Earth Science Reviewer PDF

**Earth Science Reviewer** **Wastes and Its Types** **Definition of Wastes** - **Wastes** are unwanted or unusable materials and are regarded as substances which are of no use. - **According to DENR Secretary Maria Antonia Yulo-Loyzaga:** - "The Philippines generates at least 61 b...

**Earth Science Reviewer** **Wastes and Its Types** **Definition of Wastes** - **Wastes** are unwanted or unusable materials and are regarded as substances which are of no use. - **According to DENR Secretary Maria Antonia Yulo-Loyzaga:** - "The Philippines generates at least 61 billion metric tons of waste daily, 24 percent of which is plastic waste." **Classifications of Waste** **General Classification of Waste:** 1. **Solid Wastes** 2. **Liquid Wastes** 3. **Gaseous Wastes** **Solid Wastes** - **Definition:** Refers to any type of garbage, trash, refuse, or discarded material in solid form. - **Includes:** All plastics, Styrofoam containers, bottles, cans, papers, scrap iron, and other trash. **Liquid Waste** - **Definition:** Refers to waste materials that appear in the form of liquid matter. - **Includes:** Domestic sewage, human waste, FOG (fats, oils, and grease), vehicle and machinery oils, fertilizers and pesticides from fields, blood, body fluids, defecations from hospitals, leachate, and wastewater. **Gaseous Waste** - **Definition:** Wastes that are released in the form of gases from automobiles, factories, or burning of fossil fuels like petroleum. - **Includes:** Carbon dioxide, carbon monoxide, sulfur dioxide, oxides of nitrogen, hydrocarbons like methane, aerosols, chlorofluorocarbon (CFC), and so on. **SOURCE OF WASTES** 1. **HOUSEHOLDS** 2. **COMMERCE AND INDUSTRY** **Classifications of Waste Based on Its Origin** 1. **Municipal or Urban Wastes** 2. **Industrial & Radioactive Wastes** 3. **Agricultural & Fishery Wastes** 4. **E-Wastes** 5. **Biomedical Wastes** **Municipal or Urban Wastes** - **Definition:** Solid wastes that include household garbage, construction & demolition debris, sanitation residues, packaging materials, trade refuse, and so on. **Industrial Wastes** - **Definition:** Wastes generated by manufacturing & processing units of various industries like chemical, petroleum, coal, metal gas, sanitary & paper, and so on. **Radioactive Wastes** - **Definition:** Usually by-products of nuclear processes. Sometimes industries not directly involved in nuclear activities may also produce some radioactive wastes (e.g., radioisotopes, chemical sludge, and so on). **Agricultural Wastes** - **Definition:** Wastes generated from farming activities. These substances are mostly biodegradable. **Fishery Wastes** - **Definition:** Wastes generated due to fishery activities. These are extensively found in coastal & estuarine areas. **Biomedical Wastes** - **Definition:** Solid or liquid wastes including containers, intermediate or end products generated during diagnosis, treatment & research activities of medical sciences. **Classifications of Waste Based on Its Type** 1. **Biodegradable & Non-Biodegradable** 2. **Recyclable & Non-Recyclable** 3. **Hazardous & Non-Hazardous** **Biodegradable Waste** - **Definition:** A type of waste, typically originating from plant or animal sources, which may be degraded by other living organisms. - **Examples:** - Green waste - Food waste - Paper waste - Biodegradable plastics - Human waste - Animal manure - Sewage - Slaughterhouse waste **Non-Biodegradable Waste** - **Definition:** A type of waste that cannot be broken down by other living organisms. **Recyclable Waste** - **Definition:** A type of waste that can be reused or converted into new products or raw material. - **Includes:** - Paper including newspapers, magazines, and mixed paper - Cardboard (OCC) - Glass bottles and jars - Rigid plastic products - Metal containers, including tin, aluminum, and steel cans **Non-Recyclable Waste** - **Definition:** A type of waste that cannot be recycled such as plastic wrap, aerosol cans, batteries, ceramics, mirrors, incandescent bulbs, and so on. **Hazardous Waste** - **Definition:** A type of waste with properties that make it potentially dangerous or harmful to human health or the environment. - **Includes:** - **Radioactive wastes** (e.g., Uranium or thorium mill tailings, etc.) - **Biohazards** including discarded sharps (e.g., syringes, needles, blades); discarded blood, body fluids, defecations; pathological wastes (tissues, organs, surgical specimens, etc.); discarded cultures (e.g., bacterial cultures, fungal cultures, etc.); discarded carcasses, and so on. - **Residential Hazardous Wastes** including household cleaners; deodorizers; pesticides; herbicides; insecticides; pet care products; paint products; photographic chemicals; swimming pool chemicals; and automotive products & fluids. Ex. Households Wastes, Ordinary Industrial Waste, Solid Waste, Construction Waste, Organic Waste, WasteWater, Sludge from Wastewater treatment Plants, Packaging and Recyclable Materials, Infectious Healthcare Waste (HIV) and Medical Waster, Bottom ash from Solid Waste Incinerators **Impacts of Waste on the Environment and Human Health** **Improper Waste Disposal Can Harm the Environment and Human Health:** 1. Climate Change 2. Air, Land, & Water Pollution 3. Loss of Biodiversity & Its Habitat 4. Spread of Infections or Diseases 5. Chemical Poisoning **Climate Change** - **Gases released from factories, automobiles, and incineration of trash piles are generally called greenhouse gases which trap heat.