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absolute and relative dating.pptx
The document discusses rock formation and dating methods, detailing how stratified rocks are formed and the processes of relative and absolute dating. It explains weathering, sediment deposition, and various laws, such as the law of superposition and the law of inclusion, used in relative dating. Additionally, it covers absolute dating through radioactive decay and the concept of half-life in determining the age of rocks.
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absolute and relative dating.pptx
- 1. Rock Formation II: Relativeand Absolute Dating mirjam nilsson
- 2. A) Describe howlayers of rocks (stratified rocks) are formed, B) Describe the different methods (relative and absolute dating) to determine the age of stratified rocks, and C) Explain how relative and absolute dating were used to determine the subdivisions of geologic time. Objectives
- 3. 20XX presentation title3 The relative age of a rock is its age when compared with the ages of other rocks The absolute age of a rock is a calculation of the number of years that have passed since the rock formed.
- 4. How Layers of RocksAre Formed
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- 6. . 20XX presentation title6 How Sediments are formed and sediments are turned into layers of new rocks. Existing rocks can be broken down into small pieces called ________. 3 Main types of Weathering: 1.___________ - caused by temperature changing. 2. __________ - when acid rain reacts with substances in rocks. 3. __________ - plants or animals can break up rocks.
- 7. Sediments can bemove away by: _______, ______, ______, ______. The combined process of weathering and transport is called ________. When sediments settle in warm place and some may sink at the bottom of the sea and this called _______. _______ when these layers the weight of the layers above compressed the ones below and are formed into sedimentary rocks. _________when substance sips between the sediments and hardened and glued together. 20XX presentation title 7
- 8. Methods to Determinethe Age of Stratified Rocks Relative dating is a method of arranging geological events based on the rock sequence. • Determining which fossils or events came first, second, third…etc… 20XX presentation title 8
- 12. Absolute Dating – determiningthe actual age of rock using radioactive decay 20XX presentation title 12
- 13. • ABSOLUTE DATING theprocess of determining an age on a specified chronology in archaeology and geology (RADIOACTIVE DECAY) • RELATIVE DATING the process of determining if one rock or geologic event is older or younger than another, without knowing their specific ages (GEOLOGIC SEQUENCING) 20XX presentation title 13
- 14. PRINCIPLES OF RELATIVEDATING • Law of Superposition States that each layer of sediment is piled on top of another layer making the one on top of the strata the youngest one, while the layer at the bottom of the strata is the oldest.
- 16. The Law ofCross-Cutting Relationship • States that igneous intrusion is always younger than the rock it cuts across • Extrusion – a lava that is cooled and hardened in a surface. • Intrusion – a magma that is cooled and hardened beneath the surface (hardened magma)
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- 19. The Law ofInclusion • The rocks that are mixed up in the formation of sediments are called INCLUSION • These rocks are always older than the layer of sediments it is embedded. 20XX presentation title 19
- 20. Law of Horizontality •Layers of sediments are originally deposited horizontally under the influence of gravity. Those strata's that are not found not in horizontal order may have been deformed by the movement of the earth’s crust. 20XX presentation title 20
- 21. Absolute Age ofRocks • RADIOMETRIC DATING – radioactive isotopes found in fossils or rocks are used. 20XX presentation title 21
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- 23. • Radioactive decay– the process by which an atomic nucleus of an unstable atom loses energy. Alpha, Beta and Gamma • The original unstable isotope is called the parent isotope, and the more stable form is called the daughter isotope. Isotopes decay at an exponential rate that that can be described in terms of half-life. • Half – life - it takes time for substance undergoing decay to decrease by half. 20XX presentation title 23
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Editor's Notes
- #4 There are two ways to talk about the ages of rocks or rock formations. These are the relative age and the absolute age. There are different techniques that are utilized to determine each of these.
- #5 Most rocks are sedimentary rocks. They are formed from older rocks that have been broken down by water or wind. The older rocks become sedimentary particles such as gravel, sand, and mud. These particles can also bury dead plants and animals. As time goes by, the particles accumulate, and those that are at the bottom of the pile become rocks. Gravel becomes conglomerate; sand becomes sandstone; and mud becomes shale or mudstone. The animals or plants buried with them become fossils. These series of events form the different layers of rocks.
- #7 Physical weathering Chemical Biological
- #8 Water, ice, wind or gravity Erosion Deposition Compaction Cementation
- #15 The layered rocks are also called strata.
- #16 Example of stratified rocks
- #17 An igneous intrusion is always younger than the rock it has intruded
- #20 The pebbles in this conglomerate are older than the conglomerate itself. a number of different things or parts that are put or grouped together to form a whole but remain distinct entities.
- #21 Due to compression
- #23 The original unstable isotope is called the parent isotope, and the more stable form is called the daughter isotope. Isotopes decay at an exponential rate that that can be described in terms of half-life. Uranium decays very slowly (it takes 4.5 billion years for its half-life to decay)