Geologic time can be determined through both relative and absolute dating methods. Relative dating relies on principles like fossil succession, cross-cutting relationships, and inclusions to determine the sequence of geological events. Absolute dating uses radioactive isotopes and their known decay rates to quantify the ages of rocks and fossils in numerical years. The development of radiometric dating techniques in the early 20th century revealed that the Earth is approximately 4.6 billion years old, much older than previously thought.
This document discusses structural geography and stratigraphy. It defines structural geography as the study of dip, strike, outcrops, inliers, outliers, discontinuities, folds, faults, joints and unconformities in rock structures. Stratigraphy is divided into lithostratigraphy, which studies rock layers based on lithology, and biostratigraphy, which uses fossil assemblages to correlate rock ages. The principles of stratigraphy include original horizontality, superposition, lateral continuity, cross-cutting relationships, inclusions, faunal succession, and uniformitarianism. Types of stratigraphy are lithostratigraphy, chronostratigraphy, biostratigraphy, magnetostratigraphy, allostratigraphy, geochron
Fossils provide evidence of ancient life on Earth. They are typically found within sedimentary rock layers and are formed through mineralization when organisms are quickly buried. Geologists use the locations of fossils within rock layers to determine their relative ages. However, the fossil record is incomplete and contains anomalies that are difficult to explain through evolution alone, such as "living fossils", misplaced fossils, and a lack of transitional forms. Absolute dating methods also have limitations and rely on assumptions about rates of decay.
Ud 6. metamorfismo y rocas metamorficasmartabiogeo
Este documento describe los procesos de metamorfismo y las rocas metamórficas. Explica que el metamorfismo ocurre debido a cambios en la temperatura, presión y circulación de fluidos en las rocas. Detalla los tres tipos principales de metamorfismo (dinámico, de contacto y regional) y describe las características de las facies metamórficas, texturas, minerales índice y clasificación de rocas metamórficas. Finalmente, relaciona el metamorfismo con los procesos tectón
El documento presenta información sobre la clasificación de diferentes tipos de rocas, incluyendo sus texturas, orígenes y minerales esenciales. Se proporcionan detalles sobre rocas sedimentarias, ígneas y metamórficas, así como sus aplicaciones. También incluye tablas sobre la clasificación geológica de rocas y descripciones petrográficas de muestras.
The document describes a petrographic study of rocks in the Vallanadu area of Tamil Nadu, India. It finds that the main rock types in the area are charnockites, khondalites, cordierite gneisses, calc-silicate rocks, and grey and pink granites. Two sets of conjugate shear systems are observed, including a NW-SE dextral shear zone conjugating with a NE-SW sinistral zone. Granites in the area formed syntectonically. The Vallanadu area experienced initial ductile deformation followed by brittle-ductile deformation during the Neoproterozoic to Cambrian period.
Tema 8 manifestaciones de la tectonica de placas 2018geopaloma
1. El documento describe los procesos tectónicos asociados a la teoría de placas tectónicas, incluyendo la formación de océanos, cordilleras, deformación de rocas y pliegues.
2. Se detalla el proceso de formación de un océano a través de cuatro etapas: abombamiento continental, rifting, mar Rojo y desarrollo del océano.
3. También se explican los procesos de formación de cordilleras, distinguiendo entre cordilleras de tipo andino asociadas a
This document provides an overview of key concepts related to cleavage, foliation, and lineation in metamorphic rocks. It defines different types of cleavage based on scale, including slaty, phyllitic, and schistosity. It also discusses crenulation and spaced cleavage. Examples are provided of slate, phyllite, schistosity, and crenulation cleavage in metamorphic rocks. The document also discusses concepts such as boudinage, gneissic structure, migmatization, mylonite, and different types of lineations. It provides examples of strain markers and describes analyzing strain in strongly deformed rocks. Finally, it discusses relationships between deformation, metamorphism, pl
This document discusses structural geography and stratigraphy. It defines structural geography as the study of dip, strike, outcrops, inliers, outliers, discontinuities, folds, faults, joints and unconformities in rock structures. Stratigraphy is divided into lithostratigraphy, which studies rock layers based on lithology, and biostratigraphy, which uses fossil assemblages to correlate rock ages. The principles of stratigraphy include original horizontality, superposition, lateral continuity, cross-cutting relationships, inclusions, faunal succession, and uniformitarianism. Types of stratigraphy are lithostratigraphy, chronostratigraphy, biostratigraphy, magnetostratigraphy, allostratigraphy, geochron
Fossils provide evidence of ancient life on Earth. They are typically found within sedimentary rock layers and are formed through mineralization when organisms are quickly buried. Geologists use the locations of fossils within rock layers to determine their relative ages. However, the fossil record is incomplete and contains anomalies that are difficult to explain through evolution alone, such as "living fossils", misplaced fossils, and a lack of transitional forms. Absolute dating methods also have limitations and rely on assumptions about rates of decay.
Ud 6. metamorfismo y rocas metamorficasmartabiogeo
Este documento describe los procesos de metamorfismo y las rocas metamórficas. Explica que el metamorfismo ocurre debido a cambios en la temperatura, presión y circulación de fluidos en las rocas. Detalla los tres tipos principales de metamorfismo (dinámico, de contacto y regional) y describe las características de las facies metamórficas, texturas, minerales índice y clasificación de rocas metamórficas. Finalmente, relaciona el metamorfismo con los procesos tectón
El documento presenta información sobre la clasificación de diferentes tipos de rocas, incluyendo sus texturas, orígenes y minerales esenciales. Se proporcionan detalles sobre rocas sedimentarias, ígneas y metamórficas, así como sus aplicaciones. También incluye tablas sobre la clasificación geológica de rocas y descripciones petrográficas de muestras.
The document describes a petrographic study of rocks in the Vallanadu area of Tamil Nadu, India. It finds that the main rock types in the area are charnockites, khondalites, cordierite gneisses, calc-silicate rocks, and grey and pink granites. Two sets of conjugate shear systems are observed, including a NW-SE dextral shear zone conjugating with a NE-SW sinistral zone. Granites in the area formed syntectonically. The Vallanadu area experienced initial ductile deformation followed by brittle-ductile deformation during the Neoproterozoic to Cambrian period.
