Weathering and Erosion and Mass Wasting PDF
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This document discusses the processes of weathering and erosion, including mechanical and chemical weathering, and different types of mass wasting, like landslides and mudflows. It also covers the factors that cause these phenomena.
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WEATHERING AND EROSION MASS WASTING Weathering - It is a process where rocks, soil and minerals are broken down or worn Mass wasting refers to the downslope movement of rock, soil, and debris under away over...
WEATHERING AND EROSION MASS WASTING Weathering - It is a process where rocks, soil and minerals are broken down or worn Mass wasting refers to the downslope movement of rock, soil, and debris under away over time by natural elements like wind, water or even plants and animals, the influence of gravity. Also called Mass Movement. Types of Weathering Soil, debris, sediment, and broken rock is called regolith. Mechanical (Physical) Weathering - Involves the physical breakdown of rocks Mass wasting is driven by gravity; erosion is driven by natural agents like wind, without change in their chemical composition ice, and water. Exfoliation - is when pressure changes cause layers of rock to crack and peel away from the main rock. These pieces then slide down the hill because I. CLASSIFICATION OF MASS WASTING of gravity. (Granite, Gneiss) 1. Very Rapid Movement Frost Wedging - It occurs when water freezes in the cracks of rocks causing No water required the rocks to break. (Limestone, Sandstone, Granite) Landslide - is the rapid movement of rock, earth, or debris down Salt Wedging - happens when water evaporates, leaving salt crystals a slope due to gravity. behind. As these crystals grow, they push against the surrounding rock, 2. Slow Movement weakening it until it cracks and breaks apart. This process is most common Little water is required in dry places like deserts. (Limestone, Sandstone, Shale) Rock creep - This is the slow movement of rock fragments down Temperature Changes - Daily and seasonal temperature changes can affect a slope. It often takes years or even centuries to happen. rocks. When it gets warm, some minerals in the rock expand, and when it Soil creep - Similar to rock creep, but involves the slow cools down, they contract. This back-andforth can weaken the rock, downhill movement of soil. Over time, it can tilt structures like making it crack and break into smaller pieces. (Any rock type) fences or trees. Abrasion - It happens when rocks are worn down and smoothed out due to Solifluction - This occurs in cold regions where the ground is friction from other rocks or materials rubbing against them. (Any rock type) frozen most of the year. The top layer melts in warmer months. This melted, wet soil slowly slides over the still-frozen ground Chemical Weathering - involves the change in composition and structure of underneath. rocks and minerals through chemical reactions 3. Rapid Movement Carbonation - It occurs when carbon dioxide dissolves in water causing Enough water is required carbonic acid to form. This acid reacts with rocks causing a chemical Earthflow - This is a type of slow-moving landslide where change. saturated soil and rock, flow down a slope, often after heavy Oxidation - Breakdown of rock by oxygen, often giving iron-rich rocks, a rainfall. rusty colored weathered surface. Mudflow - This is a fast-moving flow of water mixed with soil Hydrolysis - A process where water reacts with minerals in rocks, causing and debris, typically occurring after heavy rains or volcanic them to break down and change. activity. Sheetwash - This refers to the layer of water flowing over the Biological Weathering - breakdown of rocks through the activities of organisms, ground during heavy rain, causing erosion by washing away the such as plants and burrowing animals Types: topsoil. Organic activity from lichen and algae - Lichens and algae often live on bare rocks and take minerals from them. This process weakens the rock and II. CAUSES OF MASS WASTING makes it break down. When plants decay, they create acids that help dissolve 1. Volcanic Eruptions - Volcanic activity weakens slopes and triggers the rock too. Additionally, as these living things grow and move, they gently landslides by shaking the ground, depositing ash or lava, and melting snow scrape and push against the rock, which helps wear it down even more. or ice. Mechanism: Produce acids that break down minerals 2. Earthquake Shocks - Earthquake shocks trigger mass wasting by shaking Ex. An example of biological weathering that is caused by mosses and the ground, loosening soil and rock, and weakening slopes, which can cause lichen growing