A record of the geological events and life forms on Earth, the standard method used to divide the Earth's long natural history into manageable parts

Transcription

1 Index Fossil Radiometric dating Index Fossil Radiometric dating Eon Geologic Time Scale Eon Geologic Time Scale Period Era Period Era the principle that a sedimentary rock layer is older than the layers above it and younger than the layers below it if the layers are not disturbed the principle that a sedimentary rock layer is older than the layers above it and younger than the layers below it if the layers are not disturbed Epoch Epoch a method of determining whether an event or object, such as a fossil, is older or younger than other events or objects without referring to the object's age in years a method of determining whether an event or object, such as a fossil, is older or younger than other events or objects without referring to the object's age in years the age of an object in relation to the ages of other objects the age of an object in relation to the ages of other objects a principle that geologic processes that occurred in the past can be explained by current geologic processes a principle that geologic processes that occurred in the past can be explained by current geologic processes an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom

2 a method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope a method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope A fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread and the species that formed that fossil existed for only a short span of geologic time A fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread and the species that formed that fossil existed for only a short span of geologic time A record of the geological events and life forms on Earth, the standard method used to divide the Earth's long natural history into manageable parts A record of the geological events and life forms on Earth, the standard method used to divide the Earth's long natural history into manageable parts a unit of time equal to 1 billion years, the largest division of the geologic time scale a unit of time equal to 1 billion years, the largest division of the geologic time scale a unit of geologic time that includes two or more periods a unit of geologic time that is longer than an epoch but shorter than an era a unit of geologic time that includes two or more periods a unit of geologic time that is longer than an epoch but shorter than an era a subdivision of geologic time that is longer than an age but shorter than a period Law of Superposition a subdivision of geologic time that is longer than an age but shorter than a period Law of Superposition Relative-age Relative dating Relative-age Relative dating Geologic column Uniformitarianism Geologic column Uniformitarianism

3 Unconformity Intrusion Unconformity Intrusion Disconformity Angular unconformity Disconformity Angular unconformity Absolute age Nonconformity Absolute age Nonconformity Isotope Radioactive Decay Isotope Radioactive Decay Daughter isotope Parent isotope Daughter isotope Parent isotope Radiocarbon dating Half-life Radiocarbon dating Half-life

4 a mass of igneous rock that is formed when magma is injected into cracks in rock & cools and solidifies a mass of igneous rock that is formed when magma is injected into cracks in rock & cools and solidifies a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time - this results in uncertainty about a break how in long the passed geologic or record what happened created when during rock the layers are eroded or gap. when sediment is not deposited for a long period of time - this results in uncertainty about how long passed or what happened during the gap. when younger sediment is deposited on top of the eroded surface of older rocks that have been tilted or folded by tectonic forces when younger sediment is deposited on top of the eroded surface of older rocks that have been tilted or folded by tectonic forces the boundary between horizontal layers of old rock and younger, overlying layers that are deposited on an eroded surface. (rocks w/ horizontal layers on top of rocks w/ a different pattern of horizontal layers) the boundary between horizontal layers of old rock and younger, overlying layers that are deposited on an eroded surface. (rocks w/ horizontal layers on top of rocks w/ a different pattern of horizontal layers) when younger sedimentary rocks rest on top of older igneous or metamorphic rocks (Rocks w/ layers on top of rocks w/ NO layers) when younger sedimentary rocks rest on top of older igneous or metamorphic rocks (Rocks w/ layers on top of rocks w/ NO layers) the numeric age of an object or event, often stated in years before the present, as established by an absolute-dating process, such as radiometric dating the numeric age of an object or event, often stated in years before the present, as established by an absolute-dating process, such as radiometric dating The disintegration of an unstable atomic nucleus (parent isotope) into one or more different stable nuclei (daughter isotope) The disintegration of an unstable atomic nucleus (parent isotope) into one or more different stable nuclei (daughter isotope) an atom that has the same number of protons as other atoms of the same element do but that has a different number of neutrons an atom that has the same number of protons as other atoms of the same element do but that has a different number of neutrons An unstable isotope that decays into a specific daughter isotope as it ages A stable isotope produced by the radioactive decay of an unstable parent isotope An unstable isotope that decays into a specific daughter isotope as it ages A stable isotope produced by the radioactive decay of an unstable parent isotope the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope Uses the decay of the isotope Carbon-14 to determine the age of organic material. Uses the decay of the isotope Carbon-14 to determine the age of organic material.

5 Used to date geographical features under a million years old because over longer periods of time their rates can vary greatly, so they aren't very accurate on a long time scale. Used to date geographical features under a million years old because over longer periods of time their rates can vary greatly, so they aren't very accurate on a long time scale. Used to date objects accurately, no matter how old they are, b/c the decay process always occurs at a constant rate. Used to date objects accurately, no matter how old they are, b/c the decay process always occurs at a constant rate. used to date objects less than 70,000 years old that contain organic materials/isotopes of Carbon-14 (such as fossils, oil & coal) used to date objects less than 70,000 years old that contain organic materials/isotopes of Carbon-14 (such as fossils, oil & coal) a banded layer of sand and silt that is deposited annually in a lake, especially near ice sheets or glaciers, and that can be used to determine absolute age. a banded layer of sand and silt that is deposited annually in a lake, especially near ice sheets or glaciers, and that can be used to determine absolute age. bedding plane How much sedimentary rock is deposited over 1,000 years? bedding plane How much sedimentary rock is deposited over 1,000 years? Cross-beds Principle of Original Horizontality Cross-beds Principle of Original Horizontality Ripple marks Graded Bedding Ripple marks Graded Bedding Fault Law of Crosscutting relationships Fault Law of Crosscutting relationships