Tema 8 manifestaciones de la tectonica de placas 2018geopaloma
1. El documento describe los procesos tectónicos asociados a la teoría de placas tectónicas, incluyendo la formación de océanos, cordilleras, deformación de rocas y pliegues.
2. Se detalla el proceso de formación de un océano a través de cuatro etapas: abombamiento continental, rifting, mar Rojo y desarrollo del océano.
3. También se explican los procesos de formación de cordilleras, distinguiendo entre cordilleras de tipo andino asociadas a
This document provides an overview of key concepts related to cleavage, foliation, and lineation in metamorphic rocks. It defines different types of cleavage based on scale, including slaty, phyllitic, and schistosity. It also discusses crenulation and spaced cleavage. Examples are provided of slate, phyllite, schistosity, and crenulation cleavage in metamorphic rocks. The document also discusses concepts such as boudinage, gneissic structure, migmatization, mylonite, and different types of lineations. It provides examples of strain markers and describes analyzing strain in strongly deformed rocks. Finally, it discusses relationships between deformation, metamorphism, pl
The document discusses geologic time and methods for dating rocks. It introduces the concept of the geologic time scale, which places geologic events in chronological order. There are two main methods for dating rocks: relative dating and absolute dating. Relative dating involves determining the sequence of past events without specific numerical measurements, using principles like superposition, cross-cutting relationships, and fossil succession. Absolute dating provides specific numerical ages for rocks and fossils using radiometric dating techniques to measure the decay of radioactive elements. The principles of radiometric dating are also outlined.
Este documento describe los diferentes tipos de fracturas en rocas, incluyendo diaclasas y fallas. Explica cómo se forman fracturas debido a esfuerzos tectónicos y cómo afectan las fracturas a los yacimientos de hidrocarburos, ya sea aumentando la porosidad y permeabilidad o creando barreras. También clasifica los yacimientos de acuerdo al efecto de las fracturas y métodos para estudiar el fracturamiento a partir de información directa e indirecta.
Plutons are large masses of igneous rock that form deep underground from slowly cooling magma. They include batholiths, which are large granite formations, as well as dikes, sills, laccoliths, and lopoliths. Batholiths form from magma forcing its way into the crust, laccoliths have a flat bottom and domed top parallel to layers, and lopoliths have a depressed center and curved bottom. Sills are sheet intrusions between sedimentary layers, while dikes cut across pre-existing rocks.
This document provides an overview of igneous rocks and their formation. It discusses that igneous rocks form from the cooling of molten magma or lava. The cooling rate affects crystal size - slower cooling produces larger crystals and faster cooling produces smaller crystals. Intrusive igneous rocks cool slowly underground and have coarse grains, while extrusive rocks cool quickly at the surface and have fine grains. Texture is determined by crystal size and arrangements. Examples of textures discussed are phaneritic, aphanitic, porphyritic, glassy and pyroclastic.
Sedimentary rocks are formed by the lithification of sediments and include clastic sedimentary rocks such as sandstone and shale that are formed from fragments of pre-existing rocks transported by water, wind or ice. They also include chemical sedimentary rocks such as limestone that are formed via precipitation from solution. Sedimentary structures within these rocks provide clues about the depositional environment, and sedimentary rocks are classified based on their mineral composition, grain size, sorting and rounding. Common sedimentary rocks used in construction include sandstone, limestone and shale.
El documento trata sobre el magmatismo y el metamorfismo. Resume los tipos de magmas y su relación con la tectónica de placas, explicando cómo se forman las diferentes rocas magmáticas. También describe los procesos de cristalización del magma y la diferenciación magmática. Finalmente, menciona brevemente las principales rocas magmáticas y metamórficas.
The document discusses the rock cycle and how different types of rocks are formed. It describes:
1) The rock cycle is a series of changes where geological forces cause rocks to change from one type to another, such as igneous to sedimentary or metamorphic.
2) Igneous rocks form from the cooling of magma, either below ground (intrusive) or above ground (extrusive). Sedimentary rocks form from the compaction or cementation of sediments.
3) Metamorphic rocks are formed from existing rocks that undergo changes from heat, pressure, and chemical processes deep underground.
Sedimentary rocks form from the compaction and cementation of sediments. There are three main types: detrital (clastic) rocks that form from lithified rock fragments and minerals, chemical rocks that precipitate directly from solution, and organic rocks that accumulate from biological debris. Sedimentary rocks provide clues about past environments and climates based on their composition, structures like cross-bedding and ripples, and any fossil content. Important resources like coal and oil are also found within sedimentary basins.
This document summarizes igneous petrology and the structure and composition of the Earth's interior. It discusses how the Earth is composed of layers including the crust, mantle, outer core, and inner core. The crust is divided into oceanic and continental crust. The mantle makes up most of the Earth's volume and is composed of ultramafic rock. Heat transfer mechanisms like conduction, convection, and advection are described. The geothermal gradient and how temperature increases with depth is also summarized. Plate tectonics and mantle convection are driving the dynamic cooling of the Earth.
Este documento presenta un trabajo práctico sobre los límites y fronteras de Argentina. Consta de 7 diapositivas con preguntas sobre diferentes fronteras del país. Se analizan las fronteras con Chile, Bolivia, Paraguay y Brasil. Se pide identificar países limítrofes, ríos, ciudades fronterizas y clasificar los diferentes tipos de límites. También se incluyen enlaces a videos para observar detalles de estas fronteras y responder preguntas sobre relieves, hitos fronterizos y disputas limítro
Modes of deformation of rocks presentationmadan lal
Rocks can deform in two main ways: brittle deformation and ductile deformation. Brittle deformation occurs near the surface where pressures and temperatures are low, causing rocks to fracture. Ductile deformation occurs at depth, where high pressures and temperatures cause permanent shape changes without fracturing. The type of deformation depends on factors like pressure, temperature, strain rate, and rock composition. Hard rocks under low pressure and temperature typically undergo brittle deformation, while soft rocks at depth experience ductile deformation.
