Earth's Science: Processes and Materials PDF

Exogenic Processes or Denudation - refers to activities or phenomena that occur on the Earth’s surface - Considered as destructive and are responsible for degradation and sculpting the Earth’s surface Types of exogenic processes Weathering Erosion Mass wasting Sedimentat...

Exogenic Processes or Denudation - refers to activities or phenomena that occur on the Earth’s surface - Considered as destructive and are responsible for degradation and sculpting the Earth’s surface Types of exogenic processes Weathering Erosion Mass wasting Sedimentation Weathering - Process that breaks down rock into smaller pieces - The physical weathering happens when rock is physically broken into smaller pieces Factors that affect physical weathering Ice wedging Animals Growth of plants - the chemical weathering is the process of breaking down rock through chemical changes Erosion - Rock particles get carried away by wind, water, ice, & gravity - Begins with a process called weathering - Transport moves the sediments down to another place Weathering - causes tile rocks to break down Sedimentation - Natural process in which a material is carried to the bottom of bodies of water and forms to solid EARTH’S INTERIOR HEAT Heat - type of energy related to kinetic energy or movement of atoms - More/faster movement of atoms more heat Two sources of heat 1. Residual heat - thermal energy left over from the formation of Earth via bombardment and accretion 2. Radioactive Decay - the release of energy and energetic particles from radioactive materials heats up surrounding particles Effects of heat on the outer core Keeps it liquid Causes convection of iron/nickel Results in Earth’s magnetic field Causes thermal convection in the mangle which in turn drives plate tectonics Endogenic process - geological process that was form, originated, and located below the surface of the earth - Geologic activities such as tectonic movements, metamorphism, seismic activities and magmatism Magma - Formed under certain circumstance in special location deep in the crust or in the upper mantle - forms from partial melting of mantle rocks Partial melting - rocks undergo this process because minerals that compose them melt at different temperature - Takes place because rocks are not pure materials - As temperature rises, some minerals melt and others remain solid - If the same conditions are kaintained at any given temperature, the same mixture of solid and melted rock is maintained To understand melting, - Pressure is considered - Pressure imcreases with depth as a result of the increased weight of overlying rock - Geologist found out that as they melted rocks under various pressure, higher pressure led to higher melting points Two main mechanism through which rocks melt Decompression melting Flux melting Decompression melting - takes place within earth when a body of rock is held at approximately the same temperature but the pressure is reduced - This happens because the rock is being moved toward the surface, either at a mantle plume (a.k.a., hot spot), or in the upwelling part of a mantle convection cell. - If a rock that is hot enough to be close to its melting point is moved toward the surface, the pressure is reduced, and the rock can pass to the liquid side of its melting curve. - At this point, partial melting starts to take place. Flux melting - happens if a rock is close to its melting point and some water or carbon dioxide is added to the rock, the melting temperature is reduced and partial melting starts  - At very high temperatures (over 1300°C), most magma are entirely liquid because there is too much energy for the atoms to bond together - Silicon and oxygen combine to form silica tetrahedra, and then, as cooling continues, the tetrahedra start to link together to make chains (polymerize) Magma escaped in two forms: Intrusion Extrusion Intrusion - magma that moves up into a volcano without erupting Plutonism - all sorts of igneous geological activities taking place below the Earth's surface - In cases where magma infiltrates the Earth's crust but fails to make it to the surface, the process of magma differentiation gives birth to ideal conditions for metallogenesis and that is a kind of Plutonism Plutonites - process of crystallization takes place inside the crust, the magmatic rocks produced - another major category of igneous rock formation. Plutonites are igneous rock formations that are created when the process of crystallization and solidification of magma takes places below the Earth's surface and particularly in the crust Extrusion - an eruption of magmatic materials that causes land formation on the surface of the Earth - causes the formation of volcanoes when the gas pressure is strong enough and there are cracks in the earth's crust - Magma that came out to the surface of the earth is called the eruption - Magma that came to the surface of the earth is called lava Volcanism - describe all geological phenomena that occur on the natural