12/7/16 LEARNING TARGET. Identify and describe the three major layers of the Earth.

Transcription

1 I CAN LEARNING TARGET Identify and describe the three major layers of the Earth. 1

2 The Earth is made of many layers.. The Earth is divided into three layers: a) Crust b) Mantle c) Core Each layer is made of different compounds--- ( meaning it is composed of two or more elements ). The less densest compounds make up the crust, while the most dense make up the core. Is the outermost layer of the Earth. It s the thinnest layer. There are two types of crust: Continental found on continents (30-50km avg) Oceanic found in the ocean. (5-10km avg) Crust Which type of crust is the most dense? ß Crust 2

3 Which is denser? Both oceanic and continental crust is made of mostly of the elements silicon, oxygen, and aluminum. However, the oceanic crust is much denser than the continental crust!!! Oceanic Crustà ß Continental Crust How far have scientists drilled into the earth? 7.6 miles Only 0.2% of the distance to the earth s core 3

4 Mantle ß --mantle Is the middle layer of the earth and contains most of the Earth s mass!!! It is made mostly of hot molten liquid called magma. It is much more dense than the crust!!! Core Is mainly made of Iron, which gives the Earth s it s magnetic field!!!. It also has smaller amounts of nickel. The outer core is liquid, but the inner core is solid. Q:Why is the inner core solid? The core makes up only 1/3 of the Earth s mass!!! ß Core) 4

5 Core A: The inner core is solid because of all of the weight from the layers that rest above it. ß Core) How do we know so much about what s under Earth s surface? Through INDIRECT EVIDENCE, mostly from seismic waves caused by earthquakes (more on this later this semester...) Sometimes indirect evidence is the only option for scientists to develop a theory 5

6 LEARNING TARGET.. I CAN Identify and describe the 5 major features of the Earth. How far have scientists drilled into the earth? 7.6 miles Only 0.2% of the distance to the earth s core 6

7 Another way to look at the Earth is to examine its physical features.. Lithosphere Asthenosphere Mesosphere Outer core Inner core Lyrics And Music Often Inspires! What is the Lithosphere? The crust and part of the upper mantle combined make up the lithosphere: About 0 to100 km thick Less dense than the material below it so it floats It s divided into pieces called tectonic plates. 7

8 WHY ISN T THE LITHOSPERE HOT? The lithosphere does not get heated up to near-melting because it is losing heat rapidly to the surface - it is stuck at a temperature close to 0 C. What is the Asthenosphere? (is about 100 to 660km thick) The lithosphere float on top of a plastic -like layer called the asthenosphere It is made mostly of molten rock that flows very slowly like molasses (it s very viscous!!). 8

9 What is the Mesosphere? (Is about 660 to 2900 km thick) It is the strong lower part of the mantle that extends from the bottom of the asthenosphere to the Earth s core. This layer is more FIRM & RIGID. Rock in the lower mantle gradually strengthens with depth, but it is still capable of flow. Outer and inner core.. Outer core ( km) is liquid and composed of an iron-nickel alloy. The flowing of this liquid generates much of the Earth s magnetic field. Inner core ( km) is solid ironnickel alloy. It is hotter than the outer core, but the intense pressure keeps it solid. 9

10 Illustration of layers of the Earth: (mesosphere) Theory of Plate Tectonics Plate Tectonics Plate Boundaries Causes of Plate Tectonics 10

11 Plate Tectonics Learning Target. I can explain the theories of plate tectonics, continental drifting, and seafloor spreading. 11

12 Purpose of the lesson The purpose of the lesson is to understand how the Earth s movements can change the shape of our world in the future and how it will affect the way in which we live. What is PLATE TECTONICS? It s the theory that states: The surface of the Earth is not fixed and eternal, but it is in constant everchanging motion. 12

13 If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle. ß Alfred Wegener and the Continental Drift hypothesis.. A German meteorologist, Alfred Wegener, believed that the continents were once connected as one large super continent called. PANGAEA What does this word mean? ALL LAND 13

