Earth Sci PDF

EARTH SCI The Exogenic Processes of the Earth - The word exo means ‘from outside’ or ‘external’ and the genic word means ‘origin’. All the forces that act outside the earth’s surface and cause changes in the earth’s surface are called exogenic forces. Exogenic Processes - The word...

EARTH SCI The Exogenic Processes of the Earth - The word exo means ‘from outside’ or ‘external’ and the genic word means ‘origin’. All the forces that act outside the earth’s surface and cause changes in the earth’s surface are called exogenic forces. Exogenic Processes - The word exogenic comes from two Greek words exo and genic. The word exo means ‘from outside’ or ‘external’ and the genic word means ‘origin’. All the forces that act outside the earth’s surface and cause changes in the earth’s surface are called exogenic forces. And all these forces that are constantly acting on the surface of the crust and are causing the evolution of landforms are called exogenic processes. The four main exogenic processes are weathering, erosion, deposition, and mass wasting. 1. Weathering - Disintegration of rocks, soils, and minerals together with other materials through contact in Earth’s subsystem. (kapag may dalawang rocks na nagkiskisan tapos nag-disintegrate) Types of Weathering: A. Physical Weathering - Breakdown of rocks into pieces without any change in its composition. Factors of Physical Weathering: 1. Release of Pressure - Process wherein tectonic forces lifts deeply buried rocks close to the surface and then erosion removes overlying rock, removing the pressure and causing the rock to expand and fracture. 2. Frost Wedging - A process in which water freezes in a crack of a rock and then the expansion edges the rock apart. 3. Abrasion - A process that consists of the grinding and rounding of rock surfaces by friction and impact caused by waves and glaciers. 4. Biological & Human Activity - A process in which a crack in a rock is expanded by plant roots or broken by animals and human activities. 5. Thermal Expansion & Contraction- Occurs when temperature changes rapidly, causing the surface of the rock to heat or cool. (Cold = contract ; Hot = expand)  B. Chemical Weathering - Breaking rocks through chemical reactions that change the original rock-forming minerals. Factors of Chemical Weathering: 1. Dissolution - A process in which a mineral or rock dissolves in water forming a solution like halite (rock salt) dissolved in water. 2. Hydrolysis - A process in which a mineral reacts with water to form a new mineral that has water as part of its crystal structure like feldspar to clay. 3. Oxidation - A process in which a mineral decomposes when it reacts with oxygen like the rusting of iron. 2. Soil Erosion - The process in which Earth’s surface is worn away by wind, water, or ice. - The surface process characterized by removal of rock particles from where they were formed. Erosion moves rock debris or soil from one place to another (deposition). - Takes place during rainfall, runoff, flowing river, flooding, freezing, hurricane, wind, etc. - Agents of Erosion: Water, Ice and Glaciers, Animals, Air, Gravity, Humans 3. Mass Wasting - It is the movement of material on a downslope terrain due to gravity. Usually happens on slopes. Types of Mass Wasting: 1. Debris Flow - Happens when many sediments, usually rocks of various sizes, fall downslope. Debris flow does not need water to flow down. 2. Mudflow - Combined soil and water flow downslope. Usually happens near rivers and streams where soils or sands are moist. 3. Slumps - A slow downslope movement of loosely consolidated materials rock and soil layers. Factors of Mass Wasting: - Water - Over steepened Slopes - Vegetation Removal - Earthquakes 4. Deposition - It is the exogenic process that happens after erosion. This process adds sediments, soil and rocks to a landform or land mass. Types of Deposition: 1. Water deposition - Where a river meets the ocean is called the mouth of the river. Soil carried by a river is deposited at the mouth and new land is formed. 2. Wind Deposition - Sand dunes are large deposits of sand dropped when the wind stopped blowing. The location of the sand dunes shifts frequently. 3. Glacial Deposition - When glaciers melt, they drop or deposit the rocks they were carrying. The Endogenic Processes of the Earth Endogenic processes play a pivotal role in shaping the Earth's lithosphere, which includes the crust and the uppermost mantle. ENDOGENIC PROCESSES - The term "endogenic process" refers to the internal processes that occur within the Earth, driven by heat and other forces originating from its interior. 1. Folding - Folding is a process in which the rocks bend instead of breaking when they are subjected to forces generated by tectonic movements. Also folding occurs due to horizontal compression of rock layers by internal forces of the earth. Accordingly, this can create a variety of landforms as the surfaces of the folded rocks are eroded in due course of time. Folds are the outcome of slow deformation of rocks. - Fold mountains are created through a process called OROGENY = Wherein two or more of Earth's tectonic plates are pushed together. This movement causes layers of rock to become wrinkled and folded. 