DOCSLIB.ORG

Chapter 19. Geochronology Applied to Glacial Environments

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 19. Geochronology Applied to Glacial Environments CHAPTER GEOCHRONOLOGY APPLIED TO GLACIAL ENVIRONMENTS 19 A.J.T. Jull1,2 1University of Arizona, Tucson, AZ, United States, 2Institute for Nuclear Research, Debrecen, Hungary 19.1 INTRODUCTION There are several important dating methods used for studies of glacial environments. In all cases, we need a chronometer, such as radioactive decay, in-growth of a radionuclide, or some other process that has a well-defined function with time. A key to any of these geochronological methods is understanding the underlying assumptions of the method, and the time dependence of the signals studied. The purpose of all of these methods is to be able to establish the age of the material of interest. It is also important to know that the material being dated can be related to the geological feature studied. Sometimes, the need is for a precise age determination, in other cases, relative age or approximate ages based on qualitative estimates, may be sufficient. Hence, the goal of this chapter is to summarize those methods and discuss briefly their advantages and deficiencies. This chapter summarizes the various dating techniques which can be relevant to samples in a glacial environment. There are many different approaches to estimate the ages of glacial deposits. These can be a variety of methods using either the decay or in-growth of radionuclides, or the build-up of radiation dose measured in different ways. Other methods that can be used include dendrochronology, comparing the growth of annual bands in trees, and studying annually layered (varve) sediments. Chemical changes such as amino-acid racemization can also be used, with an understanding of the kinetics of the processes involved. There are other more qualitative methods using the correlation of layers of identifiable materials such as volcanic ash layers, palaeomagnetic signals and biostratigraphic changes (Fig. 19.1). These methods can be subdivided into four main categories: radioactive nuclide methods, radia- tive dosimetry methods, qualitative and comparative methods and chemical methods (Jull, 2013a). Each section is subdivided into the specific methods and cross-references to sources which direct the reader to each topic in more detail. 19.2 RADIOACTIVE NUCLIDES The most important geochronology methods for glacial materials involve radioactive decay. Some processes involve the decay of an isotope from a known initial composition, whereas in others, the build-up or ingrowth of an isotope produced by the decay, or a ‘daughter’ isotope will give useful Past Glacial Environments. DOI: http://dx.doi.org/10.1016/B978-0-08-100524-8.00020-8 © 2018 Elsevier Ltd. All rights reserved. 665 666 CHAPTER 19 GEOCHRONOLOGY APPLIED TO GLACIAL ENVIRONMENTS Lichenometry Tree-rings Radiocarbon Uranium/thorium Luminescence Amino acid racemization Palaeomagnetism Potassium/argon Fission track dating 1 10 100 1000 10,000 100,000 1,000,000 10,000,000 Time scale in years (logarithmic) FIGURE 19.1 Time scales of different Quaternary geochronology methods. Courtesy of Scott Elias (Royal Holloway, University of London). age information. The daughter nuclide can be radioactive itself, which leads to a more complex decay equation, since the decay of two isotopes is involved. In other cases, the in-growth may be of a stable nuclide. Since radioactive nuclide concentrations can increase or decrease with time, depending on the system of interest, we can use the concentration of the specific nuclide to estimate the age of the material. The main radioactive systems studied are given in Table 19.1. Radioactive species can be produced by three different kinds of nuclear processes: 1. Radioactive decay of a parent nuclide; 2. Production by nuclear reactions as a result of exposure to cosmic radiation; 3. In-growth of a radioactive daughter product from a longer-lived parent nuclide; 4. In-growth of a stable daughter produced from a longer-lived parent nuclide. 