14 12/7/16 And then there were two Pangaea originally broke into two large land masses connected by the Tethys Sea. Pangaea 200 million yrs ago.. These two land masses were known as: Laurasia Gondwana Continental Drifting!! Is that possible?? Because of continental drifting, the continents broke apart and moved slowly to their present day location. How did this occur? This was caused possibly by the continents plowing through the ocean floor as the Earth spins on its axis. 14

15 Watch as the continents moved throughout history to the present What proof do we have of the continents were connected? A) Fossils of animals found in both Africa and S. America such as the mesosaurus!!! B) fossils of the same ancient plants found on different continents 15

16 More proof.. C) climate clues fossils of warmweather plants in islands of the Arctic ocean (even glacial deposits in S. America, Africa, and Australia!!) More proof.. D) rock clues- similar rock structures found on different continents. 16

17 Something to think about... The Opossum, North America s lone marsupial, may be common to us, but he s also a significant clue when explaining Earth s past, present, and future How is this possible? ( hint marsupials are animals with pouches) More proof.. The Opossums. is the only Marsupial" found on the continent of North America!! He didn t swim here!! ß -How is the picture to your left proof the continents were once connected? 17

18 Other proof..parts of the Appalachian Mt. chain resemble those found in Greenland Continental Drifting and plate movement.. Quick check: According to the hypothesis of continental drifting, what made the continents move to their present day locations? "HOW STUFF WORKS" CONTINENTAL DRIFTING VIDEO CLIP Was Wegner s idea completely correct when explaining how continents move? 18

19 12/7/16 Review of continental drifting. Although Wegener used clues found in rocks, fossils, and climate to support his hypothesis of continental drifting, He was not able to explain why they broke apart. He also could not explain what caused the continents to drift. Wegener thought it was all because of the Earth spinning on its axis, but he couldn t prove his idea with facts, so other scientist of his day and age thought he was wrong!!! It wasn t until later in history that new evidence was used to support what Wegener was thinking.. Corny Clip of the Day!!! Love on the ROCKS 19

20 Plate Boundaries Learning Target. I can identify and describe the three types of plate boundaries and their individual effects on the Earth. 20

21 What s on your plate? Remember, the Earth s lithosphere is broken into sections called plates; all of our continents sit on top of them. The plates move around on top of the mantle and float like a raft. Why? There are two types of plates: Oceanic plates - plates that are below the oceans Continental plates plates that are below the continents How many plates can you count!!! Which plates include only ocean floor? There are 14 plates!!!! 21

22 Study the map of Earth s plates in Figure 26. Notice the arrows that show the direction of plate movement. Now find the Nazca plate on the map. What direction is it moving? The South American plate? What s happening? Plates and boundaries.. The place where two plates meet is known as a plate boundary. Each boundary is responsible for making different land formations and movements in the Earth s crust. 22

23 3 types of plate boundaries: Divergent Convergent Transform Remember the plates are in constant motion. When plates move, they can either: A) converge (collide) B) pull apart C) slide along side one another Either way, changes will occur along the boundaries of the plates. 23

24 #1) Divergent Boundaries Occur when two plates are moving away from each other or rifting ß à RIFTING causes SEAFLOOR SPREADING Divergent Boundaries.. Most occur at the Mid-ocean ridges Divergent boundaries that occur on land are called rift valleys (ex: Great Rift valley in Africa) 24

25 What is a rift valley? How are rift valleys formed? A rift valley is a deep valley that forms along a divergent boundary on land Rift valleys form as two slabs of Earth s crust slide apart What could eventually happen at the Great Rift Valley in Africa if the plates continue to pull apart? The rift may someday split the eastern part of Africa away from the rest of the continent 25

26 Volcanic fissures Divergent boundaries also cause volcanic fissures!!! This is a vent/crack through which lava erupts, but there is usually no explosive activity. #2) Convergent Boundaries Boundaries occur between two plates that are colliding à ß There are 3 types 26

27 Convergent Boundaries A plate boundary where two plates move toward each other. Quick check: What are the two kinds of tectonic plates? Collisions can occur between: oceanic plate and oceanic plate Oceanic plate and continental plate Continental plate and continental plate When two plates collide, the? of the plates determines which one comes out on top. Density Which plate is more dense: continental? or oceanic? oceanic!!! 27

