decaying material very quickly. The bacteria that decay the vegetation need oxygen to survive. Because these decaying layers are buried so fast the bacteria use up what oxygen there is available and can not finish the decomposition of the vegetation. The overlaying layers become so heavy that they squeeze out the water and other compounds that aid in decay. This compressed vegetation forms coal. The longer and deeper that coal is buried makes it of higher quality. Peat is the first stage of coal formation. Lignite is the next grade of coal followed by bituminous and the highest grade, anthracite. Anthracite is actually a metamorphic rock. It forms during mountain building when compaction and friction are extremely high. This form of coal burns very hot and almost smokeless. It is used in the production of high grade steel.

23. Sedimentary Rocks: (1) Limestone : is the most abundant of the non- clastic sedimentary rocks. Limestone is produced from the mineral calcite (calcium carbonate) and sediment. The main source of limestone is the limy ooze formed in the ocean. The calcium carbonate can be precipitated from ocean water or it can be formed from sea creatures that secrete lime such as algae and coral. Chalk is another type of limestone that is made up of very small single-celled organisms. Chalk is usually white or gray in color. Limestone can easily be dissolved by acids. If you drop vinegar on limestone it will fizz. Put a limestone rock into a plastic jar and cover it with vinegar. Cover the jar and watch the bubbling of the calcium carbonate and also the disintegration of the rock over a few days.

24. (2) Breccia : is formed in a very similar fashion to conglomerate. The difference between the two rocks is that breccia's rock fragments are very sharp and angular. These rock fragments have not been transported by water, wind, or glaciers long enough to be rounded and smoothed like in the conglomerate. The cementing agents silica, calcite (CaCO 3 ), and iron oxides are the same as in conglomerate.

25. (3) Conglomerate : is a clastic sedimentary rock that forms from the cementing of rounded cobble and pebble sized rock fragments. Conglomerate is formed by river movement or ocean wave action. The cementing agents that fill the spaces to form the solid rock conglomerate are silica, calcite, or iron oxides. Notice in the photo above the rounded rock particles in the conglomerate. These rounded particles make conglomerate different from breccia.

26. (4) Sandstone : is a clastic sedimentary rock that forms from the cementing together of sand sized grains forming a solid rock. Quartz is the most abundant mineral that forms sandstone. Calcium carbonate, silica, or iron has been added to the water that is in contact with the sand grains. These minerals grow crystals in the spaces around the sand grains. As the crystals fill the gaps the individual sand grains are now transformed into a solid rock.

27. (5) Halite : is common table salt. It forms where brakish (salty) lakes or sea beds dry up. This evaporation of the water causes the salt to precipitate forming the salt crystals. Halite frequently occurs in crystal form. It is usually colorless but can be reddish brown because of iron oxides in the water that it forms in. Halite has perfect cleavage and a hardness o 2.5 on the Mohs hardness scale.

28. She interviewed a scientist, Dr. Gutierrez at Southwest Missouri State University to feed her curiosity. They planned a journey to the Springfield rock quarry. Kate met Dr. Gutierrez and they traveled to the rock quarry. " Rock"in Stories Story 1: Kate was in her career development class at Cherokee Middle School. She was very interested in the subject of earth science and wanted to know more about Geology and the formation of rocks through geochemical process, such as, igneous, metamorphic and sedimentary.

29. What kind of rock would this be? What stage of the rock cycle is the rock found? Limestone - Sedimentary Kate and Dr. Gutierrez had to wear helmets to enter the rock quarry due to the blasting of slabs of stone with dynamite. Kate was overwhelmed with all the different kinds of rocks. She picked up a light whitish grey rock. Dr. Gutierrez told her the rock was composed of Calcium Carbonate, CaC0 3 , This type of rock is formed from sea creatures that secrete lime, such as algae and coral. When they die their remains pile up on the ocean floor and form this rock.

30. Dr. Gutierrez informed her that the rock she found is the parent of another kind of rock that is much harder. This rock is made up of different sizes of crystals and has many variations in color. This rock may be red, white, pink, or grey. It is used as a building material to make countertops and bathtubs. What kind of rock would this be? What stage of the rock cycle is this rock found? Marble - Metamorphic

31. The beginning of these rocks occurred 30 meters below the Earth's surface. There the rock was dark colored and fined grained. This rock is the most widespread of this stage of rocks. This rock is volcanic in origin and formed by rapid cooling and hardening of lava. What kind of rock would this be? What stage of rock cycle is this rock found? Basalt - Igneous

