G10 Science Q1 Module 4 Why Do Tectonic Plates Move? PDF

10 Science Quarter 1 - Module 4 Why Do Tectonic Plates Move? This instructional material was collaboratively developed and reviewed by educators from public schools. We encourage teachers an...

10 Science Quarter 1 - Module 4 Why Do Tectonic Plates Move? This instructional material was collaboratively developed and reviewed by educators from public schools. We encourage teachers and other education stakeholders to email their feedback, comments, and recommendations to the Department of Education, Schools Division of Cebu City. We value your feedback and recommendations. Department of Education Republic of the Philippines 1|Page Quarter 1 – Module 4: Why Do Tectonic Plates Move? Second Edition, Revised 2021 Republic Act 8293, section 176 states that: No copyright shall subsist in any work of the Government of the Philippines. However, prior approval of the government agency or office wherein the work is created shall be necessary for exploitation of such work for profit. Such agency or office may, among other things, impose as a condition the payment of royalty. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc) included in this book are owned by their respective copyright holders. Every effort has been exerted to locate and seek permission to use these materials from their respective copyright owners. The publisher and authors do not represent nor claim ownership over them. Published by the Department of Education – Division of Cebu City Schools Division Superintendent: Rhea Mar A. Angtud, EdD Development Team of the Module Writer: Bonnie James A. Saclolo, Teacher III, Cebu City National Science HS Content Editors: Dr. Deogenes R. Adoptante, Principal I, Mambaling National HS Mrs. Arnolfa A. Demellites, Principal I, Guba National HS Language Editor: Mrs. Wilma Y. Villaflor, Principal III , Don Vicente Rama Mem. ES Management Team: Dr. Rhea Mar A. Angtud, Schools Division Superintendent Dr. Bernadette A. Susvilla, Asst. Schools Division Superintendent Mrs. Grecia F. Bataluna, CID Chief Dr. Raylene S. Manawatao, EPS – Science Mrs. Vanessa L. Harayo, EPS – LRMDS Printed in the Philippines by Department of Education Division of Cebu City ROVII Office Address: Imus Avenue, Cebu City Telephone Nos: (032) 255-1516 / (032)253-9095, E-mail Address: [email protected] 2|Page  Lesson Why Do Tectonic 1 Plates Move? Introduction: The Tectonic Plates of the Earth’s lithosphere move at an average of 2 to 20 cm per year. The individual movements of these plates create different type of boundaries and consequently different geological features and activities. Finding out the explanation for these movements took a lot of effort from scientists. Different theories and concepts were put forward until the accepted scientific consensus evolved into the current theory we have today. What I Need to Know This module is based on DepEd’s Most Essential Learning Competency (MELC) Number 4 for Science 10, Quarter 1. Learning Competency: “Describe the possible causes of plate movement.” At the end of this module, you are expected accomplish the following specific learning objectives unpacked from the competency: 1. Enumerate the various theories, concepts and scientists that contributed to the current scientific explanation of why the tectonic plates move. 2. Describe the concepts put forward by each theory or concept. 3. Trace how the theories and concepts evolved into the theory of plate tectonics 4. Explain how plate tectonic theory explains the possible causes of plate movement. What I Know We would like to know how familiar you already are with this topic. Please answer the pre-test questions below. 1. Alfred Wegener is a German scientist who proposed a theory about the history of the landmasses of the world. Which of the following theories did Wegener propose? A. Continental Drift Theory C. Plate Tectonics B. Continental Shift Theory D. Seafloor Spreading Theory 3|Page  2. Which of the following is the main concept proposed by the Seafloor Spreading Theory? A. Magma forms convection cells in the mantle. B. Continents move through unmoving oceans. C. The lithosphere of the earth is divided into segments. D. Magma coming out from ocean ridges forms new seafloor. 