** - **Some of these gases like CFCs can form holes or gaps in the ozone layer resulting in an increase in UV radiation reaching the Earth's surface.** - **UV radiation and greenhouse gases increase Earth's temperature which results in a global increase in temperature, otherwise known as GLOBAL WARMING** **Air Pollution** - **Nitrogen oxides react with volatile organic compounds (VOCs) emitted by cars and petroleum industries to form ozone in the presence of sunlight.** - **Air pollution increases the risk of respiratory infections, heart disease, stroke, and lung cancer, and more severely affects people who are already ill.** **Land and Water Pollution** - **As garbage in landfills decomposes, chemicals, toxic materials, and by-products are released with the accumulated liquid called LEACHATE, contaminating both groundwater and surface water sources.** - **Chemicals not properly disposed of can pass through wastewater treatment systems and enter drinking water or oceans, leading to health hazards and harming biodiversity.** **Clogging of Waterways** **Loss of Biodiversity and Habitat** - **Dumping waste in natural areas can destroy important habitats for various species, causing habitat fragmentation and loss of biodiversity.** - **The runoff of nitrate and phosphate into lakes, rivers and streams fertilizes them and causes accelerated EUTROPHICATION or enrichment of the waters.** - **As the algae population is stimulated to grow to uncontrolled proportions, they can release harmful toxins which can easily poison aquatic species. They also deplete the oxygen in the water and in turn suffocate other aquatic creatures.** - **ACID MINE DRAINAGE is one of mining\'s most serious threats to water. A mine draining acid can devastate rivers, streams, and aquatic life for hundreds or thousands of years.** - **Annually, 2.7 million liters of oil are spilled in the seas, contaminating waters, killing organisms and causing lasting damage to ecosystems and economies.** - **Both land and sea animals die from waste left around. From sea turtles and fish dying because of plastic in the sea to animals eating hazardous materials left lying around.** **Spread of Infections or Diseases** - **Skin and blood infections resulting from direct contact with waste, and from infected wounds.** - **Eye and respiratory infections resulting from exposure to infected dust, especially during landfill operations.** - **Different diseases resulting from the bites of animals feeding on the waste.** - **Intestinal infections transmitted by flies feeding on the waste.** **Chemical Poisoning** - **Exposure to mishandled waste affects health, with children being more vulnerable to these pollutants.** - **Chemical waste release leads to poisoning and chemical burns from contact with hazardous waste mixed with general waste.** - **Burns and other injuries may result from occupational accidents at waste disposal sites or from methane gas explosions at landfill sites.** **Tectonic Stresses** **Rocks Behavior Under Stress** - Rocks originally deposited in horizontal layers can deform by tectonic forces into **folds and faults.** - **Folds** constitute twists and bends in rocks. - **Faults** are planes of detachment resulting when rocks on either side of the displacement slip past one another. **Stress** - **Definition:** The amount of force per unit area (pressure) placed on a rock. **Types of Stress** 1. **Compressional Stress** - **Definition:** Formed when the dominant force is directed towards each other. - **Effects:** Squeezes the rocks causing shortening parallel to the direction of stress and elongation perpendicular to the stress direction. - **Occurs at:** Convergent plate boundaries. 2. **Tensional Stress** - **Definition:** Occurs when the dominant force is directed away from each other. - **Effects:** Stretches the rocks causing elongation parallel to the direction of stress and shortening perpendicular to the stress direction. - **Occurs at:** Divergent plate boundaries. 3. **Shear Stress** - **Definition:** Develops when the two dominant forces are directed towards each other but not along the same axis. - **Effects:** Results in slippage and translation. - **Occurs at:** Transform plate boundaries. **Strain** - **Definition:** The change in shape or volume of the rock that experienced stress. **Stages of Deformation** 1. **Elastic Deformation** - **Definition:** The rock returns to its original shape when the stress is removed. It is a reversible strain. 2. **Plastic Deformation** - **Definition:** The rock does not return to its original shape when the stress is removed. The strain is irreversible. 