LESSON 4 - ELS.pdf

Try it! Solution One whole sheet of pad paper: 1. What are the primary sources of Earth's internal heat, and how do they contribute to geological processes like volcanism and plate tectonics? 2. How does the distribution of internal heat vary within different layers of the Earth, s...

Try it! Solution One whole sheet of pad paper: 1. What are the primary sources of Earth's internal heat, and how do they contribute to geological processes like volcanism and plate tectonics? 2. How does the distribution of internal heat vary within different layers of the Earth, such as the crust, mantle, and core, and what impact does this have on the Earth's thermal structure? 3. In what ways does the Earth's internal heat drive convection currents in the mantle, and how do these currents influence the movement of tectonic plates and the formation of geological features? 4. How do differences in magma's composition and temperature affect volcanic eruptions and the types of rocks formed? 5. How do pressure and gases like water and carbon dioxide affect the formation and movement of magma? GEOLOGIC PROCESSES INSIDE THE EARTH  Try it! REVIEW: 1. What are the different layers of the Earth? 2. Define magma. 3. How is an igneous rock formed? Earth's Internal Heat Objective At the end describe where Earth’s of the 1 internal heat comes from. lesson, you should be able to:  Learn about It! Internal Heat of the Earth The internal heat of the 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.  Learn about It! Residual Heat Extraterrestrial Impacts As proposed in the Nebular theory, the Earth was formed through accretion of particles from a rotating cloud. The accretion of fragments that results from formation of a planet.  Learn about It! Residual Heat Extraterrestrial Impacts The great amount of kinetic energy is produced by the moving extraterrestrial objects which were then converted to The accretion of fragments that results heat energy. from formation of a planet.  Learn about It! Residual Heat Gravitational Contraction Collapsed clouds occur because accretion of more materials led to an increase in the gravitational attraction causing the contraction of the Earth into a smaller volume which will then enable them to spin faster.  Learn about It! Residual Heat Gravitational Contraction The compaction of dust clouds resulted in the conversion of gravitational energy into heat energy. A collapsed cloud due to the influence of gravity.  Learn about It! Radiogenic Heat Unstable elements undergo radioactive decay to attain a more stable form. The process of radioactive decay produces heat as a byproduct. Radiogenic heat is a by-product of radioactive isotope decays.  Learn about It! Earth's Thermal Budget Earth’s thermal budget is the measure of the amount of heat that is released at the surface and produced in the interior. Most of the energy produced by Sun is absorbed and scattered by Earth on the ground and on its atmosphere.  Learn about It! Earth's Thermal Budget Around 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. Key Points The internal heat of the Earth fuels the planet’s 1 dynamic processes. Earth’s internal heat is produced by residual heat 2 (extraterrestrial impacts and gravitational contraction) and radiogenic heat. Earth’s thermal budget is the measure of the amount of 3 heat that is released at the surface and produced in the interior.  Check Your Understanding Answer the following questions. 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?  Challenge Yourself Where does the heat from Earth’s interior come from? Magmatism: How Magma is Formed Objective At the end describe how magma is of the 1 formed (magmatism). lesson, you should be able to:  Learn about It! Magma Magma is defined as molten rock material produced by partial melting of the mantle and crust. It contains liquids, gases, crystals and rock fragments. Rocks melt as a result of the addition of volatiles.  Learn about It! Formation of Magma Temperature Temperature increases with depth, which is called geothermal gradient. This increase will obviously induce melting. Temperature increases with depth in Earth’s internal structure.  Learn about It! Formation of Magma Pressure Decrease in pressure causes adiabatic decompression. As pressure is decreased, melting temperatures of materials decrease. Rocks starts to melt even with low temperature due to difference in pressures.  Learn about It! Formation of Magma 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.  Learn about It! 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.  Learn about It! Magmatism Plate boundaries can be classified as convergent, divergent, and transform. The movement of plates produces convergent, divergent and transform boundaries.  Learn about It! Classification of Magma Tholeiitic magmas or tholeiites, are produced by large degree of melting. Calc-alkaline basalts form along convergent plate boundaries above subduction zones.  