3. What is the behavior of magma in convection currents? A. Hotter magma materials rise up while cooler magma sinks down B. Cooler magma rises up while hotter magma materials sink down C. Magma currents rotate inside the outer core of the Earth D. The movement of magma in the mantle is heats up the Earth’s core 4. What layer of the earth serves as a heat source that initiates the formation of convection currents? A. core C. lithosphere B. crust D. mantle 5. Which of the following sequence correctly illustrates the progression of theories explaining why tectonic plates move? A. Seafloor Spreading  Continental Drift  Convection Currents  Earth’s Interior Layers  Plate Tectonics Theory B. Continental Drift  Seafloor Spreading  Convection Currents  Earth’s Interior Layer  Plate Tectonics Theory C. Convection Currents  Earth’s Interior Layers  Continental Drift  Seafloor Spreading  Plate Tectonics Theory D. Earth’s Interior Layers  Convection Currents  Seafloor Spreading  Continental Drift  Plate Tectonics Theory 6. Which of the following is a mechanical layer of the Earth? A. Core B. Crust C. Lithosphere D. Mantle 7. What is the name of the singular landmass that once existed some 250 million years ago? A. Eurasia B. Gondwanaland C. Laurasia D. Pangaea 8. Who proposed the theory of seafloor spreading? I. Alfred Wegener II. Harry Hess III. Robert Dietz A. I only C. II and III only B. I and II only D. I, II and III 9. Why was the theory of continental drift not accepted by scientists despite of numerous evidences that support it? A. It was not able to provide an explanation why the continents move. B. The theory required advanced concepts inaccessible during the time. C. The scientist who proposed the theory did not have a good reputation. D. A majority of the presented evidence were found out to be fabrications. 10. How do oceans get wider according to the seafloor spreading theory? When magma comes out of the ocean ridge, it ____________________________________. A. pushes the old crust upwards increasing the thickness of the crust B. melts the old crust creating a heat source which boils away the ocean water C. melts the old crust creating a trench which causes the ocean to increase its water capacity D. pushes either side of ridge away from the ridge pushing the ocean floor apart while creating new crustal material 4|Page  11. Materials in the mantle move via convection currents. Which of the following explains how a convection current is generated? A. The mantle is squeezed between the crust and the core. The heat generated from this enables convection currents to flow. B. Tectonic plates are moving. As they move, they produce friction which creates heat. This heat pushes the flow of convection currents. C. The core of the earth is much hotter than the mantle. The heat from the core flows towards the mantle fueling the convection currents. D. Heat from the sun is absorbed by the Earth’s internal layers. This constant flow of heat from the sun triggers the movement of mantle materials. 12. Which statement reflects the how plate tectonics explains the movement of landmasses and oceans? A. Oceans and continents are both part of the lithosphere. When a segment of the lithosphere moves, so do the oceans and continents. B. Oceanic crusts move to either side of an oceanic ridge and in the process pushes the continents to move also. C. Continental landmasses move through the unmoving oceans breaking oceanic crusts in the process. D. Continental landmasses move independently from oceanic seafloor. 13. Why does magma come out of mid-oceanic ridges? A. Magma from the mantle is pushed up by convection currents. B. Movement of the tectonic plates pushes magma to come out of oceanic ridges. C. Earthquakes and volcanic eruptions cause disturbance of magma in the mantle. D. The melting of oceanic crust creates an excess of magma which results in it coming out of ridges. 14. Lithospheric plates are above the asthenosphere sublayer. Why is it easy for lithospheric plates to move over it? It is because ____________________________. A. the asthenosphere has a solid smooth surface on which the lithospheric plates can easily slide B. lithospheric plates are heavy and their weight creates pressure on the asthenosphere C. the asthenosphere is partially melted and it’s materials flow like a fluid D. the lithosphere is hotter than the asthenosphere 15. Why is the unifying theory of geology named Plate Tectonic Theory? I. Tectonic comes from Latin word Tekton which means builder or carpenter II. Movement of lithospheric plates build the features of the Earth like oceans, volcanoes, mountains, etc. III. The person who proposed the theory was originally a carpenter by profession A. I only B. I and II only C. I and III D. I, II and III Do not worry if you have no idea about the answers to the questions above. We will start to learn all of them in the next section. 