This document discusses absolute dating and radiometric dating. Absolute dating determines the numeric age of a geologic object by measuring the radioactive decay of isotopes with long half-lives. Radiometric dating compares the percentages of radioactive parent isotopes to stable daughter isotopes produced after half lives to calculate the age of a sample. Examples of practice problems show how to calculate the number of half lives needed for a sample amount to decay and determine half life from initial and final isotope amounts.
Este documento describe las principales estructuras tectónicas de las cuencas de antepaís en la Amazonía peruana. Explica que las cuencas Marañón, Ucayali y Madre de Dios se desarrollaron debido a la subducción de las placas de Nazca e Inca, lo que generó el Arco de Iquitos, el Arco de Perú y el Arco de Fitzcarrald. Estas estructuras en forma de arco, junto con las zonas de alto de Contaya y alto del Shira, han influido en la sedimentación en las
This document discusses various approaches to classifying igneous rocks. It describes classifications based on fabric (grain size, presence of glass), field relations (intrusive vs extrusive), mineralogical and modal compositions, and the 1973 IUGS modal classification system. It also addresses issues with using rock analyses to determine original magma compositions, noting that degassing can cause the volatile content of erupted rocks to be lower than the magma. Analyzing volatile content in melt inclusions in phenocrysts is presented as a way to determine a rock's pre-eruption magmatic volatile contents more accurately.
Bowen’s Reaction Series
ROCKS:
There are three kinds of rocks, that are defined on the basis of how they formed.
Igneous Rocks:
are formed from the solidification of molten rock or magma.
Sedimentary Rocks:
form through when materials at the earth's surface (sediments) are buried and hardened (lithified).
Metamorphic Rocks:
are formed when older rocks are changed by heat and pressure without being melted.
The document provides an overview of the history and development of geology and methods for determining the relative and absolute ages of rock layers and fossils. It discusses two important scientists, Nicolaus Steno and James Hutton, who established principles of superposition and uniformitarianism. The document also describes how fossils are formed, different types of fossils, and how they are used to divide geologic time into eons, eras, periods, and epochs based on changes in dominant lifeforms.
This document provides an overview of the Siwalik Group, a Tertiary sedimentary formation stretching from Pakistan to Myanmar along the Himalayan foothills. It discusses the stratigraphy, sedimentation, distribution, and fossil flora and fauna of the Siwalik Group. The Siwalik Group is divided into Lower, Middle, and Upper units based on correlation of fossil fauna to Europe. It is known for its wealth of vertebrate fossils, including hominoids. The document also describes the distribution and characteristics of the Siwalik Group in various regions in India.
Nature of Igneous Rocks, Magma, Lava, Textures, Types classification,compositions,Bowen’s Reaction Series, characteristics of magma, Origin of Magmas, Evolution of Magma, Magma Differentiation,Partial Melting,Fractional Crystallization, Plate Tectonic Setting of Igneous Rocks
The document describes the different metamorphic facies defined by their mineral assemblages under varying pressure and temperature conditions within the Earth's crust and upper mantle. It outlines the key facies including zeolite, prehnite-pumpellyite, greenschist, amphibolite, granulite, blueschist, eclogite, albite-epidote hornfels, hornblende hornfels, pyroxene hornfels, and sanidinite facies. Each facies is characterized by index minerals and typical mineral assemblages that reflect the prevailing metamorphic conditions.
This document provides an overview of methods used to evaluate and date the geological record of Earth's past. Key methods discussed include examining rock formations and fossils to understand past environmental conditions and organisms. The principles of relative dating, such as superposition and cross-cutting relationships, are used to determine the relative order of geological events. Absolute dating methods like radiometric dating use the decay of radioactive isotopes to measure the precise ages of rocks in millions to billions of years, establishing the geologic time scale.
The document discusses geologic time and methods for dating rocks. It introduces the concept of the geologic time scale, which places geologic events in chronological order. There are two main methods for dating rocks: relative dating and absolute dating. Relative dating involves determining the sequence of past events without specific numerical measurements, using principles like superposition, cross-cutting relationships, and fossil succession. Absolute dating provides specific numerical ages for rocks and fossils using radiometric dating techniques to measure the decay of radioactive elements. The principles of radiometric dating are also outlined.
The document discusses geologic time and methods for dating rocks. It introduces the concept of the geologic time scale, which places geologic events in chronological order. There are two main methods for dating rocks: relative dating and absolute dating. Relative dating involves determining the sequence of past events without specific numerical measurements, using principles like superposition, cross-cutting relationships, and fossil succession. Absolute dating provides specific numerical ages for rocks and fossils using radiometric dating techniques to measure the decay of radioactive elements. The principles of radiometric dating are also outlined.
Este documento describe los diferentes tipos de fracturas en rocas, incluyendo diaclasas y fallas. Explica cómo se forman fracturas debido a esfuerzos tectónicos y cómo afectan las fracturas a los yacimientos de hidrocarburos, ya sea aumentando la porosidad y permeabilidad o creando barreras. También clasifica los yacimientos de acuerdo al efecto de las fracturas y métodos para estudiar el fracturamiento a partir de información directa e indirecta.
Plutons are large masses of igneous rock that form deep underground from slowly cooling magma. They include batholiths, which are large granite formations, as well as dikes, sills, laccoliths, and lopoliths. Batholiths form from magma forcing its way into the crust, laccoliths have a flat bottom and domed top parallel to layers, and lopoliths have a depressed center and curved bottom. Sills are sheet intrusions between sedimentary layers, while dikes cut across pre-existing rocks.
This document provides an overview of igneous rocks and their formation. It discusses that igneous rocks form from the cooling of molten magma or lava. The cooling rate affects crystal size - slower cooling produces larger crystals and faster cooling produces smaller crystals. Intrusive igneous rocks cool slowly underground and have coarse grains, while extrusive rocks cool quickly at the surface and have fine grains. Texture is determined by crystal size and arrangements. Examples of textures discussed are phaneritic, aphanitic, porphyritic, glassy and pyroclastic.
