Geo-For-Ce Finals Notes PDF

1. HEAT - a primary agent in metamorphism. - Facilitates recrystallization of minerals without melting the rock....

1. HEAT - a primary agent in metamorphism. - Facilitates recrystallization of minerals without melting the rock. - Heat originates from magma or the METAMORPHIC ROCKS geothermal gradient (temperature - Metamorphic comes from the Greek word increase with depth). means “changed form” - Rising temperature reorganizes atoms in - Comes from existing rocks that are minerals, forming new minerals. subjected to extreme heat and pressure. - Example: Gneiss forms from the heating - Created when extreme heat and pressure of shale or granite. changes the original rock into a new type of rock. 2. PRESSURE - Sedimentary, Metamorphic, and even - Pressure causes deformation and Igneous rocks can all become reorientation of minerals. Metamorphic rocks when exposed to heat - Confining Pressure: and pressure. Uniform pressure applied in all - Location: Found mainly in mountain directions. ranges (e.g., Himalayas, Alps, Rockies). Occurs with the burial of rock - Formation: Form deep in the core of beneath other layers. mountains due to high pressure. Leads to compaction and - Characteristics: Have ribbon-like layers, reorientation of minerals. a common feature in all metamorphic - Directed Stress/Differential Pressure: rocks. Pressure exerted more in one direction than others. Associated with tectonic forces. PROTOLITH Leads to foliation, where minerals align in planes. Example: Slate forms from the metamorphism of shale under differential pressure. 3. CHEMICALLY ACTIVE FLUIDS - Fluids, particularly water with dissolved ions, cause chemical reactions that alter the composition of the rock. - The original rock is referred to as the - They promote the growth of new minerals Protolith but it’s commonly referred to as by enhancing ion migration. the Parent Rock - For instance, the presence of fluids facilitates the transformation of limestone HOW METAMORPHIC ROCKS FORMED to marble. 4. TIME - Metamorphism is a process that occurs over geological timescales. - The longer the rock is subjected to heat and pressure, the more pronounced the metamorphic transformation 1 CLASSIFICATION OF METAMORPHIC ROCKS 3. GRANOBLASTIC / NON-FOLIATED ROCKS - Nonfoliated metamorphic rocks are 1. FOLIATION AND CLEAVAGE composed mainly of crystals that grow in - The most prominent textural feature of equant (equidimensional) shapes, such as regionally metamorphosed rocks is cubes and spheres, rather than in platy or foliation. elongate shapes. - Foliation is a set of flat or wavy parallel - These rocks result from metamorphic cleavage planes produced by deformation processes, such as contact of igneous and sedimentary rocks under metamorphism, in which directed pressure directed pressure. is absent, so foliation does not occur. - These foliation planes may cut through the Granoblastic Rocks include: bedding of the original sedimentary rock at Hornfels any angle or be parallel to the bedding. Quartzite - As the grade of regional metamorphism Marble increases, foliation becomes more Greenstone pronounced. Amphibolite - Slaty Cleavage: This slaty cleavage Granulite develops at small, regular intervals in the rock. 4. PORPHYROBLASTS - Found in rocks formed both by contact 2. FOLIATED ROCKS and by regional metamorphism. - Foliated rocks are rocks that possess a - Porphyroblasts form from minerals that layered appearance. are stable over a broad range of - They are formed through extreme pressures and temperatures. pressure in conjugation with heat, which - Crystals of these minerals grow large helps elongated minerals attain a foliated while the minerals of the matrix are being pattern, known as foliation. continuously recrystallized as pressures - This plating process creates thin layers and temperatures change, so they replace and directional patterns in the rocks parts of the matrix. The foliated rocks are classified according - Porphyroblasts vary in size, ranging from to four main criteria: a few millimeters to several centimeters in a. Metamorphic grade - diameter. Metamorphic grade is a general - Common minerals that form term for describing the relative porphyroblasts include garnet and temperature and pressure staurolite, although many others are also conditions under which found. metamorphic rocks form b. Grain (crystal) size c. Type of foliation d. Banding - the rock consists of alternating, thin layers (typically 1 mm to 1 cm) of two different mineral compositions. 