2. Faulting - When the tensional force is moderate, the crustal rock develops only crack (fractures) but when intense tensional force works the rock beds are dislocated and displaced, also resulting in formation of faults. Thus, faults are those fractures in the rock body along which there has been an observable amount of displacement. - Fault is a planar or gently curved fracture in the rocks of Earth’s crust, where compressional or tensional forces cause relative displacement of the rocks on the opposite sides of the fracture. Classification of Faults: 1. ACTIVE FAULTS - Active faults are structures along which we expect displacement to occur. 2. INACTIVE FAULTS - Inactive faults are structures that we can identify, but which do not have earthquakes. Types of Faults: 1. Normal Faults - The faults having displacement of both the rock blocks in opposite directions are called normal faults. - Where the hanging wall has moved downward relative to the footwall due to extensional forces, typically associated with divergent plate boundaries. - Normal faults can be observed in various geological settings, such as rift zones and areas undergoing tectonic stretching. 2. Reverse faults (Thrust fault) - Because of extreme compression, along with the tensional force, rocks snap and one block of fractured rock is pushed over the underlying block. - Where the hanging wall has moved upward relative to the footwall due to compressional forces, often associated with convergent plate boundaries. - This type of fault can result in significant geological features and can also generate powerful seismic events. 3. Lateral or strike-slip fault - This fault is formed when the rock blocks are displaced horizontally along the fault plane due to horizontal movement.  - Where the movement of tectonic plates occurs predominantly horizontally, parallel to the fault plane, in opposite directions, typically due to horizontal shearing forces. - These faults are commonly found along transform plate boundaries, such as the San Andreas Fault in California. 3. Volcanism - Volcanism is any of various processes and phenomena associated with the surficial discharge of molten rock, pyroclastic fragments, or hot water and steam, including volcanoes, geysers, and fumaroles. Volcanoes are vents, or openings in Earth's crust, that release ash, gasses and steam, and hot liquid rock called lava. When the lava cools and hardens, it forms into the cone-shaped mountain we think of as a volcano. Most of the world's volcanoes are found around the edges of tectonic plates, both on land and in the oceans. - On land, volcanoes form when one tectonic plate moves under another. Usually a thin, heavy oceanic plate subducts, or moves under, a thicker continental plate. When this happens, the ocean plate sinks into the mantle. Parts of a Volcano: 1. Ash Cloud - Cloud of gas, steam, ash, dust, and coarser fragments that form during an explosive volcanic eruption and commonly gets blown long distances. 2. Crater - a bowl-shaped geological formation at the top of a volcano. 3. Vent - any opening, as in a wall, serving as an outlet for air, smoke, fumes, or the like. 4. Throat - The uppermost section of the main vent is known as the volcano’s throat. As the entrance to the volcano, it is from here that lava and volcanic ash are ejected. 5. Lava Flow - a stream or sheet of molten or solidified lava. 6. Conduit - An underground passage magma travels through. 7. Sill - A flat piece of rock formed when magma hardens in a crack in a volcano. 8. Parasitic Cone - A small cone-shaped volcano formed by an accumulation of volcanic debris. 9. Secondary Vent - a secondary vent is a vent or tube that connects to the secondary cone for the lava to flow. 10. Magma Chamber - a reservoir of magma in the earth's crust where the magma may reside temporarily on its way from the upper mantle to the earth's surface. Types of Volcanoes based on its SHAPE: a. Composite Volcanoes (stratovolcanoes) - They have slopes that get steeper near the top of the volcano. A classic composite volcano is conical with a concave shape that is steeper near the top. They tend to form relatively quickly and do not last very long. If volcanic activity ceases, it might erode within a few tens of thousands of years. This is largely because of the presence of pyroclastic eruptive material, which is not strong. (Mayon Volcano) b. Cinder Cones (spatter cones) - Technically known as scoria cones, Cinder cones are the most common type of volcano in the world. They have straight sides and are typically less than 200 m high. They can be eroded away easily, and relatively quickly because cinder cones are made up almost exclusively of loose fragments. (Taal Volcano) c. Shield Volcanoes - Have broad rounded shapes and are the