28 When oceanic plates collide with a less dense continental plates, the more dense plate slides under (subducts) the less dense plate. The area where they meet is called the subduction zone. VOLCANOES occur at subduction zones Type 1 How do these volcanoes form? High temperature from the magma causes the rocks to melt along the subduction slab as it goes under the other plate. Magma seeps up along the plate boundary forming volcanoes. Ex: St. Andes mts along the Nazca plate and S. American plate boundary: 28

29 What would happen if the volcano in Yellowstone park were to erupt today?? When one oceanic plate collides with another oceanic plate, the more dense plate slides under the less dense plate creating a subduction zone called a TRENCH Type 2 29

30 When one continental plate collides with another continental plate This collision zone Is where mountains will form. Type 3 How does these mountains form? Because the plates are less dense than the material in the asthensosphere, the two plates collide and crumble up forming mountain ranges. There is little or no subduction here, so volcanoes do not form. 30

31 Quick Check #1: What occurs when plates carrying oceanic crust collide? (oceanic to oceanic) The more dense plate dives back into the mantle (subduction) The collision between oceanic plates causes deep-ocean trenches Quick check #2: What occurs when plates carrying oceanic and continental crust collide? The more dense oceanic crust sinks and plunges (subducts) beneath the less dense continental crust The collision between oceanic plates and continental plates can cause a volcanic eruption 31

32 Quick check #3: What occurs when plates carrying continental crust collide? (continental to continental) Plates crash head on causing mighty mountain ranges #3) Transform Fault Boundaries Occur between two plates that are sliding past each other Crust is neither created nor destroyed 32

33 What is a Fault? Is a break in the Earth s crust where slabs of rock slip past each other Ex: San Andreas Fault where many Earthquakes occur: What Earth changing event occurs on a transform boundary? Earthquakes frequently occur at transform boundaries. 33

34 Plate Boundaries Review: Action at Plate Boundaries Actions At Divergent Boundaries you will see Mid-Ocean ridges: Continuous elevated zones on the floor of all the major ocean basins The rifts at the crest represent divergent boundaries Rift valleys Deep faulted structures found along the lines of divergent plate boundaries Found on the seafloor or land Seafloor spreading Produces new oceanic crust 34

35 12/7/16 Spreading center Oceanic Rift 35

36 12/7/16 Actions Continental Rifts spreading centers can also develop within a continent and may split into two or more smaller segment forming a rift Ex: East African Rift Valley 36

37 Convergent Boundaries Subduction Zones occur when one oceanic plate is forced down into the mantle beneath a less dense plate Oceanic-Continental (type 1) Actions Denser oceanic slabs sink into asthenosphere Pockets of magma develop and rise Continental volcanic arcs form in part by volcanic activity caused by subduction beneath a continent Examples: Andes, Cascades, and the Sierra Nevadas Oceanic-Continental Convergent 37

38 Convergent Boundaries Oceanic-Oceanic (type 2) Oceanic slabs converge and the more dense one descends beneath the other; usually form deep Sea trenches. Often forms volcanoes on the ocean floor Volcanic island arcs emerge: Ex: Aleutian, Mariana Trench, Tonga Islands Aleutian island stratovolcano Oceanic-Oceanic Convergent 38

39 Continental-Continental (type 3) Plates containing continental material collide and crumble forming mountain ranges. Ex: Himalayas Convergent Boundaries Continental-Continental 39

40 Collision of India and Asia Actions Transform Fault Boundaries Plates grind past each other without destroying the crust Most join two segments of mid-ocean ridge At the time of formation, roughly parallel to direction of plate movement Aid the movement of oceanic crustal material Ex: San Andreas fault, New Madrid fault 40

41 Transform Fault Boundary So What Causes Plate Tectonics? (The continent s slow dance) 41

42 Convection Currents and the Mantle Heat Transfer Heat Transfer Earth s molten outer core is nearly as hot as the surface of the sun. Heat is transferred from the scorching hot core to the cool surface of the Earth through liquids and solids. 42

43 Convection What is convection? Ò Convection: is heat transfer by the movement of a heated fluid Ò During convection heated particles of fluid begin to flow. Transferring heat energy from one part of the fluid to another. Convection Current What is a convection current? A constant flow begins as the cooler fluid continually sinks to the bottom of the pot and the warmer fluid rises. Convection Current is the flow that transfers heat within a fluid 43