terrestrial surface, such as the creation of volcanoes and hot springs - all sorts of geological activities correlated with the flow and transportation of igneous materials Volcanoes - created and formed when energy generated by inductive currents flowing from the Earth's core towards the surface hits the upper layers in the form of pressure and smashes the overlaying rock formations Volcanites - Molten material in the form of lava that undergoes the process of crystallization on the natural terrestrial surface gives birth to rock formations known as volcanites - one of the major categories of igneous rock formations  - composed of gray, dull pink colored trakibasaltic lava with large phenocrystal and pyroclastic Metamorphism - process of change in the form and structure of rocks due to intense heat and pressure - comes from the Greek word “meta” means change and “morphe” means form - The rocks that undergo metamorphism are converted to metamorphic rocks Metamorphic agents Heat - most important factor because it provides the energy to drive the chemical changes which result in the recrystallization of minerals - The heat increases as the depth increases Pressure - also increases with depth, and the buried rocks are subjected to the force or stress - Heat and pressure cause physical changes to buried rocks Chemically active fluids - enhanced the metamorphic process - Usually, the common fluid which helps the chemical activity is water containing ions in solution - As the rocks buried deeply, the water is forced out of the rock and becomes available to aid in chemical reactions TYPES OF METAMORPHISM Regional Metamorphism - Most common form of metamorphism that occurs in broad areas. - Caused by high temperature and pressure that resulted from the thickening of the crust and plate tectonics. - Pressure as the main factor occurs in areas that have undergone deformation during orogenic events resulting in mountain belts. - Occurs in a regional/large scale. - Creates foliated metamorphic rocks such as schist and gneiss. - Occurs in convergence area, deep below mountain ranges Contact or thermal metamorphism - Takes place when the very hot magma moves up through the crystal rocks and brings with it high levels of heat. - A zone of alteration called an aereole forms in the rock that surrounds the emplaced magma body. - These surrounding rocks get heated to such an extent, their mineral structure undergoes changes. - Some examples of rocks that undergo contact metamorphism include marble and emery rock. - Occurs below the earth’s surface along magma/igneous intrusion  High-pressure metamorphism - Is the process where rocks along the subduction zone are altered due to high pressure. - Occurs at the subduction area Burial metamorphism - occurs at lower temperature and pressure which transform - sedimentary rocks that had undergone diagenesis into low grade metamorphic rocks through relatively low temperature and pressure - Partial alteration of the mineralogy and texture may occur while other sedimentary structures are usually preserved - Occurs below sedimentary rock layer Hydrothermal metamorphism - Alteration by hot, chemically aggressive water. - Dominant process near mid ocean ridge magma. Cold ocean water seeps into fractured crust Heated by magma, this water then reacts with mafic rock Hot water rises and is ejected via black smokers - Occurs in mid ocean ridges area Impact or shock metamorphism - It occurs when high-speed projectiles called meteorites (fragments of asteroids) strike the surface of the earth. - Upon impact, the energy of the rapidly moving meteorite is transformed into heat energy and shock waves that pass through surrounding rocks. - The result is pulverized, shattered, and sometimes melted rock. The products of these impacts called impactites (impactiles) include a mixture of fused fragmented rock along with glass-rich ejecta resembling volcanic bombs. - In some cases, a very dense form of quartz (coesite) and minute diamonds are found. TYPES OF METAMORPHIC ROCK Two major subdivisions of metamorphic rocks Foliated - These have a planar foliation caused by the preferred orientation (alignment) of minerals and are formed under differential stress. - They have a significant amount of sheet silicate (platy minerals) and are classified by composition, grain size, and foliation type. Non-foliated - These have no evident planar fabric or foliation, crystallized under conditions where there was no differential stress, and are comprised of equant minerals only. - These are classified mainly by the minerals present or the chemical composition of the protolith. ROCK BEHAVIORS UNDER STRESS TYPES OF STRESS IN THE EARTH CRUST Compression - This causes the rocks to push or collide with each other. - This can make the rocks cometogether or make the plates rise. - Mountains and hills could be formed when two plates collide. Tension - This is the opposite of compression. - The tension force pulls the rocks away from each other. - This force created continental