32. Whitney, a very intelligent graduate, completing her masters in Geology decided to go on a research field class for the summer. The instructor for this class was Dr. Playmate, a Geologist of Southwest Missouri State University. They traveled to the Rocky Mountains for their geological research. While hiking, they discovered an exposed cliff that had been subjected to weathering. Within this cliff they found a rock that was composed of the minerals feldspar, mica, and quartz. This rock had a banned appearance in its layers. Gneiss - Metamorphic What kind of rock would this be? What stage of rock cycle is this rock found? Story 2

33. Whitney informed her classmates that this rock can be formed from several other types of rocks. One of these rocks forms from the cementing together of small grains. Quartz is the most abundant mineral in this kind of rock. What kind of rock would this be? What stage of rock cycle is this rock found? Sandstone - Sedimentary

34. What kind of rock would this be? What stage of rock cycle is this rock found ? The rock in the cliff could also be formed from a completely different type of rock. This rock is composed of four minerals: quartz, feldspar, mica, and hornblende. This rock forms as magma cools far under the Earth's surface. Because it hardens underground, it cools slowly. This allows the crystal of the four minerals to grow large enough to be seen by the naked eye. This type of rock is excellent of building bridges and monuments because it weathers slowly. Granite - Igneous

35. Story 3: Jessica, after completing a very rough semester at Southwest Missouri State University, decided to take a vacation to Hawaii with her frequent flyer miles. She decided to go to the National Volcano Park to elevate some stress. The park encompasses diverse environments that range from seal level to the summit of the Earth's most massive volcano, Mauna Loa at 13,677 feet. After a recent volcanic eruption she took a guided tour. On this tour, she observed many different types of volcanic rock.

36. One in particular was very light colored and light in weight. This rock is so light that it floats on water. It had holes all throughout the rock. This rock is formed when lava is ejected and shot thru the air during a volcanic eruption. As the lava flies thru the air it cools and gases escape leaving the rock full of holes. This rock is used today in soap and abrasive cleaners . What kind of rock would this be? What stage of rock cycle is this rock found? Pumice - Igneous

37. They traveled on and came to a beautiful flowing stream. The guide picked up a hand full of rocks and Jessica noticed one that appeared to have many tiny rocks inside of it. This rock was formed by river movement and composed of rounded cobble and pebble sized rock fragments. What kind of rock would this be? What stage of rock cycle is this rock found? Conglomerate - Sedimentary

38. After the guided tour, Jessica to take a walk on the beach of Hawaii. As she walked, she picked up shells and rocks from the sand. She noticed one of the rocks looked like it had been formed from the cementing together of small sand sized grains. This rock looked like sandstone, but when broken, the grains of sand broke into layers. What kind of rock would this be? What stage of rock cycle is this rock found? Quartzite - Metamorphic

39. Rock Name Description Rock Type Basalt Dark colored, fine grained; formed by rapid cooling and hardening of lava flow Igneous Gabbro Dark colored, coarse-grained; similar to basalt but mostly composed of the mineral plagioclase feldspar Igneous Pumice Light colored, frothy volcanic rock; formed when lava is ejected and shot through the air during an eruption; so light is can float Igneous Rhyolite Closely related to granite, but has very fine crystals; has a glassy appearance; made up of quartz, feldspar, mica and hornblende Igneous Granite Composed of the same minerals as rhyolite; forms as magma cools far under the earth's surface Igneous Obsidian Very shiny natural volcanic glass; produced when lava cools very quickly so no crystals form; usually black or very dark green; Igneous

40. Minerals They are naturally formed solid elements or compounds having a crystalline structure and possessing physical and chemical properties. They are considered as the building units of the Lithosphere.

41. The element composing the Minerals Oxygen Oxygen in its combined form is the most abundant element composing minerals. It is found chemically combined with other elements forming OXIDES. Very few minerals are found to be composed of pure elements.

42. What is the relationship of Rocks and Minerals? Are familiar with a fruit cake? Fruit cake is a loaf of bread with nuts, raisins and glazed fruits. The fruit cake represents the rock, the nuts, raisins and glazed fruits represents the minerals.

43. Properties used in Identifying Minerals MINERALOGY is the science that deals with the identification and classification of minerals. Mineralogists subject the minerals to various tests to determine their properties.

44. Properties used in Identifying Minerals 1. Color This is the most obvious property of mineral. However, not all minerals can be identified by color for three reasons: Many minerals are colorless or else they have the same color. b) Impurities affect the real color of the mineral. c) Surface color tarnishes Example: Corundum is a colorless mineral. With traces of Chromium, it becomes red called (ruby) and with traces of iron and titanium it becomes blue called ( sapphire)

45. 2. Luster This is the property of the mineral to reflect, refract or absorb light. Some minerals “shine’ when exposed to light while others do not. Some terms used to describe luster are: BRILLIANT, DULL, PEARLY, SILKY, EARTHY and many more.