largest. The largest of all volcanoes on Earth is Mauna Loa. Most shield volcanoes are formed from fluid, basaltic lava flows and produce low viscosity, runny lava, that spreads far from the source and forms a volcano with gentle slopes. Built by repeated eruptions. Most dangerous eruption kasi mabilis nagse-spread. (Mt. Vesuvius; Pompeii) Types of Volcanoes based on its PERIODICITY: a. Active Volcanoes - Are those which continuously eject lavas, gases, and fragmental materials. About 100 % of the world's active volcanoes are situated along the perimeter of the Pacific Ocean (Ring of Fire). b. Dormant Volcanoes - Are those which have been quiescent for a long time but in which there is possibility of further eruption. It hasn’t erupted in the past 10,000 years, but it is expected to erupt again. (Mt. Fuji) c. Extinct Volcanoes - These are volcanoes in which the eruption has completely stopped and is not likely to occur. (Mt. Thielsen) 4. Earthquakes - Earthquakes are vibrations of the earth caused by ruptures and sudden movements of rocks that have been strained beyond their elastic limits. These Earthquakes can be considered as a form of energy of wave motion transmitted through the surface layer of the earth. The place of origin of earthquakes inside the earth is known as focus. Causes of Earthquakes: 1. Volcanic Eruption - All volcanic eruptions create vibrations that are manifested in the form of earthquakes. 2. Faulting - Create strains in the underlying rocks which beyond a certain point fracture creating earthquakes. 3. Plate Tectonics - Plate boundary interactions give raise to earthquakes. Seismic Waves (Earthquake Waves). 1. Body Waves - Body waves are seismic waves that travel through the body of the earth. P-Waves (P stands for primary or pressure or push-pull). These waves are also called longitudinal waves or compressional waves due to particle compression during their transport. These waves involve compression and rarefaction of the material as the wave passes through it but not rotation. P-wave is transmitted by particle movement back and forth along the direction of propagation of the wave. P-waves have the greatest speed and appear first on seismograms. Can move through solid, liquid, or gas. They leave behind a trail of compressions and rarefactions on the medium they move through. S-Waves (S stands for secondary or shear or shake). Also known as transverse waves, because particle motions are transverse to the direction of movement of the wavefront, or perpendicular to the ray. These waves involve shearing and rotation of the material as the wave passes through it, but not volume change. S-waves have speeds less than P-waves and appear on seismograms after P-waves. 2. Surface Waves - Surface waves are seismic waves that are guided along the surface of the Earth and the layers near the surface. Surface waves are larger in amplitude and longer in duration than body waves. Surface waves travel more slowly through Earth material at the planet's surface and are predominantly lower frequency than body waves. They are easily distinguished on a seismogram. Rayleigh waves - descriptively called "ground roll" in exploration seismology. The particle motion of this wave is confined to a vertical plane containing the direction of propagation and retrogrades elliptically. The particle displacements are greatest at the surface and decrease exponentially downward. Rayleigh waves show dispersion, and its velocity is not constant but varies with wavelength. This wave is like how ocean waves propagate.  Love waves - (named for A.E.H. Love, who discovered them) travels by a transverse motion of particles that is parallel to the ground surface. This wave is somewhat like S-waves. The particle motion is transverse and horizontal. Generally, Love wave velocities are greater than Rayleigh waves, so Love waves arrive before Rayleigh waves on seismographs. Magnitude VS Intensity - Magnitude is a measure of earthquake size and remains unchanged with distance from the earthquake. Intensity, however, describes the degree of shaking caused by an earthquake at a given place and decreases with distance from the earthquake epicenter. The Richter Magnitude Scale - The Richter magnitude scale (often shortened to Richter scale) is the most common standard of measurement for earthquakes. It was invented in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The Richter scale is used to rate the magnitude of an earthquake, that is the amount of energy released during an earthquake. The Modified Mercalli Intensity Scale - The Modified Mercalli intensity scale measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake. It was developed by the Italian volcanologist Giuseppe Mercalli in 1884 and expanded to include 12 degrees of intensity in 1902 by Adolfo Cancani. It was modified again by Harry O. Wood and Frank Neumann in 1931. It is known today as the Modified Mercalli Intensity Scale. Intensity Shaking Description/Damage I Not felt Not felt except by a very few under