Learn about It! Classification of Magma 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. Key Points Magma is defined as molten rock material produced 1 by partial melting of the mantle and crust. Magmatism occurs along plate boundaries or 2 margins and sometimes within the plate. Magmas are classified according to the ratio 3 between the alkalis and silica content.  Check Your Understanding 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.  Challenge Yourself What would be the temperature of Earth as one goes down deep within Earth?  Try it! Identify the types of boundaries: Volcanoes and Volcanism Objective At the end describe what happens of the 1 after magma is formed lesson, you (volcanism). should be able to:  Learn about It! Volcanism Volcanism is the process where magma rises to the surface of the Earth as lava. It can be viewed as a destructive event as it could damage infrastructures, cause injuries and short-term climate change and also a constructive process as seen in the Earth’s early history.  Learn about It! Volcanism 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.  Learn about It! 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. Most of the geological hotspots in the world are either near or on the plate boundaries.  Learn about It! Formation of Volcano In divergent plate boundaries, volcanism manifests as ridges or fissures where products of decompression melting erupt. Convergent plate boundaries host large number of volcanoes. Lava flows and pyroclastic materials make up these volcanoes.  Learn about It! Lava Flows Lava flows may be classified as pahoehoe (pronounced as “pah-hoy- hoy”) and aa (pronounced as ah-ah). Lava Flow  Learn about It! Types of Lava Flows Pahoehoe has a smooth and ropy surface. Aa has jagged and angular corners. Lava flows can be classified as pahoehoe (left) or aa (right) lava flow  Learn about It! Volcanic Rocks Lava that solidifies forms volcanic rocks. Minerals comprising these rocks are fine-grained compared to plutonic rocks which are coarser. Solidifying Lava  Learn about It! Volcanic Rocks Examples of these rocks are basalt, andesite, and rhyolite. Basalt Key Points Volcanism is the process where magma rises to the 1 surface of the Earth as lava. A volcano is a hill or mountain where lava, pyroclastic 2 materials, and gases erupt. It can form along plate boundaries or within the plate. 3 Lava flows may be classified as pahoehoe and aa.  Check Your Understanding 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. Plutonism Objective At the end describe what happens of the 1 after magma is formed lesson, you (plutonism). should be able to:  Learn about It! Plutonism Plutonism theory states that rocks were formed from heat- driven processes. This heat comes from the interior of the Earth. Another fundamental aspect of plutonism is that the processes are constant and slow.  Learn about It! Neptunism Neptunist theory of the origin of granites states that these rocks are the oldest precipitates from a primordial sea. Plutonism opposed Neptunism’s idea of the origin of granites.  Learn about It! Plutons As magma rises to the crust, it can displace the host or country rock to form structures called plutons. The term plutonic can be used to classify rocks which formed in the interior of the Earth. This is the opposite of volcanic rocks which form on the crust.  Learn about It! Plutons Some examples of plutonic rocks are gabbro, diorite, and granite. Basalt  Learn about It! Classification of Plutons Plutons vary in sizes and shape and may be classified as discordant or concordant structures. A dike and sill complex which are considered as sedimentary beds.  Learn about It! Classification of Plutons 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. A dike and sill complex which are considered as sedimentary beds.  Learn about It! Classification of Plutons Concordant bodies are those that are injected parallel to features in the country rock such as sedimentary beds. A dike and sill complex which are considered as sedimentary beds. Key Points The term plutonic can be used to classify rocks 1 which formed in the interior of the Earth. Neptunist theory of the origin of granites states that 2 these rocks are the oldest precipitates from a primordial sea. They vary in sizes and shape and may be classified 3 as discordant or concordant structures.  Challenge Yourself What is the difference between the plutonist and neptunist theory? What is Metamorphism?  explain metamorphism 1 and how it happens; and Objectives describe some processes At the end involved in of the lesson, you metamorphisms such as should be 2 recrystallization, able to: neocrystallization, phase change, pressure solution, and plastic deformation.  Learn about It! Metamorphism It came from a Greek word meta which means to change and morph means form. It is the process of changing the characteristics of a rock as a result of changes in temperature, pressure, or Slate is a product of metamorphism reactions with hot fluids. from a protolith which is shale.  