How Rocks Weather PDF

# Earth and Life Science ## Describing How Rocks Undergo Weathering ### S11/12ES-lb-11 **Hi! Our topic is about describing how rocks undergo weathering. Let's begin.** ## **LEARNING OBJECTIVES** - Define and explain weathering. - List down the different agents of weathering. - Enumerate and descr...

# Earth and Life Science ## Describing How Rocks Undergo Weathering ### S11/12ES-lb-11 **Hi! Our topic is about describing how rocks undergo weathering. Let's begin.** ## **LEARNING OBJECTIVES** - Define and explain weathering. - List down the different agents of weathering. - Enumerate and describe the types of weathering. - Describe the components of each type of weathering. **Here are the things that we should learn by the end of this lesson.** ## Weathering - process where rocks are broken down into smaller pieces, worn away, or dissolved - caused by abiotic and biotic factors **Weathering is the process where rocks are broken down into smaller pieces, worn away, or dissolved. This is because of many biotic and abiotic factors. Biotic factors are those caused by biological agents like animals and humans. Abiotic factors are the non-living, physical and chemical components of the environment. Weathering does not involve transportation of materials during decomposition.** ## Weathering - **Weathering Agents:** - Water - Temperature - Atmospheric - Biotic - **Rate of weathering is affected by:** - amount of exposed surface area - mineral composition of rock - prevailing climate **Weathering is influenced by different weathering agents such as water, temperature, atmospheric, and biotic. The most significant is water as it can directly affect the physical and chemical compositions of rocks. This is followed by temperature, then atmospheric gasses composed of oxygen, carbon dioxide, and water vapor. Rate of weathering is affected by amount of exposed surface area, mineral composition of rock, and the prevailing climate.** ## Types of Weathering - **Chemical Weathering** - **Mechanical or Physical Weathering** - **Organic or Biological Weathering** **There are three types of weathering. First is the chemical weathering with three major processes including dissolution, hydrolysis, and oxidation. Second is the mechanical or physical weathering with three major processes including frost wedging, exfoliation, and thermal expansion and contraction. Third is the organic or biological weathering.** ## Chemical Weathering - changes due to chemical activities - modifies rock composition - agents of chemical weathering: - Oxygen - rainwater - carbon dioxide - acids **The first type of weathering is the chemical weathering. Chemical weathering is the changing of rocks due to chemical activities. Chemical weathering modifies the physical and chemical composition of rocks due to activities of different chemical weathering agents like oxygen, rain water, carbon dioxide, and acids.** ## Chemical Weathering - Products of chemical weathering: - Clays minerals - Metal ores - Oxide minerals - Rounding boulders **Common products of chemical weathering are clay minerals, metal ores, oxide materials and noticeable rounding of boulders, or big rocks.** ## Chemical Weathering: Major Processes - **1. Dissolution** - elements dissolve in water - **2. Hydrolysis** - positive ions are replaced by active hydrogen ions that comes with water - **3. Oxidation** - oxygen interacts with minerals **There are three major processes in chemical weathering, Dissolution, Hydrolysis, and Oxidation. Dissolution happens when elements are dissolved in water, partially or completely. Hydrolysis is an active action of hydrogen ions to replace positive ions in the mineral. Oxidation is the reaction of oxygen with minerals, leading to changed oxidation state of an ion.** ## Mechanical or Physical Weathering - due to physical stresses - Changes the physical attributes but composition stays the same - Occurs due to changes in temperature and pressure **The second type of weathering is the mechanical or physical weathering. This happens due to the physical stresses that rocks encounter. In this process only the physical attributes of the rocks change, while its composition stays the same. The process of mechanical weathering is stimulated by changes in temperature and pressure.** ## Mechanical or Physical Weathering: Major Processes - Frost wedging - Exfoliation - Thermal expansion and contraction **The major processes in mechanical weathering are frost wedging, exfoliation, and thermal expansion and contraction.** ## Mechanical Weathering: Major Processes ### Frost Wedging - key agent is water - affected by changes in temperature - exerts force on the rack which leads to cracking and separation of particles - common in high altitude areas **Water plays and important role in frost wedging. This process is mainly affected by the changes in temperature, which leads to the expansion and contraction of water molecules inside the rocks. The constant expansion and contraction exerts force on the rock which results to cracking and eventually, separation of rock particles from each other. This process is common in high altitude areas where consistent freeze-thaw cycle occurs.** ## Mechanical Weathering: Major Processes ### Exfoliation - detachment of sheets of rocks due to instability in pressure - pressure inside the rock is greater than pressure on surface of the rock permitting expansion **Exfoliation is the detachment of layers or sheets of rocks from the surface. This is also known as onion-skin weathering because of the appearance of the thin sheets. The process starts when rocks are either brought above or below the surface then exposed to changes in pressure permitting expansion. Commonly, rocks brought above the surface have greater internal pressure than the surface causing rocks to crack then exfoliates.** ## Mechanical Weathering: Major Processes ### Thermal Expansion and Contraction - Alternate expanding and contraction of crystals due to heating and cooling - Extreme and sudden change in temperature - Campfires **Thermal expansion and contraction is a process where alternating expanding and contraction of mineral crystals in the rock structure due to heating and cooling. This happens over a long period of constant temperature change but can immediately happen during extreme and sudden change in temperature like in campfires.** ## Types of Weathering ### Biological Weathering - plants, animals, and microorganisms as agents of rock disintegration - integration of mechanical and chemical weathering - plants growing on rocks **The last type of weathering is biological weathering. Biological weathering is the disintegration of rocks due to biological activities of organisms such as plants, animals, and microorganisms. Mechanical and chemical weathering progresses biological weathering. One good example is when rocks are broken down into pieces because of the pressure exerted on it by roots as well as the chemicals released during root growth.** ## Types of Weathering ### Biological Weathering - lichen and algae inhabiting rock surface - lichen releases organic acids the minerals are consumed by the algae - process increases susceptibility of rocks to mechanical and chemical weathering **Biological weathering is also exhibited by the symbiotic relationship of a lichen and algae living on rocks. Lichen releases organic acids that break down rocks into minerals. These minerals are consequently consumed by the algae. If this process continues, the lichen-algae interaction gaps and holes in the rocks which makes it more susceptible to chemical and mechanical weathering.** ## Summary - **Chemical Weathering** - **Mechanical or Physical Weathering** - **Organic or Biological Weathering** **There are three types of weathering. First is the chemical weathering with three major processes including dissolution, hydrolysis, and oxidation. Second is the mechanical or physical weathering with three major processes including frost wedging, exfoliation, and thermal expansion and contraction. Third is the organic or biological weathering.**