5|Page  What’s In To make sure you we are in the same page, let us review some concepts from the previous modules. Refer to the map above and answer the following review questions. If you are able to answer most of these, it means you are ready for this module. Otherwise, you should go back to the previous modules. 1) The Eurasian plate and Indian plate form a convergent boundary (marked A in the map). If we draw arrows above the map to indicate each plate movement, they would be: a. Indian plate – upwards and Eurasian plate – downwards b. Indian plate – downwards and Eurasian plate – upwards c. Indian plate – towards left and Eurasian plate – towards right d. Indian plate – towards right and Eurasian plate – towards left 2) What geological feature is formed between the divergent boundary (marked B in the map) between South American and African plates? a. Mountain Ranges c. Oceanic Ridge b. Volcanic Island Arc d. Rift Valley 6|Page  3) The area marked C in the map is where an edge of the North American plate slide past a part of the Pacific plate. What type of boundary is formed by this interaction? a. Convergent Boundary c. Divergent Boundary b. Transform Fault Boundary d. Hotspot Area 4) In the continent of Africa stretching from Jordan to Mozambique there is a geological formation called the East African Rift Valley. What can be inferred from this fact? a. The African plate is diverging and if this continues it will break into two new tectonic plates b. The African plate is converging and if this continues mountain ranges will be formed in East Africa c. The African plate forms a transform fault boundary with one of its neighboring plate forming this rift valley d. East Africa was formed from volcanic island arcs in the past. 5) Why are there many volcanoes and trenches in the Philippines? a. Majority of the Philippine islands are on the Eurasian plate and the oceanic Philippine plate subducts under it forming volcanoes b. The Philippines gets hit with a lot of earthquakes and they result into the formation of land volcanoes along the archipelago c. There are a lot of hotspots underneath the archipelago and they feed magma towards the crust forming the volcanoes d. Most of the archipelago was formed from the magma that rose up from the mantle because of the divergence between the Eurasian plate and the Philippine plate. What’s New Science is often trial and error. We are able to have our current understanding of plate tectonics today because of previous theories and ideas put forward by several scientists. Let us find out what these were. Task 1: Theories and Concepts on related to Plate Tectonic Movement Analyze the table below and answer the questions afterwards: Theory / Who proposed the What the theory / concept describes in a Concept theory? nutshell “Continents were once connected as one Continental Drift landmass called Pangaea. It broke down into Alfred Wegener Theory individual continental landmasses which moved through unmoving oceans/seafloor.” 7|Page  “Hot magma rises up from the mantle and creates a crack in the Earth’s crust which we Sea Floor Harry Hess and call an ocean ridge. The magma pushes the Spreading Robert Dietz two sides of the seafloor causing each to move Theory sideward. This magma fills in the gap then solidifies and forms new seafloor.” “In the mantle, magma materials rise up as they are heated up and sink down as they cool. This Convection (Not credited to forms magma currents that circulate from the Current specific person/s) deeper parts of the mantle up to the bottom boundary of the lithospheric plates and back down.” “The Earth’s layers are Crust, Mantle, Outer Core and Inner Core. The inner core is made up of nickel and iron, is the hottest and is solid Interior (Not credited to because of the tremendous pressure exerted by Structure of the specific person/s) the layers above. The outer core has the same Earth composition but it is cooler and is in liquid state. The mantle contains a layer which is plastic-like and therefore flows like a fluid.” Answer the following questions on a separate sheet of paper: 1) What aspect of the continental drift theory is opposed by the seafloor spreading theory? Explain how they differ. Hint question: What do the continental drift theory and the seafloor spreading theory say about the oceans/seafloor? 2) How does the concept of convection current support seafloor-spreading theory? Hint question: Which important material mentioned in seafloor spreading theory is also present in convection currents? 3) Elaborate how the interior structure of the Earth implicitly explains the existence of convection currents. Hint: What does temperature have to do with convection currents? 