Earth's Internal Heat PDF

Unit 11 Geologic Processes Inside Earth Table of Contents Table of Contents 1 Essential Questions 4 Review 4 Lesson 11.1: Earth’s Internal Heat...

Unit 11 Geologic Processes Inside Earth Table of Contents Table of Contents 1 Essential Questions 4 Review 4 Lesson 11.1: Earth’s Internal Heat 5 Objective 5 Warm-Up 5 Learn about It 6 Key Points 9 Web Links 10 Check Your Understanding 10 Challenge Yourself 12 Lesson 11.2: Magmatism: How Magma is Formed 13 Objectives 13 Warm-Up 13 Learn about It 14 Key Points 18 Web Links 19 Check Your Understanding 19 Challenge Yourself 21 Lesson 11.3: Volcanoes and Volcanism 22 Objectives 22 Warm-Up 22 Learn about It 23 Key Points 26 Web Links 26 Check Your Understanding 27 Challenge Yourself 28 Lesson 11.4: Plutonism 29 Objectives 29  Warm-Up 29 Learn about It 30 Key Points 32 Web Links 32 Check Your Understanding 33 Challenge Yourself 34 Laboratory Activity 35 Performance Task 36 Self Check 37 Key Words 38 Wrap Up 39 Photo Credits 39 References 40 2 EARTH SCIENCE | GRADE 11/12 Unit 11 Geologic Processes Inside Earth Is the mentos-coke volcano experiment familiar to you? It is probably one of the most famous science experiments that are considered a part of every person's childhood. When you were a kid, you were so amaze on how the diet coke immediately explodes as soon as the mentos is dropped in it. This experiment might be a cool simulation on how a volcano erupts. However, you might feel the opposite if a real volcano erupted in your locality. If you have experienced the devastating effects of volcanic eruption, you might realize that the mentos-coke experiment is so far from the real thing. Being in a country that is located in the Pacific Ring of Fire, volcanic eruptions and earthquakes are inevitable. 3  Essential Questions At the end of this unit, you should be able to answer the following questions. Where does the heat from the interior of Earth come from? What is the difference between magma and lava? How magma are being formed? Why do volcanic eruptions occur? Why do rocks formed within Earth different from the rocks formed on Earth’s surface? Review The crust is the uppermost and thinnest layer of Earth. It can be classified into continental and oceanic crust. The mantle is the layer below the crust. Its uppermost part, together with the crust, makes up the lithosphere. The lower mantle is called the mesosphere. Mantle convection is necessary to transfer heat and drive processes on the surface of the planet. It is a result of different temperature and pressure conditions in the plastic mantle, which can flow, and leads to hotspot activity at the surface. The innermost layer is the core, both composed of iron with subordinate nickel. It can be divided into the liquid outer core and the solid inner core. It is the hottest layer where temperatures could reach up to 700 o C. Rocks are classified into three – igneous, sedimentary, and metamorphic rocks– categorized based on minerals present, texture, and formational process. 4  Lesson 11.1: Earth’s Internal Heat Objective In this lesson, you should be able to: describe where Earth’s internal heat comes from. When you are sunbathing, you are aware that the heat is coming from the sun above you. How about the heat down below? Are you aware of it? You should know about the heat in the interior of Earth since this builds mountains, moves continents, and causes earthquakes. Where does all of this internal heat come from? Warm-Up Moving Molecules Materials: three beakers hot, room temperature and cold water. food coloring timer Procedure: 1. Pour water into three beakers. Beaker 1 = hot water; Beaker 2 = room temp water; Beaker 3 = cold water. 2. Put a drop of food coloring in each beaker. Start the timer as soon as the food coloring is dropped. Make sure not to disturb the water. 3. Stop the timer when the clear water turns into a tinge of color. Refer to the illustration to know what is the exact thing that you are looking for. Record. 5 Guide Questions: 1. What happened to the molecules in each beaker? Take note that the food coloring serves as “molecular movement detector”. 2. Which beaker changed color first? What can you infer with the kinetic energy of molecules in that beaker? 3. Accretion of dusts in space creates high kinetic energy which will then yield to high heat energy. How is this related to the beaker that changed color first? Learn about It The internal heat of Earth fuels the planet’s dynamic processes including plate movements, earthquakes, and volcanism. This heat is produced by residual heat (extraterrestrial impacts and gravitational contraction) and radiogenic heat. Residual Heat Extraterrestrial Impacts As proposed in the Nebular theory, Earth was formed through accretion of particles from a rotating cloud. Earth grew larger as more and more materials are bombarded and integrated to the protoplanet. These objects, which include metal-rich and rocky fragments, travel at very high velocity about 30,000-50,000 km/hr. The great amount of kinetic energy is produced by the moving objects which were then converted to heat energy. Fig. 1. The accretion of fragments that results from formation of a planet. 