46. 3. Streak The color of the fine powder of the mineral made against a streak plate. Some minerals have streaks similar to their color. Others have streaks different from their colors. Gold is yellow, and its streak is also yellow. Pyrite (known as fool’s gold) has a greenish-black streak. Hematite is black but its streak is red.

47. Identifying Minerals by Streak Gold(top ), platinum (middle) and copper (bottom) have characteristic streak colors, best seen on a black streak plate.

48. 4. Crystal Form Minerals are usually crystalline and some minerals have enchanting crystals. Crystal form reveals the arrangement of atoms in a mineral. The atoms of each mineral are arranged in a definite geometric pattern. Each mineral had its own definite atomic arrangement which is helpful in identifying that particular mineral.

49. 5) Cleavage and Fracture This property reveal the structure of a mineral. Cleavage is the splitting of the mineral readily along certain planes to produce flat and smooth surfaces. Uneven breaks or cracks that form uneven surfaces are called FRACTURE.

50. 6. Specific Gravity This is the number that tells how many times denser the minerals is than an equal volume of water. In determining the specific gravity of a mineral. Its volume and mass are first determined. Then the density is computed using the formula: D = M / V

51. The resulting density is compared with the density of water which is equal to 1 g/cm3. For example, the density of silver is 10.6 g/cc. This is then compared to the density of water. Thus, Silver is 10.6 times denser than water. Specific gravity = density of silver / density of water = 10.6 g/cc / 1g/cc = 10.6

52. Specific Gravity of Some Minerals Minerals Specific Gravity Gold 19.3 Mercury 13.6 Platinum 21.5 Silver 10.6 Copper 9.0 Zinc 7.1 Pyrite 5.2 Garnet 4.2 Diamond 3.5 Talc 2.8 Calcite 2.7 Quartz 2.6

53. 7. Hardness This is the resistance of a mineral to being scratched. The test for the hardness of a mineral involves the use of scale invented by Friedrich Mohs .

54. The Moh’s Scale of Hardness 1. Talc 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum 10. Diamond

55. The Forces the Construct the Earth’s Surface

56. Diastrophism or Crustal Warping Pertains to all the movements of the solid parts of the earth. Great forces act on the crust causing it to move. Sometimes: the movement is so strong and sudden that we can feel the shaking of the ground. the movement may be so slow that we can not feel them, can only be detected by a seismograph. The great forces that cause the felt and unfelt movements of the crust have been identified as pushes (compression) and pulls (tension) exerted on the crust over long period of time.

57. Direction of Forces and the Movement they Produce 1. Upward forces Upward forces cause the local widespread rising or uplift of the crust. These forces are responsible for the emergence of small islands in the deep seas of the pacific. The discovery of the fossil remains of marine organisms in the rock layers of high areas indicates that these layers were pushed up from under the water of the ocean.

58. 2. Downward Forces Downward forces cause the local or widespread sinking or subsidence of the crust. These forces caused the disappearance of small islands in the pacific in the historic past. The fossil remains found in the rock layers reveal that there was at one time a land bridge connecting Asia and North Africa. Such a land bridge and many more have been submerge or pushed underwater by great forces.

59. 3. Sideward Forces Sideward forces cause the horizontal motion of the crust called thrust. Large masses of rocks slide and slip against each other into new position. Sometimes rock masses bend, tilt, or wrinkle due to these sideward forces.

60. Effects of Diastrophism The movement of the crust brought about by the interaction of the forces described has resulted in the formation of the different surface features of the earth.

61. 1. Folding Folding occurs when the crust crumples or wrinkles due to compressions or pushes from opposite directions.

62. As the crust is crumpled, the rock strata become tilted.

63. The materials of the crust are dense and rigid, but under great heat and pressure, they soften and can be deformed. The crest or upward curve of a fold is called anticline. The trough or downward curve is called syncline.

64. The crest may form mountains, hills or ridges and the trough may form valley.

65. 2. Faulting Faulting occurs when a rock masses of the crust are pulled apart (tension) forming cracks or fractures on the crust. The tensional forces go beyond the elastic limit of the crust that it yields to the stress by breaking.