3. **Fracture** - **Definition:** An irreversible strain wherein the material breaks in response to stress. **Classification of Rocks Under Stress** - **Brittle** - **Conditions:** ↓ temperature, ↓ confining pressure, and ↑ strain rate. - **Composition:** May be composed of minerals like quartz, olivine, and feldspars. - **Ductile** - **Conditions:** ↑ temperature, ↑ confining pressure, and ↓ strain rate. - **Composition:** May be composed of clay minerals, micas, and calcite. **Factors Affecting Rock Behavior** 1. **Temperature** - **High Temperature and Pressure:** More ductile. 2. **Confining Pressure** 3. **Strain Rate** - **High Strain Rate:** More brittle. 4. **Composition** - **Quartz, Olivine, Feldspar:** Tend to be more brittle. - **Mica, Kaolinite, Calcite:** Tend to be more ductile. **Metamorphism** **Definition of Metamorphism** - **Metamorphism:** The transformation of existing rock (**the protolith**) to rock with a different mineral composition or texture. - **Conditions:** Occurs at extreme temperatures and pressures higher than 200 ˚C and 300 MPa (Mega Pascals). - **State:** All changes (physical or chemical) occur in the solid state (no melting involved). **Two Main Types of Metamorphism** 1. **Regional Metamorphism** - **Occurs Over:** Huge areas exposed to high degrees of distortion under differential stress, such as in mountain ranges. - **Produces:** Foliated metamorphic rocks such as slate, schist, and gneiss. - **Foliation:** Can occur when a differential stress develops in rocks, wherein the pressure acting on all sides of the rock is not equal. Rounded grains flatten perpendicular to the direction of maximum compressional stress. Sheet silicates and minerals with an elongated habit grow with their sheets or direction of elongation perpendicular to the direction of maximum stress. - **Metamorphic Grade:** Pertains to the temperature and/or pressure conditions to which a rock has been subjected during metamorphism. There is a direct correlation between the grain size of metamorphic rocks and the metamorphic grade. 2. **Contact Metamorphism** - **Occurs Near:** Igneous intrusions. - **Produces:** Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite. - **Process:** Occurs nearby igneous intrusions and comes from high temperatures related with the igneous intrusion. Limited to a zone called a metamorphic aureole which surrounds the intrusive magma. - **Temperature Rise:** Existing rocks in direct contact with magma have their temperature rise and become infiltrated with fluid from the magma. **Magmatism** **Definition of Magmatism** - **Magmatism:** The formation and motion of magma below Earth\'s surface. - **Transformation:** The transformation of some fraction of the mass of a solid rock into a liquid. **Partial Melting** - **Definition:** It is the transformation of some fraction of the mass of a solid rock into a liquid. - **Can Happen Due to:** 1. **Decompression Melting** - **Definition:** Melting due to decrease in pressure. - **Process:** Decrease in pressure affecting a hot mantle rock at a constant temperature permits melting, forming magma. 2. **Flux Melting** - **Definition:** Melting because of the addition of **volatiles**---compounds that have low boiling points. - **Process:** Volatiles mix with hot, dry rock, **decreasing the rock's melting point** and helping break chemical bonds to allow melting. The added water is a **flux**, and this type of melting is called **flux-induced melting.** 3. **Heat Transfer Melting** - **Definition:** Melting due to heat transfer from rising magma. - **Process:** Occurs when rising magma brings heat up with it and melts overlying or surrounding rock (not to scale) **Tectonic Settings Where Magma is Formed** 1. **Mid-Ocean Ridges** - **Process:** Rising magma in mantle convection cells brings heat to the surface, transferring heat to overlying rocks. The **transfer of heat to convection is** Accompanied by a decrease in pressure or \"**decompression**\" associated with the spreading of lithospheric plates, these two work together promoting partial melting of rocks along the spreading center. 2. **Mantle Plumes or Hot Spots** - **Process:** Like mid-oceanic ridges, the **transfer of heat and decompression** result to magma generation. The source of heat for mantle plumes is much deeper 3. **Subduction Zones** - **Process:** Oceanic crustal rocks are formed along spreading centers beneath seawater. Presence of water during generation results in hydrous minerals. As the oceanic slab is down-thrust along subduction zones, temperature and pressure changes bring about mineral instability and the release of water to surrounding hot rocks, **lowering the melting point of rocks** and causing partial melting or magma generation. **Magma Rises or cools and crystallizes in place** **Physical Properties that Determine Migration of Magma:** 1. **Density** - **Definition:** Substance\'s mass **per unit of volume.