6 Gravitational Contraction Have you ever tried to watch a skating competition? One of the tricks of the contestant that amazes people is when they spin so fast without falling. If you are a keen observer, they can only do the trick if they bring in their arms. Extending their arms while attempting to spin fast will result in a failure of the act. This is possible because rotational velocity is inversely proportional to radius. The skater is similar to a collapsed cloud of dust as it forms into planets. Collapsed clouds occur because accretion of more materials led to an increase in the gravitational attraction causing the contraction of Earth into a smaller volume which will then enable them to spin faster. The compaction resulted in the conversion of gravitational energy into heat energy. Fig. 2. A collapsed cloud due to the influence of gravity. Radiogenic Heat Unstable elements undergo radioactive decay to attain a more stable form. The process of radioactive decay produces heat as a byproduct. The young Earth had more of these unstable elements producing greater amount of energy compared to today’s radioactive decay. At present, this process mostly occurs at the mantle, which is enriched in radioactive isotopes. 7 Heat from the core is transferred from the interior to the surface mainly through convection. According to studies, Earth is releasing heat from the surface at a rate of about 46 Terawatts. The value coming from the two main sources, primordial heat and radioactive decay, is still in debate. Fig. 3. Radiogenic heat is a by-product of radioactive isotope decays. Earth’s Thermal Budget Planning budget is important especially if you are the breadwinner of the family. You need to ensure that your income will tally to the expenses spent and savings kept. This also holds true for Earth's thermal budget. It needs to ensure that absorbed solar radiation is balanced to the radiated ones. Keeping Earth’s energy budget ensures that the average temperature on Earth remains stable and that life continues to exist. Earth’s thermal budget is the measure of the amount of heat that is released at the surface and produced in the interior. Some believe that Earth’s internal budget is completely balanced and that same amount of heat is released and produced in the planet. This idea is based on the notion that if more heat is generated than released, the mantle would heat up and discharge large amounts of heat in order to reach thermal equilibrium. More recent theories, however, suggest otherwise. They believe that Earth is cooling down. Figure 4 shows that Earth's albedo is 0.3 which means 30% of the solar energy that reaches the surface of Earth is reflected back to space by the clouds, atmosphere and light-colored areas (deserts and areas covered with ice and snow). The remaining 70% of the solar energy is absorbed by the atmosphere, land, and oceans. The absorbed energy drives wind and ocean currents. These currents 8 distribute the heat throughout the planet since more sunlight shines on equatorial region than polar regions. All this solar energy absorbed by the atmosphere, air, land, and oceans must be radiated back to space. Therefore, energy in should always equal to energy out. Fig. 4. Most of the energy produced by Sun is absorbed and scattered by Earth on the ground and on its atmosphere. Key Points The internal heat of Earth fuels the planet’s dynamic processes including plate movements, earthquakes, and volcanism. Earth’s internal heat is produced by residual heat (extraterrestrial impacts and gravitational contraction) and radiogenic heat. ○ Extraterrestrial impacts- Great amount of kinetic energy is produced by the accreting objects which were then converted to heat energy. ○ Gravitational contraction - The collapsed cloud of dust resulted in the conversion of gravitational energy into heat energy. ○ Radiogenic heat - The process of radioactive decay produces heat as a byproduct. Earth’s thermal budget is the measure of the amount of heat that is released at the surface and produced in the interior. 9  Web Links For further information, you can check the following web links: Explore this interactive animation to go deep down the center of Earth and identify the events that could happen in a specific portion of Earth down below. BBC. n.d. ‘Journey to the Centre of the Earth.’ http://www.bbc.com/future/bespoke/story/20150306-journey-to-the-centre-of-earth/ Sing a song about the layers of earth in the tune of love yourself. User:Parr. 2016. ‘Crust, Mantle, Core Song.’ https://www.youtube.com/watch?v=plNigVkMyL8 Watch this short video clip to know why it is hot underground. User:MinuteEarth. 2014. ‘Why is it Hot Underground?’ https://www.youtube.com/watch?v=mOSpRzW2i_4 Check Your Understanding A. Read and analyze the following statements given. Write true if the statement is correct and false if it is incorrect. 1. The internal heat of Earth fuels the planet’s dynamic processes including plate movements, earthquakes, and volcanism. 