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Lesson 12 Endogenic Processes S11 12ES Ic 16 S11 12ES Ic 18

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  Lesson Plan in Earth and Life Science (Earth Science Lesson 12: Endogenic Processes) Date: ________________ I.   OBJECTIVES (General) 1. Describe what happens after magma is formed ( S11/12ES-Ic-16 ) and 2. Compare and contrast the formation of the different types of igneous rocks ( S11/12ES-Ic-18 ) (Specific) 1. Explain how and why magma rises up, 2. Understand the concept of Bowen’s reaction series, and 3. Identify, understand, and explain magmatic differentiation mechanisms operating  beneath the surface of the Earth II.   SUBJECT MATTER A.   Topics: Endogenic Processes B.   Reference: Earth and Life Science TG pp. 97-103 C.   Materials: TG, Audio-Video Facilities, video clips, printed images III.   PROCEDURE A.   INTRODUCTION (5 min) Communicate learning objectives 1. Introduce the following learning objectives using the suggested protocols (Verbatim, Own Words, Read-aloud) a. I can identify and explain the different magmatic processes occurring beneath the surface of the Earth.  b. I can compare and contrast the formation of the different igneous rock types 2. Review a. Review the different types of igneous rocks based on silica content.  b. Review the processes for magma generation and where it is generated. Use the following table to quickly run through these. B. MOTIVATION (5 min) 1. Encourage class participation by asking a question that will guide the students’ focus to the topics to be discussed, such as: What happens to magma after it is formed?   Note:  The teacher can guide the students by asking some questions that lead to the expected answers. Example leading questions: (1) Do you think magma rises or stays in place? (2) What happens to the composition of magma as it rises up? C. INSTRUCTION   DELIVERY (35 min)  1. Discuss why and how magma rises up  (Monroe et al., Physical Geology, 2007, p107). Density contrast: magma is less dense than the surrounding country rock. Magma rises faster when the density contrast between the magma and the country rock is greater. At deeper levels , magma passes through mineral grain boundaries and cracks in the surrounding rock. When enough mass and buoyancy is attained, the overlying surrounding rock is pushed aside as the magma rises. Depending on surrounding  pres sure and other factors, the magma can be ejected to the Earth’s surface or rise at shallower levels underneath. At shallower levels , magma may no longer rise because its density is almost the same as that of the country rock. The magma starts to accumulate and slowly solidifies (Fig. 2). When the magma solidifies at depth, it can form different types of plutonic bodies. Viscosity : A measure of a fluid’s resistance to flow. Magmas with low viscosity flow more easily than those with high viscosity. Temperature, silica content and volatile content control the viscosity of magma. Note: To introduce the concept of density difference, the teacher can make a demonstration on how materials of different densities behave when placed in a medium (e.g. water). The teacher can put a coin, a piece of rock, and a piece of Styrofoam on a pail/glass of water, and let the students observe what happens to these materials. A guide question will be: Which materials sink and which ones float? Let the students explain their observation. To illustrate viscosity, the teacher can make a demonstration using at least three different liquids: honey, oil, water. Using a pan, the teacher can ask a student to pour the liquid on the pan. Ask the students to observe how the different liquids flow (e.g. very fast, fast, slow etc.) on the pan. Mafic magma is less viscous than silicic (felsic) magma because it is hotter and contains less silica. 2. Introduce and briefly discuss the Bowen’s reaction series  (Carlson, D. H., Plummer, C. C., Hammersley L., Physical Geology Earth Revealed 9th ed., 2011, pp289-290) a. Certain minerals are stable at higher melting temperature and crystallize before those stable at lower temperatures.  b. This series explain how minerals are formed under different temperature conditions, given that all the required elements for certain minerals are present. c. There are two branches, the discontinuous and continuous branches which happen simultaneously. The minerals in the discontinuous branch include olivine, pyroxene amphibole and biotite mica. In the discontinuous branch, there is only plagioclase,  but the Calcium and Sodium content changes from high temperature to low temperature. d. A single “parental magma” can produce various kinds of igneous rocks through magmatic differentiation. Discuss the different magmatic differentiation processes. 1. Cite only the most common and important processes. 2. Magmatic differentiation is the process of creating one or more secondary magmas from single parent magma (Tarbuck, E. J. et al Earth An Introduction to Physical Geology, 2014, p138).  