especially favorable conditions. II Weak Felt only by a few people at rest,especially on upper floors of buildings. III Weak Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated. IV Light Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sounds. Sensation like a heavy truck striking building. Standing motor cars rocked noticeably. V Moderat Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects e overturned. Pendulum clocks may stop. VI Strong Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage is slight. VII Very Damage negligible in buildings of good design and construction; slight to moderate in well-built strong ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. VIII Severe Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage is great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. XI Violent Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. X Extreme Some well-built wooden structures were destroyed, most masonry and frame structures destroyed with foundations. Rails bent. Continental Drift Theory and Earth’s Plate Tectonics According to the theory, Pangaea existed about 240 million years ago. By about 200 million years ago, this supercontinent began breaking up. Over millions of years, Pangaea separated into pieces that moved away from one another. These pieces slowly assumed their positions as the continent we recognize today… Continental Drift Theory Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics. Alfred Lothar Wegner - A German meteorologist and geophysicist who formulated the first complete statement of the continental drift hypothesis. - In the early 20th century, Wegener published a paper explaining his theory that the continental landmasses were “drifting” across the Earth, sometimes plowing through oceans and into each other. He called this movement continental drift. Pangaea About 200 million years ago, all the continents on Earth were actually one huge "supercontinent" surrounded by one enormous ocean. This gigantic continent, called Pangaea, slowly broke apart and spread out to form the continents we know today. Today, scientists think that several supercontinents like Pangaea have formed and broken up over the course of the Earth’s lifespan. Pangaea started to break into two smaller supercontinents called Laurasia and Gondwanaland during the Jurassic Period. Laurasia & Gondwana LAURASIA - a large supercontinent that existed in the northern hemisphere before it began to break up. This consists of the modern day continents of North America, Europe and Asia. GONDWANA - a large supercontinent that existed in the southern hemisphere, clustered near the Antarctic Circle. This consists of the modern-day continents of Antarctica, India, Australia, South America and Africa. Evidences of Continental Drift Theory: Evidence 1: Continental Jigsaw Puzzle - Best representation is the South America & Africa Evidence 2: Fossils Match across the Seas Evidence 3: Rock Types and Structures Match Evidence 4: Ancient Climate (Coal Deposits) LAND FORMATION - According to the Book of Genesis, God made dry land on the third day. The land had high mountains, rolling hills, flat plains, and valleys. Every part of the dry land was beautiful. (Genesis 1:9) The Plate Tectonics Theory Plate tectonics is a scientific theory that explains how major landforms are created because of Earth’s subterranean movements. The theory, which solidified in the 1960s, transformed the earth sciences by explaining many phenomena, including mountain building events, volcanoes, and earthquakes. 3 TYPES of PLATE BOUNDARIES: 1. Divergent Boundary - A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create a new oceanic crust. 2. Convergent Boundary - When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into mountains, volcanoes, trenches, and mountain ranges. Types of Convergence: - Continent‐continent Convergence → results when two continents collide. The continents were separated at one time by oceanic crust that was progressively subducted under one of the continents. Older and denser plate subducts. - Ocean‐continent Convergence → occurs when oceanic crust is subducted under continental crust. This forms an active continental margin between the subduction zone and the edge of the continent. - Ocean‐ocean Convergence → occurs when two plates carrying oceanic crust meet. One edge of ocean crust is subducted beneath the other at an ocean trench. The ocean trench curves outward toward the subducting plate over the subduction zone. 3. Transform Plate Boundary - Two plates sliding past each other forms a transform plate boundary. Natural or human-made structures that cross a transform boundary are offset — split into pieces and carried in opposite directions. No landforms created. Seafloor Spreading Theory Seafloor spreading is a geologic process in which tectonic plates—large slabs of Earth's lithosphere—split apart from each other. Seafloor spreading and other tectonic activity processes are the result of mantle convection. Mantle convection