on the face of a rock. landslides, rockfalls, and debris flows. Rock disintegration by plant growth - The most common form of 3. Weathering and Erosion - It contribute to mass wasting by breaking down biological weathering is when plant roots penetrate into cracks and crevices rocks and soil over time, making slopes weaker and more prone to collapse. of rocks and cause the rock to split or break into smaller particles through Erosion removes material from slopes, while weathering weakens them, mechanical weathering. Mechanism: Physically fragment rocks and aid soil both increasing the likelihood of landslides or other forms of downslope formation movement. Ex. An example of a tree that is growing between a crevasse in a rock 4. Intense Rainfall - causes mass wasting by saturating the soil, increasing its Burrowing and tunneling organisms - Burrowing and tunneling animals, weight, and reducing its stability, which can lead to landslides, mudslides, like worms and termites, help break down rocks by digging into them, or other downslope movements. causing them to crack and fall apart. Additionally, creatures like snails and barnacles attach to rocks and release acids that can dissolve the rock surface. III. TYPES OF MASS WASTING (Fall, Slide, Flow) Mechanism: Aerate soil and facilitate weathering 1. FALL Ex. The periwinkle snails on this rock are secreting acids that dissolve Rock Fall - Is when fragments or rock break off relatively easily from the rock. This picture is taken from a volcanic shoreline in Hawaii steep bedrock slopes, most commonly due to frost - wedging in areas where there are many freeze - thaw cycles per year. Erosion - It is the physical removal and transportation of weathered material by water, Occurs when a piece of rock or mass of rock becomes dislodged wind, ice, or gravity. and makes free -fall along steep cliff. Agents of Erosion 2. SLIDE Landslides - Are masses of rock, earth or debris moving down a slope. Water erodes rocks and the landscapes by transporting weathered materials When the force of gravity acting on a slope exceeds the resisting forces from their source to another location where they are deposited. of a slope, the slope will fail and a landslide occurs. Wind erodes materials by picking them up and temporarily transporting ✓ Translational Slide - is a type of landslide that occurs when a them from their source to another location where they are deposited, and mass of material moves down a slope along a planar surface, either stored or re-mobilized and transported to another location. such as a joint, fault, or bedding plane. Ice erosion occurs when particles are plucked up or incorporated by moving ✓ Rotational Slide - is a type of landslide that occurs when a mass ice, such as a glaciers, and are transported downhill, or when friction of soil or rock moves downward and outward along a curved between the ice and bedrock erodes materials and then transports them surface. downhill. Rock Slides - Is the sliding motion of rock along a sloping surface. Gravity facilitates the down slope transportation of loosened, weathered 3. FLOW materials and enables them to move without the aid of water, wind, or ice. Creep - The very slow — mm/y to cm/y — movement of soil or other unconsolidated material on a slope. You can't see creep happening but leaning fences and poles and broken retaining walls show where it has Agents Mechanism Common Loc Effects taken place. Carries and shapes Deserts, dry Sand dunes, Debris flow - Are hazardous flows of rock, sediment and water that Wind loose particles areas eroded landscapes surge down mountain slopes and into adjacent valleys. The material Rivers, involved is gravel-sized or larger. Transports River valleys, coastlines, Mudflow -a River of liquid and flowing mud on the surfaces of Water sediments and sediment heavy rainfall normally dry land areas, as when earth is carried by a current of water. shapes land deposition areas Continental IV. IMPACTS OF MASS WASTING Abrasion from Breaking off the Ice Glaciers Economic, Environmental, Human particles in the ice pieces of rocks (Lakes) Oso Landslide (2014), Batang Kali Landslide (2023) Movement of soil Hillsides, steep Landslides, Mass wasting threatens human communities but human activities may cause mass Gravity and rocks downhill slopes rockfalls wasting. It is responsible for shaping the earth and forming different landforms. Mass wasting is the movement of earth material under the influence of gravity It causes destruction to human beings, if it occurs in living areas COMPONENTS OF THE HYDROLOGIC CYCLE Failure The circulation of water masses seen in all spheres of the earth involves several Material Type Movement Type causative factors and components. The major components (or) elements of the VERY RAPID hydrologic cycle are: Rock Fall A large rock body FALL (>10s m/s) 1. Evaporation: Evaporation is the process of converting a liquid (or) solid Rock Soil or other overburden in some SLOW (mm/y to into a gas, through the transfer of heat energy. In hydrologic cycle, this SLIDE Slide small cases, mixed with ice cm/y) conversion is towards water vapor. Heat energy can convert water mass (or) Thick deposits of unconsolidated SLOW (mm/y to Creep FLOW ice into a vapor. sediment cm/y) The factors affecting evaporation are: a) Air Temperature b) SLOW-RAPID Slump A large rock body SLIDE Relative Humidity c) Duration of bright Sun shine. (cm/y to m/y) Loose sediment with a significant RAPID (cm/s to 2. Condensation: The process of water changing from a gas to a liquid or solid Mudflow FLOW (ice) state is called "condensation, " component of silt and clay m/s) Debris RAPID (cm/s to It is the process where the sun’s radiant energy evaporates water Sand, gravel, and larger fragments FLOW from surface water resources, including seas and oceans. This Flow m/s) water rises upwards as water vapor and reaches the atmosphere. The higher the temperature or atmospheric pressure, the more LANDFORMS water vapor the air can hold then the process of evaporation Landforms are the natural features that make up the Earth’s surface. continues until the air becomes fully saturated with maximum Landforms have different physical features such as the type of soil, water, or rocks amount of moisture. It is called as Saturation Humidity. covering the surface. Cloud Condensation Nuclei - is an object with a radius of at They are shaped by nature and take thousands or millions of years to form. least one micrometer on which water molecules can condense. 3. Precipitation: Precipitation is the process of transforming the water vapor LANDFORM PROCESSES into a liquid or solid form, depending upon the temperature of air near the 1. Internal Process - The processes that operation within the Earth or inside the clouds. Earth are called Internal processes or Endogenic Processes, “Endo” means inside. The term precipitation is a common term. It includes a variety of Internal process, primarily driven by Plate Tectonics (heat and pressure) leads to forms of precipitation. It includes mist, rain, snow, sleet, and the upliftment and sinking of the Earth’s surface at several places. Internal process hail. are building up landforms. Precipitation mainly depends on the water vapor present in the 2. External processes - also known as Exogenic Processes, “Exo” means “from atmosphere. When the air temperature is well below the freezing outside or external”. External process is continuous cycle of wearing down point, clouds may form tiny ice crystals. (denudation) and rebuilding of the land surface through weathering, erosion, and Kinds: Rain, Snow, Sleet, and Hail deposition driven by forces outside the Earth. For precipitation to form, a sequence of four processes must occur: 1) atmosphere must have sufficient water vapor present, TYPES OF LANDFORMS which is cooled to dew point, 2) growth of water droplets, and 1. MOUNTAIN - is a landform that rises high above its surroundings. It usually has 3) importation of water vapor. steep slopes and a rounded or sharp peak. Rainfall - is most common form of precipitation occurring in A mountain range is a series or chain of mountains that are close together. almost all parts of the world. In tropical regions, precipitation is a. Fold mountain - These are formed when two or more tectonic plates expected completely as rainfall. collide with each other. Snowfall - is another form of precipitation. It comes as a b. Fault-block mountain - These are formed when faults or fractures in percentage of annual precipitation. In the polar regions, Earth’s crust, push rocks upwards and downwards. precipitation is expected to be completely as snowfall c. Dome mountain - These are formed when magma under the Earth makes 4. Transpiration: Transpiration is the process of releasing the water absorbed its way towards the surface without breaking it. by the plants through their root system after utilizing the nutrients for d. Volcanic mountain - These are formed when molten rocks move building their tissues, in a specified time. upward, pushing the surface upwards and then erupt, forming a volcano. Transpiration is dominant during the growing season of crops in 2. PLATEAU - An elevated landform with a flat, table-like surface on top. Plateau agricultural lands. Most of this happens during day time, when can be built by the same forces that create mountains, but unlike mountains, their photosynthesis is active in plants. peaks are often eroded and flattened by wind and rain. The controlling factors of transpiration are: a) Solar radiation 3. PLAIN - A flat or low relief area on the surface of the earth. Plains are formed b) Wind; and c) Soil moisture primarily by erosion and the deposition of sediment. 