2. Great amount of kinetic energy is produced by the accreting objects which were then converted to heat energy. 3. Rotational velocity is directly proportional to radius. 4. Collapsed clouds occur because accretion of more materials led to an increase in the gravity causing the contraction of Earth. 5. The collapsed cloud resulted in the conversion of gravitational energy into heat energy. 6. Unstable elements undergo radioactive decay. 10  7. The process of radioactive decay produces heat as a byproduct. 8. Earth’s thermal budget is the measure of the amount of heat that is released at the surface and produced in the interior. 9. The 30% of the solar energy that reaches the surface of Earth is absorbed by the clouds, atmosphere and light-colored areas. 10. The reflected energy drives wind and ocean currents. These currents distribute the heat throughout the planet since more sunlight shines on equatorial region than polar regions. B. Answer the following question. Use the illustration below as a guide. 1. What is the total percentage of solar energy reflected? 2. What type of surfaces reflect incoming solar energy? 3. What is the total percentage of solar energy absorbed? 4. Are all the energy absorbed radiated back to space? 5. How much energy is reflected by the atmosphere? absorbed? 11  Challenge Yourself Answer the following questions. 1. Where does the heat from Earth’s interior come from? 2. Is the primitive Earth hotter than today? Defend your answer. 3. How do extraterrestrial impacts contribute to Earth’s internal heat? 4. Why do isotopes decay? How does it contribute to the heat in Earth’s interior? 5. Is heat energy balanced in Earth? 12  Lesson 11.2: Magmatism: How Magma is Formed Objectives In this lesson, you should be able to: describe how magma are being formed (magmatism). Have you tried to make s'mores on fire? While the mallows are melting, the rocks surrounding a campfire do not usually melt. Rocks usually need a very high temperature for it to melt. Therefore, molten rock also known as magma have undergone high temperature. Where on Earth is it hot enough to melt rocks? Warm-Up Rising Magma Materials: small jar large jar water food coloring cellophane rubber band Procedure: 1. Fill the small jar with colored hot water. 2. Cover the small jar with a cellophane. Use rubber bands to secure the cellophane on the small jar. 3. Poke random holes on the cellophane. 4. Pour cold water into the bigger jar. 5. Put the small jar inside the larger jar. 6. Observe what will happen to the colored water inside the small jar. 13 Guide Questions: 1. What does the colored water represent? 2. Why does the colored water rise? 3. Relate this activity to how magma reaches the surface of Earth. Learn about It Magma is defined as molten rock material produced by partial melting of the mantle and crust. It contains liquids, gases, crystals and rock fragments. The amounts of these components depend on the temperature and pressure conditions during the formation. Formation of Magma Magma can be produced by increase in temperature, decrease in pressure and addition of volatiles. Temperature Temperature increases with depth, which is called geothermal gradient. This increase will obviously induce melting. Figure 5 shows the rate of increase in temperature with depth also known as geothermal gradient. Fig. 5. Temperature increases with depth in Earth’s internal structure. 14 Pressure Decrease in pressure causes adiabatic decompression. As pressure is decreased, melting temperatures of materials decrease. As shown in Figure 6, the rock starts to melt because there is a huge pressure decrease from point A to point B even if the temperature only changed a little. Therefore, magma forms when there are decreased in pressure and constant temperature. This kind of melting is termed as decompression melting. It usually occurs in an area where hot mantle rock rises to shallower depths on Earth such as mantle plumes, beneath rifts and beneath mid ocean ridges as shown in Figure 6. Fig. 6. Rocks starts to melt even with low temperature due to difference in pressures. Volatiles Volatiles are substances that evaporate easily and can exist in gaseous form in the surface of Earth. Examples of this kind of substances are water and carbon dioxide. When volatiles mix with hot mantle rock, magma forms. As a result, rock's melting temperature decreases when more volatiles are introduced. 