19.2.1 RADIOACTIVE DECAY In a simple case, such as radiocarbon dating, the number of 14C atoms will decay with time from an initial value, according to the radioactive decay equation, originally shown by Rutherford and Soddy (Dickin, 1995), following their observations on the behaviour of radioactive species: dN 5 A 52λN (19.1) dt where the decay rate of the number of atoms with time (or activity, A) is proportional to the num- ber of radioactive atoms present (N). The ‘decay constant’ λ defines the rate of decay and this defines the probability of decay of an isotope. One can also refer to the ‘mean life’ of the isotope, which is 1/λ and sometimes stated as τ. It is more common to refer to the ‘half-life’ of the radionu- clide, which is the time for one-half of the remaining atoms to decay, which is related directly to the decay constant: 19.2 RADIOACTIVE NUCLIDES 667 Table 19.1 Radioactive Dating Methods Applicable to Glacial Environments Parent Isotopic Nuclide or System Process Half-Life Time Scale Material References 14C 14C(n,p) 14N 5730 years 0À50 ka Organic Taylor (1987) material, carbonates 230Th 238U and 75,690 years 1000À500,000 years Carbonates Schwarcz (1989), 234U (230Th) Bischoff and 245,600 years Fitzpatrick (1991) (234U) 210Pb U-series 22.3 years 0À150 years Fine-grained Olsson (1986) decay sediments sequence UÀHe U isotopes Depends on 0À300,000 years Tephras Kohn et al. (2000) α-decay parent nuclides 137Cs U fission 30 years After 1950 AD Fine-grained Pennington et al. sediments (1973) 40KÀ40Ar 40K β-decay 1.25 3 109 years 104À109 years K-bearing McDougall and minerals, Harrison (1988) bones, tephras 10Be Cosmogenic 1.38 3 106 years 5À10 Myr Quartz Gosse and Phillips 26Al nuclides (2001), Lifton et al. 36Cl 7.05 3 105 years B3 Myr Quartz (2014) 3.01 3 105 years B1 Myr Calcite, basalts 5 ln 2 t1=2 λ (19.2) If Eq. (19.1) is integrated, within the limits N 5 N0 at t 5 0 and N 5 0att 5 N, the result is a more common form of the exponential decay equation: N 5 e2λt (19.3) N0 where N0 is the number of atoms at time t 5 0 and N is the number of atoms at any time t.An example is shown in Fig. 19.1 of the decay of a nuclide with a half-life of 5568 years, the value used in radiocarbon dating calculations. 19.2.2 IN-GROWTH OF A RADIONUCLIDE In-growth of a radioactive species occurs when it is produced either from the decay of another radionuclide, or produced directly in the sample by irradiation. The latter example occurs often in the case of in situ cosmogenic nuclide studies (Granger, 2014). An example is the in-growth of a radionuclide, such as in the 231PaÀ235U system. In the case of these daughter-in-growth approaches, it is useful to use the activity (e.g., the decay rate) of the 668 CHAPTER 19 GEOCHRONOLOGY APPLIED TO GLACIAL ENVIRONMENTS 235 231 nuclide instead of the number of atoms. U(t1/2 7.04 Ma) decays to Th, however the half-life 231 of this nuclide is very short (t1/2 25.5 h) and can be ignored, so it decays rapidly to Pa (t1/2 32.76 ka). In this case, 231Pa increases with time due to the decay of the long-lived parent nuclide 235U, which decays very slowly, so that (Ku, 1968, 2000): 2λ231t A231 5 A235ð1 2 e Þ (19.4) In this case, the activity 231Pa starts from zero and builds up to an equilibrium defined by the 231 decay rate of Pa, so that at equilibrium (t .. t1/2) the production rate of 231 is equal to the decay rate of 235U. It is important to understand that this equation works because the decay rate of the unstable daughter is much shorter than that of the parent. If the two half-lives were comparable, the decay constant (λ) would be the difference between the two values. 230 230 A more complex case occurs for Th (t1/2 75,690 years). In this case, Th increases 234 with time due to the decay of the parent nuclides U(t1/2 245,600 years), which is produced from 238U decay (Cheng et al., 2013). Because the half-life of 230Th is very low compared to the parent 238U, therefore Eq. (19.4) would be correct if the intermediate daughter product, 234U, was always in secular equilibrium with the 238U(Ku, 2000). Fig. 19.2 shows an example of the in-growth of a nuclide (in this case, 230Th) with a half-life of 75,600 years). However, 234U is often not in radioac- tive equilibrium with 238U, due to the effects of selective dissolution of 234U. When the activity 230 A234 does not equal A238 then we also have to include Th arising from the ‘unsupported’ decay of 234U. Hence, the amount of 230Th produced is a product of the decay of both the excess 234U and the 238U. The result is a more complex equation, described in detail in the section on UÀTh dating (Cohen, 2005). Finally, we have the case where we have a stable daughter product of the radioactive decay. This allows us to know the original concentration of the parent (P0), since the value is P0 5 P 1 D, where P is the current value of the parent and D is the current value of the daughter. This is valuable in a Radioactive decay 1,000,000 900,000 800,000 700,000 600,000 500,000 Number 400,000 300,000 200,000 100,000 0 0 5000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000 Time (years) FIGURE 19.2 Exponential decay of a radionuclide (14C) calculated with a half-life of 5568 years.
