Relative Dating Key Concept Scientists Can Interpret the Sequence of 2 Events in Earth’S History by Studying Rock Layers
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Geologic Time Two Ways to Date Geologic Events Steno's Laws
Frank Press • Raymond Siever • John Grotzinger • Thomas H. Jordan Understanding Earth Fourth Edition Chapter 10: The Rock Record and the Geologic Time Scale Lecture Slides prepared by Peter Copeland • Bill Dupré Copyright © 2004 by W. H. Freeman & Company Geologic Time Two Ways to Date Geologic Events A major difference between geologists and most other 1) relative dating (fossils, structure, cross- scientists is their concept of time. cutting relationships): how old a rock is compared to surrounding rocks A "long" time may not be important unless it is greater than 1 million years 2) absolute dating (isotopic, tree rings, etc.): actual number of years since the rock was formed Steno's Laws Principle of Superposition Nicholas Steno (1669) In a sequence of undisturbed • Principle of Superposition layered rocks, the oldest rocks are • Principle of Original on the bottom. Horizontality These laws apply to both sedimentary and volcanic rocks. Principle of Original Horizontality Layered strata are deposited horizontal or nearly horizontal or nearly parallel to the Earth’s surface. Fig. 10.3 Paleontology • The study of life in the past based on the fossil of plants and animals. Fossil: evidence of past life • Fossils that are preserved in sedimentary rocks are used to determine: 1) relative age 2) the environment of deposition Fig. 10.5 Unconformity A buried surface of erosion Fig. 10.6 Cross-cutting Relationships • Geometry of rocks that allows geologists to place rock unit in relative chronological order. • Used for relative dating. Fig. 10.8 Fig. 10.9 Fig. 10.9 Fig. 10.9 Fig. Story 10.11 Fig. -
Lab 7: Relative Dating and Geological Time
LAB 7: RELATIVE DATING AND GEOLOGICAL TIME Lab Structure Synchronous lab work Yes – virtual office hours available Asynchronous lab work Yes Lab group meeting No Quiz None – Test 2 this week Recommended additional work None Required materials Pencil Learning Objectives After carefully reading this chapter, completing the exercises within it, and answering the questions at the end, you should be able to: • Apply basic geological principles to the determination of the relative ages of rocks. • Explain the difference between relative and absolute age-dating techniques. • Summarize the history of the geological time scale and the relationships between eons, eras, periods, and epochs. • Understand the importance and significance of unconformities. • Explain why an understanding of geological time is critical to both geologists and the general public. Key Terms • Eon • Original horizontality • Era • Cross-cutting • Period • Inclusions • Relative dating • Faunal succession • Absolute dating • Unconformity • Isotopic dating • Angular unconformity • Stratigraphy • Disconformity • Strata • Nonconformity • Superposition • Paraconformity Time is the dimension that sets geology apart from most other sciences. Geological time is vast, and Earth has changed enough over that time that some of the rock types that formed in the past could not form Lab 7: Relative Dating and Geological Time | 181 today. Furthermore, as we’ve discussed, even though most geological processes are very, very slow, the vast amount of time that has passed has allowed for the formation of extraordinary geological features, as shown in Figure 7.0.1. Figure 7.0.1: Arizona’s Grand Canyon is an icon for geological time; 1,450 million years are represented by this photo. -
The Rock and Fossil Record the Rock and Fossil Record the Rock And
TheThe RockRock andand FossilFossil RecordRecord Earth’s Story and Those Who First Listened . 426 Apply . 427 Internet Connect . 428 When on Earth? . 429 Activity . 430 MathBreak . 434 Internet Connect 432, 435 Looking at Fossils . 436 QuickLab . 438 Internet Connect . 440 Time Marches On . 441 QuickLab . 443 Internet Connect . 445 Chapter Lab . 446 Chapter Review . 449 TEKS/TAKS Practice Tests . 451, 452 Feature Article . 453 Time Stands Still Pre-Reading Questions Sealed in darkness for 49 million years, this beetle still shimmers with the same metallic hues that once helped it hide among ancient plants. This rare fossil 1. How do scientists study was found in Messel, Germany. In the same rock formation, the Earth’s history? scientists have found fossilized crocodiles, bats, birds, and 2. How can you tell the age frogs. A living stag beetle (above) has a similar form and of rocks and fossils? color. Do you think that these two beetles would live in 3. What natural or human similar environments? What do you think Messel, Germany, events have caused mass was like 49 million years ago? In this chapter, you will extinctions in Earth’s learn how scientists answer these kinds of questions. history? 424 Chapter 16 Copyright © by Holt, Rinehart and Winston. All rights reserved. MAKING FOSSILS Procedure 1. You and three or four of your classmates will be given several pieces of modeling clay and a paper sack containing a few small objects. 2. Press each object firmly into a piece of clay. Try to leave an imprint showing as much detail as possible. -
Geologic Time and Geologic Maps
