Earth Science Q2 Reviewer PDF

EARTH SCIENCE rainwater, groundwater, and Q2 REVIEWER surface water. by: 11-Coulomb 3. Industrial water - used by industries...

EARTH SCIENCE rainwater, groundwater, and Q2 REVIEWER surface water. by: 11-Coulomb 3. Industrial water - used by industries, factories, and other LESSON 1: WATER & SOIL production facilities. It can be RESOURCES sourced from groundwater or surface water at the industry WATER RESOURCES AND site. MANAGEMENT 4. Medical water - used in the Water covers 71% of Earth's surface and medical industry for sterilization is classified as saline or freshwater. purposes. It kills microscopic organisms on medical tools and Saline water constitutes 97.5% of Earth's other objects to prevent water, mainly in oceans. infections. Freshwater comprises 2.5% of Earth's Water Cycle water, with a low concentration of salts The Hydrologic Cycle shows the and solutes. natural process of water’s never-ending movement within the - 79% is stored in ice caps and Earth and its atmosphere. glaciers. - 20% exists as groundwater. Water changes its state (solid, liquid, - 1% is found in other freshwater gas) to move from one place to sources like rivers, lakes, soil, and another. water vapor. Water Resources 1. Domestic water - used in homes Processes: for activities such as drinking, 1. Evaporation - water turns into cooking, bathing, and washing. vapor and rises into the It is sourced from water atmosphere companies, groundwater, and 2. Condensation - water vapor cools other supplies. and forms clouds. 3. Precipitation -water falls back to 2. Agricultural water - essential for the Earth as rain, snow, sleet, or crop irrigation and maintaining hail. livestock. Sources include 4. Snowmelt - solid precipitation (snow) turns into liquid water.  5. Groundwater flow - water moves are bacteria, viruses, fungi, and slowly underground through parasites. porous rocks and soil. - Pesticides and other chemical 6. Percolation - water seeps into the pollutants from industries could ground. result in nutrient enrichment, 7. Transpiration - plants release which occurs when a body of water vapor into the air. water receives excessive nutrients such as nitrogen and Water Pollution phosphorus. Water pollution is the anthropogenic (human-caused) contamination of water Water Management bodies. Water management refers to all activities encompassing planning, Eutrophication pollution is caused by developing, distributing, and optimizing the dumping of wastes, increasing water resources. nutrients, and decreasing oxygen levels, leading to algal blooms (massive Organizations and Laws that focus on growth of algae) and dead zones (areas Conserving Water Resources with low oxygen levels). - United Nations Environment Acid rain produces rainwater with a Programme (UNEP) is the leading lower pH than normal. environmental authority whose - Refers to any form of goals focus on sustainable precipitation with acidic development. components (causing - Water.org focuses on building acidification of water & soil wells and providing seminars that bodies), such as sulfuric or nitric tackle the importance of good acid, that fall to the ground from hygiene and practices. the atmosphere. - It is now considered an - Miya focuses on the reduction of anthropogenic process. freshwater loss through urban - It can cause the acidification of design practices. bodies of water and soil. - WaterIsLife developed “the straw”, a product that can reduce Other Factors Affecting Water Quality the chances of people being - Changes in salinity can result infected by waterborne diseases. from changes in water levels, either by dilution or an increased - Presidential Decree 1586 features concentration of salt. the identification of - Pathogen is any disease-causing environmentally critical areas agent. Examples of pathogens (ECAs). Areas such as water  bodies, mangrove areas, and Pedology- studies the soil’s chemistry, recharge areas of aquifers are formation, classification, and other identified. characteristics. - Republic Act 9275 or the Philippine Clean Water Act of Soil Formation 2004, designates water bodies 1. Rock Disintegration - forces all like rivers as water quality work together to break down management areas. (WQMA) rocks into smaller particles that - Presidential Decree 1067-IRR will eventually create soil. ensures the implementation of 2. Simple organisms thrive - simple WATER CODE or the rules that organisms grow from the indicate the appropriate disintegrated rock. utilization of water and control 3. Soil slowly develops - the soil can conservation of water resources. now support plants with roots. 