Load more

Recommended publications
  • (2016), Volume 4, Issue 2, 77-90
    ISSN 2320-5407 International Journal of Advanced Research (2016), Volume 4, Issue 2, 77-90 Journal homepage: http://www.journalijar.com INTERNATIONAL JOURNAL OF ADVANCED RESEARCH RESEARCH ARTICLE LICHENOMETRIC DATING CURVE AS APPLIED TO GLACIER RETREAT STUDIES IN THE HIMALAYAS. Gaurav K. Mishra, Santosh Joshi and Dalip K. Upreti. Lichenology Laboratory, CSIR-National Botanical Research Institute, Rana Pratap Marg, Lucknow- 226001. Manuscript Info Abstract Manuscript History: The study critically favours the importance of lichens in estimating palaeoclimatic events and its use in depicting the future discretion regarding Received: 14 December 2015 Final Accepted: 19 January 2016 glacier retreat. Besides the various lichenometric studies carried out in Indian Published Online: February 2016 Himalayan region, the world-wide classical work of different glaciologist and geologist on different applications of lichenometry is also well focused. Key words: The study also highlights the benefits, restrains, and drawbacks associated Lichens, lichenometry,glacier with the lichenometry. Being a globally accepted biological technique retreat,India. particular emphasis is given on the need of innovative approach in implementation of lichenometry in Indian Himalayan region. *Corresponding Author Gaurav K. Mishra. Copy Right, IJAR, 2016,. All rights reserved. Introduction:- Lichens are slow growing organisms and take several years to get established in nature. Lichens are a unique group of plants, comprising of two micro-organisms, fungus (mycobiont), an organism capable of producing food via photosynthesis and alga (photobiont). These photobionts are predominantly members of the chlorophyta (green algae) or cynophyta (blue-green algae or cynobacteria). The peculiar nature of lichens enables them to colonize variety of substrate like rock, boulders, bark, soil, leaf and man-made buildings.
    [Show full text]
  • Radiocarbon Dating and Its Applications in Quaternary Studies
    Eiszeitalter und Gegenwart 57/1–2 2–24 Hannover 2008 Quaternary Science Journal Radiocarbon dating and its applications in Quaternary studies *) IRKA HAJDAS Abstract: This paper gives an overview of the origin of 14C, the global carbon cycle, anthropogenic impacts on the atmospheric 14C content and the background of the radiocarbon dating method. For radiocarbon dating, important aspects are sample preparation and measurement of the 14C content. Recent advances in sample preparation allow better understanding of long-standing problems (e.g., contamination of bones), which helps to improve chronologies. In this review, various preparation techniques applied to typical sample types are described. Calibration of radiocarbon ages is the fi nal step in establishing chronologies. The present tree ring chronology-based calibration curve is being constantly pushed back in time beyond the Holocene and the Late Glacial. A reliable calibration curve covering the last 50,000-55,000 yr is of great importance for both archaeology as well as geosciences. In recent years, numerous studies have focused on the extension of the radiocarbon calibration curve (INTCAL working group) and on the reconstruction of palaeo-reservoir ages for marine records. [Die Radiokohlenstoffmethode und ihre Anwendung in der Quartärforschung] Kurzfassung: Dieser Beitrag gibt einen Überblick über die Herkunft von Radiokohlenstoff, den globalen Kohlenstoffkreislauf, anthropogene Einfl üsse auf das atmosphärische 14C und die Grundlagen der Radio- kohlenstoffmethode. Probenaufbereitung und das Messen der 14C Konzentration sind wichtige Aspekte im Zusammenhang mit der Radiokohlenstoffdatierung. Gegenwärtige Fortschritte in der Probenaufbereitung erlauben ein besseres Verstehen lang bekannter Probleme (z.B. die Kontamination von Knochen) und haben zu verbesserten Chronologien geführt.
