Weathering, Deformation of Rocks and Metamorphism PDF

WEATHERING, DEFORMATION OF ROCKS AND METAMORPHISM for Earth Science – Senior High School (Core Subject) Quarter 2 / Week 2 1  FOREWORD This self-learner kit is prepared for the senior high school students to reminisc...

WEATHERING, DEFORMATION OF ROCKS AND METAMORPHISM for Earth Science – Senior High School (Core Subject) Quarter 2 / Week 2 1  FOREWORD This self-learner kit is prepared for the senior high school students to reminisce their knowledge and to be able to learn factual events about the continuous alteration of the earth which is attributed to its never-ending geologic processes driven by internal and external forces. Weathering is one of the forces on earth that destroy rocks and landforms. Without weathering, geologic features would build up but would be less likely to break down. Moreover, rocks are created, exposed to different types of stresses, temperature and pressure which change their physical and chemical structures. With the continuous succession of how rocks form, break down and reform different geologic features were formed. This Self-Learning Kit contains the following lessons:  Weathering of rocks  Deformation of rocks  Metamorphism 2 OBJECTIVES: At the end of the lesson, students shall be able to: Describe the behavior of rocks when exposed to different types of stress and temperature and the processes that causes the breaking down of rocks. Explain how weathering, stress and temperature, influence the continuous alteration of the Earth. Help in the prevention of destroying rocks by human activities. LEARNING COMPETENCIES:  Describe how rocks undergo weathering (S11ES - IIa – 22)  Describe how rocks behave under different types of stress such as compression, pulling apart and shearing. (S11Es-IId- 27)  Describe the changes in mineral and texture of rocks due to changes in pressure and temperature (metamorphism) (S11/12ES-Ic-17) 3 I.WHAT HAPPENED PRE-ACTIVITY: Direction: Look at the photographs below. It is a monument over the portal of a castle in Westphalia, Germany. The picture shows on the (left) when the photograph was taken in 1908 and then taken again in (right) in 1968. Describe how the statue has changed and provide a possible explanation for the changes shown in the picture. Write in your activity notebook. Image from acidraingermany.weebly.com Figure 1: A statue that has changed over time. Criteria in rating the answer: Relevance - 6 points Organization - 4 points Total - 10 points II. WHAT I NEED TO KNOW DISCUSSION: 4  The Earth is constantly changing through the years. According to the Continental Drift Theory proposed by Alfred Wegener, the Earth was once a giant landmass called Pangaea. This giant landmass was broken down into several continents because of the movement beneath the Earth’s surface. If continents came from a giant landmass, can you imagine how the mountains, volcanoes, and soil are formed? Shaping the Earth’s surface involves a geological process called weathering. Weathering is the process of breaking down rocks, soils, and minerals together with other materials at or near the Earth's surface. It is different from erosion. While erosion is the process by which soil and rock particles are worn away and move elsewhere by wind, water or ice, weathering involves no moving agent of transport. It is the process of breakdown of rocks at the Earth’s surface, either by extreme temperatures or rainwater or biological activity. It simply does not involve any movement of rock material. There are three broad categories of mechanisms for weathering: 1. Physical Weathering 2. Chemical Weathering 3. Biological Weathering Physical Weathering It is also called Mechanical Weathering. Physical weathering is the process wherein rocks are broken down into smaller pieces without changing its chemical composition. These smaller pieces are just like the bigger rock, just smaller. That means the rock has changed physically without changing its composition. This can occur due to changes whether sudden or not in temperature and pressure, etc. Examples of physical weathering: Block disintegration- is caused by successive heating and cooling which causes the expansion and contraction of rocks. By nitishpriyadarshi.blogspot.com Figure 2: Weathering of rock due to successive heating and cool in 5 Frost weathering - refers to the alternate freezing and thawing of water inside the joints of the rocks, causing them to split into smaller particles or fragments. Image from Earth Science by Lumen By claremontgeography12.blogspot.com Fig. 3.a: Rock undergoing frost weathering Fig. 3.b: Frost weathering process Chemical weathering It is different from mechanical weathering because the rock changes, not just in