2  SCHIST (foliated) - forms at higher temperatures and pressures and exhibits mica crystals that are large enough to see without magnification. - Individual crystal faces may flash when the sample is turned in the light, making the rock appear to sparkle. - Other minerals such as garnet might also be visible, but it is not unusual to find that schist consists predominantly of a single mineral. SLATE (foliated) - forms from the low-grade metamorphism of shale. - Slate has microscopic clay and mica crystals that have grown perpendicular to the maximum stress direction - tends to break into flat sheets or plates, a property described as slaty cleavage GNEISS (foliated) - forms at the highest pressures and temperatures, and has crystals large enough to see with the unaided eye. - Gneiss features minerals that have separated into bands of different colours. The bands of colours are what define foliation within gneiss. Sometimes the bands are very obvious and continuous (Figure 10.17, upper right), but sometimes they are more like lenses (upper left). PHYLLITE (foliated) - is similar to slate, but has typically been heated to a higher temperature. As a result, the micas have grown larger. - They still are not visible as individual crystals, but the larger size leads to a satiny sheen on the surface. - The cleavage of phyllite is slightly wavy compared to that of slate. 3 MARBLE (non-foliated) depending on the conditions and parent - is metamorphosed limestone rock. - When it forms, the calcite crystals - Crystals remain randomly oriented recrystallize (re-form into larger blocky because pressure wasn’t substantially calcite crystals), and any sedimentary higher in any particular direction. textures and fossils that might have been - The hornfels in the figure appears to have present are destroyed. gneiss-like bands, but these reflect the - If the original limestone is pure calcite, beds of alternating sandstone and shale in then the marble will be white. On the other the protolith, not alignment of crystals due hand, if it has impurities such as clay, to metamorphism. silica, or magnesium, the marble could be - In the microscopic view, brown mica “marbled” in appearance crystals (biotite) are not aligned. QUARTZITE (non-foliated) METAMORPHISM VS. PLATE TECTONICS - is metamorphosed sandstone - Metamorphic rocks form when existing - It is dominated by quartz, and in many rocks are subjected to high heat, pressure, cases, the original quartz grains of the or chemically active fluids, causing sandstone are welded together with physical and chemical changes without additional silica. melting. This transformation typically - Sandstone often contains some clay occurs deep within Earth's crust, often minerals, feldspar or lithic fragments, so near tectonic plate boundaries. quartzite can also contain impurities. - Tectonic plates influence the formation of metamorphic rocks through processes like continental collisions, subduction, and mountain building. At convergent plate boundaries, intense pressure and heat alter rocks as they are buried or subjected to tectonic forces, driving the metamorphic process. - Soon after the theory of plate tectonics was proposed, geologists started to see how patterns of metamorphism fit into the larger framework of plate movements. HORNFELS (non-foliated) - Non-foliated metamorphic rock that normally forms during contact metamorphism of fine-grained rocks like mudstone or volcanic rocks. - Has different elongated or platy minerals (e.g., micas, pyroxene, amphibole) 4 TYPES OF METAMORPHISM Shock Metamorphism Regional metamorphism - the most widespread type of - which results from the heat and metamorphism, takes place where shock waves of a meteorite impact, both high temperatures and high transforms rock at impact site. pressures are imposed over large parts of the crust. Burial Metamorphism Contact Metamorphism - low-grade metamorphism that is caused by the progressive increase in pressure exerted by the growing layers of overlying sediments and sedimentary rocks - the heat from an igneous intrusion and by the increase in heat metamorphoses the rock associated with increased depth of immediately surrounding it. This burial. type of localized transformation normally affects only a thin zone of High-Pressure Metamorphism country rock along the zone of - along linear belts of volcanic arcs, contact. produced