8|Page  What is it Theories and Concepts on related to Plate Tectonic Movement Continental Drift Theory In 1912, Alfred Wegener, a German meteorologist, proposed a theory that about 250 million years ago, the continents were once one large landmass. He called this landmass Pangaea, a Greek word which means “All Earth”. He thought Pangaea started to break into two smaller supercontinent called Laurasia and Gondwanaland during the Jurassic Period. These smaller supercontinents broke into the continents and these continents separated and drifted apart since then. Alfred Wegener Evidence-wise, the theory of continental drift was very sound. Wegener was able to present various lines of evidences to support his claim. These evidences will be discussed in the next module. However, scientists during his time did not accept his theory because of one glaring flaw. It provided no mechanism or means of how the continental masses moved. The theory was thought to be incomplete. 9|Page Seafloor Spreading Theory Seafloor spreading theory addressed the one weakness of continental drift theory. It offered an explanation to why the continents moved. The invention of sonars and submersibles in the 1950’s and 1960’s enabled scientists to make better observations and gather new information about the ocean floor. They have discovered a system of ridges or mountains in the seafloor. These are called mid-ocean ridges. Harry Hess Robert Dietz After conducting observations and gathering multitudes of data, scientist Harry Hess, together with Robert Dietz, suggested an explanation to the continental drift. This is the Seafloor Spreading Theory. According to this theory, hot, less dense material from below the earth’s crust rises towards the surface at the mid-ocean ridge. This material flows sideways carrying the seafloor away from the ridge, and creates a crack in the crust. The magma flows out of the crack, cools down and becomes the new seafloor. Overtime, the new oceanic crust pushed the old oceanic crust far from the ridge. This movement of the oceanic floor is mechanism that causes the continents to drift. Although the Seafloor Spreading Theory is able to explain the movement of continents it actually contradicts a part of the Continental Drift Theory. According the previous theory, continents moved through unmoving oceans and that larger, sturdier continents broke through the oceanic crust. Whereas, the seafloor spreading shows that the ocean is the actual site of tectonic activity. 10 | P a g e Convection Currents in the Mantle The question of how the continents drifted was answered by the seafloor spreading theory. Continents were being pushed by the gradual spreading of the seafloor. However, another question arose. Why does magma rise up from the mantle out of the ocean ridges to start the process of seafloor spreading in the first place? The answer lies in a basic concept of heat transfer which you have learned in Grade 7. This concept is called convection. Recall that convection is defined as the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat. Various excavations and experimental drillings have taught us that the temperature of the Earth’s materials become hotter as we go deeper. It is therefore a known fact that temperatures in the deep mantle are much higher than in the asthenosphere (a mantle layer just below the lithosphere). Just as when hot air rises and cool air sinks, molten materials in the mantle also behave similarly. Hotter magma from the deeper parts of the mantle rises up (and cools down in the process) while magma from the asthenosphere (which has cooled down) sinks to the bottom. The magma that reach the bottom is again heated and the cycle repeats. This results in the formation of a circular flow of molten materials we call a convection current. The upwelling of this convection is what breaks the seafloor to form an ocean ridge and starts the process of seafloor spreading. 11 | P a g e Internal Structure of the Earth Convection currents are formed by temperature differences in the mantle and the layers below it. But how do we know for sure that this is a fact? Scientists are confident that this is the case because they have studied the internal structure of the Earth thoroughly. Using data from earthquakes that propagate internally through the Earth, they have determined its layers, their phases and boundaries. Based on composition, the Earth is made up of three layers – crust, mantle and core. But based on mechanical properties and behavior, the crust and the upper rigid solid rock part of the mantle form the lithosphere. Just below this layer is a partially molten fluid-like