6. Relative and Absolute Dating
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Short-Lived Increase in Erosion During the African Humid Period: Evidence from the Northern Kenya Rift ∗ Yannick Garcin A, , Taylor F
Earth and Planetary Science Letters 459 (2017) 58–69 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Short-lived increase in erosion during the African Humid Period: Evidence from the northern Kenya Rift ∗ Yannick Garcin a, , Taylor F. Schildgen a,b, Verónica Torres Acosta a, Daniel Melnick a,c, Julien Guillemoteau a, Jane Willenbring b,d, Manfred R. Strecker a a Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Germany b Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Telegrafenberg Potsdam, Germany c Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Casilla 567, Valdivia, Chile d Scripps Institution of Oceanography – Earth Division, University of California, San Diego, La Jolla, USA a r t i c l e i n f o a b s t r a c t Article history: The African Humid Period (AHP) between ∼15 and 5.5 cal. kyr BP caused major environmental change Received 2 June 2016 in East Africa, including filling of the Suguta Valley in the northern Kenya Rift with an extensive Received in revised form 4 November 2016 (∼2150 km2), deep (∼300 m) lake. Interfingering fluvio-lacustrine deposits of the Baragoi paleo-delta Accepted 8 November 2016 provide insights into the lake-level history and how erosion rates changed during this time, as revealed Available online 30 November 2016 by delta-volume estimates and the concentration of cosmogenic 10Be in fluvial sand. Erosion rates derived Editor: A. Yin −1 10 from delta-volume estimates range from 0.019 to 0.03 mm yr . Be-derived paleo-erosion rates at −1 Keywords: ∼11.8 cal. -
Deformation Characteristics of the Shear Zone and Movement of Block Stones in Soil–Rock Mixtures Based on Large-Sized Shear Test
applied sciences Article Deformation Characteristics of the Shear Zone and Movement of Block Stones in Soil–Rock Mixtures Based on Large-Sized Shear Test Zhiqing Li 1,2,3,*, Feng Hu 1,2,3, Shengwen Qi 1,2,3, Ruilin Hu 1,2,3, Yingxin Zhou 4 and Yawei Bai 5 1 Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; [email protected] (F.H.); [email protected] (S.Q.); [email protected] (R.H.) 2 College of Earth and Planetary Science, University of Chinese Academy of Sciences, Beijing 100049, China 3 Innovation Academy of Earth Science, Chinese Academy of Sciences, Beijing 100029, China 4 Yunnan Chuyao Expressway Construction Headquarters, Chuxiong 675000, China; [email protected] 5 Henan Yaoluanxi Expressway Construction Co. LTD, Luanchuan 471521, China; [email protected] * Correspondence: [email protected] or [email protected]; Tel.: +86-13671264387 Received: 27 July 2020; Accepted: 15 September 2020; Published: 17 September 2020 Abstract: Soil–rock mixtures (SRM) have the characteristics of distinct heterogeneity and an obvious structural effect, which make their physical and mechanical properties very complex. This study aimed to investigate the deformation properties and failure mode of the shear zone as well as the movement of block stones in SRM experimentally, not only considering SRM shear strength. The particle composition and proportion of specimens were based on field samples from an SRM slope along national highway 318 in Xigaze, Tibet. Shear zone deformation tests were carried out using an SRM-1000 large-sized geotechnical apparatus controlled by a motor servo, considering the effects of different stone contents by mass (0, 30%, 50%, 70%), vertical pressures (50, 100, 200, 300, and 400 kPa), and block stone sizes (9.5–19.0, 19.0–31.5, and 31.5–53.0 mm). -
Weathering, Erosion, and Susceptibility to Weathering Henri Robert George Kenneth Hack
Weathering, erosion, and susceptibility to weathering Henri Robert George Kenneth Hack To cite this version: Henri Robert George Kenneth Hack. Weathering, erosion, and susceptibility to weathering. Kanji, Milton; He, Manchao; Ribeira e Sousa, Luis. Soft Rock Mechanics and Engineering, Springer Inter- national Publishing, pp.291-333, 2020, 9783030294779. 10.1007/978-3-030-29477-9. hal-03096505 HAL Id: hal-03096505 https://hal.archives-ouvertes.fr/hal-03096505 Submitted on 5 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Published in: Hack, H.R.G.K., 2020. Weathering, erosion and susceptibility to weathering. 1 In: Kanji, M., He, M., Ribeira E Sousa, L. (Eds), Soft Rock Mechanics and Engineering, 1 ed, Ch. 11. Springer Nature Switzerland AG, Cham, Switzerland. ISBN: 9783030294779. DOI: 10.1007/978303029477-9_11. pp. 291-333. Weathering, erosion, and susceptibility to weathering H. Robert G.K. Hack Engineering Geology, ESA, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente Enschede, The Netherlands e-mail: [email protected] phone: +31624505442 Abstract: Soft grounds are often the result of weathering. Weathering is the chemical and physical change in time of ground under influence of atmosphere, hydrosphere, cryosphere, biosphere, and nuclear radiation (temperature, rain, circulating groundwater, vegetation, etc.). -