66. Different Tensional Stress and its Effects

67. In some instances, parallel faults may occur in the crust. The area between two parallel faults may eventually sink as the downward forces act on it. The sunken area is called a graben and it may form rift valley. The risen area is called a horst and it may become a plateau.

68. Types of Faulting

69. We can now conclude that through great stretches of time, ocean floors have been lifted up, high areas have been thruster, pushed down, pushed and pulled sideways many times. Careful observations indicate that these processes are still going on and affecting the crust. Where do the forces that shape the earth come from?

70. Causes of Diastrophism 1. Continental Drift Theory This theory was proposed by Alfred Wegener, a German scientist in 1915.

71. According to him, 200 million years ago, there was only a single supercontinent called Pangaea situated at the center near the equator.

72. This single supercontinent broke up into pieces which drifted slowly away from each other. The pieces formed the continents of today. As the continents drifted apart, they rubbed and collided against each other forming the surface features of today.

73. http://www.youtube.com/watch?v=3HDb9Ijynfo&feature=related Assignment: 1. Make at least 300 words reaction paper on the video presentation. 2. Long bond paper. 3. Hand written. 4. Follow the web site below

74. 2. The Theory of Seafloor Spreading In 1920, five years after Wegener’s theory was formulated, the existence of the mid-oceanic ridges were discovered using an echo-sounding device like a sonar.

75. A break or rift was found at the middle of the ridge running along its length where basaltic magma wells out to the surface.

76. This basaltic magma solidified forming a “new crust”.

77. The new crust pushes the old crust causing the ocean floor to spread.

78. The force according to theory caused the breaking and drifting apart of the continents. The mid-oceanic ridges are believed to be the remnants of the continents that drifted. The ocean floor has been estimated to be spreading at the rate of 5 cm per year. This rate may seem slow, but for the past 200 million years, all the existing ocean basin were generated through this slow movement.

79. An exploration using a research ship named Glomar Challenger drilled through the crust and gathered several rock samples from both sides of the mid-oceanic ridge.

80. Radioactive dating technique proved that the rocks found from about the same distance from the rift on both sides are of the same age and rock type. The rocks taken near the ridge were relatively younger than those further from the ridge.

81. If new crust is continuously being formed, does it mean that the earth’s diameter is expanding? Scientists explain that as a new crust is formed at the mid-oceanic ridges, elsewhere on earth, the old crust is being destroyed at the same rate that it is created. The region where the old crust is being destroyed is called the subduction zone.

82. Here in the subduction zone, the old crust is plunged into high pressure and high temperature environment. Thus, some of the materials melt and may migrate upward giving rise to volcanic eruptions.

83. http://www.youtube.com/watch?v=ep2_axAA9Mw&feature=related

84. 3. The Plate Tectonic Theory This theory proposed that the Lithosphere is divided into six major plates.

85. The plate may be composed of the continental crust on top of the oceanic crust or may be composed of the oceanic crust alone.

86. The plates are slowly, but nevertheless continually in motion. The movement of plates is believed to be caused by the convection currents in the mantle. As the magma from the lower mantle rises from deep within the earth and spreads laterally, the plates are set in motion. Thus, the movement of the plates generates earthquakes, volcanic activities, as well as pushes and pulls causing the deformation of large masses of rocks.

87. Thus, the movement of the plates generates earthquakes, volcanic activities, as well as pushes and pulls causing the deformation of large masses of rocks.

88. As the movement of the plates goes on, interaction occurs along their plate boundaries. Plate boundary is the place where two plates meet.

89. The plate boundaries 1. Spreading or divergent boundary An area where two plates move apart leaves a gap between them. The gap formed is immediately filled up with molten materials that wells up from the lower mantle.

90. The Atlantic ocean, the Great Rift Valley of Africa and the Red Sea are believed to be formed by this type of movement of the plates.

91. 2. Colliding or convergent boundary This is an area where two plates move toward each other. As the plates collide, the leading edges of one plate is bent downward allowing it to slide beneath the other. As all cases, the denser materials plunge beneath the surface.

92. The colliding boundary is the site where the old crust is being destroyed ( subduction zone). The Himalayan Mountain Ranges, Andes Mountain, and the Marianas Trench are believed to be formed by this type of plate movement.

93. Andes Mountain

94. 3. Fracture or transform boundary This is the area where two plates move past each other, sliding, scraping and deforming the edges of continents.

95. The San Andreas Fault of California is a famous example. The Pacific plate is moving towards northeast past the North American plate. Los Angeles is located on a plate situated on one side of the fault. San Francisco is located on another plate. In about 10 t0 15 million years, Los Angeles and San Francisco will be located next to each other.