Sedimentary rocks are formed by the lithification of sediments and include clastic sedimentary rocks such as sandstone and shale that are formed from fragments of pre-existing rocks transported by water, wind or ice. They also include chemical sedimentary rocks such as limestone that are formed via precipitation from solution. Sedimentary structures within these rocks provide clues about the depositional environment, and sedimentary rocks are classified based on their mineral composition, grain size, sorting and rounding. Common sedimentary rocks used in construction include sandstone, limestone and shale.
El documento trata sobre el magmatismo y el metamorfismo. Resume los tipos de magmas y su relación con la tectónica de placas, explicando cómo se forman las diferentes rocas magmáticas. También describe los procesos de cristalización del magma y la diferenciación magmática. Finalmente, menciona brevemente las principales rocas magmáticas y metamórficas.
The document discusses the rock cycle and how different types of rocks are formed. It describes:
1) The rock cycle is a series of changes where geological forces cause rocks to change from one type to another, such as igneous to sedimentary or metamorphic.
2) Igneous rocks form from the cooling of magma, either below ground (intrusive) or above ground (extrusive). Sedimentary rocks form from the compaction or cementation of sediments.
3) Metamorphic rocks are formed from existing rocks that undergo changes from heat, pressure, and chemical processes deep underground.
Sedimentary rocks form from the compaction and cementation of sediments. There are three main types: detrital (clastic) rocks that form from lithified rock fragments and minerals, chemical rocks that precipitate directly from solution, and organic rocks that accumulate from biological debris. Sedimentary rocks provide clues about past environments and climates based on their composition, structures like cross-bedding and ripples, and any fossil content. Important resources like coal and oil are also found within sedimentary basins.
This document summarizes igneous petrology and the structure and composition of the Earth's interior. It discusses how the Earth is composed of layers including the crust, mantle, outer core, and inner core. The crust is divided into oceanic and continental crust. The mantle makes up most of the Earth's volume and is composed of ultramafic rock. Heat transfer mechanisms like conduction, convection, and advection are described. The geothermal gradient and how temperature increases with depth is also summarized. Plate tectonics and mantle convection are driving the dynamic cooling of the Earth.
Este documento presenta un trabajo práctico sobre los límites y fronteras de Argentina. Consta de 7 diapositivas con preguntas sobre diferentes fronteras del país. Se analizan las fronteras con Chile, Bolivia, Paraguay y Brasil. Se pide identificar países limítrofes, ríos, ciudades fronterizas y clasificar los diferentes tipos de límites. También se incluyen enlaces a videos para observar detalles de estas fronteras y responder preguntas sobre relieves, hitos fronterizos y disputas limítro
Modes of deformation of rocks presentationmadan lal
Rocks can deform in two main ways: brittle deformation and ductile deformation. Brittle deformation occurs near the surface where pressures and temperatures are low, causing rocks to fracture. Ductile deformation occurs at depth, where high pressures and temperatures cause permanent shape changes without fracturing. The type of deformation depends on factors like pressure, temperature, strain rate, and rock composition. Hard rocks under low pressure and temperature typically undergo brittle deformation, while soft rocks at depth experience ductile deformation.
This document discusses absolute dating and radiometric dating. Absolute dating determines the numeric age of a geologic object by measuring the radioactive decay of isotopes with long half-lives. Radiometric dating compares the percentages of radioactive parent isotopes to stable daughter isotopes produced after half lives to calculate the age of a sample. Examples of practice problems show how to calculate the number of half lives needed for a sample amount to decay and determine half life from initial and final isotope amounts.
Este documento describe las principales estructuras tectónicas de las cuencas de antepaís en la Amazonía peruana. Explica que las cuencas Marañón, Ucayali y Madre de Dios se desarrollaron debido a la subducción de las placas de Nazca e Inca, lo que generó el Arco de Iquitos, el Arco de Perú y el Arco de Fitzcarrald. Estas estructuras en forma de arco, junto con las zonas de alto de Contaya y alto del Shira, han influido en la sedimentación en las
This document discusses various approaches to classifying igneous rocks. It describes classifications based on fabric (grain size, presence of glass), field relations (intrusive vs extrusive), mineralogical and modal compositions, and the 1973 IUGS modal classification system. It also addresses issues with using rock analyses to determine original magma compositions, noting that degassing can cause the volatile content of erupted rocks to be lower than the magma. Analyzing volatile content in melt inclusions in phenocrysts is presented as a way to determine a rock's pre-eruption magmatic volatile contents more accurately.
Bowen’s Reaction Series
ROCKS:
There are three kinds of rocks, that are defined on the basis of how they formed.
Igneous Rocks:
are formed from the solidification of molten rock or magma.
Sedimentary Rocks:
form through when materials at the earth's surface (sediments) are buried and hardened (lithified).
Metamorphic Rocks:
are formed when older rocks are changed by heat and pressure without being melted.
The document provides an overview of the history and development of geology and methods for determining the relative and absolute ages of rock layers and fossils. It discusses two important scientists, Nicolaus Steno and James Hutton, who established principles of superposition and uniformitarianism. The document also describes how fossils are formed, different types of fossils, and how they are used to divide geologic time into eons, eras, periods, and epochs based on changes in dominant lifeforms.
This document provides an overview of the Siwalik Group, a Tertiary sedimentary formation stretching from Pakistan to Myanmar along the Himalayan foothills. It discusses the stratigraphy, sedimentation, distribution, and fossil flora and fauna of the Siwalik Group. The Siwalik Group is divided into Lower, Middle, and Upper units based on correlation of fossil fauna to Europe. It is known for its wealth of vertebrate fossils, including hominoids. The document also describes the distribution and characteristics of the Siwalik Group in various regions in India.