5. Evapotranspiration: Evapotranspiration is the combined effect of both 4. VALLEY - A low-lying area of land between hills or mountains that are formed evaporation of water from the soil, surface, water bodies, snow, ice and due to the actions of glaciers and rivers over million of years. V-shaped valleys transpiration from vegetation. are formed by the flowing rivers and U-shaped valleys are formed due to glaciers. In an agricultural irrigated land, it is difficult to separate 5. ISLAND - A piece of land which is surrounded by water from all sides. A group evaporation from transpiration. of islands is called an archipelago. The total water loss due to both evaporation and transpiration is a. Oceanic Islands - are those that rise to the surface from the floors of the called as evapotranspiration. ocean basins. These are formed primary through volcanic activity. b. Continental Islands - are simply unsubmerged parts of the continental The actual evapotranspiration depends mainly on: a) shelf that are entirely surrounded by water. Atmospheric factors b) Soil water characteristics and c) 6. HILLS - A landform higher than the surrounding land with a visible summit. Hills Physiological factors of the crops and other vegetation may formed by geological processes such as erosion, volcanic activity and the 6. Surface Runoff: Runoff is the quantity of water that is discharged (“runs movement of tectonic plate. off”) from a drainage basin during a given time period. The term runoff refers to the overland flow of water, after every rainfall or snowmelt. Initially, Runoff starts as small streams and THE HYDROLOGIC CYCLE the water gets added from many such streams. Finally, all of The Earth contains enormous amounts of water in the form of reservoirs. Water these reach and confluence with a lake or stream or directly with exists in the atmosphere, lithosphere, hydrosphere and biosphere. Among all these seas. segments, water masses are in continuous circulation. Factors Controlling Runoff: 1. Rainfall – Intensity and Type. It is, in general, called as the hydrologic cycle. It is also called as the World’s 2. Duration of Rainfall. 3. Distribution of Rainfall. 4. Great Water Cycle, since it is the driving wheel for all the movements of Direction of Storm Movement. 5. Soil Moisture Condition available water resources on the planet earth 7. Infiltration: Infiltration is the downward percolation of rainwater (or) snow melt water into the soil horizons. The downward movement of water THE WORLD’S WATER happens in the top soil layer, especially through the smaller pore spaces The world’s water is not in static form. It is in continuous motion. It also present in the soils transforms from one state to another. The water gets temporarily stored and 8. Interception: Interception is the process of retaining water on the leaves of moved in the form of surface water in rivers, lakes, ponds, ice caps, and below vegetation. A small amount of rainfall is intercepted by vegetation. the surface as groundwater. Oceans form the biggest and largest water reservoirs. The rainfall which is not intercepted is known as through fall. All these water bodies are called water reservoirs. The water which reaches the ground via steps and that is called as stemflow. THE EARTH AS A WATER PLANET 9. Groundwater baseflow: The rainwater that is falling over the ground The planet earth is called as the water planet. It is due to the fact that the earth is surface percolates down through the soil and reaches the groundwater zone. probably the only planet, in the solar system, which has a huge mass of water. Depending upon the slope of the groundwater system, the On the planet earth, the primitive life got originated only from the water mass. groundwater moves towards the rivers, lakes or the oceans. This Most of the earth’s surface is covered with water. flow of groundwater is known as baseflow. 10. Sublimation: Snow covered zones also experience losses of water through CONCEPT OF HYDROLOGIC CYCLE direct evaporation. The process of direct evaporation of snow into water Water gets transformed from liquid to solid, solid to liquid, liquid to vapor, vapor vapor is known as sublimation. The solid does not pass through a liquid to liquid and vapor to solid states. state for evaporation. It is very difficult to distinguish between evaporation The sun’s radiation, acceleration due to gravity, ability of the water to flow and and sublimation from snow. several other properties of water, make this transformation more effective and regular.