by continent-continent collision, occurs at high pressures. Seafloor Metamorphism DIFFERENT TYPES OF METAMORPHISM ARE LIKELY TO OCCUR IN DIFFERENT PLATE TECTONIC SETTINGS Continental Interiors - Contact metamorphism, burial metamorphism, and perhaps regional metamorphism occur at different levels in the crust. Shock metamorphism is likely to be best - is often associated with mid ocean preserved in continental interiors ridges. Hot basaltic lava at a because their large areal extent seafloor spreading center heats provides a large target area to infiltrating seawater, which starts to record rare meteorite impact circulate through the newly forming events oceanic crust by convection. 5  Divergent Plate Boundaries Tectonic Plates: - Seafloor metamorphism and - Plates fit like a puzzle and constantly contact metamorphism around move. plutons intruding into the oceanic - Plate boundaries contain many faults crust occur at divergent plate where earthquakes occur. boundaries CAUSES OF EARTHQUAKES Convergent Plate Boundaries - Plate edges can become stuck due to - Regional metamorphism, roughness. high-pressure and ultra-high - Stress builds up until edges break free pressure metamorphism, and along faults, causing earthquakes. contact metamorphism. - Earth's major earthquakes occur along tectonic plate boundaries, mainly in two Transform Faults belts: - In oceanic settings, seafloor 1. Circum-Pacific Belt (Pacific Ring metamorphism may occur. In both of Fire): oceanic and continental settings, - Surrounds the Pacific we find extensive metamorphism Ocean. caused by shearing forces along - Releases 80% of Earth's transform faults. - seismic energy. 2. Alpide Belt: - Extends from the Mediterranean through Asia. Other Active Zones: EARTHQUAKES Oceanic Ridges and Rift Valleys: - a sudden shaking of the ground caused by - Arctic and Atlantic Oceans the release of energy through seismic - East Africa waves - occur along faults at the edges of tectonic Reason for Patterns: plates - Earthquake activity aligns with Earth's - Annual Frequency: ~50,000 noticeable tectonic plate structure earthquakes worldwide. - Significant Damage: ~100 earthquakes CAUSES OF EARTHQUAKES annually impact populated areas. - Earthquakes are caused by the sudden Seismology: study of earthquakes; release of energy in the Earth's crust established in early 20th century when rocks under stress break along Fault/Fault Plane: Surface where Earth's faults, creating seismic waves that make blocks slip past one another. the ground shake. Hypocenter: The location beneath Earth's - The energy can be released by: surface where an earthquake starts. 1. Elastic strain. Epicenter: The point on Earth's surface 2. Gravity. directly above the hypocenter. 3. Chemical reactions. 4. Motion of massive bodies. Earth’s Structure: - The release of elastic strain is the most - Four layers: inner core, outer core, mantle, important cause because it is the only and crust. form of energy that can be stored in - Crust + upper mantle = a thin, fragmented sufficient quantities in the Earth to produce outer layer. major disturbances. 6 TECTONIC EARTHQUAKE - Hot, molten rock (magma) is - earthquakes associated with elastic strain buoyant, meaning it has a lower type of energy release density than surrounding rocks, Cause: causing it to rise through the crust - Occur when accumulated strain in and erupt on the surface. rocks exceeds their strength, - Similar principle to how hot air causing fractures along faults. rises, like in a hot air balloon. - Explained by the elastic rebound Temperature at Depth: theory - At depths > 20 km, temperature Example: ranges from 800-1,600°C. - 1906 San Francisco earthquake: Factors Affecting Eruption: Triggered by a 430 km rupture on - Viscosity (how easily magma the San Andreas Fault. flows). Fault Movement: - Gas content (H2O, CO2, S). - Rocks shift back to a less strained Types of Eruptions: position, generating seismic 1. Explosive Eruption: waves. - Large amounts of gas and - Types of movement: high viscosity (sticky) 1. Strike-slip: Horizontal magma. movement. - Example: Shaking a 2. Dip-slip: Vertical movement carbonated drink and (normal or reverse). releasing the cap. Range of Displacement: 2. Effusive Eruption: - Small to large shifts. - Small amounts of gas - Examples: and/or low viscosity (runny) 1976 Tangshan earthquake magma. 