4. Soil develops to support thick Soil vegetation - the soil can now Processes that happen with the soil: handle varieties of plants. - Hydrologic cycle - Nitrogen cycle Factors Affecting the Formation of Soil - Carbon cycle - Parent material - where regolith comes from Soil - Residual soil - soil that forms in - an unconsolidated regolith the area where the parent modified over time by water, air, material is and organic material. - Transported soil - soil transported - Rock and mineral fragments in by different kinds of media. the soil are known as regoliths. - This is where the subsystems Time - the characteristics of soil change meet. depending on how long it is exposed to - Soil with 45% minerals, 25% air, forces and elements. 25% water, and 5% organic Climate - affects the formation of soil materials is believed to be in through temperature and precipitation. good condition for plant growth. Organisms - plants and animals that Edaphology - the study of soil as a contribute to the number of organic habitat for organisms and assesses how materials found in the soil. Also includes different organisms can survive and use decomposition, consumption of plants, soil as subsistence. etc. Topography - involves the characteristics of the surface of the land. Soil formation and composition are affected by factors like erosion and slope. Weathering - Processes that break down rocks and can be accelerated by factors like plants and animals. Horizons of Soil 1. Organic Layer - composed of many organic materials and is usually rich in organisms. 2. A Horizon - composed of minerals - A way of classifying soil based on and humus. This is where plants its particle composition. This live. involves how much clay, silt, and 3. E Horizon (Horizon of elluviation) sand are found in the soil. - eluviation is the washing out of minerals and soil particles by - To determine the soil type, the water. percentages must be plotted into 4. B Horizon - where washed-out the soil triangle. Each and leached materials are found. corresponding component is 5. C Horizon - lowest layer; where found on one side of the triangle plant material is found, and little which is marked with numbers soil formation. from 0-100. Note that the intersection of the percentage of Soil Texture soil on each side determines the The proportions of the differently-sized soil type. particles within it. This influences how water and air pass through or are Arable Land - a land that can be used retained. for farming. It has the following: Basic Types: Sand, Silt, Clay - ample nutrients (carbon dioxide, nitrogen, oxygen, phosphorus, Soil Triangle etc.) - proper aeration - an adequate amount of water Humans rely on agricultural land for food crops and domestic animal rearing. The type of soil affects whether the land - Alfisols - very fertile and is arable or not. moderately weathered. Found near old rivers, hills, and 9 Orders of Soil in the Philippines plateaus. Fruiting plants grow here. - Andisols - come from volcanic - Inceptisols- slightly developed ash and are considered to be soils. Occur along terraces, young. Found in volcanic areas. alluvial plains, mountains, and Many fruiting plants grow on hills. Rice and fruit trees grow andisols. here. - Histosols - high in organic - Entisols - underdeveloped soils. material; found in wetlands and Frequent disturbance Desert. with poor water drainage. Commonly found near coastal The land use and locations of these soils areas, lakes, and marshes. in the country vary based on type. Coconuts and mangroves grow on these. Mariano and Valmidiano’s Map (1973) - Oxisols - highly weathered, with no distinct layers, and found in tropical regions.Found in hilly areas. Grass and cogon grow on top of these. - Vertisols - have high amounts of clay which shrinks and expands depending on water content. Found in plains where rice and vegetable crops are found. - Ultisols - heavily weathered and subjected to high amounts of leaching. Found in elevated areas, terraces, and mountains. Pineapples, cassava, banana, and forest tree species grow on - Andisols, histosols, and mollisols these. were not included in the map. - Mollisols - found in grrasslands - Histosols and mollisols were and are rich in humus. Found in observed to a limited extent. alluvial fans with mixed volcanic - Ultisols cover 41.5% of the land and sedimentary materials. area of the country which is Coffee and banana plants grow approx. 