** - **Process:** Magma is **less dense** than the surrounding country rock, Magma **rises faster** when the difference in density between the magma and the surrounding rock is greater. At **deeper levels,** magma passes through mineral grain boundaries and cracks in the surrounding rock. When enough mass and buoyancy is attained, the overlying surrounding rock is pushed aside as the magma rises. Depending on surrounding pressure and other factors, the magma can be ejected to the Earth\'s surface or rise at shallower levels underneath. At **shallower levels**, magma may no longer rise because its density is almost the same as that of the country rock. The magma starts to accumulate and slowly solidifies. 2. **Viscosity** - **Definition:** A measure of the fluid's resistance to flow. - **Factors Affecting Viscosity:** - **Temperature:** Increase in temperature = decrease in viscosity. - **Silica Content:** More silica content = more viscous. - **Dissolved Water:** Increase in dissolved water = decrease in viscosity. **Bowen's Reaction Series** - **Developed by:** Canadian geologist **Norman L. Bowen** - **Definition:** Describes the temperature at which minerals crystallize when cooled or melt when heated, Certain minerals are stable at higher melting temperature and crystallize before those stable at lower temperatures, Crystallization in the continuous and discontinuous branches takes. place at the same time. - **Branches:** 1. **Continuous Branch** - **Minerals:** This represents minerals that form continuously as temperature decrease contains only Plagioclase feldspar, changing from calcium-rich to sodium-rich as temperature drops. 2. **Discontinuous Branch** - **Minerals:** This represents the minerals that **crystallize at distinct temperature intervals**. **Olivine** is the first mineral to form. and it forms at a very high temperature. As the magma cools, we see the formation of **pyroxene. amphibole** and finally **biotite.** **Magmatic Differentiation** - **Definition:** The process whereby an **originally homogeneous magma changes** its composition or becomes **heterogeneous.** - **Shapes Rocks Through:** 1. **Fractional Crystallization** - **Definition:** A chemical process where the composition of a liquid magma changes due to **crystallization**. **Crystal Settling** occurs when dense minerals sink to the bottom of a magma chamber. 2. **Partial Melting** - **Definition:** Minerals formed under **low temperature conditions** are the first to melt from the parent rock when exposed to higher temperature and/or pressure. Silica-rich rock-forming minerals **have lower melting points** than ferromagnesian minerals. Each stage of partial melting produces rocks enriched in **silica** (and depleted in ferromagnesian minerals). As an example, partial melting of an ultramafic rock in the mantle produces a basaltic magma (mafic). 3. **Magma Mixing** - **Definition:** Occurs when **two different magmas rises**, with the more buoyant mass overtaking the more slowly rising body, mixing to form an **intermediate** magma. 4. **Crustal Assimilation** - **Definition:** Contamination of magma by **crustal rocks**, where **crust is mixed up with rising magma.** - **Xenolith:** is a piece of rock trapped in another type of rock. Most of the time, a xenolith is a rock embedded in magma while the magma was cooling. **Weathering** **Definition of Weathering** - **Weathering:** The breakdown or disintegration of rocks and their minerals into smaller fragments and/or decay and transformation into other substances. - **Erosion:** refers to displacement of solids such as water, wind, and ice - **Weathering:** refers to the decomposition of soils and their minerals and rocks through direct contact with the earths athmosphere **General Classification of Weathering:** 1. **Physical Weathering** 2. **Chemical Weathering** 3. **Biological Weathering** **Physical Weathering (Mechanical Weathering)** - **Definition:** Breaking apart rocks and crystals through different processes without changing their chemical composition. - **Processes:** 1. **Frost Wedging** - **Cause:** Repeated cycles of freezing and thawing. - **Most Prevalent in:** Mountainous regions with daily freeze-thaw cycles. 2. **Thermal Expansion** - **Cause:** Minerals subjected to different temperature ranges expand and contract. - **Effects:** Rapid temperature fluctuations cause individual grains in rocks to expand and contract at different rates, leading to fractures. - **Examples:** Deserts with rapid temperature changes. 3. **Exfoliation (Unloading, Sheeting, or Onion Skin Weathering)** - **Definition:** Happens in regions with large masses of igneous rocks. It is caused by the pressure release as overburden is eroded away. The process of removing overlying rocks is called **unloading**. As the pressure is released, expansion of the rock causes concentric layers of cracks to form within the igneous body. (These layered "sheets" are then broken off by continued weathering. 4. **Abrasion** - **Definition:** the breakdown of rocks that is caused by **Impact and friction.** - **Occurs during:** Collision of rocks, sand, and silt due to current or waves along a stream or seashore causing sharp edges and corner to wear off and become rounded. 