Nature of Igneous Rocks, Magma, Lava, Textures, Types classification,compositions,Bowen’s Reaction Series, characteristics of magma, Origin of Magmas, Evolution of Magma, Magma Differentiation,Partial Melting,Fractional Crystallization, Plate Tectonic Setting of Igneous Rocks
The document describes the different metamorphic facies defined by their mineral assemblages under varying pressure and temperature conditions within the Earth's crust and upper mantle. It outlines the key facies including zeolite, prehnite-pumpellyite, greenschist, amphibolite, granulite, blueschist, eclogite, albite-epidote hornfels, hornblende hornfels, pyroxene hornfels, and sanidinite facies. Each facies is characterized by index minerals and typical mineral assemblages that reflect the prevailing metamorphic conditions.
This document provides an overview of methods used to evaluate and date the geological record of Earth's past. Key methods discussed include examining rock formations and fossils to understand past environmental conditions and organisms. The principles of relative dating, such as superposition and cross-cutting relationships, are used to determine the relative order of geological events. Absolute dating methods like radiometric dating use the decay of radioactive isotopes to measure the precise ages of rocks in millions to billions of years, establishing the geologic time scale.
The document discusses geologic time and methods for dating rocks. It introduces the concept of the geologic time scale, which places geologic events in chronological order. There are two main methods for dating rocks: relative dating and absolute dating. Relative dating involves determining the sequence of past events without specific numerical measurements, using principles like superposition, cross-cutting relationships, and fossil succession. Absolute dating provides specific numerical ages for rocks and fossils using radiometric dating techniques to measure the decay of radioactive elements. The principles of radiometric dating are also outlined.
The document discusses geological time and methods for determining the relative ages of rocks and fossils. It introduces concepts like uniformitarianism, superposition, cross-cutting relationships, and index fossils that allow scientists to correlate rock layers across different locations. Modern dating techniques like radioactive decay allow assignment of absolute ages by measuring the decay of isotopes. The geological time scale is divided into eras, periods, and epochs with defined spans of time defined by dominant forms of life.
This document provides an overview of key concepts in understanding Earth's history through studying rock layers and fossils. It describes how geologists use relative dating principles like superposition and cross-cutting relationships to determine the relative ages of stratified rocks. Absolute dating techniques like radiometric dating using radioactive isotopes are also discussed. Together, these methods were used to construct the geologic time scale which divides Earth's history into standardized eons, eras, periods, and epochs. Marker fossils are important for identifying specific time periods. Examples of past Earth environments, organisms, and geological changes are shown for different eras.
The document discusses geologic time and methods used by geologists to determine the relative and absolute ages of rocks. It provides information on:
1) Principles of relative dating used to determine the ordering of rock layers, such as superposition and cross-cutting relationships.
2) Radiometric dating techniques that allow scientists to determine the absolute age of rocks in years by measuring the decay of radioactive isotopes.
3) How these methods have been used to develop the geologic time scale which divides Earth's history into eons, eras, periods and epochs.
The document discusses the history of determining the age of the Earth. It begins with pre-scientific beliefs that the Earth was only a few thousand years old based on biblical accounts. Starting in the 1600s, scholars began speculating on the Earth's origins but with little field work. In the late 1600s, Steno formulated principles of stratigraphy and rock layering that helped establish relative dating of formations. By the 1700-1800s, studies of strata, fossils, earthquakes, and erosion led to acceptance that the Earth was much older than previously believed. Radiometric dating methods developed in the 1800s-1900s allowed estimation of absolute ages, showing the Earth to be billions of years old.
This document discusses key concepts in stratigraphy, including:
- Stratigraphy deals with rock succession through time and space, telling the story of the Earth's history.
- There are different types of stratigraphy based on lithology, time, fossils, magnetism, and seismic characteristics.
- Stratification is based on principles like superposition, original horizontality, lateral continuity, and cross-cutting relationships.
- Unconformities represent gaps in the geologic record where no rocks were deposited for long periods of time.
This document discusses methods that geologists use to determine the age of rocks and develop the geologic timescale. It explains that relative dating uses principles like superposition and cross-cutting relationships to determine the relative order of formations, while absolute dating uses radioactive decay and half-lives to determine precise numerical ages. Examples of radiometric dating techniques are provided, such as carbon-14 dating and potassium-argon dating. The major eras and periods of the geologic timescale are also outlined, from the Precambrian Eon to the current Cenozoic Era.
Time is closely related with geology. The geological timescale is a method of finding the relation between the events that have taken place in the history of the time. This presentation will give you a general knowledge about the relation of time and geology. Cheers!
The document discusses the field of historical geology and stratigraphy. It provides definitions, principles, and methods used in stratigraphy, including:
- Stratigraphy is the study of rock layers and their relationships. It provides clues about the Earth's past.
- Basic principles of relative age dating include superposition, original horizontality, faunal succession, and cross-cutting relationships.
- Rock units can be correlated between locations by matching rock types and fossil content.
- The geologic time scale is used to divide Earth's history into standardized eons, eras, periods, and epochs based on stratigraphy and fossil evidence.
Unit 4 - Fossils and Geologic Time (2017/2018)Josh Macha
This document discusses methods for determining the relative and absolute ages of rocks and fossils. It explains key principles like uniformitarianism, superposition, and cross-cutting relationships that are used to determine relative age. Absolute dating methods discussed include radiometric dating, varve counting, and analyzing rates of erosion and deposition. The document also provides an overview of the geologic time scale, major eras, periods of time defined by significant evolutionary events, and the emergence and evolution of early hominids.
The document discusses the history of theories of plate tectonics. It describes how early theories viewed the Earth's crust as rigid and unmoving, but accumulating evidence from seafloor mapping, core sampling, and studies across scientific disciplines demonstrated that the crust is made up of mobile tectonic plates that move and interact along boundaries. The modern theory of plate tectonics explains continental drift, mountain building, volcanism and earthquakes based on the dynamics of divergent, convergent, and transform plate boundaries.
