Sci10_LM_U1.pdf

10 Science PY Learner’s Materia...

10 Science PY Learner’s Material Unit 1 O C E D This book was collaboratively developed and reviewed by educators from public and private schools, colleges, and/or universities. We encourage EP teachers and other education stakeholders to email their feedback, comments, and recommendations to the Department of Education at [email protected]. We value your feedback and recommendations. D Department of Education Republic of the Philippines i All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Science – Grade 10 Learner’s Material First Edition 2015 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 royalties. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this book are owned by their respective copyright holders. DepEd is represented by the Filipinas Copyright Licensing Society (FILCOLS), Inc. in seeking permission to use these materials from their respective copyright owners. PY All means have been exhausted in seeking permission to use these materials. The publisher and authors do not represent nor claim ownership over them. Only institutions and companies which have entered an agreement with FILCOLS and only within the agreed framework may copy from this Learner’s Material. Those who have not entered in an agreement with FILCOLS must, if they wish to copy, O contact the publishers and authors directly. Authors and publishers may email or contact FILCOLS at [email protected] or (02) 439-2204, respectively. Published by the Department of Education C Secretary: Br. Armin A. Luistro FSC Undersecretary: Dina S. Ocampo, PhD D Development Team of the Learner’s Material E Authors: Herma D. Acosta, Liza A. Alvarez, Dave G. Angeles, Ruby D. Arre, Ma. Pilar P. Carmona, Aurelia S. Garcia, Arlen Gatpo, Judith F. Marcaida, Ma. Regaele A. Olarte, Marivic S. Rosales, Nilo G. Salazar EP Reviewers: Eligio C. Obille Jr., Marlene B. Ferido, Ma. Helen DH Catalan, Vic Marie Camacho, Lilia M. Rabago, Cerilina M. Maramag Illustrators: Joseph V. Bales, Ramon C. Gatpo, Regaele A. Olarte, Marivic S. Rosales, Ruel C. Quindoy, Antonio I. Basilla, Jose Leo Vic O. Albaño DepEd Specialists: Joseph R. Jacob, Maria Amparo R. Ventura D Photo Credits: Herma D. Acosta, Dave G. Angeles, Liza A. Alvarez, Ruby D. Arre, Aurelia S. Garcia, Judith F. Marcaida, Regaele A. Olarte, Jane Chavarria, Nilo G. Salazar Layout Artists: Matthew Daniel V. Leysa and Mary Grace Ann G. Cadisal Printed in the Philippines by REX Book Store, Inc. Department of Education-Instructional Materials Council Secretariat (DepEd-IMCS) Office Address: 5th Floor Mabini Building, DepEd Complex Meralco Avenue, Pasig City Philippines 1600 Telefax: (02) 634-1054, 634-1072 E-mail Address: [email protected] ii All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  TABLE OF CONTENTS Unit 1: Earth and Space Overview Module 1: Plate Tectonics I. Introduction ----------------------------------------------------------------------------------3 II. Learning Competencies/Objectives ---------------------------------------------------4 III. Pre-Assessment --------------------------------------------------------------------------4 IV. Reading Resources and Instructional Activities -----------------------------------6 PY Activity 1: Find the Center ----------------------------------------------------------8 Activity 2: Let’s Mark the Boundaries ------------------------------------------11 Activity 3: Head on Collision -----------------------------------------------------16 O Activity 4: Going Separate Ways -----------------------------------------------25 Activity 5: Slide and Shake ------------------------------------------------------29 C Activity 6: Drop It Like Its “Hot Spot” ------------------------------------------31 V. Summative Assessment ----------------------------------------------------------------34 D VI. Summary/Synthesis/Feedback ------------------------------------------------------35 Glossary of Terms ------------------------------------------------------------------36 E References and Links -------------------------------------------------------------37 EP Module 2: The Earth’s Interior I. Introduction --------------------------------------------------------------------------------39 II. Learning Competencies/Objectives -------------------------------------------------40 D III. Pre-Assessment -------------------------------------------------------------------------40 IV. Reading Resources and Instructional Activities ----------------------------------43 Activity 1: Amazing Waves!-------------------------------------------------------47 Activity 2: Our Dynamic Earth-----------------------------------------------------52 Activity 3: Let’s Fit It!----------------------------------------------------------------58 Activity 4: Drifted Supercontinent!-----------------------------------------------59 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Activity 5: Split and Separate!----------------------------------------------------66 Activity 6: How fast does it go!----------------------------------------------------69 Activity 7: Push me up and aside!-----------------------------------------------70 V. Summative Assessment ---------------------------------------------------------------74 VI. Summary/Synthesis/Feedback ------------------------------------------------------77 Glossary of Terms ------------------------------------------------------------------78 References and Links -------------------------------------------------------------79 PY O C E D EP D All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  UNIT 1 Earth and Space PY O C E D EP D 1 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Unit 1: Earth and Space Overview In your Grade 9 Science, part of your lessons was about volcanoes. You have learned about the position of the Philippines in the Ring of Fire and its relationship to the presence of active and inactive volcanoes in our country. In this quarter, the topics will focus solely on a theory that explains the existence of volcanoes and other geologic features. You have two modules to understand this theory better. PY In the first module, you will use some of your science skills such as graphing, measuring, analyzing and interpreting data, and inferring for you to attain the desired outcomes. What are the outcomes that are expected from you? First, you should identify the types of boundaries created because of lithospheric movements. O Secondly, you must relate the movement of Earth’s lithosphere to the occurrence of different geologic changes. And finally, you will explain the processes that are taking place along