1999 Taiwan earthquake (slips up - Magma just trickles out as to 8 meters). lava flows. VOLCANO HOW DO VOLCANOES WORK? - Heat and pressure cause rocks to melt and form magma. - Magma needs to get out, too much pressure - Rise in temperature or drop in pressure causes magma to form faster. - Magma is forced onto Earth’s surface. - It dries and hardens, this happens many times over thousands of years. - Eventually a mountain called a volcano is formed. - A volcano is a place on the Earth’s surface where hot, molten rock (called magma) breaks through. - It is a vent or 'chimney' that connects molten rock (magma) from within the Earth’s crust to the Earth's surface. - The volcano includes the surrounding cone of erupted material. HOW AND WHY DO VOLCANOES ERUPT? Magma Movement: 7 The relationships between plate tectonics and volcanism are shown above. Magma is formed at MEASURING MAGNITUDE three main plate-tectonic settings: divergent Richter scale: Logarithmic, each unit boundaries (decompression melting), increase = 10x ground motion, 32x convergent boundaries (flux melting), and energy. mantle plumes (decompression melting). Moment Magnitude: Based on physical fault characteristics; more accurate for At a spreading ridge, hot mantle rock gradually large quakes. rises through convection, moving at a rate of centimeters per year. EARTHQUAKE HAZARDS When this rock reaches approximately 60 Earthquake hazards include primary and kilometers below the surface, decompression secondary effects that result from causes partial melting to begin. seismic activity. In the triangular region, around 10% of the Primary Hazards: Fault rupture and ultramafic mantle rock melts, generating mafic ground shaking. magma that ascends towards the spreading axis, Secondary Hazards: Landslides, where tectonic plates are pulling apart. tsunamis, fires, and structural collapse. This magma fills vertical fractures created by the Impact Scope: Earthquakes don’t only spreading and flows onto the seafloor, forming affect structures; they also impact basaltic pillow structures and lava flows. communities, economies, and An example of this spreading-ridge volcanism is ecosystems. found about 200 kilometers off the west coast. PRIMARY HAZARDS: FAULTING AND MAGNITUDE GROUND SHAKING - The total energy released by an Ground Shaking: Causes destabilization earthquake. and collapse of buildings. - A number which is a measure of energy Impact of Acceleration: Near the released in an earthquake epicenter, ground acceleration can exceed - Total energy, constant, depends on fault gravity, lifting objects off the ground. rupture. Infrastructure Damage: Buildings, bridges, and roads are severely affected, INTENSITY especially in dense urban areas. - The level of shaking and effects felt at Casualty Risk: Falling debris and specific locations. collapsing structures are the main causes - Intensity at a place is a measure of the of casualties. strength of shaking during earthquake - Effect at the surface, variable, depends on GROUND FAILURE: LANDSLIDES AND SOIL location and geology. LIQUEFACTION Landslides: Caused by shaking in hilly or mountainous areas, leading to rapid ground movement. Soil Liquefaction: Occurs when water-saturated soil behaves like liquid, causing structures to sink or tilt. Impact on Buildings: Structures on affected land lose stability, leading to additional risk and destruction. SECONDARY HAZARD: TSUNAMI Cause: Underwater earthquakes, especially in subduction zones, displace large amounts of seawater. 8  Speed and Impact: Tsunamis travel at - the process of evaluating the potential risk jetliner speeds in open water and reach and impact of earthquakes on a specific destructive heights near coastlines. area, region, or community. Deadliest Earthquake Hazard: Tsunamis - involves estimating the likelihood and have the potential to cause widespread potential consequences of seismic events, destruction and high casualty rates. such as ground shaking, liquefaction, landslides, and tsunamis FIRES AS A SECONDARY HAZARD Cause: Ruptured gas lines, downed BUILDING CODES AND power lines, and broken water mains that STANDARDS impede firefighting. - Building codes specify minimum standards Destructive Power: Fires often spread for the construction of buildings. The uncontrollably post-quake, especially codes themselves are not legally binding. when infrastructure is damaged. They serve, rather, as "models" for legal Historical Example: San Francisco jurisdictions to utilize when developing earthquake of 1906, where fires caused