size of pieces, but in composition. That is, one type of mineral changes into a different mineral. Chemical weathering works through chemical reactions that cause changes in the minerals, rocks and minerals are reacting to acids, oxygen, carbon, and water. That is why no two rocks ever look exactly the same. It's also the reason that we have those awesome looking caves and unique rock formations all over the world. Three different processes of chemical weathering: Water is the most important agent of chemical weathering. Two other important agents of chemical weathering are carbon dioxide and oxygen. Hydrolysis -is the chemical breakdown of a substance when combined with water. The addition of water in the rock increases its volume which changes the shape. Eventually, the water together with other elements breaks down the rock. www.worldatlas.com claremontgeography12.blogspot.com 6  Figure 4: Rocks break due to water and other elements Oxidation- refers to the reaction of oxygen with metal elements in a rock, forming oxides. An easily recognizable example of this is rust. Rust, for example, is iron oxide. When rocks, particularly those with iron in them, are exposed to air and water, the iron undergoes oxidation, which can weaken the rocks and make them crumble. Image from Earth Eclipse maritimematters.com Figure 5: Metals in rocks react with oxygen Carbonation-occurs when carbonic acid (usually carbon dioxide mixing with water) reacts with minerals in rock. Most often this occurs simply with the carbon dioxide in air dissolving in rainwater and falling to the surface. The chemical reaction that takes place between carbonic acid and typically some form of calcium carbonate yields calcium bicarbonate, which is soluble and gets washed away with the rainwater. Carbonic acid is a very common in nature where it works to dissolve rock. Pollutants, such as sulfur and nitrogen, from fossil fuel burning, create sulfuric and nitric acid. Sulfuric and nitric acids are the two main components of acid rain, which accelerate chemical weathering. Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read. Acid rain has also damaged many historic buildings and monuments. pennydrivessouth.blogspot.com www.goodearthgraphics,com Figure 6: Rock samples whose minerals react with carbonic acid. 7 Biological Weathering Biotic or Biological Weathering is the disintegration of rocks caused by living organisms such as plants, animals, humans. Image by jhlui1.wordpress.com www.as.uky.edu Figure 7.a: Biological weathering by plants www.slideshare.net Figure 7.b: Biological weathering by animals 8  www.slideshare.net listverse.com Figure 8: Weathering due to human activities Weathering is a natural process, but human activities can speed it up. For example, certain kinds of air pollution increase the rate of weathering. Burning coal, natural gas, and petroleum releases chemicals such as nitrogen oxide and sulfur dioxide into the atmosphere. When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain. Influences on Weathering The rate at which weathering occurs is dependent on rock, mineral and climate types. Different rock and mineral types weather at different rates. Igneous rock weathers slowly because it is difficult for water to penetrate the rock due to the tightness of crystal interlocking. Limestone, however, weathers relatively faster and will weather even faster when it comes in contact with water and acids like carbonic acid. Climate also has an effect on the rates at which rock weathers. Chemical weathering is going to occur frequently in 9 warm tropical climates due to all the precipitation. The more precipitation an area has the quicker the weathering rates. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Weathering and erosion constantly change the rocky landscape of Earth. Yes, rock is a naturally formed, non-living earth material. Rocks are remembered that was made of collections of our assignment. mineral grains that are held together in a firm, solid mass. I saw some rocks on the way here and I Vectorstock.com What is a rock?  It is naturally occurring mixtures of minerals, mineraloids, glass or organic matter.  Rocks are continually changed by many processes such as weathering, erosion, compaction, cementation, melting and cooling.  Stress is the force applied to an object. In geology, stress is the force per unit area that is placed on a rock.  When rocks deform, they are said to strain. A strain is a change in size, shape, or volume of a material. Types of Stress  Tensional Stress which acts in opposite directions, pulling rock apart or stretching it. Tension can happen in two ways. Two separate plates can move farther away from each other, or the ends of one plate can move in 10  different directions. Some scientists think tension stress caused the ancient, massive continent Pangaea to break off into the seven continents we have today.  