the boundaries. C In the second module, you will perform an activity that will allow you to probe the Earth’s interior by analyzing the behavior of seismic waves (Primary D and Secondary waves). You will also have an opportunity to simulate one of the properties of the materials present in the mantle. E Lastly, included in the module, and the most important part is the series of activities that will give you an idea about the driving mechanism behind the EP motion of Earth’s lithosphere. D 2 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Unit 1 MODULE 1 PLATE TECTONICS I. Introduction PY Our country is blessed with so many land features such as mountains and volcanoes. These features can be sources of different minerals or can be used for agricultural purposes. For example, we have the majestic and world renowned Mayon Volcano. Because of its activity, it produces fertile slopes O and plains which are used by the locals to grow their crops. Also, found in the northeastern coast of Luzon, we have the Sierra Madre mountain range which is home to many endemic species of flora and fauna. C Have you ever wondered why our country is endowed with these kind of geologic features? Well, if your answer is YES, then this module will help you find the answer to your question. D In this module, we will study thoroughly the framework that will enable us to understand how and why several features of the Earth continuously change. E This theory is what we call “Plate Tectonics.” This describes the events within the Earth that give rise to mountain EP ranges, volcanoes, earthquake belts, and other features of the Earth’s surface. At the end of Module 1, you are expected to answer the key question below: D What is the relationship among the locations of volcanoes, earthquake epicenters, and mountain ranges? 3 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  II. Learning Competencies/Objectives In this module, you should be able to: 1. Describe the distribution of active volcanoes, earthquake epicenters, and major mountain belts. 2. Describe the different types of plate boundaries. 3. Explain the different processes that occur along the plate boundaries. III. Pre-Assessment Choose the letter of the correct answer. PY Displacement (cm) O C Time (seconds) D For questions 1 and 2, refer to the figure above: 1. You were provided with data showing the arrival time of the P and E S-waves recorded from three seismic stations. Which of these can you possibly determine? EP a. the damage at the focus c. the intensity of the earthquake b. the distance to the earthquake d. the location of the epicenter 2. From the seismogram, the distance to the epicenter can be determined by measuring D a. the arrival time of surface wave b. the difference in the arrival times of the P and S-waves c. the ratio of the amplitude of the largest P and S-waves d. the speed of the surface wave 3. When two tectonic plates collide, the oceanic crust usually subducts beneath the continental crust because it is a. denser than continental crust c. thicker than continental crust b. less dense than continental crust d. thinner than continental crust 4 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  4. If you visit a place in the Pacific known to be along converging plates, which of these should you NOT expect to see? a. active volcanoes c. rift valleys b. mountain ranges d. volcanic islands 5. You are an oceanographer and want to map the ocean floor on the east coast of the Philippines. As you do your study, you notice that there is a portion in the ocean floor which is relatively much deeper than the rest. What most likely is that deeper part? a. linear sea c. rift valley b. oceanic ridge d. trench PY 6. What do you expect to find at a mid-ocean ridge? a. relatively young rocks c. thick accumulation of sediments b. reverse fault d. very ancient rocks 7. Crustal plate A is moving away from crustal plate B. What is the O expected average rate of change in position between A and B? a. a few centimeters per year c. a few millimeters per century b. a few meters per month d. a few millimeters per day C 8. Which plate boundary is formed between the Philippine plate and the Eurasian plate? D a. convergent c. reverse fault b. divergent d. transform fault E 9. Which of these is false about lithosperic plates: a. have the same thickness everywhere EP b. include the crust and upper mantle c. thickest in the mountain regions d. vary in thickness 10. Which of these is NOT true about the Philippine islands? D a. most are part of the Philippine Mobile Belt, except for Palawan, Mindoro, and Zamboanga b. formed because of the convergence of the Philippine plate and the Pacific plate c. originated geologically in an oceanic-oceanic convergence d. some are products of subduction process 5 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  IV. Reading Resources and Instructional Activities What is Plate Tectonics? Earth’s lithosphere consists of layers, the crust and the upper part of the mantle. This part of the module will focus on the outermost layer which is called crust. The crust is made of a variety of solid rocks like sedimentary, metamorphic, and igneous. It has an average density of 2.8 g/cm3 and its thickness ranges from 5 to 50 km. The crust is thickest in a part where a relatively young mountain is present and thinnest along the ocean floor. PY Continental crust Oceanic crust O C E D Mantle Figure 1. Kinds of crust EP You will notice from Figure 1 that there are two kinds of crust: the thicker but less dense continental crust and the oceanic crust which is relatively thinner but denser than continental crust. D According to the plate tectonics model, the entire lithosphere of the Earth is broken into numerous segments called plates (see Figure 2). 