layer called the asthenosphere. This configuration allows convection currents to form especially in the fluid-like asthenosphere layer. Also, the presence of the mechanical layer called lithosphere means that continents and oceans do not move on their own. A whole lithospheric plate or segment moves carrying the continents and seafloor. The composition and temperature of each layer is determined from a combination of direct observation, earthquake wave data, chemical analysis of materials coming out from volcanoes and ridges, composition analysis of asteroids (said to be the building blocks of planets), mathematical calculations from fluid dynamics and materials science, computer simulation of early solar system planet formation and mathematical reconciliation of the density of the Earth to its orbital behavior around the Sun as dictated by the gravitational laws. 12 | P a g e  Looking at the temperature of the Earth’s layers we can see that the core is the hottest. This supports the concept of convection current formation. The core serves as the source that heats up materials at the bottom of the mantle layer kickstarting the circular movement of molten rock and magma. The mantle especially the asthenosphere acts like the heated fluid. The lithosphere floating on top of the asthenosphere is affected by any movement in the fluid. Movement of lithospheric plates When a lithospheric plate splits into two by forming an ocean ridge, the segments move apart. As this motion continues, they are bound to collide with neighboring plates forming subduction zones where one of the colliding plates sink under the other (as explained by modules 2 and 3). When this happens, there are three factors for the motion of the lithospheric plates. 1. Ridge Push – this refers to the force of rising magma as it punches through the oceanic ridge. 2. Mantle Drag – this refers to the sideward force exerted by the moving convection current underneath the lithosphere. 3. Slab Pull – the downward force due to the weight of the subducting slab. 13 | P a g e  What’s More Plate Tectonic Theory – How we got there? Today, the unifying theory of geology is the Theory of Plate Tectonics.Tectonics comes from the Latin word Tekton which means builder or carpenter. Indeed, the processes that Plate Tectonics describes can explain how the features of the earth such as mountains, volcanoes, trenches etc. are formed or built. As discussed in the previous activities, this theory was built on top of other theories and concepts that came before it. In this activity we will try to reconstruct the plate tectonic theory from the mentioned concepts. Below are statements from the previous theories and concepts before the Plate Tectonic Theory was formed. If we eliminate the ones that were proven wrong and retain only the ones that are proven correct, we should be able to form the current version of the Theory of Plate Tectonics. TASKS: 1) Below are a pair of opposing statements from different theories or concepts. Evaluate each statement. Write a checkmark “√” on its box if the concept is considered the more correct statement. Write an “X” it is the less correct one of the two. Example: Theory 1 versus Theory 2 √ This is statement is the more correct This is statement is the less correct one of X one of the two statements the two statements. A. Continental Drift Theory versus Seafloor Spreading Theory The continents move but the The seafloor also drifts/moves just like the oceans/seafloor do not. continents. B. Continental Drift Theory versus Seafloor Spreading Theory There is no explanation for why the The continents move because of the continents move. movement of the seafloor. C. Convection Current versus Seafloor Spreading Theory The upward direction of convection There is no explanation why magma rises currents causes magma to rise up up out of mid-ocean ridges out of mid-ocean ridges D. Internal Layers of the Earth versus Seafloor Spreading Theory Continents (continental crust) and The continents and oceans/seafloor move oceans (oceanic crust) are part of or drift on their own. the lithosphere and so when the lithosphere moves so do they. 14 | P a g e  E. Seafloor Spreading Theory versus Internal Layers of the Earth Magma coming out from mid-ocean Magma coming out from mid-ocean ridges ridges push the seafloor to the push segments of the lithosphere to the sides. sides. F. Internal Layers of the Earth versus Continental Drift Theory Lithospheric plates move. Continents move through unmoving Continents are part of lithospheric oceans. plates. G. Convection Current versus Internal Layers of the Earth It is