This document discusses geologic time and stratigraphy. It begins by outlining the tools used, including principles of stratigraphy and the geologic timescale. It then discusses how geology establishes the relative and absolute ages of events by placing rocks and fossils in chronological order. Key methods discussed include lithostratigraphy, biostratigraphy, magnetic stratigraphy, and radiometric dating. The document also outlines the major divisions of the geologic timescale from eons to epochs. It notes how fossil evidence and major extinction events define era boundaries.
This document discusses various topics related to biblical creationism and challenges to an old earth view from the perspective of real science. It begins with an overview of biblical timelines from Adam to the exile and return. It then covers the history of geology and how geology is often taught, emphasizing an old earth viewpoint. Next, it discusses commonly used geological dating methods like strata layering and index fossils, highlighting problems with these methods and how they better support a global flood model. Living index fossils that contradict their supposed extinct dates are also presented as evidence against this dating method. Overall, the document promotes a young earth creationist perspective and critiques aspects of modern geology.
The document discusses the formation and study of rock layers through stratigraphy. It describes key concepts like uniformitarianism, which states geological processes have remained the same over time. Stratigraphic laws help determine the order and age of rock layers, such as the law of superposition stating older layers are below younger ones. Unconformities occur when rock layers are eroded or disturbed before new layers form. Geologists correlate rock layers between locations based on matching characteristics like color, fossils, or layer sequences to understand the geologic history of an area.
This Powerpoint Presentaion is used for my 11th Grade Earth Science Reporting as a major requirement for our sujbect. It talks about the tectonic processes and Plate boundaries with its theories..
Introduction
Stratigraphy is the study of strata (sedimentary layers) in the Earth's crust, it is the relationship between rocks and time.
Stratigrapher are concerned with the observation, description and interpretation of direct and tangible evidence in rocks to determine the history of the Earth.
The combination of sedimentology and stratigraphy allows us to build up pictures of the Earth’s surface at different times in different places and relate them to each other through the relative ages of rocks
A more modern way of stating the same principle is that the laws of nature (laws of chemistry and physics) that have operated in the same way since the beginning of time.
And thus if we understand the physical and chemical principles by which nature operates, we can assume that nature operated the same way in the past.
Basic principles of stratigraphy
Principle of Uniformitarianism
Principle of Lateral Horizontality
Principle of Superposition
Principle of Cross-cutting Relations
Principle of Inclusions
Principle of Chilled Margins
Correlation
This document discusses key concepts in relative dating of geologic materials. It introduces important figures like James Hutton and Charles Lyell who were influential in developing theories of geology. The key principles of relative dating are described, including the law of superposition, law of original horizontality, and law of cross-cutting relationships. The document also discusses using index fossils and unconformities to correlate rock layers between locations and determine their relative ages.
This document provides an overview of Earth's history and geology. It explains that Earth is geologically active with huge amounts of energy acting on its surface and interior. Observable evidence today can provide information about past processes and events. It then describes various aspects of Earth's structure like the crust, mantle, core and tectonic plates. It discusses geological processes like erosion, sedimentation, and the rock cycle. It also outlines plate tectonics and features at plate boundaries like divergent, convergent and transform boundaries. Key terms are defined like seismic, fossil, and stratigraphy. The conclusion notes that rather than being serene, Earth is a dynamic world that is constantly changing.
The document discusses the history of the Earth and methods used to determine geological timescales. It describes how rocks form records of past events and processes. Early scientists estimated the age of the Earth to be between 24-100 million years based on studies of heat loss and sodium accumulation in oceans. The principle of uniformitarianism states that past and present geological processes were similar. Relative dating methods order events but do not provide absolute ages. Radiometric dating using radioactive isotopes provides absolute ages and was used to construct the geologic timescale in eras, periods, and epochs marked by significant events in Earth's history.
4. In what order did these events occur in
American History?
A B C
D E
5. Relative Time
• Tools
– Smith
• Fossil Succession
– Steno
• Superposition
• Original horizontality
– Lyell
• Cross-cutting relationships
• Intrusions
• Inclusions
6. Principle of fossil succession
• Fossils occur in a consistent vertical order in
sedimentary rocks all over the world.
(William"Strata Bill" Smith, late 1700's, England).
• This principle is valid and does not depend on any
pre-existing ideas of evolution. (In fact, Charles
Darwin's ideas on evolution did not appear until
50 years later - 1858).
7. Principle of fossil succession
Geologists interpret fossil succession to be the result of
evolution - the natural appearance and disappearance of
species through time.
"Fossil species succeed one another in a definite and
recognizable order"
Fossils at the base of a thick sequence of sediments
(so older, by previous principles) are less like
present-day species than those near the top
8. Principle of fossil succession
* Fossils unlike present-day species, but like
each other, are found in widely separated
sites
* A fossil species which is observed to occur
above (and so younger than, by previous
principles) a second fossil species in one
locality will always occur above that second
species, wherever found.
11. Unconformities
1.Angular unconformities
Implies tectonic deformation and erosion of underlying
strata.
2.Nonconformity
Sedimentary strata overlying igneous or metamorphic
rocks (in an erosional - not intrusive- contact)
3.Disconformity
An irregular surface of erosion between two units of
parallel strata
22. Intrusions vs Unconformities
• A xenolith is a fragment of country rocks
which has been broken off during an
intrusion, and has become surrounded by
magma. The xenolith is older than the
igneous rock which contains it.
• Through erosion and resedimentation,
younger rocks will often have pieces of the
older rock included (sedimentary).