6 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  PY O C http://pubs.usgs.gov Figure 2. Map of Plate boundaries D As shown in Figure 2, there are seven relatively large plates and a number of smaller ones, including the Philippine plate. The plates move very E slowly but constantly, and this movement is called tectonics; thus the theory of moving lithospheric plates is called plate tectonics. EP Before we study more about plate tectonics, let’s discuss first one of the consequences of moving crustal plates which is crucial in studying plate tectonics: earthquake. D You have learned in your Grade 8 Science that an earthquake releases three types of seismic waves; Primary (P-waves), Secondary (S-waves), and Long surface waves (L-waves). The first two travel into the Earth’s interior while the last one on the surface. These waves travel at different velocities; thus, do not arrive at a seismic recording station at the same time. The farther the recording instrument is from the focus, the greater the difference in arrival times of the first P-wave compared to the first S-wave. The difference in the arrival time will tell us the distance of the earthquake’s focus from the seismic recording station. However, it does not tell in which direction it came from. 7 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  If we have at least three recording stations that can tell how far away from them the earthquake occurred, the epicenter can be determined using the triangulation method. It uses distance information from three seismic stations to locate the earthquake epicenter. On a map, circles are drawn around each seismic station. The radii of the circles are scaled to the estimated distance from the station to the earthquake. The three circles will intersect at one point that locates the earthquake. The next activity will give you a first-hand experience on how to locate earthquake epicenter. Activity 1 PY Find the Center Objective: Locate the epicenter of an earthquake using the triangulation method. Materials: O hypothetical records of earthquake waves Philippine map drawing compass and ruler C Procedure: 1. Study the data showing the difference in the arrival time of P-wave D and S-wave on three seismic recording stations. Time difference in the E arrival time of P-wave Distance of epicenter Recording station and S-wave from the station (km) EP (seconds) Batangas 44.8 Puerto Princesa 32 Davao 38.4 D 2. Compute the distance of the epicenter from each of the stations using this formula: d= Td x 100 km 8 seconds Where: d = distance (km) Td = time difference in the arrival time of P-wave and S-wave (seconds) This formula is suited because 8 seconds is the interval between the times of arrival of the P-wave and S-wave at a distance of 100 km. 8 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  3. Choose one of the recording stations and measure the computed distance on the map scale (the scale of the map in Figure 3 is 1.5 cm: 200 km). Set your compass for that computed distance. 4. Center your compass on the station you have chosen. Draw a circle. 5. Repeat steps 3 and 4 for the rest of the stations. You should get three circles that intersect or nearly intersect at a point. This intersection is the epicenter. PY O C E D EP D http://earthquake.usgs.gov Figure 3. Map of the Philippines 9 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Q1. Where is the epicenter of this hypothetical earthquake? Q2. What difficulty will you encounter if you only have data from two recording stations? In the previous activity, the hypothetical earthquake happened locally, that is why we use the formula stated in the procedure. But, if the earthquake took place at a far greater distance, seismologists use the distance-time graph similar to the figure below in determining the location of the epicenter. PY Time (minutes) O C D Distance (km) from Epicenter E http://stream2.cma.gov.cn/pub/comet/Environment/TsunamiWarningSystems/comet/tsunami/ warningsystem/print.htm EP Figure 4. Distance-time graph The distance-time graph above shows that the S-P interval is about 10 minutes. D Q3. What is the distance of the epicenter from the seismic station? Q4. What do you think is the importance of determining the epicenter of an earthquake? Determining the location of earthquake epicenters plays a vital role in laying the foundations of plate tectonics. Let us see how early geologists used the plotted positions of earthquake epicenters throughout the world in conceptualizing crustal movements. 10 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Activity 2 Let’s Mark the Boundaries Objectives: Describe the distribution of active volcanoes, earthquake epicenters, and major mountain belts. Determine the scientific basis for dividing the Lithospheric plates. Materials: Figure 5: Map of earthquake distribution Figure 6: Map of active volcanoes of the world Figure 7: Mountain ranges of the world PY 2 pieces plastic sheet used for book cover, same size as a book page marking pens (two different colors) O C E D EP D http://marc.fournier.free.free.fr Figure 5. Map of earthquake distribution (Red, green, and blue dots represent earthquake epicenters) 11 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Procedure: 1. Study Figure 5 showing the earthquake distribution around the world. Trace the approximate locations of several earthquake “clusters” using a marking pen on one of the plastic sheets. Q5. How are earthquakes distributed on the map? Q6. Where are they located? Q7. Where are there no earthquakes? Q8. Why is it important for us to identify areas which are prone to PY earthquakes? O C E D EP D http://pubs.usgs.gov/gip/volc/fig34.html Figure 6. Map of active volcanoes (Red areas represent presence of volcanoes) 2. Study the map of active volcanoes in Figure 6. Q9. How are volcanoes distributed? Q10. Where are they located? Q11. Based on the map, mention a country that is unlikely to experience a volcanic eruption. 12 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  3. On the second plastic sheet, sketch the approximate locations of several volcanoes using a marking pen. 4. Place the earthquake plastic sheet over the volcano plastic sheet. Q12. Compare the location of majority of earthquake epicenters with the location of volcanoes around the world. PY O C D http://www.clipart.dk.co.uk/1068/az/Earth/Mountain_ranges Figure 7. Mountain ranges of the world E 5. Study Figure 7, the orange portions indicate mountain ranges of the world. EP Q13. How will you relate the distribution of mountain ranges with the distribution of earthquake epicenters and volcanoes? D 6. Now that you have seen the location of volcanoes, mountain ranges, and majority of earthquake epicenters, study Figure 2 on page 7, Map of Plate boundaries once more. Q14. What do you think is the basis of scientists in dividing Earth’s lithosphere into several plates? The places on Earth where most of the earthquakes originated or some mountains and volcanoes were formed mark the boundaries of each lithospheric plate. As mentioned earlier, each plate is slowly moving relative to each other, causing geologic events to happen along their boundaries. 