NAME GEOLOGIC TIME AND GEOLOGIC MAPS I. Introduction There are two types of geologic time, relative and absolute. In the case of relative time geologic events are arranged in their order of occurrence. No attempt is made to determine the actual time at which they occurred. For example, in a sequence of flat lying rocks, shale is on top of sandstone. The shale, therefore, must by younger (deposited after the sandstone), but how much younger is not known. In the case of absolute time the actual age of the geologic event is determined. This is usually done using a radiometric-dating technique. II. Relative geologic age In this section several techniques are considered for determining the relative age of geologic events. For example, four sedimentary rocks are piled-up as shown on Figure 1. A must have been deposited first and is the oldest. D must have been deposited last and is the youngest. This is an example of a general geologic law known as the Law of Superposition. This law states that in any pile of sedimentary strata that has not been disturbed by folding or overturning since accumulation, the youngest stratum is at the top and the oldest is at the base. While this may seem to be a simple observation, this principle of superposition (or stratigraphic succession) is the basis of the geologic column which lists rock units in their relative order of formation. As a second example, Figure 2 shows a sandstone that has been cut by two dikes (igneous intrusions that are tabular in shape).The sandstone, A, is the oldest rock since it is intruded by both dikes. -
Soils in the Geologic Record
in the Geologic Record 2021 Soils Planner Natural Resources Conservation Service Words From the Deputy Chief Soils are essential for life on Earth. They are the source of nutrients for plants, the medium that stores and releases water to plants, and the material in which plants anchor to the Earth’s surface. Soils filter pollutants and thereby purify water, store atmospheric carbon and thereby reduce greenhouse gasses, and support structures and thereby provide the foundation on which civilization erects buildings and constructs roads. Given the vast On February 2, 2020, the USDA, Natural importance of soil, it’s no wonder that the U.S. Government has Resources Conservation Service (NRCS) an agency, NRCS, devoted to preserving this essential resource. welcomed Dr. Luis “Louie” Tupas as the NRCS Deputy Chief for Soil Science and Resource Less widely recognized than the value of soil in maintaining Assessment. Dr. Tupas brings knowledge and experience of global change and climate impacts life is the importance of the knowledge gained from soils in the on agriculture, forestry, and other landscapes to the geologic record. Fossil soils, or “paleosols,” help us understand NRCS. He has been with USDA since 2004. the history of the Earth. This planner focuses on these soils in the geologic record. It provides examples of how paleosols can retain Dr. Tupas, a career member of the Senior Executive Service since 2014, served as the Deputy Director information about climates and ecosystems of the prehistoric for Bioenergy, Climate, and Environment, the Acting past. By understanding this deep history, we can obtain a better Deputy Director for Food Science and Nutrition, and understanding of modern climate, current biodiversity, and the Director for International Programs at USDA, ongoing soil formation and destruction. -
A GEOLOGIC RECORD of the FIRST BILLION YEARS of MARS HISTORY. John F. Mustard1 and James W. Head1 1Department of Earth, Environm
49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083) 2604.pdf A GEOLOGIC RECORD OF THE FIRST BILLION YEARS OF MARS HISTORY. John F. Mustard1 and James W. Head1 1Department of Earth, Environmental and Planetary Sciences, Box 1846, Brown University, Provi- dence, RI 02912 ([email protected]) Introduction: A compelling record of the first bil- standing solar system evolution question is the exist- lion years of Mars geologic evolution is spectacularly ence, or not, of a period of heavy bombardment ≈500 presented in a compact region at the intersection of Myr after accretion of the terrestrial planets. Except Isidis impact basin and Syrtis Major volcanic province for the Moon, we have no definitive dates for basins (Fig. 1). In this well-exposed region is a well-ordered formed in the Solar System. Radiometric systems in stratigraphy of geologic units spanning Noachian to crystalline igneous rocks exposed by Isidis would like- Early Hesperian times [1]. Geologic units can be de- ly have been reset and thus contain evidence of the finitively associated with the Isidis basin-forming im- impact providing a key data point for understanding pact (≈3.9 Ga, [2]) as well as pristine igneous and basin forming processes in the Solar System. Further- aqueously altered Noachian crust that pre-date the more the Isidis basin impacted onto the rim of the hy- Isidis event. The rich collection of well defined units pothesized Borealis Basin [7]. Given this proximity spanning ≈500 Myr of time in a compact region is at- there is a possibility that some fragments may have tractive for the collection of samples. -
Scientific Dating of Pleistocene Sites: Guidelines for Best Practice Contents