drifts and mid-ocean ridges. It moved the oceanic crust away from each other that resulted in the rising of less dense rocks coming from the mantle. Shear force - The shear force pushes the crust in different directions. - Shearing results in the breaking of the large parts of the crust into smaller sizes. This force always happens along the plate boundaries. - Plate boundaries are the location where the two plates meet. - When the two plates rub each other and move in opposite directions, it creates friction. This friction leads to the shaking of the Earth’s ground or earthquake. THE FORMATION OF FAULTS AND FOLDS Tectonic plates - The Earth’s crust is divided into plates, known as tectonic plates, and these plates move due to the convection currents in the Earth’s interior. Plate movements - The movement of the plates depends on the boundaries between them. These boundaries can be convergent, divergent, or transform. - In a convergent boundary, the plates move or collide to each other. When the plates move away from each other, they are in a divergent boundary. Finally, when plates slide past each other, they are in a transform boundary. - Plate movements cause rocks to be deformed due to compressional stress at convergent boundaries, tensional stress at divergent boundaries, or shear stress at transform boundaries. Due to these stresses, rocks experience changes in volume and shape. Plate boundaries (convergence) - Oceanic-continental convergence - Oceanic-oceanic convergence - Continental-continental ROCK DEFORMATION Compressional stress - causes rocks to be squeezed into each other  Tensional stress - pulls rocks apart and SHEAR STRESS causes rocks to slide opposite each other. Fracture - When subjected to stress, rocks can deform by either breaking (fracture) or bending (fold). - Since the pressure and temperature are low at the Earth’s surface, rocks tend to break or fracture when subjected to compressional and tensional stresses. This means that the pressure exerted in the blocks of rocks exceeds the rock’s internal strength. - Fractures can either be a fault or a joint. - A fault is a break in the rock where there is considerable movement on the fracture surface while a joint is a break where there is no considerable movement. TWO TYPES OF FAULT Dip-slip faults - involve the vertical movement of the blocks of rock. These movements are described based on the direction of the motion of the hanging wall with respect to the footwall. A hanging wall is a block of rock that rests on the fault plane while a footwall is the one below the fault plane. - Dip-slip faults can either be normal or a reverse fault. A normal fault is caused by tensional stress, it is characterized by the hanging wall moving downward with respect to the footwall. A reverse fault, wherein the hanging wall moves upward, is formed by compressional stress. Strike-slip fault - involves a horizontal movement of blocks of rock and is caused by shear stress LIST OF ACTIVE FAULT LINES IN THE PHILIPPINES - Marikina Valley Fault (montalban, san mateo, marikina, pasig, taguig, muntinlupa, san pedro, binan, carmona, santa rosa, calamba, tagaytay, oriental mindoro) - Western Philippine Fault (Luzon sea, Mindoro strait, Panay gulf, sulu sea) - Eastern Philippine Fault (philippine sea) - Southern of Mindanao (moro gulf, Celebes sea) - Central Philippine Fault (entire Ilocos Norte, aurora, quezon, masbate, eastern leyte, southern leyte, agusan del norte, agusan del sur, davao del norte) Folds - Deep within the crust, where pressure and temperature are high, rocks are plastic-like; thus, they do not break but they tend to bend or fold. When rocks become thinner, they are pulled apart. Types of fold Anticline - When blocks of rock are bent upwards, they form anticline structures Synclines- are formed when blocks of rock bend downwards Monoclines- slightly bent rock from the parallel undeformed layers forms monoclines Metamorphism Definition: Process by which the structure or mineral content of a rock changes under heat and pressure while remaining solid. Types of Metamorphism: ○ Contact Metamorphism: Caused by heat near magma. ○ Shear Metamorphism: Caused by pressure in fault zones. ○ Regional Metamorphism: Affects large areas, often during mountain building. ○ Hydrothermal Metamorphism: Chemical changes due to hot, mineral-rich water. Rocks Foliated Rocks: Display layers (e.g., slate, schist, gneiss). Non-foliated Rocks: Do not have layers (e.g., marble, quartzite). Key Terms Foliation: Layering caused by alignment of minerals. Metamorphic Grade: The intensity of temperature and pressure during metamorphism. Structure and Temperatures 1. Crust: ○ Continental Crust: 300–500°C, mainly granite. ○ Oceanic Crust: 0–1000°C, mainly basalt. 2. Mantle: ○ Upper Mantle (including the Lithosphere): 500–900°C. ○ Asthenosphere: 1300°C, semi-fluid and enables plate movement. ○ Lower Mantle: Up to 4000°C, denser and hotter. 