5. **Salt Crystallization (Honeycomb Weathering)** - **Cause:** Salt crystals wear away rock through mechanical weathering. - **Process:** Salts in rocks expand due to thermal action, hydration, and crystallization, favored in areas of alternating wetting and drying conditions. - **Haloclasty:** Produces this distinctive **honeycomb pattern in coastal areas.** **Chemical Weathering** - **Definition:** The process in which rocks and other materials are broken down by chemical reactions, predominantly by water and dissolved chemicals. - **Processes:** 1. **Dissolution** - **Definition:** Rocks are dissolved when exposed to rainwater. - **Examples:** Limestone (calcite or CaCO₃) and rock salts (halite or NaCl) are rocks that form solvent solutions when exposed to rainwater, surface waters, or even ground water - **Formation:** Stalactites and stalagmites in caves are brought about by this chemical weathering 2. **Hydrolysis** - **Definition:** Chemical reactions caused by **water** altering the size and chemical compositions of minerals, lessening their resistance to weathering. - **Effects:** Produces crystal rocks and clay minerals such as calcium, potassium, and sodium ions whenever minerals are hydrolyzed. 3. **Oxidation** - **Definition:** Components of minerals **combine with free oxygen** in the atmosphere **forming oxides.** - **Effects:** Iron oxidizes, causing rocks to decompose and develop rusty red colors. 4. **Carbonation** - **Definition:** **Mixing of water with carbon dioxide** to form **carbonic acid,** Chemical weathering takes place when the **rock minerals react with weak carbonic acid** formed when water combines with carbon dioxide in the atmosphere. - **Effects:** Carbonic acid acts on the rock by breaking down and dissolving its mineral contents. The dissolved materials are washed away by ground water, and the soluble ions are stored in the groundwater supply. Rocks such as limestone and feldspar experience this type of chemical weathering more. **Biological Weathering** - **Definition:** Weathering resulting from plant, animal, and microbial influences. - **Processes:** 1. **Root Growth** - **Effect:** Tree roots spread and make cracks in rocks. 2. **Organic Acids** - **Effect:** Living and decaying plants and fungi produce carbonic acid, breaking down rocks. 3. **Burrowing Animals** - **Effect:** Move rock fragments to the surface, exposing rocks to more intense weathering processes. **Structure and Evolution of Ocean Basins** **Definition of Ocean Basins** - **Ocean Basins:** **Bowl-shaped depressions** in the earth, with complex topography along its deep seafloor. **Components of Ocean Basins** 1. **Coastal Plain** 2. **Coastline or Shoreline** 3. **Deep-Ocean Basins** 4. **Continental Margin** **Continental Margin** - **Definition:** The **submerged outer edge of the continent** where continental crust transitions into oceanic crust. - **Components:** - **Continental Shelf:** Submerged nearshore border of a continent that slopes gradually and extends to a point of steeper descent to the ocean bottom. - **Shelf Break:** Edge of the continental shelf that transitions into the continental slope. - **Continental Slope:** Slope between the outer edge of the continental shelf and the deep ocean floor, often cut by **submarine canyons.** - **Continental Rise:** A wide, gentle incline from an abyssal plain to a continental slope. **Deep-Ocean Basins** - **Definition:** Covers the greatest portion of the Earth\'s surface. - **Geographic Features:** - **Trenches:** Long, relatively narrow canyon-like features parallel to continental margins. - **Abyssal Plains:** **Extremely flat, sediment-covered stretches of the ocean floor,** usually found at depths of 3,000--6,000 meters, interrupted by occasional **volcanoes**, mostly extinct, called **seamounts** - **Ocean Ridges and Rises:** Continuous ranges of undersea volcanic mountains formed when tectonic plates diverge. - **Mid**-**Ocean Ridges:** broad, linear swells along divergent plate boundaries in ocean basins. - **Submarine Mountainous Regions** **Types of Continental Margin** 1. **Active Continental Margin** - **Definition:** It is a coastal region that is characterized by **mountain-building** activity including **earthquakes, volcanic activity, and tectonic motion** resulting from movement of tectonic plates. 2. **Passive Margin** - **Definition:** This occur where the transition from land to sea is **NOT** associated with **an active plate boundary**. Passive continental margins are characterized by **wide beaches, barrier islands, broad coastal plains**. **FORMATION OF OCEAN BASINS** **Wilson Cycle** - **Definition:** A **6-stage cycle** proposed by Canadian geophysicist **J. Tuzo Wilson** (1908--1993) that includes **continental break-up, drifting, collision, and re-assembly of the continent.** **Phases of the Wilson Cycle** 1. **Opening Phase** 2. **Closing Phase** **Stages of the Wilson Cycle** 1. **Embryonic Stage: Rift Basin (A continent rifts apart)** - **Process:** A **warm hot spot** underneath a stable Continental Craton **heats up the craton** (continent) and causes it to swell upwards and in the breakup zone the **continental crust gets thinner and thinner and starts to crack**, which eventually causes the continent to break into two continents. - **Example:** East Africa Great Rift Valley. 