13 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Let’s take a look at the relative motion of the crustal plates in the figure below. PY O https://www.bucknell.edu/majors-and-minors/geology/location/geologic-history-of-central- pennsylvania/plate-tectonics.html Figure 8. Map showing the relative motion of plates (Arrows indicate the direction of motion) C Types of Plate Boundaries Studying plate boundaries is important because along these boundaries D deformation of the lithosphere is happening. These geologic events have a great impact not only on the environment but also on us. E There are three distinct types of plate boundaries, which are differentiated by the type of movement they exhibit. EP The first type of plate boundary is termed divergent boundary wherein plates move apart, creating a zone of tension. Can you identify adjacent plates depicting divergent boundary on Figure 8? Let’s take the case of the Philippine plate and the Eurasian plate. You D will notice that the two plates are moving toward each other. This is an example of a zone where plates collide, and this second type of plate boundary is called convergent plate boundary. The third type is the transform fault boundary where plates slide or grind past each other without diverging or converging. The best example of this plate boundary is the San Andreas fault which is bounded by the North American plate and the Pacific plate. 14 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Plate Plate Asthenosphere A. DIVERGENT PLATE BOUNDARY PY Plate Plate O Asthenosphere B. CONVERGENT PLATE BOUNDARY C E D Plate Asthenosphere Plate EP C. TRANSFORM FAULT BOUNDARY http://earthsci8.wikispaces.com/ Figure 9. Three types of Plate Boundaries D 15 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  After learning the different types of plate boundaries, let us now explore the various effects of plate tectonics on Earth’s lithosphere. Activity 3 Head-On Collision Part A: Converging Continental Plate and Oceanic Plate Objectives: Explain the processes that occur along convergent boundaries. PY Determine the consequences of colliding plates. Procedure: 1. Study Figure 10 showing a cross-sectional diagram of plates that are converging, and answer the questions that follow. O C E D EP D Figure 10. Cross-sectional diagram of converging continental and oceanic plates Q15. What type of plate is Plate A? What about Plate B? Why do you say so? 16 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Q16. Describe what happens to Plate A as it collides with Plate B? Why? Q17. What do you think may happen to the leading edge of Plate A as it continues to move downward? Why? Q18. What do you call this molten material? Q19. What is formed on top of Plate B? Q20. As the plates continue to grind against each other, what other geologic event could take place? PY Converging Oceanic Crust Leading Plate and Continental Crust Leading Plate O The previous activity depicts what happens during collision of two plates; one has continental edge while the other has an oceanic edge. From the diagram, it is clear that this event gives rise to the formation of a volcanic C arc near the edge of a continental leading plate. The reason for this is because the denser oceanic crust (Plate A) undergoes what we call subduction process or the bending of the crust towards the mantle. Since the mantle is hotter than the crust, the tendency is, the subducted crust melt forming magma. Addition D of volatile material such as water will cause the magma to become less dense, hence allowing it to rise and reach the crust once again and causing volcanic E activities on the continental leading plate. For the oceanic crust, one important geologic feature is formed, and that EP is the trench. Also called submarine valleys, ocean trenches are the deepest part of the ocean. One of the deepest is the Philippine trench with a depth of 10 540 meters. Another subsequent effect of the continuous grinding of plates against D each other is the occurrence of earthquakes. The subduction of plate can cause earthquakes at varying depths. Most parts of the world experience occasional shallow earthquakes – where the focus is within 60 km of the Earth’s surface. Of the total energy released by earthquakes, 85% comes from shallow earthquakes. Meanwhile, about 12% of energy originates from intermediate earthquakes or those quakes with a focal depth range of 60 to 300 km. Lastly, are the deep earthquakes whose origin is more than 300 km to 700 km below the Earth’s surface. 17 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Activity 3 Head-On Collision Part B: Convergence of Two Oceanic Plates Procedure: 1. Study Figure 11. It shows a cross-section of two converging oceanic plates. 2. Using your knowledge gained from the previous activity, identify the geologic events or features resulting from this collision. PY Ocean Water O C Oceanic Plate A Oceanic Plate B E D www.marinebio.net EP Figure 11. Cross-sectional diagram of converging oceanic plates Q21. What are the geologic processes/events that will occur because of this plate movement? D Q22. What geologic features might form at the surface of Plate A? Q23. If the edge of Plate A suddenly flicks upward, a large amount of water may be displaced. What could be formed at the surface of the ocean? 18 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Convergence of Oceanic Plates Like the first type of convergent boundaries discussed earlier, converging oceanic plates will cause formation of trenches, and these trenches will become sources of earthquakes. Underwater earthquakes, especially the stronger ones, can generate tsunamis. The Japanese term for “harbor wave,” tsunami is a series of ocean waves with very long wavelengths (typically hundreds of kilometers) caused by large-scale disturbances of the ocean. The leading edge of the subducted plate will eventually reach the mantle causing it to melt and turn into magma. The molten material will rise to the surface creating a volcanic island arc parallel to the trench. Volcanic island arc PY is a chain of volcanoes position in an arc shape as seen in figure below. Accretionary Volcanic wedge island Oceanic Forearc ark crust Trench basin O Backarc region C E D EP Magma Lithosphere 100-km depth http://bwbearthenviro2011.wikispaces.com D Figure 12. Formation of a volcanic island arc Formation of the Philippine Archipelago Many parts of the Philippines originated from oceanic-oceanic convergence. This resulted from the collision of two oceanic plates, with one of the plates diving under the other. 