3. Core: ○ Outer Core: 4000–6000°C, liquid iron alloy. ○ Inner Core: About 5000°C, solid iron due to extreme pressure. Key Processes Plate Tectonics: Movement of crustal plates on the asthenosphere. Convection in Mantle: Drives tectonic movements, fueled by heat from the core. Temperature and Pressure Increases with depth, causing rocks to transition between solid, molten, or semi-molten states.  1. Asthenosphere: Semi-fluid layer below the lithosphere. 2. Foliation: Alignment of minerals in a rock due to stress. 3. Metamorphism: Transformation of rocks under heat and pressure. 4. Lithosphere: The rigid outer layer of the Earth (crust + upper mantle). 5. Mantle: Thick layer beneath the crust, involved in tectonic activity. 6. Moho (Mohorovicic Discontinuity): Boundary between crust and mantle. 7. Converge/Diverge: Movement of tectonic plates towards/away from each other. Abraham Ortelius - A Brabantian cartographer and geographer and known as the creator of the first modern atlas (Theatrum Orbis Terrarum or Theatre of the World) - first to underline the geometrical similarity between the coasts of America and Europe-Africa and to propose continental drift as an explanation Continental Drift Theory - refers to the movement of the Earth’s continents relative to each other, appearing to “drift” across the ocean bed - theory is publish in the book, “Origin of Continents and Oceans” by Alfred Wegener Alfred Wegener - fully developed the continental drift theory - German meteorologist - According to Wegener, the continents were once joined together in a one large landmass called “supercontinent” or “Pangaea” Wegener’s Evidence Topographic Evidence Fossil Correlation Rock Formation Paleoclimatic Evidence Topographic Evidence - Wegener noticed that the continents seemed to fit together. - The “good fit” suggested that just like neighboring pieces of a jigsaw puzzle, the continents were once connected in a single supercontinent. - He pieced together the map of Africa and South America. Fossil Correlation  - Fossils are traces and remains of organism that lived in pre-historic times - One of Wegener’s example is the remains of Mesosaurus - Before Pangea broke apart, similar layers of rocks were formed in Antarctica, Australia, South America, Africa and India. Glossopteris fossils were found in the rocks on each continent Rock Formation - Rocks and fossils in the continents located in the southern hemisphere exhibit identical pattern known as “Gondwana Sequence”. - These rocks were of the same age and type - The US Appalachian Mountains are similar to Greenland and Europe Paleoclimatic Evidence - Wegener considered as evidence the glacial till deposits in the northern and southern latitudes. - It was said that the Earth’s climate has not changed, instead the positions of the continents have changed. - The discovery of fossils from tropical plants in the form of COAL DEPOSITS in Antarctica. - Possibly, Antarctica used to be close to the equator where the climate is warmer. SEA-FLOOR SPREADING MID-OCEAN RIDGE - The undersea mountain chain where new ocean floor is produced, a divergent plate boundary SONAR - A device that determines the distance of an object under water by recording echoes of sound waves. THE SONAR IS USED TO MAP THE OCEAN FLOOR - Sonar bounces sound waves off underwater objects and then records the echoes of these sound waves. - The time it takes for the echo to arrive indicates the distance to the object. EVIDENCE FOR SEA-FLOOR SPREADING - In the 1960s, Harry Hess examined maps of the mid-ocean ridge. He proposed that the ocean floors move like conveyor belts, carrying the continents with them. SEA-FLOOR SPREADING - The process by which molten material adds new oceanic crust to the ocean floor. Evidences for sea-floor spreading in 1960s EVIDENCE FROM MOLTEN MATERIAL - Alvin’s crew found strange rocks shaped like pillows or like toothpaste squeezed from a tube. - Such rocks can form only when molten material hardens quickly after erupting under water. - The presence of these rocks showed that molten material has erupted again and again from cracks along the central valley of the mid-ocean ridge. EVIDENCE FROM MAGNETIC STRIPES EVIDENCE FROM DRILLING SAMPLES - When scientists sampled the rocks, they found that the further away from the ridge, the rocks were older they were. - The younger rocks were always in the center of the ridges. DEEP-OCEAN TRENCHES - A deep valley along the ocean floor through which the oceanic crust slowly sinks towards the mantle. SUBDUCTION - The process by which ocean crust sinks through a deep-ocean trench and back into the mantle, a convergent plate boundary. WHAT HAPPENS TO THE OCEAN FLOOR AT DEEP OCEAN TRENCHES?? - At deep-ocean trenches, two plates collide causing the denser of the two plates to dive back into the mantle. This process is known as subduction. - Over tens of millions of years, this material melts back into molten material and may rise again as a new oceanic crust. WHAT IS THE PROCESS OF SEA-FLOOR SPREADING?? - At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. - Over tens of millions of