15 Primary magmas from the mantle are basaltic in composition. As it ascends on or near the surface, the composition changes. Along the way, some of the components may solidify decreasing some components. Country rock may also be assimilated to the melt. Magmas may reach the surface or stay inside magma chambers. These chambers have sizes ranging from one kilometer up to several tens of kilometers. Once magma extrudes onto the surface, it is known as lava. Fig. 7. Rocks melt as a result of the addition of volatiles. Magmatism Magmatism occurs along plate boundaries or margins and sometimes within the plate. Cracks on Earth's crust are the result of these plate boundaries. In effect, hot mantle rock penetrates the crust and becomes magma. Plate boundaries can be classified as convergent, divergent, and transform. Convergent plate boundaries are settings where two plates move towards each other. The plates converging can be oceanic crust to oceanic crust, oceanic crust to continental crust, or continental crust to continental crust. As these plates collide, magma formation, earthquakes or mountain building were formed. In regions where plates move away from each other, divergent boundaries are formed. As the plates move apart, thin, fractured rocks formed. These provide a means for the hot mantle to reach the surface. As a result, volcanic activity occurs. 16 Transform boundaries are those where plates slide past one another connecting the other two boundaries. As a result, earthquakes occur. Fig. 8. The movement of plates produces convergent, divergent and transform boundaries. Classification of Magma Magmas are classified according to the ratio between the alkalis and silica content. The compositions are dependent on the degree of partial melting and the source rock. Tholeiitic magmas or tholeiites, are produced by large degree of melting. In settings where plates diverge, tholeiites form as mid-ocean ridge basalts (MORB). These magmas make up the bulk of ocean floor, about 70% of Earth’s crust. Tholeiites may also be emplaced from ascent of mantle plumes as continental flood basalts or large igneous provinces. Examples of this intraplate process are the Deccan trapps in India and the Karoo basalts in southern Africa. Lastly, subduction zones can also produce tholeiites. All these are distinctly different from one another. Calc-alkaline basalts form along convergent plate boundaries above subduction zones. They are silica saturated and are of higher potassium content compared to tholeiitic magmas. 17 Alkaline basalts form from smaller degree of partial melting, which results in alkali-rich and silica depleted magma of diverse compositions. They can be found in intraplate settings such as aHawaHawaii. It is believed that the hotspot underneath the region produces tholeiitic basalts which then change into alkaline basalt in its waning stages. Carbonatites are the only magmas that are not produced by silicate source rock. They are enriched in carbonate minerals like dolomite and calcite. The origin of this carbonate-enriched melt is still a mystery to scientists. Key Points Magma is defined as molten rock material produced by partial melting of the mantle and crust. It contains liquids, gases, crystals and rock fragments. Temperature increases with depth, which is called geothermal gradient. Decrease in pressure causes adiabatic decompression. As pressure is decreased, melting temperatures of materials decrease. Volatiles are substances that evaporate easily and can exist in gaseous form in the surface of Earth. Magmatism occurs along plate boundaries or margins and sometimes within the plate. Magmas are classified according to the ratio between the alkalis and silica content. ○ Tholeiitic magmas or tholeiites, are produced by large degree of melting. In settings where plates diverge, tholeiites form as mid-ocean ridge basalts (MORB). ○ Calc-alkaline basalts form along convergent plate boundaries above subduction zones. ○ Alkaline basalts form from smaller degree of partial melting, which results in alkali-rich and silica depleted magma of diverse compositions. ○ Carbonatites are the only magmas that are not produced by silicate source rock. 18  Web Links For further information, you can check the following web links: Click this link to explore more about magmas. American Museum of Natural History. n.d. ‘Interactive: Different Magmas, Different Volcanoes.’ https://www.amnh.org/explore/science-bulletins/earth/documentaries/yellowstone- monitoring-the-fire-below/interactive-different-magmas-different-volcanoes/ Sing a song entitled “Magma Rising Up!” to deepen knowledge on magma formation. User: Parr. 2013. ‘Magma Rising Up Song.’ https://www.youtube.com/watch?v=tGm2ymM0Gaw Watch this short video clip to know more about the types of magmas. User: Roman, Raul. 2014. ‘Different Types of Magma.’ https://www.youtube.com/watch?v=L2fo-d25_Xw Check Your Understanding A. Label each of the following boundaries as convergent, divergent or transform. Relate each identified boundary type on how it affect magma formation. ____________________________________ ____________________________________ 19  ____________________________________ ____________________________________ ____________________________________ ____________________________________ B. Read and analyze the following statements given. Write true if the statement is correct and false if incorrect. 1. The increase in temperature with depth is known as geothermal gradient. 2. As pressure is decreased, melting temperatures of materials increase. 3. Volatiles are substances that cannot evaporate easily and can exist in gaseous form in the surface of Earth. 4. When volatiles mix with hot mantle rock, magma forms. 5. Rock's melting temperature increases when volatiles are introduced. 