8.6 million hectares. on these. 1991 - Improper cultivation practices The Philippines had 10 million hectares can alter soil particle size which of agricultural land. Crops and plants affects water and nutrient include rice, corn, coconut, sugarcane, movement in the soil. and banana. Well-irrigated lands are - Urbanization increases the almost exclusively riced lands. amount of pollution. - Overgrazing contributes to the Conserving and Protecting Soil erosion of soil. Resources Organizations that Seek to Conserve Soil Degradation - the change in soil the Soil health that results in a decreased capacity of the soil to support - Food and Agriculture organisms. With the current rate of soil Organization (FAO) aims to make degradation, we may lose the topsoil in agricultural activities more 60 years. sustainable. Physical Factors - include rainfall, - Asia Soil Conservation Network runoff, floods, wind erosion, tillage, and for the Humic Tropics (ASOCON) mass movements. It also triggers works to increase awareness of erosion and alteration of the soil proper soil conservation composition. practices. - British Society of Soil Science Biological Factors - these include poor studies soils and encourages farming practices and alteration of participants who are interested organism composition. in soil use. - Land Institute aims to end soil Chemical Factors - include the erosion. alteration of soil pH and buildup or leaching of nutrients in the soil. In The Philippines: - Soil Conservation and Anthropogenic Factors Management Division (SCMD), a - Deforestation exposes the soil technical division of the Bureau and affects the retention of of Soils and Water Management. water. (BSWM), plays a role in the - Pesticides and fertilizers can alter implementation of sustainable the composition of soil and land management to address organisms. land degradation. - Industries and mining activities reduce nutrients or increase the number of toxins in the soil. LESSON 2: GEOLOGIC PROCESSES ON 2. Reducing Farmland Conversion EARTH’S SURFACE 3. Planting Vegetation EROSION 4. Application of Organic Fertilizers - Transportation of weathered 5. Constructing Retaining Walls rocks How do plants prevent soil erosion? - Driven by natural agents like running water, wind, and glaciers TYPES OF EROSION 1. Water Erosion 2. Wind Erosion - Mainly occurs in deserts 3. Glacial Erosion CAUSES OF EROSION MASS WASTING - Downslope movement of rock, 1. Erodibility - Susceptibility of soil regolith (unconsolidated to erosion material), and soil driven by the force of gravity 2. Texture - Proportion of different particle sizes (sand, silt, and clay) - Can occur with or without the within the soil presence of a transporting medium 3. Overgrazing - Occurs when livestock graze an area SLOPE - Steepness or incline of a land excessively, leading to the surface depletion of vegetation cover 4. Cutting - Removal of vegetation, particularly trees and shrubs 5. Contaminants - Harmful substances that can degrade soil quality FACTORS THAT CAUSE WEAKENING OF SLOPES PREVENTING SOIL EROSION 1. Undercutting by Water 1. Steep terrains are shaped to produce flat areas Undercutting - When a stream (river) or - Damp Sand - Contains some waves erode the bottom of a slope or moisture, increasing cohesion cliff and stability - Can lead to oversteepened - Dry Sand - Has low cohesion (the slopes, which are steeper than ability of particles to stick the natural angle at which together), making it less stable materials can rest without sliding and more likely to slide. - Increases the chance of it - Water-Saturated Sand - When collapsing. saturated, sand can lose its strength and become more prone Angle of Repose - Steepest angle at to sliding because the water can which different materials, such as sand separate the grains. or gravel, can stay stable without sliding down - Fine Sand - Generally has a low angle of repose; can’t be as steep without sliding - Coarse Sand - Has a higher angle of repose; can be a bit steeper before it starts to slide Cohesion - Attraction between Angular Pebbles - Can have an even molecules of same substance (e.g. water higher angle because their shape allows droplets) them to fit together tightly Adhesion - Attraction between molecules of difference substances (e.g. water sticking to a glass) 3. Role of Vegetation - Plants have extensive root systems which hold the soil together, thus 2. Influence of Moisture on Soil preventing mass wasting or soil Stability - When soil is slightly erosion. wet, water creates surface tension, which helps create a 4. Impact of Deforestation - high angle of repose, and hold Removal of vegetation the soil grains together. (deforestation) can lead to  increased mass wasting, surface moderately moves particularly after heavy rainfall downslope (permafrost melting) - Less plants = less root support = - Produces ripples soil more vulnerable to erosion 5. Geological Factors - Presence of joints, ratures, and bedding planes may influence the occurrence of mass wasting TYPES OF MASS WASTING 3. Slump - When blocks of material 1. Soil Creep - Slow, gradual move from extremely to downhill movement of rock under moderately slow downhill along a the influence of gravity concave, curved surface - Produces ripples - Often results in the formation of a crescent-shaped scarp at the top and a bulging toe at the bottom of the slope 2. Solifluction - When water-saturated soil over frozen 4. Earthflow - Contains less water - Contains significant amount of content and less fluid than gravel, rocks, and even larger mudflows pieces of debris 7. Debris Slide (Debris Avalanche) Very rapid downslope movement of a mixture of rock, soil, 5. Mudflow - Highly saturated flows vegetation, and other debris that resemble wet concrete due to its high water content 8. Rock Fall - Quickest type of mass 6. Debris Flow - Mixture of clay, silt, wasting with extremely rapid, sand, and rock fragments in free-falling rocks which more than half of the material is made up of coarse particles that are larger than sand grains  - Transportation medium affects how and where the particles settle: - Water can carry a range of particle sizes, with faster water currents transporting larger particles. - Wind primarily transports finer particles like sand and silt, which settle when the wind's velocity decreases. MEASURES TO PREVENT DISASTERS SPHERICITY 1. Hazard maps are used to identify - Degree of by which a material areas susceptible to landslides. approaches the shape of a sphere 2. Engineering measures are also applied before any hillslope - High sphericity particles are development. easier to transport because their smooth, rounded shape reduces 3. Soft mitigation measures such as resistance, allowing them to information and educational move more freely through water campaigns. or wind. SEDIMENTS - Low sphericity particles, with - Loose, unconsolidated solid angular shapes, face more particles from weathering and resistance, making them harder erosion of pre-existing rocks, to transport. precipitation of minerals dissolved in water, and remains ROUNDNESS of plants and animals - Degree of abrasion a sediment particle has undergone, as SEDIMENTATION observed by the sharpness or - Process where solid materials smoothness of its edges and (sediments) are deposited corners horizontally after being carried by different agents such as - Well-rounded sediments have water, wind, ice, or gravity smoother, less angular edges, typically due to long-distance  transport and continuous PROPERTIES OF SEDIMENTS collision with other particles. SORTING - Angular sediments have sharp - Degree of uniformity in grain edges, indicating they have not sizes been transported far from their source. - Influenced by the energy of the transporting medium - Well-sorted sediments contain grains of similar size, often resulting from consistent transport conditions (e.g., wind or waves). - Poorly sorted sediments have a mix of particle sizes, indicating varying transport energy (e.g., a river that changes flow rate). - The energy of the transporting medium (water or wind) determines sediment movement and deposition. - High energy, like fast river Wentworth Scale (1922) - Classifies currents, can carry larger sediment particles based on their particles (e.g., gravel). When the diameter, expressed in phi (φ) units, energy decreases, heavier which are the negative logarithm of the particles settle first, followed by particle's size in millimeters lighter ones as the flow slows. - Similarly, wind can transport fine sand and silt, but they settle when the wind speed drops. Thus, the energy level directly affects where and which particles are deposited. When the velocity is high, the medium can carry larger  particles, but as the velocity - Process of decomposition and decreases, the energy also drops, disintegration of rocks leading to deposition. PHYSICAL/MECHANICAL WEATHERING - Rocks are broken down into smaller pieces - No change in chemical composition - Factors: Fluctuating temperature and pressure, and biological activity. 1. Abrasion - Physically worn down by EFFECTS OF SEDIMENTATION contact with other materials. (wind, water, ice 1. Natural sedimentation helps add or rocks) nutrients to the soil, and most of the time develops the coastal 2. Thermal Action habitats such as coral reefs, - Constant cycle of lagoons, and wetlands. expansion and contraction, causes rocks 2. Corals are mostly affected when to fracture and break there is excessive sedimentation. down into smaller pieces. Since corals do not move, sediments simply lie on top of 3. Frost Wedging them, and later on kill them. - Repeated cycles of freezing and thawing of 3. Siltation is a type of pollution ice. that occurs when silt or clay dominates a body of water. FROST WEDGING HAS 3 CONDITIONS: 4. It refers to the increased amount - Sufficient moisture; of suspended sediments and - Pre-existing cracks or pore accumulation of fine particles at spaces and fractures by which the bottom of a stream. water can penetrate; - Temperature frequently rises and LESSON 3: WEATHERING falls past above or below freezing point. WEATHERING  4. Salt Crystal Growth - Carbon Dioxide + Water = - Salt crystals are left in Carbonic acid pore spaces when - Reaction of CO2 with seawater evaporates. water to form carbonic acid, which then reacts 5. Biological Activity with minerals like - Plants and animals reduce carbonates (e.g., limestone the size of rock, becoming & marble) to dissolve susceptible to weathering. them. 6. Unloading or Exfoliation 5. Chelation - Erosion or uplift, thick - Organic acids, often from layers of sediments are plant roots or decaying removed. organic matter, form complexes with metal ions CHEMICAL WEATHERING - Easily removed by water - Changed into other substances that have different physical and 6. Acid Rain (Sulfuring and Nitric chemical compositions. Acid) - AGENTS: water, strong acids, and - Caused by industrial oxygen. pollutants like SO2 and NO2 1. Dissolution - Forms H2SO4 and HNO3 in - Minerals dissolve in water the atmosphere, which - Often enhanced by acids then reacts with minerals. like carbonic acid. - FACTORS OF WEATHERING OF ROCKS 2. Hydrolysis - Surface Area - Water reacts with a - Climate mineral to form a new - Rock Composition mineral. 3. Oxidation - Minerals interact with oxygen, often forming oxides. - Common with iron-bearing minerals. 4. Carbonation  RESISTANCE TO WEATHERING - Collapsed clouds occur because the accretion of more materials leads to an increase in gravitational attraction causing the contraction of the Earth into a smaller volume which will then enable it to spin faster - Compaction of dust clouds resulted in conversion of gravitational energy into Slow Weathering - Quartz heat energy. Fast Weathering - Olivine RADIOGENIC HEAT - Unstable elements undergo LESSON 4: INTERNAL HEAT OF THE radioactive decay to attain EARTH PLATE TECTONICS stable form - Process of radioactive decay Internal Heat of Earth produces heat as byproduct - Fuels the planet’s dynamic processes Decay Radiation Model - Produced by residual heat Type Emitted (extraterrestrial impacts and gravitational contraction) and Alpha radiogenic heat Decay RESIDUAL HEAT Extraterrestrial Impacts Beta - According to Nebular Decay Theory, Earth was formed through the accretion of particles from a rotating Positron cloud. Emission - kinetic energy produced by moving extraterrestrial Electron X rays objects is converted to Capture heat energy. Gravitational Impacts  gaseous form in the surface of Gamma Emission Earth - Ex: Water and Carbon Dioxide Spontaneo Neutrons - Magma forms when us fission volatiles mix with hot mantle rock ADDITIONAL TERMS: a. Geotherm - temperature MAGMATISM as a function of depth - Magma b. Solidus - conditions at Molten rock material which rock starts to melt produced by partial c. Liquidus - conditions at melting of mantle and which rock completely crust melts Has liquid, gases, crystals, and rock fragments VOLCANISM - Occurs along plate boundaries or - Process where magma rises to margins and sometimes within the surface as lava plates. Cracks on Earth’s crust - Destructive event ( damage are the result of these plate infrastructures, cause injuries, boundaries short-term climate changes) , a - In effect, hot mantle rock constructive process penetrates the crust and - Atmosphere was formed through becomes magma release of volcanic gases and - Classifications of Plate new oceanic crust is continuously Boundaries: Convergent, produced along mid-oceanic Divergent, Transform ridges - formed many islands FORMATION OF MAGMA 1. Temperature - increases with FORMATION OF VOLCANO depth called geothermal gradient - Volcano - Increase induces melting A hill or mountain where 2. Pressure - decrease causes adiabatic decompression lava, pyroclastic materials, - Pressure ↓ = Melting temp and gases erupt of materials ↓ Can form along plate 3. Volatiles - substances that boundaries or within evaporate easily and can exist in plates - Divergent plate boundaries = volcanism manifest as ridges or  fissures where products of Discordant structures - cut decompression melting erupt across existing structures - Convergent plate boundary host - Ex: dike (igneous large no. of volcanoes ( made up body that cuts of lava flows and pyroclastic across bedding materials) surfaces or other structures of the TYPES OF LAVA FLOW country rock) 1. Pahoehoe Concordant bodies - Pronounced pa-hoy-hoy - Injected parallel to - Smooth and ropy surface features in the 2. Aa country rock such - Pronounced ah-ah as sedimentary - Jagged and angular beds corners METAMORPHISM VOLCANIC ROCKS - Greek word “meta” meaning to - Formed when lava solidifies change and “morph” meaning - Minerals in these rocks are form fine-grained compared to - Process of changing the plutonic rocks which are coarser characteristics of a rock as a - Ex: basalt, andesite, rhyolite result of changes in temperature , pressure, or reactions with hot PLUTONISM THEORY fluids - States that rocks are formed from heat-driven processes. (heat LESSON 5: PLATE TECTONICS from Earth’s interior) - Fundamental aspect is the PLATE TECTONICS THEORY constant and slow processes - The lithosphere behaves as a strong, rigid layer which is broken PLUTONS into segments known as plates. - When magma rises to the crusts, it displaces host/country rock to form structures called plutons - Term “Plutonic” can be used to classify rock formed in the Earth’s interior, opposite of volcanic rocks which form on the crust - Ex: gabbro, diorite, granite - CLASSIFICATIONS: Gravitational Factors: 1. Tension - when two plates move Ridge Push - force that causes away from each other —pulls and hotter, less dense material to stretches rock. force itself up through a ridge. Landform created: continental Slab Pull - pulling of oceanic rifts and mid-ocean ridges lithosphere downward at subduction zones 2. Compression - when two plates are pushing toward each other — EVIDENCES OF PLATE TECTONICS squeezes rock causing it to fold THEORY or break. 1. Hotspots Landform created: Ocean 2. Paleomagnetism - study of Trenches and mountain ranges magnetism in rocks to learn about Earth’s magnetic field and 3. Shearing - when two blocks of its history. rock are pushing in opposite 3. Apparent Polar Wandering (APW) directions — sliding motion 4. Deep Sea Drilling Project causes rock to break or change shape CONTINENTAL DRIFT HYPOTHESIS Landforms created: Faults and - continents were originally Fault Zones connected with each other and then drifted apart TYPES OF DEFORMATION 1. Elastic - rock returns to original CONTINENTAL DRIFT THEORY shape - Proposed by Alfred Wegener 2. Ductile - rock reshapes without - states that the movement of breaking plates caused and is still causing 3. Brittle - causes breakage the movement of continents FAULTS EVIDENCES OF CONTINENTAL DRIFT - A discernible displacement where THEORY: rocks grind or slide past each 1. Continental Fit other. 