2. **Juvenile Stage: Young Passive Margin (A new ocean forms through seafloor spreading)** - **Process:** The spreading of earth plates starts, and a **small ocean has formed** between the newly broken up continents. This boundary is called a **divergent boundary.** - **Example:** Red Sea. 3. **Mature Stage: Mature Passive Margin (Continental drift forms large ocean basins)** - **Process:** When a large ocean has formed between two continental margins and spreading still occurs. A **well-developed mid-ocean ridge has formed** along the divergent boundary. - **Example:** Atlantic Ocean. 4. **Declining Stage: Oceanic Subduction (Subduction Begins)** - **Process:** At this stage, a **subduction zone has formed**, and the ocean begins to close-up. One of the simplest ways a subduction zone forms is at the edge of a continent, where one tectonic plate is subdued below another tectonic plate. This is a **Convergent boundary.** - **Example:** Pacific Ocean. 5. **Terminal Stage: Mature Subduction (The ocean basins begins to close due to subduction)** - **Process:** At this stage, the **continents are almost colliding.** Formation of magma happens deep in the subduction zone and small mountains are building up. In the subduction zone **both metamorphism, folding, and faulting occurs.** The boundary is convergent, and the sea at this stage is narrow and irregular. - **Example:** Mediterranean Sea. 6. **Suturing Stage: Continental Orogen (Two Continents collide and the ocean basins close)** - **Process:** This is the final stage, before the mountain range eventually erode down to a peneplain. At this stage, the **two continents** moving towards each other will collide and a **mountain range** forms. **Ex.** Himalayas Mountains **Methods of Determining Age of Rocks** **Relative Dating** - **Definition:** A method for determining the **approximate age** of a rock layer or geologic event by **comparing it to other rock layers or events.** - **Geologic Principles:** - Rocks that **cross-cut** are **always younger** than the rocks they cut across. - **Inclusions** are always **older** than the rock itself. - Rocks above an **unconformity** are **younger** than the rocks below. - The **oldest rocks** are at the **bottom of a strata** and the **youngest** are at the **top**, even if the strata become deformed. **Absolute Dating** - **Definition:** A method for determining the **exact age of rocks in years.** - **Common Technique:** Radiometric dating or Radioisotope dating **Radiometric Dating** - **Definition:** An absolute dating method used to determine the age of rocks and minerals by measuring the **amount of radioisotope** the object contains against the **decay product** it contains. - **Radioactive Decay:** Process by which **unstable isotopes transform** to **stable isotopes** of the same or different elements while losing energy by releasing **radiation.** - **Components:** - **Parent Isotope:** The atomic nucleus that undergoes radioactive decay. - **Daughter Isotope:** The isotope that forms because of radioactive decay. - **Half-Life:** The **amount of time** it takes **for half of the parent isotopes** to decay to daughter isotopes. **Types of Radiometric Dating** 1. **Uranium-Lead Dating** - **Definition:** One of the **most accurate** radiometric dating methods, often used to date **ancient rocks**. - **Application:** Usually performed on **zircon crystals.** 2. **Radiocarbon Dating (Carbon-14 Dating)** - **Definition:** Used to measure the age of **once-living materials** between 100 and 50,000 years old. Usually used to determine ages of **human fossils** and **habitation sites.** 3. **Potassium-Argon Dating** - **Definition:** A radiometric dating method used to date **age of rocks and minerals** that are **100,000 years to over a billion years old.** **Stratified Rocks** **Definition of Stratified Rocks** - **Stratified Rocks:** Rock strata defined as horizontal layers of sedimentary rock, usually visually distinguishable from adjacent layers due to differing composition. **Formation of Stratified Rocks** - **Sediments:** Solid particles that move through water or across land and settle in new places. Examples include **boulders, pebbles, cobbles, sand, silt, and clay.** - **Sedimentary Rocks Formation Areas:** Deltas, beaches, rivers, glaciers, sand dunes, shallow seas, and deep oceans. - **Stratification:** Process that occurs due to layering in most sedimentary rocks and in igneous rocks formed at the Earth\'s surface. **Strata** - **Definition:** Rock Strata can be defined as **horizontal layers of sedimentary rock.** Which are usually visually distinguishable from adjacent layers due to their differing composition - **Stratum:** may be a bed or lamina - **Components:** - **Beds:** Sedimentary strata **greater than 1 cm thick.** - **Laminae:** Sedimentary strata **less than 1 cm thick.