6. Once magma extrudes onto the surface, it is known as lava. 7. Magmatism occurs along plate boundaries or margins and sometimes within the plate. 8. Alkaline basalts are the only magmas that are not produced by silicate source rock. 9. Tholeiitic magmas or tholeiites, are produced by large degree of melting. 10. Magmas are classified according to the ratio between the alkalis and silica content. 20  Challenge Yourself Answer the following questions. 1. What would be the temperature of Earth as one goes down deep within Earth? 2. What is the relationship between the amount of volatiles and melting temperature? 3. How are plate boundaries related to magmatism? 4. Why is adiabatic compression important? 5. What is the difference between the four classifications of magma? 21  Lesson 11.3: Volcanoes and Volcanism Objectives In this lesson, you should be able to: describe what happens after magma is formed (volcanism). You are probably familiar with news about volcanic eruptions, or you might be on site when a volcano erupts. Volcanic eruptions are so dramatic that it became plots of some movies. The scenes provide a vivid image of red-hot lava spewing out of a volcano. However, movies failed to provide the entire history of volcanoes. How do volcanoes form and why do eruptions occur? Warm-Up Volcano in a Beaker Materials: Candle Matchsticks Beaker Stove or any heat source Sand Procedure: 1. Light the candle for about 20 seconds. Tilt the candle to pour drops of wax in the beaker (roughly 2-3 teaspoons). Allow the melted wax to harden. 2. Cover the wax with sand. (about 1 inch) 3. Carefully pour water on the beaker. Wait for the water to be clear to make sure all the sand has settled. 4. Use alcohol lamp, burner or stove to heat the contents of the beaker. Wait for the hot wax to erupt. 22 Guide Questions: 1. What do the wax, sand, and water represent? 2. What happened when the wax erupted and reaches the water surface? 3. What is the difference between the wax beneath the sand and the wax that reaches the water surface? What do you think it represents? Learn about It Volcanism Volcanism is the process where magma rises to the surface of Earth as lava. From human perspective, it can be viewed as a destructive event as it could damage infrastructures, cause injuries and short-term climate change. From another perspective, volcanism is a constructive process as seen in Earth’s early history. The atmosphere was formed through release of volcanic gases and new oceanic crust is continuously produced along mid-oceanic ridges. Many islands are also formed through volcanic processes. Formation of Volcano A volcano is a hill or mountain where lava, pyroclastic materials, and gases erupt. It can form along plate boundaries or within the plate. In divergent plate boundaries, volcanism manifests as ridges or fissures where products of decompression melting erupt. Examples are the mid-ocean ridges and the Great African Rift. Convergent plate boundaries host large number of volcanoes. Lava flows and pyroclastic materials make up these volcanoes. Here, subduction melting forms elongated chains of volcanoes following the shape of the trench, called volcanic or island arcs. Mount Pinatubo and Mount Mayon are situated near this type of plate boundary. The best example for intraplate volcanism is Mauna Loa and Kilauea in Hawaii. These volcanoes are situated within the plate far from a divergent or convergent boundary. It is believed that a hot mantle plume is the source of magma. 23 Fig. 10. Most of the geological hotspots in the world are either near or on the plate boundaries. Lava Flows Lava flows move slowly and follow low areas. Upper surfaces which are exposed to air cool faster than the remaining part of the melt to form lava tube. If a part of the tube collapses, the actively flowing lava is exposed forming a skylight. Lava flows may be classified as pahoehoe (pronounced as “pah-hoy-hoy”) and aa (pronounced as ah-ah). Pahoehoe has a smooth and ropy surface while aa has jagged and angular corners. Columnar joints may also be formed from lava flows. They have distinctive pattern of columns bounded by fractures. As the lava cools, contraction takes place producing forces that result in the formation of joints. 24  Fig. 11. Lava flows can be classified as pahoehoe (left) or aa (right) lava flow Lava that solidifies forms volcanic rocks. Examples of these are basalt, andesite, and rhyolite. Minerals comprising these rocks are fine-grained compared to plutonic rocks which are coarser. Obsidian (a rock composed mainly of volcanic glass), pumice and scoria may also be spewed out during eruptions. Fig. 12. The common rocks formed out of solidified lava. From left to right: rhyolite, andesite, basalt Volcanism also takes place in the nearby terrestrial planets. In our planet, volcanism occurs in hotspots, rifting and subduction zones. Mars and Venus have volcanism related to hotspots which produced extensive basaltic plains. 