is the slow, churning motion of Earth’s mantle. Convection currents carry heat from the lower mantle and core to the lithosphere. Convection currents also “recycle” lithospheric materials back to the mantle. The History of the Earth “The natural history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geological change and biological evolution.” The Geologic Time Scale - The Geologic Time Scale is a fundamental tool used by geologists and other Earth scientists to understand and describe the history of our planet. It is a system for organizing the history of the Earth into units of time, from the smallest to the largest, based on the events and processes that have occurred. Since then, the Geologic Time Scale has continued to evolve and be refined. Today, it is a sophisticated tool that is used by geologists and other Earth scientists to study the history of the planet and the evolution of life on Earth. The Geologic Time Scale is divided into several large units of time, including eons, eras, periods, and epochs, and it provides a framework for understanding the relationships between events in Earth’s history. - In conclusion, the development and evolution of the Geologic Time Scale has been a slow and ongoing process, spanning several centuries and involving contributions from many scientists. Today, it is a critical tool for understanding the history of our planet, and it continues to be refined as new data and techniques become available. - The Geologic Time Scale is a record of the life forms and geologic events in Earth's history. Since then, the Geologic Time Scale has continued to evolve and be refined. - It is used by geologists and other Earth scientists to study the history of the planet and the evolution of life on Earth. 1. EON - measured in billions of years, is the longest time unit of the geologic time scale. 2. ERA - defined by the differences in life-forms found in rock and measured in hundreds of millions to billions of years. 3. PERIOD - measured in tens of millions of years to hundreds of millions of years, are defined by the life-forms that were abundant or became extinct during the time. 4. EPOCH - the smallest unit & are usually measured in millions of years to tens of millions of years. The Geologic Timeline of the Earth The Precambrian Super Eon: - The Precambrian Earth saw bombardment by large objects, separation of the crust into the first continents and ocean basins, mobilization of crustal plates, transition of the atmosphere from reducing to oxidizing, and the origin and evolution of early life. Hadean Eon: 4.5 to 4.0 billion years ago - Named after the Greek god and ruler of the underworld, Hades; inspired from the brutal, hell-like conditions of the earth and the constant barrage and bombardment of colossal meteorites and comets. The oldest eon, dates from 4.5 to 4.0 billion years ago. Characterized by an extremely hot temperature due to several mechanisms such as asteroid impacts, gravitational compression, and radioactive decay. - Earth collided with planet “Theia”, which is the reason for the creation of the moon, and why the earth is tilted. Archean Eon: 4.0 to 2.5 billion years ago - Derived from the Greek word “archaios”, which means the beginning or origin. Formation of the first continents (cratons) and the first oceans. The first evidence of modern plate tectonics is found at the end of the Archean eon, indicating the occurrence of at last some continental lithosphere. Appearance of the first prokaryotic bacteria “cyanobacteria”. Proterozoic Eon: 2.5 billion to 541 million years ago - Meaning “earlier life”, eon of time after the Archean eon. Oxygen accumulated in the atmosphere through photosynthesis performed by early-life form organisms. First multicellular and eukaryotic organisms appeared. THE START OF BIODIVERSITY: The Phanerozoic Eon - Referred to as “the eon of visible life”. Extending about 541 million years ago to the present time. Rapid expansion and evolution of biological forms as well as the formation of ecological niches. Composed of three major eras: Paleozoic Era: - The earliest of the three geologic eras of the phanerozoic eon and the longest of the three phanerozoic eras, lasting from 541 million years to approximately 252 million years ago. Characterized by formation of the supercontinent and widespread of plants and early vertebrate life forms. Cambrian Period: The first geological period of the Paleozoic era, and of the phanerozoic eon, occurred approximately 541 to 485 million years ago. Produced the most intense burst of evolution through the phenomenon known as “the Cambrian Explosion”, which gave life to an incredible diversity including major animal groups alive today. Trilobites (early marine life na fossils na) are common. Earliest forms of vertebrates appeared. Ordovician Period:  The second of six periods of the Paleozoic era which spanned from 485 to 443 million years ago. During this period, the majority of the area in the northern portion of the world is almost entirely