Compressional Stress acts toward each other, pushing or squeezing rock together. Compression causes rocks to fold or break. Compression is the most common stress at convergent plate boundaries.  Shear Stress causes two planes of material to slide past each other. This is the most common stress found at transform plate boundaries. Shear stresses may act toward or away from each other, but they do so along different lines of action, causing rock to twist or tear. https://earthquake.usgs.gov/learn/glossary/?term=shear%20stress Figure 9: Types of Stress Stages of Deformation Elastic deformation The strain or the deformation is temporary. It is reversed when the source of stress is removed. Ductile Deformation The strain is permanent. There is irreversible change in shape or size that is not recovered when stress is removed. 11  It is also Fracture known as brittle deformation. The strain is irreversible that https://decoratingideas9.blogspot.com/2019/12/brittlresults to the breakage of rock due to the loe-deformation-geology.htmsl s of consistency of a body under the influence of stress. Figure 10: Ductile and Brittle Deformations Fracture It is also known as brittle deformation. The strain is irreversible that results to the breakage of rock due to the loss of consistency of a body under the influence of stress. FACTORS AFFECTING THE DEFORMATION OF ROCKS a. Temperature - At high temperature molecules and their bonds can stretch and move, thus materials will behave in more ductile manner. At low temperature, rocks tend to deform brittlely. Heat makes materials softer. b. Pressure - At high confining pressure materials are less likely to fracture because the pressure of the surroundings tends to hinder the formation of fractures. At low confining stress, material will be brittle and tend to fracture sooner. c. Strain Rate or deformation rate – A sudden change in shape causes brittle deformation, whereas a slow change in shape causes ductile deformation. For example, if you hit a marble bench with a hammer, it shatters, but if you leave the bench alone for a century, it gradually sags without breaking. d. Rock Type or Composition: Some rock types are softer than others; for example, halite (rock salt) deforms in a ductile way under conditions in which granite deforms brittlely. Some minerals are very brittle. This is due to the chemical bond types that hold them together. Thus, the mineralogical composition of the rock will be a factor in determining the deformational behavior of the rock. FYI! What a rock does in response to stress depends on many factors and 12  how long it was exposed to the stress. It seems difficult to imagine that rocks would not just simply break when exposed to stress. At the Earth's surface, rocks usually break quite quickly once stress is applied. But deeper in the crust, where temperatures and pressures are higher, rocks are more likely to deform plastically. Sudden stress, like a hit with a hammer, is more likely to make a rock break. Stress applied over time often leads to plastic deformation. TRIVIA When rocks are squeezed or shortened, the stress is compressional. When rocks are pulled in opposite directions, the stress is tensional. When a body of rock is distorted, the stress is shear. Metamorphism of Rocks When you expose igneous rocks to intense heat and pressure, they could undergo metamorphism. Metamorphism is the process of change in the form and structure of rocks due to intense heat and pressure. It comes from the Greek word “metamorphoun” meaning transform or change shape. The rocks that undergo metamorphism are converted to metamorphic rocks. Figure 11: Rock samples that have undergone contact metamorphism. Types of Metamorphism 1. Contact metamorphism is the process where the country rock adjacent to the igneous intrusions is altered by the high heat coming from the intrusions. Country rocks are rocks surrounding the igneous intrusions. Igneous intrusions 13 form when molten magma moves and seeps through fractures and in between crystals of rocks. The zone of metamorphosis that surrounds the intrusions is called halo or aureole. Some examples of rocks that undergo contact metamorphism include marble and emery rock. 2. Dynamic metamorphism is the process where rocks along the fault zones are altered due to high pressure. The rocks that are formed with this type of metamorphism are called mylonites. Mylonites are compact, fine-grained rocks with thin laminations or layers. Figure 12: Rock sample that is formed by dynamic metamorphism. 