Correlating Foreland Basin Subsidence with Eclogite Metamorphism
ATI..ANTic GEOLOGY 79 Loading the Laurentian margin: correlating foreland basin subsidence with eclogite metamorphism 2 3 4 John WF. Waldron•, R.A. Jamieson , G.S. Stockmal and L.A. Quinn 1Geology Department, Saint Mary '.S' University, Halifax, Nova Scotia B3H 3C3, Canada 'Department ofEarth Sciences, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada 1Geological Survey of Canada (Calgary), 3303-33rd Street Northwest, Calgary, Alberta T2L 2A 7, Canada 'Department ofGeology, Brandon University, Brandon, Manitoba R7A 6A9, Canada Paleozoic loading of the former Laurentian continental de Lys Supergroup) are exposed in the Baie Verte Peninsula margin is recorded both in the subsidence history of the Ap and elsewhere. These units record Barrovian metamorphism palachian foreland basin and in metamorphic rocks now ex with peak temperatures around 700 to 750°C at 7 to 9 kbar; humed in internal parts of the Newfoundland Humber zone. isotopic data indicate that peak temperatures were reached in The Cambrian-Ordovician passive margin ofLaurentia Early Silurian time ('Salinian orogeny'), followed by rapid ex underwent a transition to a foreland basin setting beginning humation. Amphibolite facies metamorphism overprints an in Early Ordovician time. Middle Ordovician ('Taconian ') foreland earlier eclogite facies assemblage, for which minimum pres basin sediments (Table Head and Goose Tickle groups), in sures of 1.2 GPa at 500°C require burial of the Laurentian part derived from the Humber Arm Allochthon, are relatively margin beneath at least 40 km of overburden, which may have thin (ca. 250 m in offshore industry seismic data, thinning to included thrust sheets of continental margin rocks and the west). -
Metamorphism Associated with Extensional Rifting of Gondwana
Geological Society, London, Special Publications Basement and cover rock history in western Tethys: HT-LP metamorphism associated with extensional rifting of Gondwana Robert Hall Geological Society, London, Special Publications 1988; v. 37; p. 41-50 doi:10.1144/GSL.SP.1988.037.01.04 Email alerting click here to receive free email alerts when new articles cite this article service Permission click here to seek permission to re-use all or part of this article request Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection Notes Downloaded by Robert Hall on 26 November 2007 © 1988 Geological Society of London Basement and cover rock history in western Tethys: HT-LP metamorphism associated with extensional rifting of Gondwana Robert Hall ABSTRACT: High-temperature-low-pressure metamorphism of the deep crust is probable during continental lithospheric extension. The 75-65 Ma cooling ages of metamorphic and magmatic rocks preserved in overthrust crystalline slices in the southern Aegean are most plausibly explained by late Cretaceous extension of the Apulian continental margin, rather than by subduction-related magmatism. Metamorphism and magmatism at depth can be correlated with those stratigraphic features of the cover sequences that indicate extension. In particular, the puzzling 'premier flysch' of the region is interpreted as one consequence of peripheral uplift associated with stretching. Introduction observed in overthrust terrains, but evidence of the extensional history of the margin may also be discernible from interpretation of the sedimen- Many recent models for the evolution of passive tary sequences deposited within the former con- continental margins imply the possibility of a tinental margin. -
A Nonlinear Response of Sahel Rainfall to Atlantic Warming