    [Show full text]
  • Forensic Radiocarbon Dating of Human Remains: the Past, the Present, and the Future
    AEFS 1.1 (2017) 3–16 Archaeological and Environmental Forensic Science ISSN (print) 2052-3378 https://doi.org.10.1558/aefs.30715 Archaeological and Environmental Forensic Science ISSN (online) 2052-3386 Forensic Radiocarbon Dating of Human Remains: The Past, the Present, and the Future Fiona Brock1 and Gordon T. Cook2 1. Cranfield Forensic Institute, Cranfield University 2. Scottish Universities Environmental Research Centre [email protected] Radiocarbon dating is a valuable tool for the forensic examination of human remains in answering questions as to whether the remains are of forensic or medico-legal interest or archaeological in date. The technique is also potentially capable of providing the year of birth and/or death of an individual. Atmospheric radiocarbon levels are cur- rently enhanced relative to the natural level due to the release of large quantities of radiocarbon (14C) during the atmospheric nuclear weapons testing of the 1950s and 1960s. This spike, or “bomb-pulse,” can, in some instances, provide precision dates to within 1–2 calendar years. However, atmospheric 14C activity has been declining since the end of atmospheric weapons testing in 1963 and is likely to drop below the natural level by the mid-twenty-first century, with implications for the application of radio- carbon dating to forensic specimens. Introduction Radiocarbon dating is most routinely applied to archaeological and environmental studies, but in some instances can be a very powerful tool for forensic specimens. Radiocarbon (14C) is produced naturally in the upper atmosphere by the interaction of cosmic rays on nitrogen-14 (14N). The 14C produced is rapidly oxidised to carbon dioxide, which then either enters the terrestrial biosphere via photosynthesis and proceeds along the food chain via herbivores and omnivores, and subsequently car- nivores, or exchanges into marine reservoirs where it again enters the food chain by photosynthesis.
    [Show full text]
  • Isotopegeochemistry Chapter4
    Isotope Geochemistry W. M. White Chapter 4 GEOCHRONOLOGY III: OTHER DATING METHODS 4.1 COSMOGENIC NUCLIDES 4.1.1 Cosmic Rays in the Atmosphere As the name implies, cosmogenic nuclides are produced by cosmic rays colliding with atoms in the atmosphere and the surface of the solid Earth. Nuclides so created may be stable or radioactive. Radio- active cosmogenic nuclides, like the U decay series nuclides, have half-lives sufficiently short that they would not exist in the Earth if they were not continually produced. Assuming that the production rate is constant through time, then the abundance of a cosmogenic nuclide in a reservoir isolated from cos- mic ray production is simply given by: −λt N = N0e 4.1 Hence if we know N0 and measure N, we can calculate t. Table 4.1 lists the radioactive cosmogenic nu- clides of principal interest. As we shall, cosmic ray interactions can also produce rare stable nuclides, and their abundance can also be used to measure geologic time. A number of different nuclear reactions create cosmogenic nuclides. “Cosmic rays” are high-energy (several GeV up to 1019 eV!) atomic nuclei, mainly of H and He (because these constitute most of the matter in the universe), but nuclei of all the elements have been recognized. To put these kinds of ener- gies in perspective, the previous gen- eration of accelerators for physics ex- Table 4.1. Data on Cosmogenic Nuclides periments, such as the Cornell Elec- -1 tron Storage Ring produce energies in Nuclide Half-life, years Decay constant, yr the 10’s of GeV (1010 eV); while 14C 5730 1.209x 10-4 CERN’s Large Hadron Collider, 3H 12.33 5.62 x 10-2 mankind’s most powerful accelerator, 10Be 1.500 × 106 4.62 x 10-7 located on the Franco-Swiss border 26Al 7.16 × 105 9.68x 10-5 near Geneva produces energies of 36Cl 3.08 × 105 2.25x 10-6 ~10 TeV range (1013 eV).