ocean. Marine invertebrates flourished and the first jawless fish appeared. On land, the first plants appeared. Silurian Period: The third and acclaimed as the shortest period of the Paleozoic era, lasting from only 443 to 419 million years ago. Stabilization of the earth’s general climate. Melting of large glacial formation which gave way to a substantial rise in the levels of the major seas. Rapid spread of jawless fish and highly significant appearances of both the first freshwater and jawed fishes. Development of the first vascular plants. May have marked the beginning of the first terrestrial animal life. Devonian Period: The fourth period of the Paleozoic era which occurred from 419 to 358 million years ago. Appearance of ferns, seed plants, and the first trees and first forests. First terrestrial arthropods including wingless insects and earliest arachnids. Sometimes referred to as “the age of fishes”, due to marine life diversity. Appearance of the first amphibians. Carboniferous Period: The fifth period of the Paleozoic era which lasted from 358 to 298 million years ago. Carboniferous, which means “carbon-bearing”, amount of coal produced in the vast swamp forests during this period. Occurrence of one of the greatest evolutionary innovations: the amniote egg, which provided the animals the ability to lay eggs. Appearance of the first form of reptiles. Permian Period: The sixth and final period of the Paleozoic era which ranged from 298 to 251 million years ago. Early formation of the supercontinent Pangaea. Proliferation of early forms of reptiles and other gymnosperms (non-flowering). Phenomenon known as “the great dying”, (or Permian-Triassic Extinction, around 96% life of earth died) which is acknowledged as the largest mass extinction in the history of life on earth. Mesozoic Era - The second of the three geologic eras of the phanerozoic eon, lasting from 251 million years to 65 million years ago. Mesozoic means “middle animals”, this is due to the drastic change in the world fauna compared to what has been seen in the Paleozoic era. A time of great change in the terrestrial vegetation. Triassic Period: The first and recognized as the shortest period of the Mesozoic era, spanning only from 251 to 201 million years ago. The supercontinent Pangaea finished forming, altering the global climate and water circulation. Reptiles increased in diversity and in number. Appearance of the first dinosaur. First mammals emerged; tiny, fur-bearing, mouse-like animals derived from reptiles. Jurassic Period: The second period of the Mesozoic era which occurred from 201 to 145 million years ago. Dubbed as “the age of reptiles”. Propagation and domination of dinosaurs on the land fauna. Oceans exhibit a wide diversity of marine animals. Characterized by vertebrates taking to the air and the appearance of the first bird. Phenomenon known as “Triassic-Jurassic Extinction” had occurred due to a major volcanic eruption and asteroid impact causing the death of 80% of the population. Cretaceous Period: The third, last, and longest period of the Mesozoic era which ranged from 145 to 66 million years ago. Continuation of the drifting apart of the supercontinent Pangaea, which led to regional differences in the floras and faunas between the northern and southern continents. Appearance of the first flowering  plants or angiosperms. Many modern groups of insects diversified. Marked with the phenomenon known as “The Cretaceous-Tertiary Extinction” which wiped out 60%-76% of the population and the extinction of the dinosaurs. Cenozoic Era (the recent era) - The recent and third of the three geologic eras of the phanerozoic eon, lasting from 66 million years ago to the present day. Cenozoic which means “new life” and is sometimes referred to as “the age of mammals”, due to the dominant terrestrial fauna. Interval of time during which the continents have assumed their current configuration. Tertiary or Paleogene Period: The first period of the Cenozoic era, which occurred from 66 to 23 million years ago; known as the earliest division of the tertiary period. Derived from the Greek word which means “ancient-born”. ➔ Paleocene Epoch: continents drift towards their current positions; fern spikes and development of modern plant species. ➔ Eocene Epoch: development of modern orders of mammals; open savannah-like vegetation. ➔ Oligocene Epoch: temperate and subtropical climatic conditions; terrestrial and vertebrate faunas become diverse and abundant. Neogene Period: The second period of the Cenozoic era which lasted from 23 to 2.6 million years ago. Derived the Greek word which means “new born”, designed to give emphasis that the marine and terrestrial fossils found in the strata of this time are closely related. ➔ Miocene Epoch: modern, land-dwelling animals such as giraffes, elephants, antelopes, and dears; horse evolution occurred in North America, first dogs and bears appeared. ➔ Pliocene Epoch: colder and drier climate; mastodons (elephant-like animals) had a great