Consultation Draft Scientific Dating of Pleistocene Sites: Guidelines for Best Practice Contents Foreword............................................................................................................................. 3 PART 1 - OVERVIEW .............................................................................................................. 3 1. Introduction .............................................................................................................. 3 The Quaternary stratigraphical framework ........................................................................ 4 Palaeogeography ........................................................................................................... 6 Fitting the archaeological record into this dynamic landscape .............................................. 6 Shorter-timescale division of the Late Pleistocene .............................................................. 7 2. Scientific Dating methods for the Pleistocene ................................................................. 8 Radiometric methods ..................................................................................................... 8 Trapped Charge Methods................................................................................................ 9 Other scientific dating methods ......................................................................................10 Relative dating methods ................................................................................................10 -
Personal Details: Relative Dating Methods Archaeology; Principles
Component-I (A) – Personal details: Archaeology; Principles and Methods Relative Dating Methods Prof. P. Bhaskar Reddy Sri Venkateswara University, Tirupati. Prof. K.P. Rao University of Hyderabad, Hyderabad. Prof. K. Rajan Pondicherry University, Pondicherry. Prof. R. N. Singh Banaras Hindu University, Varanasi. 1 Component-I (B) – Description of module: Subject Name Indian Culture Paper Name Archaeology; Principles and Methods Module Name/Title Relative Dating Methods Module Id IC / APM / 17 Pre requisites Objectives Archaeology / Stratigraphy / Dating / Keywords Geochronology E-Text (Quadrant-I) : 1. Introduction In archaeology, the material unearthed in the excavations and archaeological remains surfaced and documented in the explorations are dated by following two methods namely, absolute dating method and relative dating method. In the former method, the artefacts are being preciously dated using various scientific techniques and in a few cases it is dated based on the hidden historical data available with historical documents such as inscriptions, copper plates, seals, coins, inscribed portrait sculptures and monuments. In the latter method, a tentative date is achieved based on archaeological stratigraphy, seriation, palaeography, linguistic style, context, art and architectural features. Though the absolute dates are the most desirable one, the significance of relative dates increases manifold when the absolute dates are not available. Till advent of the scientific techniques, most of the archaeological and historical objects were dated based on relative dating methods. Archaeologists are resorted to the use of relative dating techniques when the absolute dates are not possible or feasible. Estimation of the age was merely a guess work in the initial stage of archaeological investigation particularly in 18th-19th centuries. -
Utah's Geologic Timeline Utah Seed Standard 7.2.6: Make an Argument from Evidence for How the Geologic Time Scale Shows the Ag
Utah’s Geologic Timeline Utah SEEd Standard 7.2.6: Make an argument from evidence for how the geologic time scale shows the age and history of Earth. Emphasize scientific evidence from rock strata, the fossil record, and the principles of relative dating, such as superposition, uniformitarianism, and recognizing unconformities. (ESS1.C) Activity Details: The students begin with a blank calendar and a list of events in the Earth’s, and additionally Utah’s, history. These events span billions of years, but such numbers are too large to visualize and compare. In order to help the mind understand such enormous lengths of time, the year of the event is scaled to what it would Be proportionate to a calendar year (numBers are from The Utah Geological Survey and Kentucky Geological Survey). The students go through the list and fill out their calendar to visualize the geologic timeline of the Earth and Utah, and then answer some analysis questions to help solidify their understanding. Students will need four differently-colored colored pencils or crayons to complete the activity. Background: The following information is taken from The Utah Geological Survey, written by Mark Milligan. It may Be helpful to define some of the terms with the students so they understand where and how ages come from. Geologists generally know the age of a rock By determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale. Development of the geologic time scale and dating of formations and rocks relies upon two fundamentally different ways of telling time: relative and absolute. -
Relative Dating Unit B