2. Fossil Evidence - Some rock fracture because of 3. Similarities in rocks and stress mountains across continents 4. Glacial Evidence TYPES OF FAULTS - Normal fault TYPES OF STRESS - Reverse fault - Strike-slip fault (Left lateral and Right lateral) - Oblique fault  Mid-Oceanic Ridge - comprises 20% of the ocean floor's surface the developed concepts helped explain the formation of this ridge. Guyot - seamount with a flat top WILSON CYCLE - proposed by J. Tuzo Wilson - cyclical opening and closing of LESSON 6: SEAFLOOR SPREADING ocean basins caused by the AND WILSON CYCLE movement of the Earth's plates - Scientists were able to estimate that 1. Embryonic rift = Rift valleys the ocean has an average depth of 3.7 2. Young ocean = Narrow seaways kilometers. Aside from the bizarre with central depression and marine life, various geologic structures young active spreading ridge can be found in the ocean basin. 3. Mature ocean = Large ocean basins with active spreading Hydrothermal vents - are openings in ridge the seafloor where heated water, often 4. Declining ocean = Island arcs rich in minerals, is released from and deep ocean trenches round beneath Earth's crust ocean margins White smokers - mostly silicon 5. Terminal ocean = Young deposits and emits lighter plumes mountains and restricted of cooler fluid seaways Black smokers - iron sulfide 6. Continental orogen = Young deposits and emits dark plumes extensive high mountains of hot mineral-rich fluid SEAFLOOR SPREADING HYPOTHESIS - proposed by Harry Hess and Robert Dietz - explains the formation of oceanic crust Paleomagnetic evidence - magnetic orientation of the oceanic crust and the age of rocks help support that the ocean floor is spreading LESSON 7: FORMATION OF LANDFORMS AND PLATE BOUNDARIES DIVERGENT BOUNDARIES - Formed when two plates move away from each other from resulting rising of molten material - Can from continental rifts - Also results in the birth of an ocean floor OCCURRENCES AND EXAMPLES CONVERGENT BOUNDARIES LESSON 8: RELATIVE DATING AND ABSOLUTE DATING STRATIGRAPHY MODEL Stratigraphy - refers to the branch of geology that studies stratified or layered rocks in terms of time and space Stratification - is the layering that occurs in most sedimentary rocks -Formed when two plates move STENO’S LAW toward each other - Nicolaus Steno formulated a set OCCURRENCES AND EXAMPLES of principles describing layers of sedimentary rocks Applications: dating rocks; use of fossils in geological studies; use of sedimentary rocks for studying Earth’s history 1. Law of Original Horizontality TRANSFORM BOUNDARIES - this states that sediments - Formed when two plates slide are generally deposited against each other horizontally - Only occurs between two continental plates - Forms fault zones/ faults as a result 2. Law of Lateral Continuity RELATIVE AND ABSOLUTE DATING - layers of sediments spread out in all directions until Relative Dating they thin out at the edge - uses the laws of stratigraphy and of the depositional basin does not give a numerical or grade into a different estimate of age (qualitative) kind of sediment - gives the relative age of the remains - less specific - cheaper and time-efficient Absolute Dating (Numerical Dating) - allows the determination of the 3. Law of Superposition exact numerical age of rocks and - states that in an fossils (quantitative) undisturbed sequence of - uses radiometric techniques sedimentary rocks, beds - more specific on top are younger than - more expensive and the beds found below and time-consuming each layer is younger than the one beneath it. ISOTOPIC SYSTEMS Isotopes - elements that have a different number of neutrons Half-life - the time it takes for half of the isotope to decay 4. Principle of Cross-Cutting Radioactive Decay - unstable atomic Relationship nuclei lose energy by emitting radiation - this states that geologic features that cut across rocks are younger than the rocks which they cut through FORMULAS TO BE USED: Example: The half-life of Zn-71 is 2.4 Example: minutes. If one had 100g at the beginning, how many grams would be left after 7.2 minutes had elapsed? Example: Potassium is a ubiquitous element found in many rocks. If there are only 40% of K-40 (with a half-life of 1.25 billion years) remaining in your rock sample, how old is the rock?