statutes and regulations. more damage than the quake itself. - The main purpose of building codes are to HUMAN CONSEQUENCES OF EARTHQUAKES protect public health, safety and general Loss of Life and Injuries: Most welfare as they relate to the construction casualties result from falling debris and and occupancy of buildings and collapsing buildings. structures. Psychological Impact: Survivors - The building code becomes law of a experience trauma, PTSD, and other particular jurisdiction when formally psychological effects. enacted by the appropriate governmental Social Impact: Homelessness and family or private authority. separations are common; in some cases, children are left orphaned. STRUCTURAL DESIGN ECONOMIC AND ENVIRONMENTAL CONSEQUENCES Economic Losses: Cost of rebuilding, loss of businesses, and economic instability. Environmental Impact: Landslides, pollution from ruptured pipelines, and damage to ecosystems. Long-Term Recovery: Rebuilding requires extensive resources, often placing strain on national economies. SEISMIC HAZARD VS. SEISMIC RISK - In the context of the impact of seismic Seismic Hazard: Measures the likelihood events on building, the subject of the and intensity of earthquake shaking in an structure is at the forefront. area. - Buildings need to have strong structural Seismic Risk: Includes damage potential, systems in place to withstand casualties, and economic impact; earthquakes. influenced by the population and - Using the proper structural systems, infrastructure. architects can improve a building’s Importance of Distinction: Knowing both capacity to withstand seismic forces and hazard and risk helps in developing reduce damage. targeted preparedness plans. SEISMIC HAZARD ASSESSMENT 9  Several building structures are designed seismic energy, reducing forces on the to support buildings and withstand building. earthquakes, including: 1. Reinforced Concrete Structures REDUCED DOWNTIME 2. Steel Structures - Quick recovery and minimal repair 3. Timber Structures requirements reduce downtime and 4. Hybrid Systems economic losses. MATERIAL SELECTION SUSTAINABILITY - Material selection in structural engineering - incorporate sustainable design principles involves choosing the most suitable to minimize environmental impact. materials for a given project based on factors such as design requirements, load capacity, environmental impact, and cost-effectiveness. - It requires a careful evaluation of various materials, including metals, concrete, timber, and composites, to identify the most appropriate option that optimizes HYDROLOGICAL CYCLE / WATER CYCLE both strength and sustainability. - describes the continuous movement of water between the Earth's surface and the CONSTRUCTION TECHNIQUES atmosphere. - Construction techniques refer to the It involves five key processes: methods, processes, and technologies used to build, assemble, and install structures, infrastructure, and buildings. - These techniques involve various materials, tools, and equipment to ensure safe, efficient, and sustainable construction practices. REDUCED DAMAGE - Reduced damage is rooted in the concept of "damage control." - The focus is on developing buildings that can absorb and dissipate seismic energy while sustaining minimal, repairable damage. - Engineers achieve this by localizing 1. Evaporation: The process where damage to known locations, making a substance changes from a liquid repairs or replacements easier if an to a gas, with water being the earthquake occurs. primary focus in meteorology. It - Ductility: requires energy, which can come Ductility allows structures to deform from sources like the sun, without failing, helping absorb seismic atmosphere, or Earth. This energy and reduce damage. process also cools surfaces, as - Redundancy: seen in sweating or water Redundant load paths ensure buildings evaporation on skin. can resist seismic forces even if some 2. Transpiration: The evaporation elements are damaged. of water from plants through - Energy Dissipation: small openings called stomata on Devices like dampers and isolators absorb the underside of leaves. It is mostly 10  a passive process influenced by atmospheric humidity and soil moisture. Only 1% of the transpired water is used for plant growth, while the remaining 99% is released into the atmosphere. 