7080 JOURNAL OF CLIMATE VOLUME 26 A Nonlinear Response of Sahel Rainfall to Atlantic Warming NARESH NEUPANE AND KERRY H. COOK Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas (Manuscript received 24 July 2012, in final form 2 February 2013) ABSTRACT The response over West Africa to uniform warming of the Atlantic Ocean is analyzed using idealized simulations with a regional climate model. With warming of 1 and 1.5 K, rainfall rates increase by 30%–50% over most of West Africa. With Atlantic warming of 2 K and higher, coastal precipitation increases but Sahel rainfall decreases substantially. This nonlinear response in Sahel rainfall is the focus of this analysis. Atlantic warming is accompanied by decreases in low-level geopotential heights in the Gulf of Guinea and in the large- scale meridional geopotential height gradient. This leads to easterly wind anomalies in the central Sahel. With Atlantic warming below 2 K, these easterly anomalies support moisture transport from the Gulf of Guinea and precipitation increases. With Atlantic warming over 2 K, the easterly anomalies reverse the westerly flow over the Sahel. The resulting dry air advection into the Sahel reduces precipitation. Increased low-level moisture provides moist static energy to initiate convection with Atlantic warming at 1.5 K and below, while decreased moisture and stable thermal profiles suppress convection with additional warming. In all simula- tions, the southerly monsoon flow onto the Guinean coast is maintained and precipitation in that region increases. The relevance of these results to the global warming problem is limited by the focus on Atlantic warming alone. -
Earth Science Power Standards
Macomb Intermediate School District High School Science Power Standards Document Earth Science The Michigan High School Science Content Expectations establish what every student is expected to know and be able to do by the end of high school. They also outline the parameters for receiving high school credit as dictated by state law. To aid teachers and administrators in meeting these expectations the Macomb ISD has undertaken the task of identifying those content expectations which can be considered power standards. The critical characteristics1 for selecting a power standard are: • Endurance – knowledge and skills of value beyond a single test date. • Leverage - knowledge and skills that will be of value in multiple disciplines. • Readiness - knowledge and skills necessary for the next level of learning. The selection of power standards is not intended to relieve teachers of the responsibility for teaching all content expectations. Rather, it gives the school district a common focus and acts as a safety net of standards that all students must learn prior to leaving their current level. The following document utilizes the unit design including the big ideas and real world contexts, as developed in the science companion documents for the Michigan High School Science Content Expectations. 1 Dr. Douglas Reeves, Center for Performance Assessment Unit 1: Organizing Principles of Earth Science Big Idea Processes, events and features on Earth result from energy transfer and movement of matter through interconnected Earth systems. Contextual Understandings Earth science is an umbrella term for the scientific disciplines of geology, meteorology, climatology, hydrology, oceanography, and astronomy. Earth systems science has given an improved, interdisciplinary perspective to researchers in fields concerned with global change, such as climate change and geologic history. -
Stage 1А–Аdesired Results
www.nextgenscience.org STAGE 1 – DESIRED RESULTS Unit Title: Earth’s Place in the Universe Grade Level: 6 Length/Timing of Unit: Teacher(s)/Designer(s): Pascack Valley Regional Science Committee Science State standards addressed (verbatim): MSESS11 . Develop and use a model of the Earthsunmoon system to describe the cyclic patterns of lunar phases, eclipses of the sun and moon, and seasons. [Clarification Statement: Examples of models can be physical, graphical, or conceptual.] MSESS12. Develop and use a model to describe the role of gravity in the motions within galaxies and the solar system. [Clarification Statement: Emphasis for the model is on gravity as the force that holds together the solar system and Milky Way galaxy and controls orbital motions within them. Examples of models can be physical (such as the analogy of distance along a football field or computer visualizations of elliptical orbits) or conceptual (such as mathematical proportions relative to the size of familiar objects such as students’ school or state).] [Assessment Boundary: Assessment does not include Kepler’s Laws of orbital motion or the apparent retrograde motion of the planets as viewed from Earth.] MSESS13. Analyze and interpret data to determine scale properties of objects in the solar system. [Clarification Statement: Emphasis is on the analysis of data from Earthbased instruments, spacebased telescopes, and spacecraft to determine similarities and differences among solar system objects. Examples of scale properties include the sizes of an object’s layers (such as crust and atmosphere), surface features (such as volcanoes), and orbital radius. -