not clear what drives the The core heats up materials in the mantle temperature differences that create making them rise up initiating the convection currents formation of convection currents. H. Internal Layers of the Earth versus Convection Current Convection currents are possible in It is not clear why convection currents are the mantle because molten magma possible in the mantle. especially in the asthenosphere is fluid-like. 2) Construct the Plate Tectonic Theory by listing the statements that you marked with a “√” in number 1. If there are still contradicting statements among the ones marked “√”, choose which one is more updated or more correct. Plate Tectonic Theory tells us that: _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ What I Have Learned The statements below are concepts postulated to be true by the Plate Tectonic Theory. As was discussed above, the concepts of this theory evolved from continental drift, seafloor spreading, convection currents and internal structure of the Earth. TASK: To find out if you understood what these concepts are and how they evolved, read the statements and identify the origin of the concepts. You can write multiple answers to each number if it applies. Options: continental drift theory convection current seafloor spreading theory internal structure of the Earth plate tectonic theory 15 | P a g e __________________1) The earth has three compositional layers - crust, mantle and core. The mantle is divided into three sublayers - the uppermost rigid part of the mantle, the asthenosphere and the mesosphere. In a similar manner, the core is subdivided into the liquid outer core and the solid inner core. __________________2) Aside from compositional layers, the Earth's interior can also be divided into mechanical layers. This is based on their mechanical properties like phase and movement but NOT on composition. __________________3) The crust and the first sublayer of the mantle (the uppermost rigid part of the mantle) are both solid and they are observed to move together. Thus, the two form the outermost mechanical layer of the Earth - the lithosphere. The second sublayer of the mantle - the asthenosphere has different mechanical properties compared to the lithosphere because it is partially melted and it flows like a fluid. It is considered to be another mechanical layer. __________________4) The earth's hard outermost mechanical layer, the lithosphere, is fragmented into several segments called lithospheric/tectonic plates. __________________5) These plates float on top of a fluid-like mechanical layer called the asthenosphere. __________________6) Materials in the mantle which includes the asthenosphere form convection currents. __________________7) Convection currents form when the materials at the bottom of the mantle are much hotter than the materials at the top of the mantle. The hotter materials float up while the colder materials sink down forming a circular flow of magma. __________________8) The movement of convection currents in the asthenosphere drags the lithospheric plates floating above it causing them to move. __________________9) The materials at the bottom of the mantle are hotter because they absorb the heat coming from the core. The core of the Earth is the hottest compositional layer. __________________10) When a convection current moves up it could create a crack in the lithosphere into which magma could come out. We usually find these cracks in the ocean floor. We call them mid-oceanic ridges. __________________11) Continental crusts and oceanic crusts are part of the lithosphere. __________________12) The continents move but not on their own. It is because continental crusts are part of the lithosphere and the lithosphere moves. __________________13) The oceans move but not on their own. It is because oceanic crusts are part of the lithosphere and the lithosphere moves. __________________14) The movements of the tectonic plates (which was caused by the convection currents) in turn causes the formation of the three types of boundary interactions discussed in module 2. __________________15) The different boundary interactions form geological features such as earthquakes, tsunamis, mid-oceanic ridges, rift valleys, mountains, land volcanoes, underwater volcanoes, volcanic islands and trenches. 