44 Convection and the Earth s Mantle Where does the heat source for the Earth s currents come from? Earth s mantle responds to heat. Convection currents flow in the Asthenosphere. The heat source for these currents come from the Earth s core. Convection and the Earth s Mantle This is an overall view of what currents look like 44

45 Convection and the Earth s Mantle Convection Currents cause plate tectonics!!! Hot magma in the Earth moves toward the surface, cools, then sinks again. This creates convection currents beneath the plates that cause the plates to move. 45

46 What causes plates to move? Because there is an unequal distribution of heat, hot plastic like rock is forced to the top of the surface where it will cool, thickens (denser), and sink. It s the transfer of heat inside the Earth that provides the energy to move the plates and causes many of our surface features to form. Plates move at a rate of between and centimeters per year. one ten 46

47 Figure 29: Posing Questions What questions would you need to answer in order to predict where the continents will be in 50 million years? You would need answers to how fast and in what direction each plate is moving How do we know the plates are really moving? A) We can feel it in the form of seismic waves from earthquakes!! (seismic waves tells scientist important information about the interior of the earth). B) We can see it as volcanoes erupt! C) We can see it from how our land changes from the volcanoes and earthquakes!!! 47

48 Learning Target. I can explain the theories of plate tectonics, continental drifting, and seafloor spreading. Sea-Floor Spreading (the other theory) 48

49 Mountains and Valleys Under Water?...How is that possible?? The tallest mountains, deepest valleys, and flattest plains are found in the depths of the ocean During World War I, scientists used underwater sound waves (sonar) to detect the varying depths of the ocean. The longer it takes to echo off the ocean bottom and come back to the ship, the deeper the water is. Mid-ocean ridges Researchers discovered an underwater system of ridges (mountains) and trenches. In the Atlantic, Pacific, and other oceans around the world are a system of ridges called mid-ocean ridges (mountains). These were formed by the movement of the Earth s tectonic plates. 49

50 Activity on the Ocean Floor As tectonic plates push apart, mountains and valleys form along the sea floor. In some of these ridges are long rift valleys where volcanic eruptions and earthquakes occur from time to time. These volcanoes are very active. When they erupt, lava cools to form new seafloor. Some of the volcanoes are visible above the ocean surface. in fact, the U.S. has a state that was formed from underwater volcanoes.can you name it? When the volcanoes get large enough, they poke out of the water as seamounts. These are what formed the Hawaiian Islands. Seamounts 50

51 12/7/16 Pictures of Mid-Atlantic Ridge As seen on a map.. mid-ocean ridge on land in ICELAND How is this possible?? As the sea floor spreads, magma seeps up to the crust and flows from the cracks (It cools, solidifies, and forms new seafloor. Quick Check: What type of Rock will form at the midocean ridge? (While this is happening, it is moving away from the ridges and becoming denser and colder). 51

52 How does the magma enter into the ocean floor?. The openings (or cracks) where the magma actually enters the ocean floor are also referred to as the Rift Zones.. Rift Zone What proof do scientist give us to show that this is actually happening? 52

53 Proof #1- Age of the rocks This colder and denser seafloor sinks and continues to form ridges. While drilling into the seafloor, scientists collected and tested rock samples. As a result the scientist realized that the rocks became increasingly older the farther they were from the ridges. The Proof It s all in the rocks! In other words, Scientist discovered that younger rock is found near the mid-ocean ridges and older rock is found farther away!! 53

54 Earth s Seafloor Spreading: Question: So if the ocean floor is spreading, does this mean that Earth is actually getting bigger? What is happening to older rock as the seafloor spreads apart? Subduction zones/trenches As old rock moves further away from the midocean ridges, it is pushed into the subduction zone/ trenches where it is then melted and recycled. (Keep in mind the deeper down into the Earth, the temperature and pressure increases.) 54

55 Proof #2- Exotic life forms Proof also comes from the life forms that live near the ridges. (Ex: mussels, giant clams, and tube worms) The warmth from the magma generate heat for these creatures to live here!!! 55