years, the process continues until the oldest ocean floor collides with the continental crust. - The more dense oceanic crust subducts (sinks) back into the mantle at a deep-ocean trench. SUBDUCTION AND EARTH’S OCEANS SUBDUCTION IN THE PACIFIC OCEAN - Subduction in the pacific ocean is occurring at a greater rate than sea-floor is expanding. - This is caused by a large amount of trenches. WHAT WILL HAPPEN TO THE PACIFIC OCEAN IN THE FUTURE?? - The pacific is destined to vanish as Earth’s continents meld into a new supercontinent. - The pacific ocean’s days are numbered, according to a new supercomputer simulation of earth’s ever-drifting tectonic plates. - The good news?? Our planet’s oldest ocean still has another 300 million years to go. SUBDUCTION IN THE ATLANTIC - The Atlantic ocean is expanding at a greater rate than subducting. - This is because of the low number of trenches in the Atlantic. - Over time the entire ocean gets larger and pushes against the continents. The Structure and Evolution of Ocean Basins Overview of Ocean Basins Ocean basins cover about 70% of the Earth's surface. They are large areas below sea level and contain the majority of the planet's water, resembling a bowl. Oceanic Basin Landforms Key topographical features of ocean basins include: ○ Continental Shelf ○ Seamounts ○ Abyssal Plain ○ Mid-Ocean Ridge ○ Deep Ocean Trench ○ Guyot ○ Continental Rise Sonar and Bathymetry Technologies like echo sounders, side-scan sonar, and satellites are used to map ocean basin features. Bathymetry: Measurement of ocean depths and underwater topography, achieved through sonar. Structures of Ocean Basins 1. Mid-Oceanic Ridge ○ Accounts for 23% of Earth's surface. ○ Found at the center of ocean basins, may include volcanic islands like Iceland. 2. Ocean Trench ○ Long, steep depressions that are the deepest parts of the ocean.  3. Abyssal Hill/Plain ○ Abyssal hills are raised features on the ocean floor. ○ Abyssal plains are flat areas covered with sediment from continental areas. 4. Seamounts ○ Submerged volcanic mountains that can reach heights of up to 10,000 feet. 5. Guyot ○ A seamount with a flat top, formed due to erosive wave processes. 6. Continental Rise ○ Gently sloping area at the base of the continental slope, formed by sediment deposits from submarine canyons. 7. Continental Shelf ○ A shallow and gently sloping area of the continental crust. 8. Continental Slope ○ Extends from the continental shelf and slopes down to the ocean floor, marked by a shelf break. Major Divisions of Ocean Basins 1. Continental Margins ○ Submarine edges characterized by lighter continental crust compared to adjacent oceanic crust. ○ Includes continental shelf, slope, and rise. 2. Deep-Ocean Basins ○ Areas of the ocean with deep water, covering most of Earth's surface. 3. Mid-Ocean Ridges ○ Occur along divergent plate boundaries where new ocean floor is formed. Characteristics of Oceanic Landforms Unique physical and geological features exist beneath oceans, yet most areas remain unexplored due to their vastness (70% of Earth's surface is covered by oceans). Collaboration is ongoing within the scientific community to better understand these features. Evolution of Ocean Basins Formed due to tectonic forces, especially from volcanic activity at mid-ocean ridges. Oldest oceanic rocks are around 200 million years old, while oceanic crust is younger than continental crust due to subduction. Subduction Zones Found at continental margins where oceanic meets continental crust. Responsible for creating ocean trenches. The Wilson Cycle  A model explaining the formation and destruction of ocean basins during the life cycle of supercontinents. Five Ocean Basins Ranked by Size 1. Pacific Ocean - largest and deepest (65,200,000 sqkm) 2. Atlantic Ocean 3. Indian Ocean 4. Southern Ocean 5. Arctic Ocean Ocean Basin and Continent Boundaries Continental crust is thicker and lighter than the denser oceanic crust, which lies lower than sea level. Age of Oceanic Crust Spreading rates indicate that the crust under the Pacific Ocean could form in about 100 million years, with age patterns evident in oceanic crust. Types of Plate Movements 1. Divergent Boundaries: Plates pull apart from each other. New crust forms as magma rises to fill the gap, often creating mid-ocean ridges. 2. Convergent Boundaries: Plates collide and one plate may subduct beneath another. This can result in the formation of mountains, trenches, and volcanic arcs (e.g., Himalayas, Marianas Trench). 3. Transform Boundaries: Plates slide past each other horizontally. This movement can cause earthquakes (e.g., San Andreas Fault). Geological Features from Plate Movements Mountains: Formed at convergent boundaries. Volcanic Arcs: Result from subduction of oceanic plates beneath continental plates. Ocean Trenches: Deep features formed at convergent boundaries where one plate sinks below another. Ridges: Formed at divergent boundaries where new crust is created. Importance of Plate Tectonics  Understanding plate movements helps explain the distribution of earthquakes, volcanic activity, and the formation of various landforms. The theory of plate tectonics supports the concept of continental drift and seafloor spreading. Types of Plate Boundaries 1. Divergent Plate Boundaries Definition: Two lithospheric plates move away from each other. Examples: Mid-Atlantic Ridge, East Africa Rift Valley. Geological Effects: Formation of rift valleys and oceanic ridges. Shallow earthquake activity and volcanic activity. 