27. History of
Geologic Time
• Geologic Systems
– Body of rock that
contains fossils of
diverse animal life
– Corresponds to
geologic period
• Sedgewick
– Named Cambrian
• Murchison
– Named Silurian
28. Stratigraphy
• Study of stratified rocks, especially their
geometric relations, compositions, origins, and
age relations
• Stratigraphic units
– Strata
• Distinguished by some physical, chemical, or paleontological
property
• Units of time based on ages of strata
– Geologic Systems
• Correlation
– Demonstrate correspondence between geographically
separated parts of a stratigraphic unit
• Lithologic
• Temporal
29. Units of Time
• Time-rock unit
– Chronostratigraphic unit
– All the strata in the world deposited during a particular interval
of time
• Erathem, System, Series, Stage
• Time unit
– Geochronologic unit
– Interval during which a time-rock unit is formed
• Eras, Period, Epoch, Age
• Boundary stratotype
– Boundary between two systems, series or stages, formally
defined at a single locality
30. Geologic Time Scale
• Chronologic units - Time/Age
– Eons (largest):
– Era
– Periods
– Epochs
– Ages
31. Geologic Time Scale
• Geochronologic Units = Place
– Eon (largest) = Eon
– Era = Era
– System = Period
– Series = Epoch
– Stage = Age
32. Biostratigraphy
• Biostratigraphic unit
– Defined and characterized by their fossil content
• Stratigraphic range
– Total vertical interval through which that species
occurs in strata, from lowermost to uppermost
occurrence
33. Biostratigraphy
• Index fossil
– Abundant enough in the stratigraphic record to be
found easily
– Easily distinguished from other taxa
– Geographically widespread and thus can be used to
correlate rocks over a large area
– Occurs in many kinds of sedimentary rocks and
therefore can be found in many places
– Has a narrow stratigraphic range, which allows for
precise correlation if its mere presence is used to
define a zone
34. Magnetic Stratigraphy
• Use of magnetic
properties of a rock to
characterize and
correlate rock units
• Magnetic field
– Reversals in polarity of
field are recorded in
rocks when they
crystallize or settle
from water
35. Magnetic
Stratigraphy
• Chron
– Polarity time-rock unit
– Period of normal or
reversed polarity
• Normal interval
– Same as today
– Black
• Reversed interval
– Opposite to today
– White
36. Lithostratigraphy
• Subdivision of the stratigraphic record on the basis of
physical or chemical characteristics of rock
• Lithostratigraphic units
– Formation
• Local three-dimensional bodies of rock
– Group
– Member
• Stratigraphic section
– Local outcrop of a formation that displays a continuous vertical
sequence
• Type section
– Locality where the unit is well exposed, that defines the unit
37. Lithologic Correlation
• Cross-sections of
strata
– Establish geometric
relationships
– Interpret mode of
origin
38. Lithologic Correlation
• Grand Canyon
– McKee
– Used Trilobite
biostratigraphy to
determine age
relationships
– Eastern portion of
units is younger than
western
39. Facies
• Transgression
– Landward migration of
shoreline
– Grand Canyon
• Cambrian transgression
• Facies
– Set of characteristics of a body
of rock that presents a
particular environment
• Facies changes
– Later changes in the
characteristics of ancient strata
40. Absolute Age
• 4.6 billion years old
• Early estimates
– Salts in the ocean
• 90 million years old
– Accumulation of sediment
• 100 m.y. or less
• Gaps in stratigraphic record
• Unconformities represent large breaks in accumulation
• Didn’t include metamorphosed sedimentary rocks
– Earth’s temperature
• Kelvin
• 20-40 million years old
41. Absolute Ages
• How old is the Earth?
• 4.6 billion years (4,600,000,000 years)
• Radiometric dating (Uranium, Thorium).
Mass spectrometer.
42. Early Attempts
• 1654 Archbishop Usher (Ireland), genealogy
in Bible Earth was created October 22, 4004
BC,
• 9:00 am was added later
• Earth was 6000 years old.
• Led to the Doctrine of Catastrophism:
• Earth was shaped by series of giant disasters.
• Many processes fit into a short time scale.
43. Early Attempts
• 1770's, 1780's "Revolution"
• James Hutton, Father of Geology (Scotland)
1726-1797.
• Published Theory of the Earth in 1785.
44. Hutton
• Hadrian's Wall built by Romans,
after 1500 years no change.
Suspected that Earth was much
older.
• Slow processes shape earth.
• Mountains arise continuously as
a balance against erosion and
weathering
45. Hutton
• Doctrine of Uniformitarianism: "Present is key to
the past".
• The physical and chemical laws that govern nature
are uniform
•
• Unconformity at Siccar Point, Scotland
• "No vestige of a beginning, no prospect of an end"
46. Charles Lyell
• Charles Lyell 1800's compared amount of
evolution shown by marine mollusks in the
various series of the Tertiary System with the
amount that had occurred since the beginning
of the Pleistocene.
• Estimated 80 million years for the Cenozoic
alone.
47. Various Geologists
• Thickness of total sedimentary record
divided by average sedimentation rates (in
mm/yr).
• In 1860, calculated to be about 3 million
years old.
• In 1910, calculated to be about 1.6 billion
years old.
48. Lord Kelvin
• In 1897, Lord Kelvin
assumed that the Earth was
originally molten and
calculated a date based on
cooling through conduction
and radiation.
• Age of Earth was calculated
to be about 24-40 million
years.
49. Lord Kelvin
• Problem: Earth has an internal heat source
(radioactive decay)
• Discovery of radioactivity by Henri
Becquerel in 1896.
50. John Joly
• In 1899 - 1901, John Joly (Irish) calculated
the rate of delivery of salt to the ocean. River
water has only a small concentration of salts.
Rivers flow to the sea.
• Evaporative concentration of salts.
• Age of Ocean = Total salt in oceans (in grams)
divided by rate of salt added (grams per year)
• Age of Earth = 90-100 million years.
51. John Joly
• Problems: no way to account for recycled
salt, salt incorporated into clay minerals, salt
deposits.
52. von Helmholtz and Newcomb
The German physicist Hermann von Helmholtz and the American
astronomer Simon Newcomb joined in by independently
calculating the amount of time it would take for the Sun to
condense down to its current diameter and brightness from the
nebula of gas and dust from which it was born.
100 million years, consistent with Thomson's calculations.
However, they assumed that the Sun was only glowing from the
heat of its gravitational contraction. They knew of no other ways
for it to produce its energy.
53. Rutherford and Boltwood
• In 1905, they used radioactive decay to
measure the age of rocks and minerals.
• Uranium decay produces He, leading to a
date of 500 million years.