25  Key Points Volcanism is the process where magma rises to the surface of Earth as lava. A volcano is a hill or mountain where lava, pyroclastic materials, and gases erupt. It can form along plate boundaries or within the plate. ○ In divergent plate boundaries, volcanism manifests as ridges or fissures where products of decompression melting erupt. ○ Convergent plate boundaries host a large number of volcanoes. Lava flows and pyroclastic materials make up these volcanoes. Lava flows may be classified as pahoehoe (pronounced as “pah-hoy-hoy”) and aa (pronounced as ah-ah). ○ Pahoehoe has a smooth and ropy surface. ○ aa has jagged and angular corners. Web Links For further information, you can check the following web links: Click this link to view an interactive map of active volcanoes and recent earthquakes worldwide. Volcano Discovery. 2018. ‘Interactive Map of Active Volcanoes and Recent Earthquakes World-wide.’ https://earthquakes.volcanodiscovery.com/ Sing this song in the tune of Gentleman by Psy to be more familiar on volcanism. User: Parr. 2013. ‘Volcanic Eruptions Song.’ https://www.youtube.com/watch?v=R9PgmUcaCDM Play this interactive game entitled volcano island. You were tasked to become a mayor of an island to protect the people in your locality. Harvard. N.d. ‘Volcano Island.’ https://www.cfa.harvard.edu/earthscope/volcano_island/ 26  Check Your Understanding A. Answer the crossword puzzle below. Use the clues below as a guide. Across 6. A process where magma rises to the surface of Earth as lava. 8. It is a hill or mountain where lava, pyroclastic materials, and gases erupt. 9. They have distinctive pattern of columns bounded by fractures. 10. A type of rock that forms when lava solidifies. Down 1. A type of volcanism wherein volcanoes are situated within the plate far from a divergent or convergent boundary. 2. Lava flows having a smooth and ropy surface 3. Plate boundaries that host large number of volcanoes. 4. A type of plate boundaries wherein volcanism manifests as ridges or fissures where products of decompression melting erupt. 5. A type of plate boundaries where earthquakes occur. 7. Lava flows having jagged and angular corners. 27  Challenge Yourself Answer the following questions. 1. Why is volcanism considered a constructive and destructive process? 2. What is the difference of pahoehoe and a lava flow? 3. Why does the texture of volcanic rocks fine-grained? 4. What is the difference of volcanoes formed from divergent plate boundary to volcanoes formed from convergent plate boundary? 5. Could volcanism only take place on our planet? Why or why not? 28  Lesson 11.4: Plutonism Objectives In this lesson, you should be able to: describe what happens after magma is formed (plutonism). You often associate magma with volcanoes but have you seen magma personally? By definition, magma is formed deep within Earth. Therefore, you will be burnt if you attempted to reach the surface of Earth where magma is formed. You only see the hot molten rock in the form of lava. The difference between magma and lava is important especially if distinguishing the classifications of rocks which are volcanic and plutonic rocks. What is the difference between plutonic and volcanic rocks? Warm-Up Marshmallow Crystals Materials: marshmallows toothpicks 3 plates Procedure: 1. On the first plate, put marshmallows and toothpicks in random order. This represents glassy igneous rocks such as pumice and obsidian. 2. On the second plate, three marshmallows and three toothpicks are connected to form a triangle. Repeat the steps until you have 20 triangles. The triangles represent microscopic crystals that have formed in the magma. The rest of the marshmallows and toothpicks represent magma that has not crystallized. This represents basalt and andesite in lava flows which have microscopic crystals. 29  3. On the third plate, connect all the triangles previously made to form one large crystal. This represents crystals that have cooled deep underground in plutons. Guide Questions: 1. What is the difference between the crystals in the three plates? 2. Why do plutons have larger crystals? Hint: Consider where they originate and the time it takes for them to reach the surface. 3. Why do some rocks do not form large crystals? Learn about It Plutonism In the 18th century, James Hutton’s theory of plutonism was recognized. His theory states that rocks were formed from heat-driven processes. This heat comes from the interior of Earth. Another fundamental aspect of plutonism is that the processes are constant and slow. This theory was not widely accepted during Hutton’s lifetime but became the foundation of modern geology. Plutonism opposed Neptunism’s idea of the origin of granites. Neptunist theory of the origin of granites states that these rocks are the oldest precipitates from a primordial sea. Hutton, on the other hand, proposed that granites are intrusive igneous rocks. He observed that granites cut across sediment layers, thus, granite must have been injected into country rock making it younger than the sediments. Fig. 13. The common plutonic rocks found in nature. From left to right: gabbro, diorite, granite, and peridotite. 