a. Crystal Fractionation    –  a chemical process by which the composition of a liquid, such as magma, changes due to crystallization. Common mechanism for crystal fractionation is crystal settling. This means that denser minerals crystallize first and settle down while the lighter minerals crystallize at the latter stages.  b. Partial Melting  - as described in Bowen’s reaction series, quartz and muscovite are  basically the most stable minerals at the Earth’s surface, making them the first ones to melt from the parent rock once exposed in higher temperature and/or pressure. Partial melting of an ultramafic rock in the mantle produces a basaltic magma (Carlson, D. H., Plummer, C. C., Hammersley L., Physical Geology Earth Revealed 9th ed, 2011, p292). c. Magma mixing    –   this may occur when two different magma rises up, with the more  buoyant mass overtakes the more slowly rising body. Convective flow then mixes the two magmas, generating a single, intermediate (between the two parent magmas) magma (Tarbuck, E. J. et al Earth An Introduction to Physical Geology, 2014, p139). 3. Discuss the relationship of the different igneous rock types and the environment of formation: a. Basalt and basaltic magma : form when hot rocks in the mantle slowly rise and encounter lower pressures. This leads to decompression melting (melting due to reduced pressures). This commonly occurs along places where plates are moving away from each other (i.e. extensional plate boundaries such as continental rifts and hotspots. This type of magma has low viscosity, low silica, high iron and low volatile (H2O) contents.  b. Rhyolite and rhyolitic magma : formed by either (1) melting of mantle fluxed by water and sediments carried into the mantle in subduction zones; and /or (2) interaction of mantle derived basaltic magmas with continental crust. The magma is highly viscous with relatively high silica, low iron and high volatile (H2O) contents. c. Andesite and andesitic magma : Andesitic magmas maybe formed in a variety of ways: some are formed when water and sediments on the ocean floor are pushed into the mantle along subduction zones, leading to melting in the mantle. Others are formed when hot basaltic magma interact with continental crust on the way to the Earth’s surface, which likewise leads to mel ting. The silica, iron and volatile (H 2 O) contents and viscosity are intermediate between basalt and rhyolite. D. PRACTICE (15 min) Conceptual mapping of the Bowen’s reaction series. 1. Pre-activity:  Before the class starts, the teacher has to prepare two sets of blank diagram of the Bowen’s reaction series in a Manila paper, flash cards for the different  parameters, minerals and rock types (Refer to the Bowen’s reaction series diagram  provided in the Instruction delivery section). 2. During the activity:  Group the class into two. Give the teams five minutes to paste the flash cards into the diagram in their correct places. Make sure that the students do not refer to their notes and just dwell on how much they learned and understood during the class discussions. Each group to present their answers in front of the class (five minutes each). Note: The activity may be modified depending on the resourcefulness of the teacher. E. ENRICHMENT Assignment: A report to be submitted on the next day: Draw a schematic of a cross section of the earth, showing the different layers of the earth. Include and label (when necessary) the following parts of the illustration:  1. Different tectonic settings where magma is generated 2. The type of melting that is usually associated with the settings identified in # 1 3. Heat transfer mechanisms and the direction of heat transfer (through arrows) Further research  —   Below the drawing, note the different zones where magma is formed, and cite one known location of each. IV. EVALUATION Summary Questions: [Easy] 1. What are the two primary sources of the Earth's internal heat? Answer : Primordial heat and radioactive heat. 2. Cite three tectonic settings where magma is formed. Answer : mid-oceanic ridges, hot spots and subduction zones 3. What is the role of volatiles in the partial melting of rocks? Answer: Volatiles help break the chemical bond in rocks, and at the same time, lower the melting temperature of rocks. [Difficult] 1. What is decompression melting? Answer: Decompression melting is occurring by reducing the pressure at a constant temperature. 2. How is the Earth's internal heat redistributed? Answer : Magma transfers the heat from the Earth’s interior to the surface when it rises. 3. Describe how rising magma causes melting. Answer:  Rising magma from the mantle brings heat with it which can melt the surrounding rocks at the shallower depths. 2.4 (Test) Geologic Processes Inside the Earth Earth Materials and Processes 1.   Where does the internal heat of the earth come from? A.   crust and core B.   mantle only C.   crust and mantle D.   mantle and core 2.   It is a semi-liquid mixture of rocks found in the lower portion of the crust and upper part of the mantle. A.   lava B.   magma C.   minerals D.   soil 3.   Who developed the idea about plutonism? A.   James Hutton B.   Alfred Wegener C.   Charles Darwin D.   Aristotle
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