19 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Majority of the islands in the Philippine archipelago are considered as part of the Philippine Mobile Belt. These islands were formed 65 million years ago at the southern edge of the Philippine Sea Plate and are considered as part of island arcs. Other parts of the Philippines, such as Palawan, Mindoro, and the Zamboanga Peninsula are all highland sections of the Sundaland block of the Eurasian plate (see Figure 13). PY O C E D Figure 13. Sundaland block of Eurasian Plate which includes Palawan, Mindoro, and Zamboanga EP The Philippine Mobile Belt eventually collided with the Sundaland block which explains the presence of trenches, such as the Manila-Negros-Cotabato Trench System, and the Sulu Trench, as shown in Figure 14. D 20 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  PY O C E D EP D Figure 14. Distribution of Active Faults and Trenches in the Philippines 21 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  On the eastern side of the Philippines, trenches like the Philippine Trench and East Luzon Trough are both products of subducting Philippine Sea Plate beneath the archipelago. PY ATE A PL E SE IPPIN O PHIL C D http://www.earthobservatory.sg/resources/images-graphics/subduction-zone-beneath- E philippines Figure 15. Subduction of Philippine Sea Plate EP Aside from the formation of trenches and troughs, the downward movement of oceanic lithospheres underneath the Philippine Archipelago creates active volcanic chains. For example, the descent of the West Philippine Sea oceanic lithosphere along the Manila Trench created a volcanic chain from Taiwan to Mindoro. Some of the known active volcanoes in this chain are D Pinatubo in Central Luzon and Taal in Batangas. Also, the constant dipping movement of slabs induces frequent moderate to strong earthquakes at various depths, gives rise to mountain ranges and develops the geologic character of the Philippine Archipelago. 22 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Activity 3 Head-On Collision Part C: Two Continental Plates Converging Materials: modeling clay 2 blocks of wood paper Procedure: PY 1. On a piece of paper, flatten the modeling clay with the palm of your hand. 2. Cut the clay into four strips; each strip should be 0.5 cm thick, 4 cm O wide, and 12 cm long. 3. Put 4 strips one on top of the other. C 4. Place a block of wood at each end of the clay strips and slowly push the two blocks together. Observe what happens to the clay. E D EP D Q24. What happened to the strips of clay as they were pushed from opposite ends? Q25. If the strips of clay represent the Earth’s lithosphere, what do you think is formed in the lithosphere? Q26. What other geologic event could take place with this type of plate movement aside from your answer in Q25? 23 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Q27. In terms of the consequences on the Earth’s lithosphere, how will you differentiate this type of convergent plate boundary with the other two? When two continental plates converge, a collision zone is formed. Unlike the other two types of convergent boundaries, subduction ceases for this particular type of convergence. No trench, no volcano, and definitely no island arc are created during this process. Instead, what is created is a large group of tall mountains called mountain range. PY O C http://whybecausescience.com/category/vulcanism/ Figure 16. Formation of mountain range About 40 to 50 million years ago, two large land masses, India and D Eurasia, collided to begin the formation of the most visible product of plate tectonics - the Himalayas. Since subduction is impossible between two colliding continental plates, pressure is released by pushing the crusts upward and E forming the Himalayan peaks. EP Also, collision of continental plates is associated with shallow earthquake activities. D http://pubs.usgs.gov/ Figure 17. Collision of the Eurasian and Indian plates 24 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  After learning the effects of convergent plate boundaries on the Earth’s lithosphere, it’s time for us to move on to the next type of plate boundary: the divergent plate boundary. Activity 4 Going Separate Ways Objectives: Explain the processes that occur along divergent boundaries. Determine the results of plates that are moving apart. Materials: PY photographs of Rift Valleys and Oceanic Ridges Procedure: 1. Analyze the photographs of rift valleys (topmost pictures) and O oceanic ridges below, and answer the questions that follow. C E D EP D http://www.adelaidenow.com.au/, http://www.wildjunket.com/, http://www.jnb-birds.com/ Figure 18. Rift valleys and oceanic ridges 25 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Q28. What are common in the four pictures? Q29. Millions of years ago, the land masses in each picture were once connected. What do you think is happening to the Earth’s crust in those pictures? Q30. If this event continues for millions of years, what do you think will be the effect on the crust? Q31. Complete the drawing below to illustrate your answer in question number 30. PY O At present C E D After millions of years EP Divergence of Plates Formation of rift valleys and oceanic ridges are indications that the crust D is spreading or splitting apart. In this case, the plates are forming divergent plate boundaries wherein they tend to move apart. Most divergent boundaries are situated along underwater mountain ranges called oceanic ridges. As the plates separate, new materials from the mantle ooze up to fill the gap. These materials will slowly cool to produce new ocean floor. The spreading rate at these ridges may vary from 2 to 20 cm per year. Although a very slow process, divergence of plates ensures a continuous supply of new materials from the mantle. The Mid-Atlantic Ocean ridge is an example of spreading center which causes the divergence of the South American plate and the African plate. 26 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  PY O Figure 19. Formation of Mid-Ocean ridge (Diagram by Phyllis Newbill) C When a spreading center develops within a continent, the crust may break into several segments. The breaking leads to the formation of down D faulted valleys called rift valleys. It is also associated with the rising of hot materials from the mantle. E The rift valley increases its length and depth as the spreading continues. At this point, the valley develops into a linear sea, similar to the Red Sea today. EP D 27 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  PY O C E D http://www.moorlandschool.co.uk/earth/tectonic.htm Figure 20. Development of a rift valley EP In Grade 8, you were introduced to different types of fault such as normal, reverse, and strike-slip. You also learned that faults are fractures in the Earth’s crust created by different types of forces acting on the lithosphere. D There is one type of plate boundary that resembles the strike-slip fault. Though much larger, transform fault boundary is similar to strike-slip fault in terms of the relative motion of adjacent slabs of rock. To find out more about this kind of plate boundary, the next activity will let you simulate the event that could happen out of this boundary. 