3. Regional metamorphism is the most common form of metamorphism that occurs in broad areas that does not show any relationship to igneous rocks. This is associated with tectonic forces that produce compressional stresses in the rocks, such as when two continental masses collide. It usually results in forming metamorphic rocks that are strongly foliated, such as slates, schists, and gneisses. Regionally metamorphosed rocks occur in the cores of fold/thrust mountain belts or in eroded mountain ranges. Compressive stresses result in folding of rock and thickening of the crust, which tends to push rocks to deeper levels where they are subjected to higher temperatures and pressures. An example would be the Himalayan Range. At this continent convergent boundary, sedimentary rocks have been both thrust up to great heights (nearly 9,000 m above sea level) and also buried to great depths. 14  SLATE PHYLLITE SCHIST GNEISS INCREASING METAMORPHIC GRADE marlimillerphoto.com Figure 13. Metamorphic Rocks. From left to right: slate, phyllite, schist, gneiss. With increasing temperature and pressure, metamorphic grade also increases. The higher the metamorphic grade, the more changed the rock will be from its original form. 15 References: Carlson, D. H., Plummer, C. C., Hammersley L., Physical Geology Earth Revealed 9th edition, 2011. “Classification of Metamorphic Rocks”. https://www.radford.edu/jtso/GeologyofVirginia/Rocks/GeologyOfVAR ocks2-5d.html. “Deformation of Rocks”. EarthSci.org. http://earthsci.org/education/teacher/basicgeol/deform/deform.html. retrieved Nov. 19, 2020. “Deformation of Rocks”. http://www3.uma.pt/sprada/documentos/aulas/Geologia_de_Engenh aria_Topografia/Biblio/Deformation_of_Rock.pdf. retrieved Nov. 19, 2020. Earth and Life Science book by DIWA (SHS series pp.42-47) Earth and Life Science Teaching Guide for Senior High School pp.42-89 “Earthquake Glossary”. https://earthquake.usgs.gov/learn/glossary/?term=shear%20stress. “Geological Processes Inside the Earth,” Quipper School, last modified August 12, 2016. https://link.quipper.com/en/organizations/547ffb03d2b76d000200 2352/curriculum#curriculum. Harris, Amy. “What is Deformation in Earth Science?”. https://sciencing.com/deformation-earth-science-21924.html. updated April 24, 2017. Quipperschool.com.ph Web search: applustopper.com for Weathering. Weathering by National Geographic Society. Lumenlearning.com/geophysical. 16 ACKNOWLEDGMENT DIVISION OF NEGROS ORIENTAL SENEN PRISCILLO P. PAULIN, CESO V Schools Division Superintendent FAY C. LUAREZ, Ph.D., Ed.D, TM Assistant Schools Division Superintendent NILITA L. RAGAY Assistant Schools Division Superintendent FAY C. LUAREZ, Ph.D., Ed.D.,TM Acting CID Chief RACHEL B. PICARDAL, Ed.D. SGOD Chief ARNOLD R. JUNGCO PSDS – Division Science Coordinator ROSELA R. ABIERA LR Manager ELMAR L. CABRERA PDO MARICEL S. RASID Librarian MARIA AMELI A. LASMARIAS Writer KOREN O. BALBUENA Lay-out Artist MEMBERS OF THE QUALITY ASSURANCE TEAM (Alpha) LIEZEL A. AGOR MARY JOYCEN A. ALAM-ALAM EUFRATES G. ANSOK JR. JOAN Y. BUBULI LIELIN A. DE LA ZERNA THOMAS JOGIE U. TOLEDO MEMBERS OF THE QUALITY ASSURANCE TEAM (Beta) 17  JOAN Y. BUBULI LIELIN A. DE LA ZERNA MIEL C. PACULANANG ARJIE T. PALUMPA DISCLAIMER The information, activities and assessments used in this material are designed to provide accessible learning modality to the teachers and learners of the Division of Negros Oriental. The contents of this module are carefully researched, chosen, and evaluated to comply with the set learning competencies. The writers and evaluator were clearly instructed to give credits to information and illustrations used to substantiate this material. All content is subject to copyright and may not be reproduced in any form without expressed written consent from the division. SYNOPSIS Weathering describes the breaking down of rocks and minerals on the surface of the earth. Water, ice, acids, plants, animals, and changes in temperature are all agents of weathering. These could be destructive occurrences that leave significant changes on the landscape and even in the ecosystem of an area. 18 Metamorphism and different types of stress causes the change in rock formation when exposed to temperature and pressure is also emphasized. These geologic processes contribute to the continuous alteration in form and shape of the earth. ABOUT THE AUTHOR Maria AmeliA.Lasmarias, RN, LPT Maria Ameli A. Lasmarias - Graduated Bachelor of Science in Nursing in University of Bohol, Tagbilaran City, Bohol. She was active in Nursing practice locally and abroad from 1990- 2015. She earned Education units from Presbyterian Theological College, Dumaguete City and STI West Negros, Bacolod City. Currently, a Senior High School teacher in Jose B. Cardenas Memorial High School-Main Campus, Canlaon City. 19