3. Condensation: The process of water vapor changing into liquid, forming clouds, dew, or - Global water abundance: 1.4 billion cubic water on cold surfaces. It occurs kilometers. due to a difference between air - Water is unevenly distributed, with temperature and dewpoint freshwater in rivers and lakes being temperature. small but vital for human use. 4. Precipitation: occurs when tiny - Reservoirs maintain balance through: condensation particles collide and Inflows: Rain, streams. grow too large for rising air to Outflows: Evaporation. support, causing them to fall to - Reservoir size remains stable when Earth. It can take the form of rain, inflows equal outflows. hail, snow, or sleet. Precipitation - The time water spends in a reservoir is is the primary source of fresh called its residence time. water on Earth, with the world receiving an average of 38½" (980 WATER BUDGET mm) annually over oceans and - assess the availability and sustainability of land. water supplies. 5. Runoff: occurs when excessive - Balance the rate of water storage change precipitation saturates the ground, with inflows and outflows in an area (e.g., preventing further absorption. It watershed). forms rivers and lakes, with most - Provide a foundation for effective water returning to the oceans and water-resource and environmental some evaporating to restart the planning. hydrologic cycle. A portion - Human activities (e.g., agriculture and percolates into the soil, urbanization) significantly impact the replenishing groundwater, or is natural water cycle. absorbed by plants for - These activities alter factors such as transpiration. infiltration, runoff, and evaporation. - Water budgets help assess the effects of - Water on Earth is stored in various these changes on the overall water cycle. reservoirs, including: Oceans (largest) THE WATER-BUDGET EQUATION Glaciers - states that the difference between the Groundwater rates of water flowing into and out of an Lakes accounting unit is balanced by a change in Rivers water storage. Atmosphere - The water-budget equation is simple yet Biosphere (smallest) universal, applicable over all space and - Water moves between these reservoirs time scales. through processes like evaporation, - It can be used for studies ranging from precipitation, and groundwater flow. rapid infiltration in a laboratory soil column to continental-scale droughts over decades or centuries. 11  EFFECT OF CHANGING CLIMATE TO WATER RESOURCES - Water is essential for human life and economic activities (e.g., drinking, agriculture, energy production). - Climate change is altering the water cycle, leading to water scarcity and flooding. - These changes disrupt water availability and quality, affecting human life and economic activities globally. - The water-budget equation is simple, KEY IMPACTS OF CLIMATE CHANGE ON universal, and adaptable, with minimal WATER RESOURCES assumptions about water movement and Warming Temperatures: storage: - Increased evaporation leading to water scarcity in some regions. - Altered precipitation patterns, causing more intense rainfall events and droughts. - Accelerated melting of glaciers and snowpack, impacting seasonal water flow and contributing to sea-level rise. - Water-budget equations can be Water Supply: expressed in terms of volumes, fluxes - Decreased water availability due to (volume per time), or flux densities droughts and increased (volume per area per time). They are often evaporation. organized in spreadsheets or tables, like - Strained water supplies for the example from Thornthwaite and agriculture, drinking water, and Mather (1955) for Seabrook, New industry. Jersey. Water Quality: - Increased pollution from runoff and erosion. - Saline intrusion into freshwater sources. IMPACTS ON OTHER SECTORS Energy production: Reduced water availability for hydroelectric power and thermal power plants. Infrastructure: Damage to water infrastructure due to extreme weather events. Human health: Waterborne diseases and heat-related illnesses. Agriculture: Reduced crop yields and water scarcity for irrigation. Ecosystems: Loss of biodiversity and habitat degradation. 12 ADAPTATION STRATEGIES - Water conservation - Improved water management - Protecting watersheds ADDITIONAL CONSIDERATIONS Equity and Environmental Justice: Disproportionate impacts on marginalized communities and Indigenous populations. Economic Implications: Impacts on agriculture, energy, and tourism industries. Global Cooperation: International cooperation is essential to address transboundary water issues and climate change mitigation. 13