28 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Activity 5 Slide and Shake Objective: determine the effect of transform-fault boundary on the Earth’s crust. Materials: four blocks of wood: blocks 1 and 4 measures 5 cm x 5 cm x 10 cm while blocks 2 and 3 measures 5 cm x 5 cm x 15 cm two hook screws sandpaper PY Procedure: 1. Attach a hook screw on one end of Blocks 2 and 3. O 2. Arrange the blocks as shown in the illustration below. 3. Place sandpaper on the side of the blocks where they all meet. C 4. Slowly pull Blocks 2 and 3 on its hook screw to the direction indicated by the arrow. Observe the motion of the blocks. E D EP Q32. Were you able to pull the blocks of wood easily? Why or why not? D Q33. What can you say about the relative motion of blocks 1 and 2? How about blocks 3 and 4? Q34. How will you describe the interaction between blocks 2 and 3 as you pull each block? Q35. What is the interaction between blocks 1 and 3? How about between blocks 2 and 4? 29 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Transform Fault Boundaries If the blocks of wood in Activity 6 were to represent the lithospheric plates, you will notice that there were two sets of divergent plate boundaries (between blocks 1 and 2, and blocks 3 and 4). But since the plates were adjacent to each other, a new type of boundary is manifested and that is the transform fault boundary. Most transform faults join two segments of a mid-ocean ridge (represented by the gaps between 1 and 2, and between 3 and 4). Remember that the presence of a ridge is an indication of diverging plates, and as the plates diverge between the two segments of the mid-ocean ridge, the adjacent slabs of crust are grinding past each other (blocks 2 and 3, blocks 1 and 3, and PY blocks 2 and 4). Although most transform faults are located within the ocean basins, there are a few that cut through the continental crust. An example of this is the O San Andreas fault. The immediate concerns about transform fault boundaries are earthquake activities triggered by movements along the fault system. C E D EP D sanandreasfault.org Figure 21. San Andreas Fault It was stated at the beginning of this module that majority of tectonic activities like earthquakes, mountain formations, and volcanic activities happen along or near plate boundaries. But there are some cases wherein activities take place in the middle of a plate. Let’s take the case of the Hawaiian islands. Here, we can find some of the largest and most active volcanoes of the world. If we’re going to look at Hawaii, it is situated right in the middle of Pacific plate and not along the boundaries. 30 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  What causes the formation of this chain of volcanic islands? The answer lies in an area called hot spot. To better understand this, let’s perform the next activity. Activity 6 Drop It Like It’s “Hot Spot” Objective: Relate hot spot with plate tectonics Materials: alcohol lamp test tube test tube holder PY bond paper (2 sheets) match water Procedure: 1. Attach one end of the bond paper to the end of another bond paper. O 2. Fill 3/4 of the test tube with water and heat it over an alcohol lamp. 3. While waiting for the water to boil, place the paper on top of the test C tube. Be sure that the two are in contact. E D EP D 4. Once the water starts boiling and fumes are coming out, hold the paper in the same position for the next 10 seconds. 5. After 10 seconds, move the bond paper very slowly and horizontally by 10 centimeters. See to it that the paper and test tube are still in contact. 6. Repeat step 5 after another 10 seconds and observe. Q36. What can you see on the surface of the bond paper? 31 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Q37. Let’s say that the paper represents the Earth’s crust; what do you think is represented by the water in the test tube? Q38. What geologic feature do you think will be formed at the surface of the crust? Q39. Which of the features, at the surface of the crust, will be the oldest? the youngest? Label these on your paper. Q40. Which of the features will be the most active? The least active? Label these on your paper. PY Activity 6 gave you an idea how tectonic activities could also happen within a plate and not just along the boundaries. This idea started when extensive mapping of seafloor volcanoes in the Pacific revealed a chain of volcanic structures extending from the Hawaiian O Islands to Midway Islands. When geologists determined the age of each volcanic island through radiometric dating, they noticed that the farther the volcano from Hawaii is, the older and less active it is. C Scientists suggested that there is a source of molten materials from the mantle called mantle plume that formed the volcanic island chains. As the D Pacific plate moves, different parts of it will be on top of the mantle plume to receive the molten materials, thus creating the volcanic islands. Continuing plate movement eventually carries the island beyond the hot spot, cutting it E off from the magma source, and volcanism ceases. As one island volcano becomes extinct, another develops over the hot spot, and the cycle is repeated. EP This process of volcano growth and death, over many millions of years, has left a long trail of volcanic islands and seamounts across the Pacific Ocean floor. Progressively older D Ocean Mantle plume http://www.geo.hunter.cuny.edu/ Figure 22. Hot spot forming a chain of volcanoes 32 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Performance Task At this point, we are quite aware that our country is susceptible to different disasters such as earthquakes, volcanic eruptions, and tsunamis. Therefore, it is a must for us to prepare and ensure our safety and survival when these disasters strike. For this activity, your goal is to help your family prepare for an impending emergency. Your task is to prepare an emergency kit for the whole family. Decide what items should be in your emergency kit and be ready to present it in class. The scoring rubric below will be used in assessing your kit. PY 1 pt. 2 pts. 3 pts. 4 pts. Survival Kit None of the A few of At least 8 items At least Items items are the items are clearly 10 items O necessary are clearly necessary for are clearly for survival necessary survival during necessary for during or for survival or after a survival during after a C during or after disaster. or after a disaster. a disaster. disaster. Labels and None of A few of At least 8 of At least 10 D Uses the items the items the items are items are are labeled are labeled labeled properly labeled properly and properly and and a reason properly and E there is no a reason for for each item is a reason for reason for each item is included on a each item is EP including it in included on separate sheet stated on a the survival a separate of paper. separate sheet kit. sheet of of paper. paper. 