16 | P a g e  What I Can Do Debunking local myths about Earthquakes A popular myth in our country is about Bernardo Carpio. He is said to be a strong giant who is trapped between two mountains. It is said that when he moves his shoulders, he shakes the mountains and create earthquakes. Another myth explaining the occurrence of earthquakes originates in the Visayas area. According to old local folk, there is a giant wild boar that roams underneath the ground causing it to shake. Whenever an earthquake occurs, you must therefore drive the boar away by saying “Buwa! Buwa!” loudly. Now that you know the correct scientific explanation for the movements of tectonic plates. How would you explain to the advocates of these myths the correct scientific concepts? TASK: Make a creative presentation expounding on the correct explanation on why earthquakes occur based on the movement of lithospheric plates. Focus on why the scientific explanation makes more sense than these myths. The presentation must be convincing but still respectful to the myths that are part of our cultural identity. The output could be a comics strip, an explainer video, a creative drawing, a poem, song, a rap or any creative expression that is able to explain the concepts. Refer to the rubrics below for the criteria for scoring. RUBRICS: Score Conceptual explanation Creativity Cultural Respect The output was able to Creative effort was very explain the scientific much evident in the The output recognizes that concepts and why it is output. And the artistic the myths are an important 5 better to trust the elements are in part of the culture and scientific explanation than harmony with each treats them with respect the myths other. The output was able to Creative effort was explain the scientific The output treats the evident in the output but concepts well but was not myths with respect but 4 the individual creative able to present it as a does not recognize its elements are not in better alternative to local importance to the culture harmony myths Some creative effort 50% to 74% of the The output discusses the was evident and the 3 explanations were myths in a slightly positive elements are in accurate way harmony 17 | P a g e  Some creative effort Less than 50% of the was evident and the The output discusses the 2 explanation were elements are in not in myths in a neutral manner accurate harmony The output was not able There has no creative The output discusses the 1 to explain any of the input evident in the myths in a negative way concepts necessary output Assessment It’s time to check what you have learned! Select the letter corresponding to the correct answer. Write your answers on a separate sheet of paper. 1. What is the function of the Earth’s core in sustaining convection currents in the mantle? A. Nothing. The core does not have a part in creating convection currents. B. It absorbs all the heat generated by the movement of the currents. C. The core serves as the heat source that initiates convection currents. D. It counters the movement of the convection current to make them stable. 2. The theory of plate tectonics evolved from previous theories and concepts put forward by several scientists before its conception. Which theories and concepts are part of this evolution? I. continental drift III. convection currents II. seafloor spreading IV. internal structure of Earth A. I only B. I and II only C. II and IV only D. I, II, III and IV 3. Who proposed the continental drift theory? A. Alfred Wegener C. Robert Dietz B. Harry Hess D. Frederick Vine 4. Which theory first proposed that magma from the mantle comes out of the ocean ridges and form new seafloor? A. continental drift theory B. seafloor spreading theory C. theory of convection currents D. theory of the internal structure of the Earth 5. Why are there convection currents in the mantle? There are convection currents in the mantle because __________________________. A. hotter materials at the deeper mantle float up while cooler materials sink down B. cooler materials at the deeper mantle float up while hotter materials sink down C. the rotation of the earth around its axis disturbs the magma in the layer D. moving lithospheric plates drag the magma below it to move 6. What was the one weakness of the theory of continental drift? A. It did not explain why the continents move. B. The theory was not supported by evidences. C. Majority of the presented evidence were fabrications. D. The scientist who proposed it was not popular enough. 