30 The term plutonic can be used to classify rocks which formed in the interior of Earth. This is the opposite of volcanic rocks which form on the crust. Some examples of plutonic rocks are gabbro, diorite, and granite. They have grains that are much coarser compared to volcanic equivalents. Classification of Plutons As magma rises to the crust, it can displace the host or country rock to form structures called plutons. Uplift and erosion expose these structures. They vary in sizes and shape and may be classified as discordant or concordant structures. Discordant structures are those that cut across existing structures. An example of the discordant structure is a dike. A dike is an igneous body that cuts across bedding surfaces or other structures of the country rock. Fig. 14. A dike and sill complex which are considered as sedimentary beds. Concordant bodies are those that are injected parallel to features in the country rock such as sedimentary beds. An example is a sill. Sills are nearly horizontal igneous bodies that form when magma exploits weak spots between the sedimentary beds or other structures. Plutons may occur as massive intrusive bodies like batholiths. Batholiths are by far the largest intrusive igneous bodies with lengths of up to several hundreds of kilometers and width of up to 100 kilometers. They have surface exposures greater than 100 square kilometers. Smaller plutons are termed stocks. 31  Key Points Plutonism theory states that rocks were formed from heat-driven processes. Neptunist theory of the origin of granites states that these rocks are the oldest precipitates from a primordial sea. The term plutonic can be used to classify rocks which formed in the interior of Earth. This is the opposite of volcanic rocks which form on the crust. They vary in sizes and shape and may be classified as discordant or concordant structures. ○ Discordant structures are those that cut across existing structures. ○ Concordant bodies are those that are injected parallel to features in the country rock such as sedimentary beds. Batholiths are by far the largest intrusive igneous bodies with lengths of up to several hundreds of kilometers and width of up to 100 kilometers. Web Links For further information, you can check the following web links: Watch this short video clip to know more about the difference of volcanic and plutonic rocks. User: Jenks, London. 2015. ‘Igneous Rocks Introduction.’ https://www.youtube.com/watch?v=Uvft8XI4nao Listen to this story entitled once a pluton to know more about the formation of plutonic rocks. User: BANZ1111. 2008. ‘Once A Pluton.’ https://www.youtube.com/watch?v=W2xnZ-2HNW4 32  Check Your Understanding A. Look for words that are related to the topic discussed in this lesson. Then, give a short definition or description to the words that you found. Word Definition or Description B_______H D__E G_____E L__A 33  M___A N_______M P______C R__K P_______M S__L V______C R__K Challenge Yourself Answer the following questions. 1. What is the difference between the plutonist and neptunist theory? 2. How would you compare plutonic and volcanic rocks? 3. Based on the texture of plutonic rocks, what can you infer about its origin? 4. Why do plutonic rocks have large crystals? 5. What is the classification of plutonic rocks? Describe each. 34  Laboratory Activity Activity 8.1 Lava Viscosity Objective At the end of this laboratory activity, the students should be able to: demonstrate volcanic landforms formation, primarily intrusive. Materials and Equipment chocolate sauce gelatin large bowl syringe (10-20 cc) aluminum pie plate vertical supports of pie tin (wood, tubes, paper towel tubes) Procedure 1. Follow the directions on the package of gelatin. Place the gelatin on a large bowl. 2. Poke several holes on the aluminum pie tin. Make sure it’s big enough to fit the tip of the syringe. 3. Prepare a hot water bath for the gelatin mold. Dip the gelatin mold for few seconds to loosen the edges. 4. Transfer the gelatin mold to the aluminum pie tin. 5. Put the vertical supports on top of the table. Make sure that the height is taller than the length of the syringe. 6. Suck the chocolate sauce using the syringe. 7. Insert the tip of the syringe into one of the holes in the aluminum pie tin. Watch as the chocolate sauce goes up into the gelatin mold. 35  8. Repeat step 7 in all the holes or until the gelatin mold breaks up. Guide Questions 1. How can you describe the movement of magma (represented by chocolate sauce) through the model? 2. Refer to your answer to question no. 1, why do you think the magma moved that way? 3. Is there a difference in the direction of magma flow (chocolate sauce) when the syringe is inserted into different parts of the volcano (gelatin mold)? 4. How can you compare the movement of chocolate sauce in the gelatin mold to that of magma flow in real volcanoes? Performance Task Geologic Hazards Goal Your task is to conduct a survey on the possible geologic hazards that your community might experience after a volcanic eruption. Role You are tasked to become a researcher/surveyor. Audience The target audience is a senior high school class. Situation You need to survey your classmates or the people in the community about the hazards that you might experience after a volcanic eruption. Product, Performance and Purpose You need to create a survey to be informed on what to do before, during, and after an eruption. 