** **Stratigraphy** - **Definition:** The **study of rock strata** and the **layering of rocks.** **Four Basic Principles (Steno's Laws of Stratigraphy):** - **Definition and Developed by:** 17^th^ century Danish Geologist **Nicolaus Steno**, Describe the **way that sedimentary rocks are deposited and layered.** 1. **Law of Original Horizontality:** Layers of sedimentary rocks are originally deposited flat. 2. **Law of Superposition:** Younger layers of rock sit atop older layers 3. **Law of Lateral Continuity:** Layers of rocks are continuous until they encounter other solid bodies that block their deposition or until they are acted upon by agents that appeared after deposition take place. 4. **Law of Cross-Cutting Relationships:** Rock Layers A and B must be older than the intrusion ( C ) that disturbs them. (Later reinforced by **James Hutton**). **Geologic dikes** are large slabs of rock that cuts through another type of rock. 5. **Law of Inclusions:** This law, developed by **Charles Lyell**, states that rock fragments, or **inclusions**, found within a rock are **older than the rock itself.** 6. **Law of Unconformities:** This law is credited to **James Hutton** who discovered a feature later known as **unconformity---surface of non-deposition or erosion.** **Unconformities** - **Definition:** Gaps in the geological record, or breaks in time between rock layers, that are **caused by a pause in sediment deposition** or erosion of existing rocks. - **Types:** - **Angular Unconformity:** A geological feature that occurs when older, **tilted rock layers are eroded** and then **covered by younger, horizontal layers** of rock - **Nonconformity:** Contact that separates a **younger sedimentary rock** unit from an **igneous intrusive rock or metamorphic rock** unit. - **Disconformity:** Erosional contacts that are **parallel to** the bedding planes of the upper and lower sedimentary rock units. **Plate Movements** **Continents** - **Definition:** one of Earth's **seven main divisions of land**. **Continental Drift Theory** - **Definition:** In 1912, **Alfred Wegener**, a German meteorologist and geophysicist, proposed the Continental Drift Theory. The **Continental Drift Theory** states that the continents were once joined together, and over time had drifted apart. **Plate Tectonics Theory** - **Definition:** The theory that Earth\'s outer shell is divided into **several plates that glide over Earth\'s mantle**, it explains how major **landforms are created due to Earth\'s subterranean movements.** **Tectonic Plates** - **Definition:** Segments or pieces of the earth\'s crust and uppermost mantle that together constitute the lithosphere. **Plate Driving Forces** 1. **Mantle Convection** - **Process:** Drives tectonic plates by rising hot material over mid-ocean ridges and sinks into deep trenches. Which keeps the plates moving along the Earth's Surface. 2. **Plate Boundaries** - **Definition:** The edge where two plates meet. - **Types of Boundaries:** Divergent, Convergent, and Transform. **Earth's Crust is divided into Two Types: Oceanic Crust and Continental Crust** **Types of Plate Boundaries and Associated Landforms** 1. **Divergent Plate Boundaries** - **Definition:** Plates move apart from one another. The magma from the mantle rises forming new crust (oceanic crust). **Earthquakes** occurs when plates move over the mantle. - **Mid-Ocean Ridges:** These are continuous range of undersea volcanic mountains formed **when two oceanic tectonic plates diverge** or move apart from each other. - **Rift Valleys:** A lowland region that are formed when **two continental tectonic plates diverge** or move apart from each other. - **Shield Volcanoes:** These volcanoes are usually constructed almost entirely of basaltic and/or andesitic lava flows which were very fluid when erupted. They are much **wider than they are tall.** - **Normal Fault:** the hanging wall slips down relative to the footwall. 2. **Convergent Plate Boundaries** - **Definition:** It usually involves an oceanic plate and a continental plate. The plates move towards one another, and this movement can cause earthquakes and volcanoes. - **Ocean Trenches:** These are steep depressions exceeding 6000 meters in depth, where **old oceanic crust** from one tectonic plate **subducts** or is pushed beneath another plate. **Subduction** happens because the oceanic plate is denser than the continental plate. - **Stratovolcanoes (Composite Volcanoes):** These volcanoes have relatively **steep sides** and **are more cone-shaped** than shield volcanoes. - **Fold Mountains:** These are formed when **two continental plates collide**, neither can sink and so the land buckles upwards. - **Reverse fault** is one in which the **hanging wall moves up** relative to the footwall. - About 80% of earthquakes occur where plates are pushed together, called **convergent boundaries**. 