54. Rutherford and Boltwood
In 1907, Boltwood suspected that lead was the
stable end product of the decay of uranium.
Published the age of a sample of urananite
based on Uranium-Lead dating.
Date was 1.64 billion years.
55. Age of Earth
• So far, oldest dated Earth rocks are 3.96 billion
years.
• Canadian Shield. (NW Territories near Great
Slave Lake, 3.96 byr).
• Detrital Zircons in sedimentary rocks are 4.1 - 4.4
byr
• Older rocks include meteorites and moon rocks
with dates on the order of 4.6 billion years.
56. Geologic Time Scale.
The age for the base of
each division is in
accordance with
recommendations of the
International
Commission on
Stratigraphy for the
year 2000.
58. The standard geologic
time scale for the
Paleozoic and other eras
developed without
benefit of a grand plan.
Instead, it developed by
the compilation of “type
sections” for each of the
systems.
64. Absolute Age
• Radioactive decay
– Becquerel, 1895
• Uranium undergoes spontaneous decay
• Atoms release subatomic particles and energy
• Change to another element
– Parent isotope decays/daughter isotope
produced
65. Principles of Radiometric Dating
• Naturally-occurring radioactive materials
break down into other materials at known
rates. This is known as radioactive decay.
• Radioactive parent elements decay to stable
daughter elements.
66. What is an Isotope?
• Nuclide of an element with different masses
67. Absolute Age
• Three modes of decay
– Loss of alpha particle
• Convert parent into
element that has nucleus
containing two fewer
protons
– Loss of beta particle
• Convert parent into
element whose nucleus
contains one more proton
by losing an electron
– Capture of beta particle
• Convert parent into
element whose nucleus
has one less proton
68. Absolute Age
• Radiometric dating
– Radioactive isotopes
decay at constant
geometric rate
• After a certain amount
of time, half of the
parent present will
survive and half will
decay to daughter
• Half-life
– Interval of time for half
of parent to decay
69. Absolute Age
• Useful isotopes
– Uranium 238 and thorium 232
• Zircon grains
– Uranium 238 and lead 206
• Fission track dating
– Rubidium-Strontium
– Potassium-Argon, Argon-Argon
– Radiocarbon dating
• Produced in upper atmosphere
• Half life = 5730 years
• Maximum age for dating: 70,000 years
• Bone, teeth, wood
70. Absolute Age
• Fission-Track Dating
– Measure decay of
uranium 238 by
counting number of
tracks
– Tracks formed by
subatomic particles
that fly apart upon
decay
71. Radioactive parent isotopes and
their stable daughter products
Each radioactive isotope has its own
unique half-life.
A half-life is the time it takes for half
of the parent radioactive element to
decay to a daughter product.
72. Radioactive parent isotopes and
their stable daughter products
Radioactive Parent Stable Daughter Half Life
Potassium 40 Argon 40 1.25 billion yrs
Rubidium 87 Strontium 87 48.8 billion yrs
Thorium 232 Lead 208 14 billion years
Uranium 235 Lead 207 704 million years
Uranium 238 Lead 206 4.47 billion years
Carbon 14 Nitrogen 14 5730 years
76. Radioactive Decay
• Beta particles
• penetrate hundreds of times farther than
alpha particles, but easily stopped compared
with neutrons and gamma rays.
• charge = -1
• mass = negligible
78. Datable Minerals
• Most minerals which contain radioactive isotopes
are in igneous rocks. The dates they give indicate
the time the magma cooled.
• Potassium 40 is found in:
• potassium feldspar (orthoclase)
• muscovite
• amphibole
• glauconite (greensand; found in some
sedimentary rocks; rare)
•
79. Datable Rocks
• Radioactive elements tend to become
concentrated in the residual melt that
forms during the crystallization of
igneous rocks. More common in
SIALIC rocks (granite, granite
pegmatite) and continental crust.
80. Datable Rocks
• Radioactive isotopes don't tell much about
the age of sedimentary rocks (or fossils).
The radioactive minerals in sedimentary
rocks are derived from the weathering of
igneous rocks. If the sedimentary rock were
dated, the age date would be the time of
cooling of the magma that formed the
igneous rock. The date would not tell
anything about when the sedimentary rock
formed.
82. 14
How does Carbon dating work?
• Cosmic rays from the sun
strike Nitrogen 14 atoms in
the atmosphere and cause
them to turn into
radioactive 14C, which
combines with oxygen to
form radioactive CO2.
83. 14
How does Carbon dating work?
• Living things are in
equilibrium with the
atmosphere, and the
radioactive CO2 is absorbed
and used by plants. The
radioactive CO2 gets into the
food chain and the carbon
cycle.
84. 14
How does Carbon dating work?
• All living things contain a constant ratio of 14C to 12C (1
in a trillion).
• At death, 14C exchange ceases and any 14C in the tissues
of the organism begins to decay to Nitrogen 14, and is
not replenished by new 14C.
85. 14
How does Carbon dating work?
• The change in the 14C to 12C ratio is the basis for
dating.
• The half-life is so short (5730 years) that this
method can only be used on materials less than
50,000 years old.
• Assumes that the rate of 14C production (and
hence the amount of cosmic rays striking the
Earth) has been constant.
86. Deviation of carbon-14 ages to true ages from
the present back to about 5000 B.C. Data are
obtained from analysis of bristle cone pines from
the western United States. Calculations of carbon-
14 are based on half-life of 5730 years.
(Adapted from Ralph, E. K., Michael, H. N., and Han, M. C. 1973. Radiocarbon
dates and reality. MASCA Newsletter 9:1.)
87. Absolute Age
• Best candidates for
most radiometric
dating are igneous
– Not necessarily useful
for sediments
• Error in age estimate
can be sizable
88. Absolute Age
• Absolute ages change
– Error increases in older
rocks
– Techniques change
• Biostratigraphic
correlations are
usually more accurate
– Radiometric dates used
when fossils not
present
89. How old is the Old Red Sandstone?
a. Older than 425 myr
b. Younger than 370 myr
c. Between 425 and 370 myr
d. Have no idea