evolutionary diversification; appearance of the first primates and australopithecines, the first creatures that can be termed human. Quaternary Period (current period): The current and most recent of the three periods under Cenozoic era, spanning from 2.8 million years ago to the current time. Characterized by several periods of glaciations, commonly referred to as “ice age” which resulted in rapid changes in climate and sea level. Rapid changes in life forms, both flora and fauna and known for the rise of modern humans. ➔ Pleistocene Epoch: Informally referred to as “the great ice age”, this is the time during which a succession of glacial and interglacial climate cycles occurred; characterized by the presence of distinctively large mammals and birds; and saw the evolution and expansion of our own species, Homo sapiens. ➔ Holocene Epoch: Recognized as “the age of man”, since it has witnessed all of humanity’s recorded history and the rise and fall of its civilizations and characterized by the great advancement and development of human knowledge and technology. ➔ Anthropocene Epoch: The “Age of Humans”. Start of naming geologic-time terms needs to define what exactly the boundary is, where it appears in the rock strata.. Proposed epoch of today. Fossils: Evidence of Past Life Any preserved body part, excrement, or impression of an organism that lived in the distant past. They are the traces of organisms and were preserved by natural processes or catastrophic events. Types of Fossils: 1. Mold Fossil - It is an impression fossil and a fossilized imprint form in the substrate. 2. Cast Fossil - Are produced when a mold fills with sediment and then hardens into rock. 3. Trace Fossil - Also known as ichnofossils. Contain information about preserved footprints, trails, burrows, or any stamps that reveal about how things lived. 4. True-form Fossil - Are large body parts of an organism that has been substituted by minerals (amber). Relative Dating and Absolute Dating Relative dating tells how old something is in relation to other objects but cannot provide a year or specific date of use. considers how old artifacts and sites are, in comparison to other artifacts and sites. Stratigraphy and style are both used for relative dating. Principle of Original Horizontality: This principle states that layers of sediment are originally deposited horizontally under the action of gravity. This means that any "sloping" of layers must have occurred after the layers formed. Principle of Superposition: A vertical set of strata (layers) is a chronological record of the geologic history of the strata. Youngest layers are on top and oldest on bottom. Principle of Lateral Continuity: Originally extended in all directions until they thinned to zero or terminated against the edges of their original or deposition basin. Principle of Cross-Cutting Relationship: The geologic feature which cuts another is the younger of the two features. Absolute dating provides a specific calendar year for the occupation of a site. Radioactive dating is a method of dating rocks and minerals using radioactive isotopes. This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks. Isotopes are variations of an element that have different numbers of neutrons in the nucleus. Isotopes can be thought of as variations of an element. Radioactive isotopes are species of an element that have unstable combinations of neutrons and protons. Types of Radioactive Dating: Parent Daughter Half Life (years) Dating Range (years) Uranium-238 Lead-206 4,500 million 10 - 4,600 million Potassium-40 Argon-40 1,300 million 0.05 to 4,600 million Rubidium-87 Strontium-87 47,000million 10 - 4,600 million Carbon-14 Nitrogen-14 5,730 years 100- 70,000 years Uranium-Lead Dating: Uranium-Lead (U-Pb) dating is the most reliable method for dating Quaternary sedimentary carbonate and silica, and fossils particularly outside the range of radiocarbon. Quaternary geology provides a record of climate change and geologically recent changes in environment. Potassium-Argon Dating: Potassium-Argon (K-Ar) dating is the most widely applied technique of radiometric dating. Potassium is a component in many common minerals and can be used to determine the ages of igneous and metamorphic rocks. The Potassium Argon dating method is the measurement of the accumulation of Argon in a mineral. Rubidium-Strontium Dating: The rubidium-strontium dating method is a radiometric dating technique, used by scientists to determine the age of rocks and minerals from their content of specific isotopes of rubidium and strontium. One of the two naturally occurring isotopes of rubidium, ⁸⁷Rb, decays to ⁸⁷Sr with a half-life of 49.23 billion years. Carbon-14 Dating: Radiocarbon dating, or carbon-14 dating, is a scientific method that can accurately determine the age of organic materials as old as approximately 60,000 years. First developed in the late 1940s at the University of Chicago by Willard Libby, the technique is based on the decay of the carbon-14 isotope.