    [Show full text]
  • A Review of Lichenometric Dating of Glacial Moraines in Alaska a Review of Lichenometric Dating of Glacial Moraines in Alaska
    A REVIEW OF LICHENOMETRIC DATING OF GLACIAL MORAINES IN ALASKA A REVIEW OF LICHENOMETRIC DATING OF GLACIAL MORAINES IN ALASKA BY GREGORY C. WILES1, DAVID J. BARCLAY2 AND NICOLÁS E.YOUNG3 1Department of Geology, The College of Wooster, Wooster, USA 2Geology Department, State University of New York at Cortland, Cortland, USA 3Department of Geology, University at Buffalo, Buffalo, NY, USA Wiles, G.C., Barclay, D.J. and Young, N.E., 2010: A review of li- scarred trees provide high precision records span- chenometric dating of glacial moraines in Alaska. Geogr. Ann., 92 ning the past 2000 years (Barclay et al. 2009). A (1): 101–109. However, many other glacier forefields in Alaska ABSTRACT. In Alaska, lichenometry continues to be are beyond the latitudinal or altitudinal tree line in an important technique for dating late Holocene locations where tree-ring based dating methods moraines. Research completed during the 1970s cannot be applied. through the early 1990s developed lichen dating Lichenometry is a key method for dating curves for five regions in the Arctic and subarctic Alaskan Holocene glacier histories beyond the tree mountain ranges beyond altitudinal and latitudinal treelines. Although these dating curves are still in line. Some of the earliest well-replicated glacier use across Alaska, little progress has been made in histories in Alaska were based on lichen dates of the past decade in updating or extending them or in moraines (Denton and Karlén 1973a, b, 1977; developing new curves. Comparison of results from Calkin and Ellis 1980, 1984; Ellis and Calkin 1984) recent moraine-dating studies based on these five and the method continues to be applied today (e.g.
    [Show full text]
  • Paleomagnetism and U-Pb Geochronology of the Late Cretaceous Chisulryoung Volcanic Formation, Korea
    Jeong et al. Earth, Planets and Space (2015) 67:66 DOI 10.1186/s40623-015-0242-y FULL PAPER Open Access Paleomagnetism and U-Pb geochronology of the late Cretaceous Chisulryoung Volcanic Formation, Korea: tectonic evolution of the Korean Peninsula Doohee Jeong1, Yongjae Yu1*, Seong-Jae Doh2, Dongwoo Suk3 and Jeongmin Kim4 Abstract Late Cretaceous Chisulryoung Volcanic Formation (CVF) in southeastern Korea contains four ash-flow ignimbrite units (A1, A2, A3, and A4) and three intervening volcano-sedimentary layers (S1, S2, and S3). Reliable U-Pb ages obtained for zircons from the base and top of the CVF were 72.8 ± 1.7 Ma and 67.7 ± 2.1 Ma, respectively. Paleomagnetic analysis on pyroclastic units yielded mean magnetic directions and virtual geomagnetic poles (VGPs) as D/I = 19.1°/49.2° (α95 =4.2°,k = 76.5) and VGP = 73.1°N/232.1°E (A95 =3.7°,N =3)forA1,D/I = 24.9°/52.9° (α95 =5.9°,k =61.7)and VGP = 69.4°N/217.3°E (A95 =5.6°,N=11) for A3, and D/I = 10.9°/50.1° (α95 =5.6°,k = 38.6) and VGP = 79.8°N/ 242.4°E (A95 =5.0°,N = 18) for A4. Our best estimates of the paleopoles for A1, A3, and A4 are in remarkable agreement with the reference apparent polar wander path of China in late Cretaceous to early Paleogene, confirming that Korea has been rigidly attached to China (by implication to Eurasia) at least since the Cretaceous. The compiled paleomagnetic data of the Korean Peninsula suggest that the mode of clockwise rotations weakened since the mid-Jurassic.
    [Show full text]
  • The Geologic Time Scale Is the Eon
    Exploring Geologic Time Poster Illustrated Teacher's Guide #35-1145 Paper #35-1146 Laminated Background Geologic Time Scale Basics The history of the Earth covers a vast expanse of time, so scientists divide it into smaller sections that are associ- ated with particular events that have occurred in the past.The approximate time range of each time span is shown on the poster.The largest time span of the geologic time scale is the eon. It is an indefinitely long period of time that contains at least two eras. Geologic time is divided into two eons.The more ancient eon is called the Precambrian, and the more recent is the Phanerozoic. Each eon is subdivided into smaller spans called eras.The Precambrian eon is divided from most ancient into the Hadean era, Archean era, and Proterozoic era. See Figure 1. Precambrian Eon Proterozoic Era 2500 - 550 million years ago Archaean Era 3800 - 2500 million years ago Hadean Era 4600 - 3800 million years ago Figure 1. Eras of the Precambrian Eon Single-celled and simple multicelled organisms first developed during the Precambrian eon. There are many fos- sils from this time because the sea-dwelling creatures were trapped in sediments and preserved. The Phanerozoic eon is subdivided into three eras – the Paleozoic era, Mesozoic era, and Cenozoic era. An era is often divided into several smaller time spans called periods. For example, the Paleozoic era is divided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous,and Permian periods. Paleozoic Era Permian Period 300 - 250 million years ago Carboniferous Period 350 - 300 million years ago Devonian Period 400 - 350 million years ago Silurian Period 450 - 400 million years ago Ordovician Period 500 - 450 million years ago Cambrian Period 550 - 500 million years ago Figure 2.