1 pt. 2 pts. 3 pts. 4 pts. D Neatness The kit is not The kit is The kit is done The kit and Effort organized. somewhat well with some is neatly exerted It looks like organized organization organized the student and it looks and labeling. and labeled threw it like the It appears the as necessary. together student ran student worked Much time and at the last out of time hard on it. effort were put minute or didn’t take into creating without much care of the this project. care. project. 33 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  V. Summative Assessment Directions: Answer the following questions; 1. Predict what geologic features could result out of this plate boundary (three possible answers). PY 2. In a hot spot, Volcano A is on top of the mantle plume, Volcano B is 10 km farther from A while Volcano C is the farthest. What can you infer about the ages of the volcanoes? O a. Volcano A is older than C c. Volcano B is the youngest b. Volcano B is the oldest C d. Volcano B is younger than C 3. Right in the middle of an island, you can find a rift valley. What type of plate boundary exists on that island? a. convergent b. divergent c. normal fault d. transform fault E D EP D 4. Plates A and B shows a divergent boundary. If plate C is adjacent to both plates and does not show any relative motion, what type of plate boundary is present between A and C? __________________ 5. What geologic event is most likely to happen at the given type of plate boundary in number 4? a. earthquake c. rift valley formation b. mountain formation d. volcanic eruption 34 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  6. You were asked to locate the epicenter of a recent earthquake. Which correct sequence of events should you follow? i. Determine the difference in the arrival time of S and P waves recorded from each of the seismological stations. ii. Use the triangulation method to locate the center. iii. Obtain data from three different seismological stations. iv. Determine the distance of the epicenter from the station. a. i, iii, ii, iv b. iii, i, iv, ii c. iii, iv, i, ii d. iv, ii, i, iii 7. What do you expect to find parallel to a trench? a. hot spot b. ocean ridge c. rift valley d. volcanic arc PY Matching type: Match column A with columns B and C A B C O Type of Plate Relative Motion of the Geologic Features/ Boundary Plates Events Present 8. Divergent a. Moving away from d. Earthquakes C each other 9. Convergent b. Moving towards each e. Mountains, other volcanoes, trenches, D and earthquakes 10. Transform fault c. Sliding past each other f. Rift valleys, oceanic E ridges, and earthquakes EP VI. Summary/Synthesis/Feedback According to the plate tectonics model, the entire lithosphere of the Earth is broken into numerous segments called plates. D Each plate is slowly but continuously moving. As a result of the motion of the plates, three types of plate boundaries were formed: Divergent, Convergent, and Transform fault boundaries. Divergent boundary is formed when plates move apart, creating a zone of tension. Convergent boundary is present when two plates collide. Transform fault is characterized by plates that are sliding past each other. Plate tectonics give rise to several geologic features and events. 35 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Glossary of Terms Continental volcanic arc mountains formed in part by igneous activity associated with subduction of oceanic lithosphere beneath a continent Convergent boundary a boundary in which two plates move toward each other, causing one of the slabs of the lithosphere to subduct beneath an overriding plate Crust the outer portion of the earth Continental Crust the thick part of the Earth’s crust, not located PY under the ocean Oceanic Crust the thin part of the Earth’s crust located under the oceans O Divergent boundary a region where the crustal plates are moving apart C Earthquake vibration of Earth due to the rapid release of energy Fault a break in a rock along which movement has D occurred Fracture any break in a rock in which no significant E movement has taken place Geology the science that studies Earth EP Hot spot a concentration of heat in the mantle capable of creating magma Magma a mass of molten rock formed at depth, including D dissolved gases and crystals. Mid-ocean ridge a continuous mass of land with long width and height on the ocean floor. Plates rigid sections of the lithosphere that move as a unit Plate tectonics a theory which suggests that Earth’s crust is made up of plates that interact in various ways, thus producing earthquakes, mountains, volcanoes, and other geologic features 36 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Primary (P) wave the first type of seismic wave to be recorded in a seismic station Rocks consolidated mixture of minerals Secondary (S) wave second type of earthquake wave to be recorded in a seismic station Seismogram a record made by a seismograph Seismograph a device used to record earthquake waves PY Subduction an event in which a slab of rock thrusts into the mantle Transform fault boundary a boundary produced when two plates slide past O each other Trench a depression in the seafloor produced by C subduction process Volcanic Island arc a chain of volcanoes that develop parallel to a D trench E References and Links EP Printed Materials: Department of Education, Bureau of Secondary Education. Project EASE Integrated Science 1, Module 12: Inside the Earth. D Department of Education, Bureau of Secondary Education (2013). Science - Grade 8 Learner’s Module. Vibal Publishing House, Inc. Punongbayan, R. et al. (1998). The Philippine Archipelago Volume 1. Tarbuck, E.J. et al. (2009). Earth Science 12th ed. Pearson Education South Asia Pte Ltd. Yumul, Jr., Graciano P., Carla B. Dimalanta, Victor B. Maglambayan and Edanjarlo J. Marquez, Tectonic Setting of a Composite Terrane: A Review of the Philippine Island Arc System, 12 Geosciences Journal 1, (March 2008), pp. 7−17. Robert Hall, Reconstructing Cenozoic SE Asia 37 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Electronic