6 Radiocarbon dating (use) Rates of erosion/deposition Radiocarbon dating (use) Rates of erosion/deposition varve Radiocarbon dating varve Radiocarbon dating 30 cm The boundary between two sedimentary rock layers 30 cm The boundary between two sedimentary rock layers states that sedimentary rocks left undisturbed will remain in horizontal layers states that sedimentary rocks left undisturbed will remain in horizontal layers slanted layers that are formed from hills of sand that have had the tops eroded off, the flat portion of the hill where the sides are closest together is the top. slanted layers that are formed from hills of sand that have had the tops eroded off, the flat portion of the hill where the sides are closest together is the top. the arrangement of layers in which the coarse and heavy particles of sediment are deposited on the bottom of layers. the arrangement of layers in which the coarse and heavy particles of sediment are deposited on the bottom of layers. small waves that form on the surface of sand as the result of the action of water or wind-they always point toward the younger layer small waves that form on the surface of sand as the result of the action of water or wind-they always point toward the younger layer the principle that a fault or body of rock is younger than any other body of rock that it cuts through a break in a body of rock along which one tectonic plate slides relative to another the principle that a fault or body of rock is younger than any other body of rock that it cuts through a break in a body of rock along which one tectonic plate slides relative to another

7 Era when mammals were the dominant life forms. Mass extinctions caused by a meteorite impacting Earth wiped out many types of organisms, including dinosaurs, at the end of this period. Era when mammals were the dominant life forms. Mass extinctions caused by a meteorite impacting Earth wiped out many types of organisms, including dinosaurs, at the end of this period. Ordovician Period Permian period Ordovician Period Permian period Pliestocene Epoch Pliocene Epoch Pliestocene Epoch Pliocene Epoch Era when reptiles - mainly dinosaurs - were the dominant life forms. Paleozoic Era Era when reptiles - mainly dinosaurs - were the dominant life forms. Paleozoic Era States that dinosaurs became extinct when a giant meteorite crashed into Earth. Triassic Period States that dinosaurs became extinct when a giant meteorite crashed into Earth. Triassic Period What abbreviation is used to mean "Million years ago" as in: Dinosaurs existed 200 million years ago? What abbreviation is used to mean "Million years ago" as in: Dinosaurs existed 200 million years ago? The division of geologic time that makes up about 88% of Earth s history, when the first known unicellular life appears. The division of geologic time that makes up about 88% of Earth s history, when the first known unicellular life appears.

8 Cretaceous Period Cenozoic Era Cretaceous Period Cenozoic Era Mass extinctions occur from major climate changes at the end of this period. Mass extinctions occur from major climate changes at the end of this period. Period when the Earth s atmosphere became oxygen-rich & reached the same levels of gasses we have today. Period when the Earth s atmosphere became oxygen-rich & reached the same levels of gasses we have today. Epoch when the last major Ice age (modern ice age) began. Epoch when modern humans appeared. Epoch when the last major Ice age (modern ice age) began. Epoch when modern humans appeared. Era when fish were the dominant life forms. Mesozoic Era Era when fish were the dominant life forms. Mesozoic Era Period when the supercontinent, Pangaea, began to break apart. The Impact hypothesis Period when the supercontinent, Pangaea, began to break apart. The Impact hypothesis Precambrian time Ma Dinosaurs existed 200 Ma Precambrian time Ma Dinosaurs existed 200 Ma

9 4 Characteristics of Index fossils Why are fossils not found in Metamorphic rocks? 4 Characteristics of Index fossils Why are fossils not found in Metamorphic rocks? Why are fossils found in Sedimentary rock? Whay are fossils not found in Igneous rocks? Why are fossils found in Sedimentary rock? Whay are fossils not found in Igneous rocks? Sedimentary rock Igneous & Metamorphic Rock Sedimentary rock Igneous & Metamorphic Rock

10 The extreme pressure or chemical reactions that form metamorphic rocks crush or destroy the fossils. The extreme pressure or chemical reactions that form metamorphic rocks crush or destroy the fossils. The extreme heat that melts rock into the magma that igneous rocks are made of burns up the fossils. The extreme heat that melts rock into the magma that igneous rocks are made of burns up the fossils. 1. Must be unique, it must have features that clearly 1. Must distinguish be unique, it it from must other have fossils. features that 2. Must clearly be abundant distinguish - the it fossil from other must fossils. occur in fairly 2. Must large be numbers abundant within - the the fossil rock must layers. occur in 3. Must fairly be large widespread numbers - a within fossil the must rock be layers. present in 3. Must rocks be widespread scattered over - a fossil a large must region be present 4. Organisms in rocks from scattered which the over fossil a large formed region must have lived 4. Organisms during a short from span which of the geologic fossil time formed (only must lived have lived during one a short ime span period) of geologic time (only lived in one ime period) Because as the sediments settle in layers, they surround the organisms. This protects the fossils from damage (kind of like a vase surrounded by packing peanuts) Because as the sediments settle in layers, they surround the organisms. This protects the fossils from damage (kind of like a vase surrounded by packing peanuts) Fossils ARE NOT found in these types of rock Fossils ARE found in this type of rock Fossils ARE NOT found in these types of rock Fossils ARE found in this type of rock