    [Show full text]
  • DECODING the PAST: the Work of Archaeologists
    to TEACHINGRT WITH THE POWER OOOF OBJECTS Smithsonian Institution November/December 1995 DECODING THE PAST: The Work of Archaeologists Inside Subjects Grades Publication of Art to Zoo is made possible Lesson Plan Social Studies 4–9 through the generous support of the Pacific Take-Home Page Science Mutual Foundation. in English/Spanish Language Arts CONTENTS Introduction page 3 Lesson Plan Step 1 page 6 Worksheet 1 page 7 Lesson Plan Step 2 page 8 Worksheet 2 page 9 Lesson Plan Step 3 page 10 Take-Home Page page 11 Take-Home Page in Spanish page 13 Resources page 15 Art to Zoo’s purpose is to help teachers bring into their classrooms the educational power of museums and other community resources. Art to Zoo draws on the Smithsonian’s hundreds of exhibitions and programs—from art, history, and science to aviation and folklife—to create classroom- ready materials for grades four through nine. Each of the four annual issues explores a single topic through an interdisciplinary, multicultural Above photo: The layering of the soil can tell archaeologists much about the past. (Big Bend Reservoir, South Dakota) approach. The Smithsonian invites teachers to duplicate Cover photo: Smithsonian Institution archaeologists take a Art to Zoo materials for educational use. break during the River Basin Survey project, circa 1950. DECODING THE PAST: The Work of Archaeologists Whether you’re ten or one hundred years old, you have a sense of the past—the human perception of the passage of time, as recent as an hour ago or as far back as a decade ago.
    [Show full text]
  • Isochron Dating Paul Giem
    Isochron Dating Paul Giem Abstract The isochron method of dating is used in multiple radiometric dating systems. An explanation of the method and its rationale are given. Mixing lines, an alternative explanation for apparent isochron lines are explained. Mixing lines do not require significant amounts of time to form. Possible ways of distinguishing mixing lines from isochron lines are explored, including believability, concordance with the geological time scale or other radiometric dates, the presence or absence of mixing hyperbolae, and the believability of daughter and reference isotope homogenization. A model for flattening of “isochron” lines utilizing fractional separation and partial mixing is developed, and its application to the problem of reducing the slope of “isochron” lines without significant time is outlined. It is concluded that there is at present a potentially viable explanation for isochron “ages” that does not require significant amounts of time that may be superior to the standard long-age explanation, and that short-age creationists need not uncritically accept the standard long-age interpretation of radiometric dates. Page 1 of 21 Isochron dating Paul Giem Isochron Dating Paul Giem This paper attempts to accomplish two objectives: First, to explain what isochron dating is and how it is done, and second, to provide an analysis of how reliable it is. In this kind of evaluation, it is important to avoid both over- and underestimates of its reliability. While I will offer tentative conclusions, substantive challenges to those conclusions are welcomed. Unfortunately, there is no way to deal with the subject without at least mentioning mathematics. This means that math phobics cannot be completely accommodated; they will at least have to see equations.
    [Show full text]
  • The Philosophy and Physics of Time Travel: the Possibility of Time Travel
    University of Minnesota Morris Digital Well University of Minnesota Morris Digital Well Honors Capstone Projects Student Scholarship 2017 The Philosophy and Physics of Time Travel: The Possibility of Time Travel Ramitha Rupasinghe University of Minnesota, Morris, [email protected] Follow this and additional works at: https://digitalcommons.morris.umn.edu/honors Part of the Philosophy Commons, and the Physics Commons Recommended Citation Rupasinghe, Ramitha, "The Philosophy and Physics of Time Travel: The Possibility of Time Travel" (2017). Honors Capstone Projects. 1. https://digitalcommons.morris.umn.edu/honors/1 This Paper is brought to you for free and open access by the Student Scholarship at University of Minnesota Morris Digital Well. It has been accepted for inclusion in Honors Capstone Projects by an authorized administrator of University of Minnesota Morris Digital Well. For more information, please contact [email protected]. The Philosophy and Physics of Time Travel: The possibility of time travel Ramitha Rupasinghe IS 4994H - Honors Capstone Project Defense Panel – Pieranna Garavaso, Michael Korth, James Togeas University of Minnesota, Morris Spring 2017 1. Introduction Time is mysterious. Philosophers and scientists have pondered the question of what time might be for centuries and yet till this day, we don’t know what it is. Everyone talks about time, in fact, it’s the most common noun per the Oxford Dictionary. It’s in everything from history to music to culture. Despite time’s mysterious nature there are a lot of things that we can discuss in a logical manner. Time travel on the other hand is even more mysterious.