Learn about It! Metamorphism The protolith is a pre-existing rock that undergoes metamorphism. It can be any types of rock. Metamorphism of the protolith changes the texture and mineralogy (mineral components) Marble cave of the original rock.  Learn about It! Different Processes Involved in Metamorphism Recrystallization ○ Process where there is growth in size of mineral grains of pre-existing materials. ○ The most common process involved in metamorphism. Example: limestone to Quartzite may be formed from marble; clay into muscovite recrystallization of quartz in mica. sandstones.  Learn about It! Different Processes Involved in Metamorphism Neocrystallization ○ It is the formation of new minerals from the pre-existing minerals due to heat. ○ Example: Phyllite is a mica-rich mineral rock. When clay undergoes neocrystallization it Formation of quartz, mica, and forms mica. garnet from neocrystallization of shale.  Learn about It! Different Processes Involved in Metamorphism Phase Change ○ It refers to the change in mineral structure but with the same chemical formula. Example: Andalusite to Kyanite. ○ Minerals with the same chemical formula but different mineral structure are called polymorphs of each other.  Learn about It! Different Processes Involved in Metamorphism Pressure Solution ○ It takes place when minerals are dissolved in areas with high pressure and recrystallize in other areas with low Changes that happen in a pressurized pressure. solution.  Learn about It! Different Processes Involved in Metamorphism Plastic deformation ○ Occurs when mineral grains soften and deform at high temperatures. Shape of minerals in the protolith and shape of the minerals in the metamorphic rock after plastic deformation. Key Points Metamorphism changes the texture and mineralogy 1 of the protolith. It involves processes such as recrystallization, 2 neocrystallization, phase change, pressure solution, and plastic deformation. Key Points Recrystallization is a process where there is growth in 3 size of mineral grains of pre-existing materials. Neocrystallization is the formation of new minerals 4 from the pre-existing minerals due to heat. Phase Change refers to the change in mineral 5 structure but with the same chemical formula. Key Points Pressure Solution takes place when minerals are 6 dissolved in areas with high pressure and recrystallize in other areas with low pressure. Plastic deformation occurs when mineral grains 7 soften and deform at high temperatures. Challenge Yourself Why is texture a basis for metamorphism? Types of Metamorphism  explain metamorphic 1 grade; Objectives distinguish prograde and At the end of the 2 retrograde lesson, you metamorphism; and should be able to: differentiate the types of 3 metamorphism.  Learn about It! Metamorphic Grade It refers to the relative temperature and pressure conditions during the formation of the metamorphic rocks. Graphical view of metamorphic grade of some metamorphic rocks.  Learn about It! Metamorphic Grade The spectrum includes the following scale: ○ Low-grade metamorphism occurs in environments where the temperature is between 200 oC to 320 oC and low-pressure values. Example: Shale to Slate ○ Intermediate metamorphism takes place at approximately at 320–450 ºC and at moderate pressures. ○ High-grade metamorphism takes place at temperatures greater than 320oC. Example Granite to Gneiss  Learn about It! Prograde Metamorphism Prograde metamorphism takes place when temperature and pressure are increased. It occurs when rocks are buried deeply. It happens when water molecules from minerals are usually squeezed out, forming “drier” rocks. Example of Phyllite this is Phyllite form from Slate.  Learn about It! Retrograde Metamorphism Retrograde metamorphism, on the other hand, happens when temperature and pressure decreases. This process requires the addition of hydrothermal fluids or water. Example of this chlorite schist form from Chlorite schist muscovite.  Learn about It! Prograde and Retrograde Metamorphism Path of prograde and retrograde metamorphism.  Learn about It! Types of Metamorphism Contact or thermal metamorphism occurs when heat is transferred from igneous intrusions to nearby rocks. A typical example of contact metamorphism.  Learn about It! Types of Metamorphism Burial metamorphism occurs when rocks are buried to depths of several hundred meters and form new low grade rocks due to the temperature increase.  Learn about It! Types of Metamorphism Dynamic metamorphism occurs when two bodies of rock slide past each other along faults, where some rocks are heated and pulverized to form new rocks. Example of this is myolite. Bodies of rock sliding past another producing mylonites.  