Sources: http://www.palawan.nfo.ph/geology/ accessed August 20, 2014 http://www.skoool.ie/ accessed March 3, 2014 http://earthds.info/ accessed March 3, 2014 http://eqseis.geosc.psu.edu/ accessed March 4, 2014 http://www.platetectonics.com/ accessed March 5, 2014 http://geology.com/ accessed March 5, 2014 http://www.nws.noaa.gov/ accessed March 6, 2014 http://csep10.phys.utk.edu/ accessed March 6, 2014 PY http://pubs.usgs.gov/ accessed March 6, 2014 http://www.moorlandschool.co.uk/earth/tectonic.htm accessed March 7, http://stream2.cma.gov.cn/pub/comet/Environment/TsunamiWarningSystems O accessed March 3 2014 https://www.bucknell.edu/majors-and-minors/geology/location/geologic- history-of-central-pennsylvania/plate-tectonics.html accessed July 1, C 2014 http://earthquake.usgs.gov D http://pubs.usgs.gov/gip/volc/fig34.html http://www.clipart.dk.co.uk/1068/az/Earth/Mountain_ranges E http://earthsci8.wikispaces.com www.maribio.net EP http://bwbearthenviro2011.wikispaces.com http://www.earthobservatory.sg/resources/images-graphics/subduction-zone- beneath-philippines D http://whybecausescience.com/category/vulcanism http://www.adelaidenow.com.au/ http://www.wildjunket.com/ http://www.jnb-birds.com/ http://www.radford.edu/jtso/GeologyofVirginia/Tectonics/ GeologyofVATectonics6-1c.html sanandreasfault.org http://www.geo.hunter.cuny.edu/ 38 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  Unit 1 MODULE 2 THE EARTH’S INTERIOR I. Introduction Scientists have studied heavenly bodies which are millions of miles PY away from Earth. Equipped with powerful telescopes and space probes, they were able to reach and examine the solar system and beyond. It seems ironic then, that we haven’t, and we couldn’t reach the center of our very own planet. O In Module 1, you have learned about the different processes and landforms along plate boundaries that slowly shaped the Earth’s surface. In Module 2, you will learn the connection between these processes with the C internal structure and mechanisms of our planet. This module will help you visualize and understand the composition and D structure of the Earth’s interior. It provides you scientific knowledge that will help you describe the different layers of the Earth as well as understand their characteristics. You will also learn concepts that explain the physical changes E that it underwent in the past. This module also consists of activities that will help you develop your critical thinking skills to have a deeper understanding EP about the planet where you live. At the end of this module, you will be able to answer the following key questions: D 1. How do the structure and composition of the Earth cause geologic activities and physical changes? 2. What are the possible causes of the lithospheric plate movements? 3. What proves the movement of the tectonic plates? 39 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  II. Learning Competencies/Objectives In this module, you should be able to: 1. Describe the internal structure of the Earth. 2. Discuss the possible causes of plate movement. 3. Enumerate the lines of evidence that support plate movement. III. Pre-Assessment Directions: A. Choose the letter of the correct answer. PY For questions 1 and 2, refer to the figure below that shows the cross section of the Earth as seismic waves travel through it. O C E D EP Seismic waves as they travel through the Earth D 1. An S-wave shadow zone is formed as seismic waves travel through the Earth’s body. Which of the following statements does this S-wave shadow zone indicate? a. The inner core is liquid. b. The inner core is solid. c. The mantle is solid. d. The outer core is liquid. 40 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  2. Why are there no P-waves or S-waves received in the P-wave shadow zone? a. P-waves are absorbed and S-waves are refracted by Earth’s outer core. b. P-waves are refracted and S-waves are absorbed by Earth’s outer core. c. Both the P-waves and S-waves are refracted by Earth’s outer core. d. Both the P-waves and S-waves are absorbed by Earth’s outer core. 3. What makes up the lithosphere? a. Continental crust b. Crust and the upper mantle PY c. Oceanic crust and continental crust d. Upper mantle 4. Miners dig into the Earth in search for precious rocks and minerals. In which layer is the deepest explorations made by miners? O a. Crust c. Mantle b. Inner core d. Outer core C 5. How do you compare the densities of the Earth’s crust, mantle, and core? a. The mantle is less dense than the core but denser than the crust. D b. The mantle is less dense than both the core and the crust. c. The mantle is denser than the core but less dense than the crust. d. The mantle is denser than both the core and the crust. E 6. The movement of the lithospheric plates is facilitated by a soft, weak EP and plastic-like layer. Which of the following layers is described in the statement? a. Asthenosphere c. Lithosphere b. Atmosphere d. Mantle D 7. Alfred Wegener is a German scientist who hypothesized that the Earth was once made up of a single large landmass called Pangaea. Which of the following theories did Wegener propose? a. Continental Drift Theory b. Continental Shift Theory c. Plate Tectonics d. Seafloor Spreading Theory 41 All rights reserved. No part of this material may be reproduced or transmitted in any form or by any means - electronic or mechanical including photocopying – without written permission from the DepEd Central Office. First Edition, 2015.  8. If you are a cartographer, what will give you an idea that the continents were once joined? a. Ocean depth b. Position of the south pole c. Shape of the continents d. Size of the Atlantic Ocean 9. Which observation was NOT instrumental in formulating the hypothesis of seafloor spreading? a. Depth of the ocean b. Identifying the location of glacial deposits c. Magnetization of the oceanic crust PY d. Thickness of seafloor sediments 10. As a new seafloor is formed at the mid-ocean ridge, the old seafloor farthest from the ridge is destroyed. Which of the stated processes describes how the oceanic crust plunges into the Earth and destroyed O at the mantle? a. Convection b. Construction c. Diversion C d. Subduction D B. Answer briefly the following questions. 1. What are the different layers of the Earth? E 2. Why is there a need to study the Earth’s layers? 3. What proves the existence of the boundary between the crust and the EP mantle? 4. What are the characteristics of the asthenosphere? 5. What do the shapes of the continents now tell us about their past? D 42 All rights reserved. No part of this material may be repro