3. **Transform Plate Boundaries** - **Definition:** Plates slide past each other in opposite directions, or in the same direction but at different speeds. A smaller number of transform faults cut continental lithosphere. - Often result in landforms such as **fault lines** and **rift valleys** - **Strike-Slip Faults:** These faults build up pressure when friction prevents plates from sliding until the pressure exceeds the force of the friction and results in an earthquake. - Shear stress is the major type of stress at **transform plate boundaries**. - **Dextral (Right-Handed)** - **Sinistral (Left-Handed)** - **Strike-Slip Fault:** When rocks on either side of a nearly vertical fault plane **move horizontally,** the movement is called **strike-slip**. **Earth\'s Internal Heat** **Sources of Earth's Internal Heat** 1. **Primordial Heat** - **Definition:** Heat generated during the Earth's formation. - **Description:** Leftover heat from the planet\'s formation about 4.5 billion years ago (BYA), which has not yet been lost. 2. **Radiogenic Heat** - **Definition:** Heat generated by the long-term decay of isotopes like uranium-235, uranium-238, potassium-40, and thorium-232 in the Earth's lithosphere. - This heat generated from the **radioactive decay** of isotopes like U-238, U-235, Th-232, and K-40 in the earth's crust and mantle. - **Radioactive Decay:** It is the emission of energy in the form of ionizing radiation. The decay produces subatomic particles that move through the earth and their energy of motion is converted into heat energy. **Heat Transfer** - **Definition:** It is the process in which the molecules are moved from the region of **higher temperature** to **lower temperature.** 1. **Conduction** - **Definition:** Transfer of heat by direct contact. - **Role:** Governs the thermal conditions in almost entire solid portions of the Earth and plays a very important role in the lithosphere. 2. **Convection** - **Definition:** Transfer of heat by molecular motion. - **Process:** Mantle convection drives tectonic plates by carrying heat from the lower mantle and core to the lithosphere. 3. **Radiation** - **Definition:** Transfer of heat by electromagnetic waves. **Seafloor Spreading** **Seafloor Spreading Theory** - **Proposed By:** American geophysicist **Harry H. Hess** in 1960. - **Definition:** The **ocean floors move like conveyor belts**, carrying the continents with them. - Using a **sonar** Hess was able to map the ocean floor and discovered the **mid-Atlantic ridge** (mid-ocean ridge) - **Sonar (Sound navigation and Ranging):** a device that bounces sound waves off underwater objects and then records the echoes of these sound waves. **Seafloor Spreading** - **Definition:** a geologic process in which **tectonic plates---**large slabs of Earth's Lithosphere**---**split apart from each other creating **new oceanic crust**. - Occurs along **mid-ocean ridges**, the longest chain of mountains in the world. - **Seafloor Spreading** and other tectonic activity processes are the result of **mantle convection** (the slow, churning motion of Earth's mantle) - **Convection currents** carry heat from the lower mantle and core to the lithosphere. Heat from the mantle\'s convection currents makes the crust **more plastic** and **less dense**. The less-dense material rises, often forming a mountain or elevated area of the seafloor. - **Hot magma rises from the mantle and erupts. The magma then spreads out, pushing older crust to both sides of the ridge**. As the molten material cools, it forms a strip of solid rock in the center of the ridge. Then more molten material splits apart the strip of solid rock that formed before, pushing it aside. - The ocean floor does not keep spreading. Instead, it sinks beneath deep underwater canyons called **deep-ocean trenches.** Where there are trenches, subduction takes place. **Subduction** is the process by which the ocean floor sinks beneath a deep-ocean trench and **back into the mantle.** **Plate Driving Forces Necessary for Seafloor Spreading** 1. **Ridge Push** - **Definition:** The gravitational force caused by the excess height of the mid-ocean ridge. 2. **Slab Pull** - **Definition:** The gravitational force caused by the weight of the cold, dense tectonic plates that sink into the mantle. **Evidence of Seafloor Spreading** 1. **Evidence from Molten Material** - **Pillow Basalt:** Formed when lava erupts underwater and rapidly cools, creating a pillow-like shape. 2. **Evidence from Magnetic Stripes** - **Magnetic Reversal (Geomagnetic Reversal):** is when the **Earth's magnetic pole switch places.** - Scientists began using **Magnetometers** to measure the magnetism of the ocean floor in the 1950s - **Iron-rich magma** becomes **magnetized** as it cools and solidifies, and the resulting rock preserves a record of the Earth\'s magnetic field at the time it formed. - The polarity reversal of the Earth\'s magnetic field can take between 1,000 and 10,000 years, but some estimates are as short as a human lifetime. The reversals are random and can happen every 10,000 years or so, or as infrequently as every 50 million years or more. 3. **Evidence from Drilling Samples** - The newest, thinnest crust is located near the center of **mid-ocean ridges**, with age, density, and thickness of oceanic crust **increases with distance** from the mid ocean ridge.