Geologic Time Part I: Relative Dating Unit B Unit A James Hutton conceived of the Principle of Uniformitarianism at Sicar Point, Scotland in 1785. Think about how much time would pass to create the rock record shown above. What sequence of events would occur to produce the above record? Unit B Unit A 1. Deposition of sediment comprising Unit A (Sedimentation rates in the deep ocean range from .0005 - .001 mm per year). How long would it take to accumulate 200 meters of sediment?) 2. burial compaction & lithification of Unit A, 3. deformation (folding) of Unit A, 4. uplift and erosion of Unit A, 5. Deposition of sediment (Unit B), 6. burial compaction & lithification of Unit B, 7. deformation (folding) of Unit B, 8. uplift and erosion of Unit B. These geologic events require millions of years of time! Principle of Original Horizontality: Layered sedimentary rock is typically deposited horizontally, but can be deformed by tectonic processes. Can you think of a depositional environment where sedimentary layers are not deposited horizontally? Geologists use sedimentary structures to determine whether sedimentary layers or beds are right-side up, vertical or overturned. The Principle of Uniformitarianism states that the “present is the key to the past.” Those processes operating at the earth’s surface today are inferred to have operated in the past, such as the mudcracks forming in a playa lake today. Note the blowing sand in the background will fill in the cracks. The mudcracks shown above formed over 1.1 billion years ago in a dry lake basin are now found in Glacier National Park, Montana. -
Museum of Natural History & Science Gallery Guide for Lost Voices
Museum of Natural History & Science Gallery Guide for Lost Voices Lost Voices is a multi-part exhibit focusing on the varied life forms that have inhabited our planet in the past. This exhibit allows for a greater understanding of the history of our planet and also of our place on it. Concepts: background extinction, Cenozoic, Cretaceous, crust, environment, eons, epoch, era, evolution, extinction, fossil, fossil record, geologic record, geologist, Holocene, Jurassic, limestone, mantle, mass extinction, Mesozoic, period, plate tectonics, Quaternary, sandstone, Tertiary, tilt, Triassic, wobble Background Information: Scientists calculate the age of the Earth at approximately 4.6 billion years, and the planet has sustained life for over three million years. During this time, many changes have taken place in climate, placement of the continents and life forms. To assist in understanding this vast period of time, scientists have divided the time into sections. The longest period of time are called eons, which are divided into eras, which are then divided into periods, which are finally divided into epochs. Most people are familiar with the Mesozoic era, which consists of the Triassic, Jurassic, and Cretaceous periods. We currently live in the Cenozoic era, the Quaternary period and the Holocene epoch. The divisions between geologic time spans are often defined by a break in the fossil record or a geologic occurrence of some magnitude, such as a sudden widespread volcanic activity. For example, all available evidence points to the division of the Cretaceous and Tertiary periods caused by a giant asteroid strike off the coast of Mexico. The asteroid strike caused the extinction of over 80 percent of the planet’s life forms and created widespread geologic activity. -
Tectonics and Crustal Evolution
Tectonics and crustal evolution Chris J. Hawkesworth, Department of Earth Sciences, University peaks and troughs of ages. Much of it has focused discussion on of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, the extent to which the generation and evolution of Earth’s crust is UK; and Department of Earth Sciences, University of St. Andrews, driven by deep-seated processes, such as mantle plumes, or is North Street, St. Andrews KY16 9AL, UK, c.j.hawkesworth@bristol primarily in response to plate tectonic processes that dominate at .ac.uk; Peter A. Cawood, Department of Earth Sciences, University relatively shallow levels. of St. Andrews, North Street, St. Andrews KY16 9AL, UK; and Bruno The cyclical nature of the geological record has been recog- Dhuime, Department of Earth Sciences, University of Bristol, Wills nized since James Hutton noted in the eighteenth century that Memorial Building, Queens Road, Bristol BS8 1RJ, UK even the oldest rocks are made up of “materials furnished from the ruins of former continents” (Hutton, 1785). The history of ABSTRACT the continental crust, at least since the end of the Archean, is marked by geological cycles that on different scales include those The continental crust is the archive of Earth’s history. Its rock shaped by individual mountain building events, and by the units record events that are heterogeneous in time with distinctive cyclic development and dispersal of supercontinents in response peaks and troughs of ages for igneous crystallization, metamor- to plate tectonics (Nance et al., 2014, and references therein). phism, continental margins, and mineralization. This temporal Successive cycles may have different features, reflecting in part distribution is argued largely to reflect the different preservation the cooling of the earth and the changing nature of the litho- potential of rocks generated in different tectonic settings, rather sphere.