2. Convergent Plate Boundaries Definition: Two lithospheric plates move toward each other. Types: Continental-Continental: Plates collide, forming mountain ranges (e.g., Himalayas). Oceanic-Oceanic: Denser oceanic plate subducts, forming island arcs (e.g., Mariana Islands). Continental-Oceanic: Oceanic plate subducts beneath continental plate, forming volcanic arcs (e.g., Andes Mountains). Geological Effects: Creation of trenches, volcanic activity, and intense earthquake activity. 3. Transform Fault Boundaries Definition: Two lithospheric plates slide past each other. Examples: San Andreas Fault. Geological Effects: Strike-slip faults leading to shallow earthquakes. No land creation or destruction. Importance of Stratified Rocks Stratified rocks, especially sedimentary rocks, contain vital information about Earth's history and the evolution of life. Geologists study these rocks to reconstruct geological events using petrology, stratigraphy, and paleontology. Key Terms  Petrology: Study of the origin, composition, structure, and classification of rocks. Stratigraphy: Study of rock layers (strata) and layering (stratifications). Paleontology: Study of ancient life, particularly fossils. Stratification Definition: The layering in sedimentary rocks and some igneous rocks formed from lava flows. Characteristics: Layers vary in thickness from millimeters to meters. Sedimentary rocks typically occur in beds, a phenomenon known as stratification or bedding. When individual beds are very thin, it is referred to as lamination. Formation Process Stratification occurs in stages; sediment deposition can temporarily cease, resulting in bedding planes that separate layers. The bedding plane marks the boundary between adjacent beds of strata. Geological Significance The study of stratified rocks helps in developing the geologic time scale, which organizes Earth's history based on rock layers and fossil records. Relative Dating: Estimates the age of a rock layer by comparing it to nearby layers. Absolute Dating: Determines the exact numerical age of a rock layer. Relative Dating Methods Stratigraphy: Assumes the lowest layer is the oldest and the topmost layer is the youngest. Biostratigraphy: Uses fossils to establish a strategy for dating. Cross Dating: Compares fossils of one layer with another layer of known dating. Absolute Dating Methods Radiometric Dating: Measures the amount of a particular radioactive isotope present in the sample. Amino Acid Dating: Determines age by the change in proteins of the sample.  Dendrochronology: Uses the number of annual growth rings of a tree to determine its age. Thermoluminescence: Determines the age based on the emissions of electrons when an object absorbs light. Relative Dating ○ Definition: Establishes the order of events without assigning a specific age. ○ Methods: Law of Superposition: In undisturbed layers, older layers are at the bottom. Principles: Original horizontality, lateral continuity, cross-cutting relationships, inclusions, unconformities, and uniformitarianism. ○ Application: Used to compare the ages of fossils and rock layers. Absolute Dating ○ Definition: Provides a specific age or date range in years. ○ Methods: Radiometric Dating: Uses the decay of radioactive isotopes (e.g., Carbon-14, Potassium-40) to determine age. Other Techniques: Luminescence dating, fission track dating. ○ Application: Assigns exact ages to fossils and rocks. Importance of Dating Both relative and absolute dating are crucial for constructing the geological time scale and understanding Earth's history, the evolution of life, and geological events. Geologic Time Scale Definition: A hierarchical timeline used to describe the age of rocks and fossils and the events that formed them. Divisions: Eons: Largest time blocks, divided into eras. Eras: Further divided into periods. Periods: Divided into epochs. Major Eons 1. Precambrian Eon (4.6 billion to 541 million years ago) Divided into three eras: Hadean, Archean, Proterozoic. Limited fossil and rock evidence available. 2. Phanerozoic Eon (541 million years ago to present)  Divided into three major eras: Paleozoic Era (541 to 252 million years ago): Known as the "Age of Fishes," marked by life evolving in oceans and colonizing land. Mesozoic Era (252 to 66 million years ago): Known as the "Age of Dinosaurs," dominated by reptiles and the formation and breakup of the supercontinent Pangaea. Cenozoic Era (66 million years ago to present): Known as the "Age of Mammals," following the extinction of dinosaurs.