Learn about It! Types of Metamorphism Regional metamorphism occurs over large areas that experience stress, such as in convergent boundaries, where one tectonic plate goes under another tectonic plate. Rocks at point A undergo regional metamorphism as it is buried to a deeper level during collision of two plates.  Learn about It! Types of Metamorphism Hydrothermal metamorphism takes place mostly along mid-ocean ridges, where ocean water is heated by nearby magma to form Hydrothermal metamorphism along a hydrothermal. mid-ocean ridge.  Learn about It! Types of Metamorphism Shock metamorphism occurs when a meteorite hits the surface of Earth & transfers a lot of heat to the place of impact, causing rocks to change. Meteorite Key Points Metamorphic grade refers to the relative temperature 1 and pressure conditions during the formation of metamorphic rocks. Prograde metamorphism takes place when pressure and temperature are increased. While, Retrograde 2 metamorphism takes place when pressure and temperature are decreased. Key Points Contact or thermal metamorphism occurs when heat 3 is transferred from igneous intrusions to nearby rocks. Burial metamorphism occurs when rocks are buried 4 to depths of several hundred meters and form new rocks due to the temperature increase. Dynamic metamorphism occurs when two bodies of 5 rock slide past each other along faults. Key Points Regional metamorphism occurs over large areas that 6 experience stress Hydrothermal metamorphism occurs mostly along 7 mid-ocean ridges, where ocean water is heated to form hydrothermal. Shock metamorphism occurs when a meteorite hits 8 the surface of Earth & transfers a lot of heat to the place of impact, causing rocks to change.  Challenge Yourself What kind of metamorphism would we expect to happen on the moon? Factors Controlling Metamorphism  1 explain how heat changes rocks; describe how rocks behave Objectives 2 under different types of stress; At the end of the explain how chemically active lesson, you 3 fluids affect rocks; and should be able to: explain how a rock takes a long 4 time to undergo metamorphosis.  Learn about It! Temperature It is affected by heat or thermal energy which triggers the chemical reaction to the rock, which can come from two sources: Igneous intrusions and Earth’s Thermometer is used to measure geothermal gradient. the degree of hotness and coldness of an object.  Learn about It! Temperature Two sources of thermal energy ○ Intrusive bodies or plutons alter the texture and mineralogy of surrounding rocks to form metamorphic rocks ○ The geothermal gradient of Earth is the rate of increase in temperature with increasing depth from the Earth’s surface.  Learn about It! Pressure Pressure increases with depth and can be classified into two types: Uniform and Differential Stress. When minerals with spaces in their lattices are subjected to high amounts of pressure, the minerals collapse forming much denser crystals.  Learn about It! Pressure Uniform stress or hydrostatic stress refers to pressure with equal amounts of force coming from all directions. Confining pressure works by squeezing rocks together, decreasing their volume.  Learn about It! Pressure Differential stress refers to the pressure that is unequal in different directions. ○ Normal stress compresses objects from two opposing directions. ○ Shear stress smears objects in the direction of Differential stress in a convergent the stress. boundary causes rocks to deform.  Learn about It! Chemically active fluids It enhances chemical reactions which alter the composition of rocks. Metasomatism is the change in the composition of a rock due to the addition or removal of substances or elements.  Learn about It! Time Metamorphism is a slow process that involves several processes. These processes are slow since metamorphic rock is formed with the protolith rock remaining in solid form. Metamorphic rocks that contain large crystals need time to form, on a scale of tens of millions of years. Key Points The process of metamorphism is controlled by four 1 factors: temperature, pressure, chemically active fluids, and time. Heat or thermal energy produced by an increase in 2 temperature triggers chemical reactions which can cause recrystallization and/or neocrystallization. Key Points When minerals with spaces in their lattices are 3 subjected to high amounts of pressure, the minerals collapse forming much denser crystals. Chemical active fluid enhances chemical reactions 4 which alter the composition of rocks. Metamorphism is a slow process that involves several 5 processes.  Check Your Understanding Write true if the statement is correct, write false if otherwise. 1. Metamorphism is a slow process. 2. Heat is absorbed by intrusive bodies from rocks. 3. Fluids only increase the size of rocks, but cannot alter the chemical composition of minerals. 4. Rocks at higher temperatures and pressures crack easily. 5. Uniform stress increases the volume of rocks. Challenge Yourself How can humans affect metamorphism of rocks?