    [Show full text]
  • Bicentennial Review
    Journal of the Geological Society, London, Vol. 164, 2007, pp. 1073–1092. Printed in Great Britain. Bicentennial Review Quaternary science 2007: a 50-year retrospective MIKE WALKER1 & JOHN LOWE2 1Department of Archaeology & Anthropology, University of Wales, Lampeter SA48 7ED, UK 2Department of Geography, Royal Holloway, University of London, Egham TW20 0EX, UK Abstract: This paper reviews 50 years of progress in understanding the recent history of the Earth as contained within the stratigraphical record of the Quaternary. It describes some of the major technological and methodological advances that have occurred in Quaternary geochronology; examines the impressive range of palaeoenvironmental evidence that has been assembled from terrestrial, marine and cryospheric archives; assesses the progress that has been made towards an understanding of Quaternary climatic variability; discusses the development of numerical modelling as a basis for explaining and predicting climatic and environmental change; and outlines the present status of the Quaternary in relation to the geological time scale. The review concludes with a consideration of the global Quaternary community and the challenge for the future. In 1957 one of the most influential figures in twentieth century available ‘laboratory’ for researching Earth-system processes. Quaternary science, Richard Foster Flint, published his seminal Moreover, although unlocking the Quaternary geological record text Glacial and Pleistocene Geology. In the Preface to this rests firmly on the use of modern analogues, the uniformitarian work, he made reference to the great changes in ‘our under- approach can be inverted so that ‘the past can provide the key to standing of Pleistocene events that had occurred over the the future’.
    [Show full text]
  • Scale and Structure of Time-Averaging (Age Mixing) in Terrestrial Gastropod Assemblages from Quaternary Eolian Deposits of the E
    Palaeogeography, Palaeoclimatology, Palaeoecology 251 (2007) 283–299 www.elsevier.com/locate/palaeo Scale and structure of time-averaging (age mixing) in terrestrial gastropod assemblages from Quaternary eolian deposits of the eastern Canary Islands ⁎ Yurena Yanes a, , Michał Kowalewski a, José Eugenio Ortiz b, Carolina Castillo c, Trinidad de Torres b, Julio de la Nuez d a Department of Geosciences, Virginia Polytechnic Institute and State University, 4044 Derring Hall, Blacksburg, VA, 24061, US b Biomolecular Stratigraphy Laboratory, Escuela Técnica Superior de Ingenieros de Minas de Madrid, C/ Ríos Rosas 21, 28003, Madrid, Spain c Departamento de Biología Animal, Facultad de Biología, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n. 38206, La Laguna, Tenerife, Canary Islands, Spain d Departamento de Edafología y Geología, Facultad de Biología, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez, s/n. 38206, La Laguna, Tenerife, Canary Islands, Spain Received 13 November 2006; received in revised form 10 March 2007; accepted 9 April 2007 Abstract Quantitative estimates of time-averaging (age mixing) in gastropod shell accumulations from Quaternary (the late Pleistocene and Holocene) eolian deposits of Canary Islands were obtained by direct dating of individual gastropods obtained from exceptionally well-preserved dune and paleosol shell assemblages. A total of 203 shells of the gastropods Theba geminata and T. arinagae, representing 44 samples (=stratigraphic horizons) from 14 sections, were dated using amino acid (isoleucine) epimerization ratios calibrated with 12 radiocarbon dates. Most samples reveal a substantial variation in shell age that exceeds the error that could be generated by dating imprecision, with the mean within-sample shell age range of 6670 years and the mean standard deviation of 2920 years.
    [Show full text]