36 Standards and Criteria Your survey should satisfy the following rubrics. Needs Successful Exemplary Below Expectations, Criteria 0% to 49% Improvement Performance Performance 50% to 74% 75% to 99% 100% Purpose Purpose is not Purpose is Purpose is stated Purpose is stated stated. unclearly stated. clearly. However, it clearly. It is not relevant to conforms to a the assessment certain goal. assessment goal. Clarity of Questions are Questions are Questions are Questions are very confusing. somewhat clear. clear but some clear. No Questions and Numerous clarifications are clarifications Response clarifications are needed. needed. Options evident. Implementation Planned timeline The timeline is not Sets forth a The survey sets does not consider realistic, sampling suitable timeline forth a suitable Plan and priorities, pilot is being utilized and pilot test but timeline, and, as Timeline testing is not but a pilot was not has not relevant, uses a planned, and considered. considered pilot test and sampling is not sampling sampling considered. techniques. Self Check This unit aims to provide comprehensive understand of the theories behind volcanic activity and magma formation. Put a check on the space provide if you agree on each statement. Check I can… describe where the internal heat in the interior of Earth comes from. explain magma formation. identify the events that will occur after magma formation. 37  Key Words Aa lava flow Lava flow that has jagged and angular corners. Batholith The largest intrusive igneous bodies with lengths of up to several hundreds of kilometers and width of up to 100 kilometers. Dike An igneous body that cuts across bedding surfaces or other structures of the country rock. Earth’s thermal The measure of the amount of heat that is released at the budget surface and produced in the interior. Geothermal gradient It states that the temperature increases with depth. Magma Molten rock material produced by partial melting of the mantle and crust. It contains liquids, gases, crystals and rock fragments. Magmatism It occurs along plate boundaries or margins and sometimes within the plate. Pahoehoe Lava flow that has a smooth and ropy surface. Plutonism It states that rocks were formed from heat driven processes. Sill These are nearly horizontal igneous bodies that form when magma exploits weak spots between the sedimentary beds or other structures. Volcanism A process where magma rises to the surface of Earth as lava. Volcano A hill or mountain where lava, pyroclastic materials, and gases erupt. It can form along plate boundaries or within the plate. 38  Wrap Up Geologic Processes Inside Earth Photo Credits Continental-continental boundary, Oceanic-oceanic boundary, Oceanic-continental, Continental-continental destructve, Continental-continental conservative, Continental-continental constructive by domdomegg is licensed under CC BY-SA 4.0 via Wikimedia Commons Fig. 11. Pahoehoe lava by Rufiyaa is licensed under CC BY-SA 4.0 via Wikimedia Commons. Fig. 12. Rhyolite, andesite by Michael Rygel is licensed under CC BY-SA 3.0 via Wikimedia Commons. 39 Fig. 13. Diorite by Amycrus is licensed under CC BY-SA 4.0 via Wikimedia Commons; Granite by Zimbres is licensed under CC BY-SA 2.0 via Wikimedia Commons.; Peridotite by Jean-Michel Harouy is licensed under CC BY-SA 4.0 via Wikimedia Commons References Department of Geological Sciences, San Diego State University. “How Volcanoes Work The Earth’s Internal Heat Energy and Interior Structure.” Accessed February 14, 2017. http://www.geology.sdsu.edu/how_volcanoes_work/Heat.html Hefferan, Kevin and O’Brien, John. 2010. Earth Materials. John Wiley & Sons, Ltd., Publication. Korenaga, Jun. 2011. Earth’s Heat Budget Clairvoyant Geoneutrinos. Macmillan Publishers. Accessed February 15, 2017. http://people.earth.yale.edu/sites/default/files/korenaga11nv.pdf Patrick, Randy Roy and Howe, Robert Crombie. 1994. Volcanism on the Terrestrial Planets. Journal of Geological Education. Tarbuck, Edward J. and Lutgens, Frederick K. 2015. Earth Science. 14th edition. Pearson Education Inc. Taylor, Alexander H. 2014. The Foundation of Modern Geology. University of Illinois Board of Trustees. Accessed February 15, 2017. https://publish.illinois.edu/ foundationofmoderngeology/ Taylor, Alexander H. 2014. Plutonism | The Foundation of Modern Geology. University of Illinois Board of Trustees. Accessed February 15, 2017. https://publish.illinois.edu/foundationofmoderngeology/plutonism/ Volcanoes and Volcanism. Accessed February 15, 2017. http://usuarios.geofisica.unam.mx/cecilia/cursos/VolcCh5_Wicander-PhysG.p df 40 Wörner Gerhard. Processes of Magma Evolution and Magmatic Suites. Encyclopedia of Life Support Systems. Accessed February 15, 2017. https://www.eolss.net/Sample-Chapters/C01/E6-15-03-04.pdf 41