18 | P a g e  7. Magma that come out of an oceanic ridge help widen the oceans. Why is this so? When magma comes out of the ocean ridge, it __________________________. A. pushes the old crust upwards increasing the thickness of the crust B. melts the old crust creating a heat source which boils away the ocean water C. melts the old crust creating a trench which causes the ocean to increase its water capacity D. pushes either side of ridge away from the ridge pushing the ocean floor apart while creating new crustal material 8. Which of the following is NOT a compositional layer of the Earth? A. Asthenosphere B. Core C. Crust D. Mantle 9. What were the names of the two supercontinents that formed when Pangaea broke off into two? A. Gondwanaland and Laurasia C. Gondwanaland and Eurasia B. Laurasia and Eurasia D. Laurasia and Tethys 10. Which statement about continents and oceans is proposed by the Plate Tectonic Theory? A. Oceans and continents are both part of the lithosphere. When a segment of the lithosphere moves, so do the oceans and continents. B. Oceanic crusts move to either side of an oceanic ridge and in the process pushes the continents to move also. C. Continental landmasses move through the unmoving oceans breaking oceanic crusts in the process. D. Continental landmasses move independently from oceanic seafloor. 11. Which theory was proposed by Harry Hess and Robert Dietz? A. continental drift theory B. seafloor spreading theory C. theory of convection currents D. theory of the internal structure of the Earth 12. Why do convection currents in the mantle exist? A. The mantle is squeezed between the crust and the core. The heat generated from this enables convection currents to flow. B. Tectonic plates are moving. As they move, they produce friction which creates heat. This heat pushes the flow of convection currents. C. The core of the earth is much hotter than the mantle. The heat from the core flows towards the mantle fueling the convection currents. D. Heat from the sun is absorbed by the Earth’s internal layers. This constant flow of heat from the sun triggers the movement of mantle materials. 13. Which best explains why molten materials from the mantle come out of oceanic ridges? A. Magma from the mantle is pushed up by convection currents. B. Movement of the tectonic plates pushes magma to come out of oceanic ridges. C. Earthquakes and volcanic eruptions cause disturbance of magma in the mantle. D. The melting of oceanic crust creates an excess of magma which results in it coming out of ridges. 19 | P a g e  14. Why is the asthenosphere important in the context of the theory of plate tectonics? A. Asthenosphere heats up the mantle and the core. B. This layer prevents the lithosphere from moving too fast. C. The asthenosphere prevents the lithosphere from melting. D. Fluid-like nature of this layer enables lithospheric plates to move. 15. Evaluate each statement below. Which of is TRUE about the plate tectonic theory? A. It is not compatible with the concepts proposed by continental drift, seafloor spreading, convection currents and internal structure of the Earth. B. This theory evolved from the concepts proposed by continental drift, seafloor spreading, convection currents and internal structure of the Earth. C. Plate tectonic theory completely disproves all the concepts proposed by both the continental drift theory and the seafloor spreading theory. D. It is the earlier theory from which continental drift theory and seafloor spreading theory was derived from. Additional Activities The activity below is only supplemental for added learning. If you have internet access, you may visit this website. 1) www.misterhelp.net a. Click on “Log in as guest”. b. Click on Plate Tectonics Supplemental Videos course. c. Watch the supplemental videos. 20 | P a g e References Books: SCIENCE 10 Learner’s Module, Department of Education, Republic of the Philippines SCIENCE 10 Teacher’s Guide, Department of Education, Republic of the Philippines Images: "File:Alfred Wegener Ca.1924-30.Jpg - Wikimedia Commons". 2020. Commons.Wikimedia.Org. https://commons.wikimedia.org/wiki/File:Alfred_Wegener_ca.1924-30.jpg. "File:Pangaea To Present.Gif - Wikimedia Commons". 2020. Commons.Wikimedia.Org. https://commons.wikimedia.org/wiki/File:Pangaea_to_present.gif. 2020. Alchetron.Com. https://alchetron.com/cdn/harry-hammond-hess-c3d7307c- 22a1-4c87-9cb8-fffc2c448bd-resize-750.jpg. 2020. Library.Ucsd.Edu. https://library.ucsd.edu/dc/object/bb4813339v/_3.jpg. 2020. Chloesgeologicalassignment2015.Weebly.Com. https://chloesgeologicalassignment2015.weebly.com/uploads/5/3/5/7/53577855/head er_images/1435900801.jpg. 2020. 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Qph.Fs.Quoracdn.Net. https://qph.fs.quoracdn.net/main-qimg- da0d2235429f8fae0c9a2c4130654d86. 23 | P a g e  For inquiries or feedback, please write or call: Department of Education – Division of Cebu City Office Address: Imus Road, Cebu City Telephone Nos.: (032) 255-1516 / (032)253-9095 E-mail Address : [email protected] 24 | P a g e