Mass Wasting and Landslides
Mass Wasting and Landslides Mass Wasting 1 Introduction Landslide and other ground failures posting substantial damage and loss of life In U.S., average 25–50 deaths; damage more than $3.5 billion For convenience, definition of landslide includes all forms of mass-wasting movements Landslide and subsidence: naturally occurred and affected by human activities Mass wasting Downslope movement of rock and soil debris under the influence of gravity Transportation of large masses of rock Very important kind of erosion 2 Mass wasting Gravity is the driving force of all mass wasting Effects of gravity on a rock lying on a hillslope 3 Boulder on a hillside Mass Movement Mass movements occur when the force of gravity exceeds the strength of the slope material Such an occurrence can be precipitated by slope-weakening events Earthquakes Floods Volcanic Activity Storms/Torrential rain Overloading the strength of the rock 4 Mass Movement Can be either slow (creep) or fast (landslides, debris flows, etc.) As terrain becomes more mountainous, the hazard increases In developed nations impacts of mass-wasting or landslides can result in millions of dollars of damage with some deaths In less developed nations damage is more extensive because of population density, lack of stringent zoning laws, scarcity of information and inadequate preparedness **We can’t always predict or prevent the occurrence of mass- wasting events, a knowledge of the processes and their relationship to local geology can lead to intelligent planning that will help -
The 2018 Long Rainy Season in Kenya: Hydrological Changes and Correlated Land Subsidence
remote sensing Article The 2018 Long Rainy Season in Kenya: Hydrological Changes and Correlated Land Subsidence Ashraf Rateb 1 and ElSayed Hermas 2,3,* 1 Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, USA; [email protected] 2 The Division of Geologic Applications and Mineral Resources, The National Authority for Remote Sensing and Space Sciences (NARSS), Cairo 1564, Egypt 3 Geography Department, Umm Al-Qura University, Makkah 21955, Saudi Arabia * Correspondence: [email protected]; Tel.: +966-12-5494-5454 Received: 28 March 2020; Accepted: 25 April 2020; Published: 28 April 2020 Abstract: The wettest 2018 long rainy season (March to May (MAM)) resulted in daily intensive rainfall events in East Africa that have seriously affected the environment and economy in many countries. Land subsidence is one of the environmental disasters that has occurred due to the long rainy season in Kenya for many years. However, it has received limited scientific attention. In this paper, we incorporate hydrological (soil moisture active–passive (SMAP) and loading models) and geodetic data (global positioning system (GPS) and interferometric synthetic aperture radar (InSAR)) to study hydrological changes and their associated subsidence potential in Kenya. Results show that widespread subsidence of more than 20 mm was associated with the MAM season in Kenya during 2018, based on SBAS InSAR measurements. The high values of land subsidence were well correlated with the areas of intense flooding during the MAM season. The widespread subsidence during the wet season has implications for the stability of the earth’s surface during the season rather than creating the possibility of potential stresses along active faults. -
5 Techniques for Prediction of Subsidence, by Germán Figueroa Vega, Soki Yamamoto, and Working Group (Section 5.3.6 by Donald C
5 Techniques for prediction of subsidence, by Germán Figueroa Vega, Soki Yamamoto, and Working Group (Section 5.3.6 by Donald C. Helm) It is very important to predict the amount of subsidence and to estimate the subsidence rate in the near future. There are many methods for predicting the amount of land subsidence due to the overdraft of fluids from aquifers. Some methods are simple and others are complex. It is preferable to use several methods whenever possible and to reach a conclusion based on the overall judgment. Both adequate and accurate data are required to obtain useful results, although these depend on the purpose, time length of the forecast, and cost. The methods used may be classified into the following categories: (1) Empirical methods; (2) semi-theoretical approach; (3) theoretical approach. 5.1 EMPIRICAL METHODS This is the method of extrapolating available data to derive the future trend. It is a time series model. The amount of subsidence, the amount of compaction, and sometimes tidal height near the sea coast, are available to plot against time. In this method, the amount of subsidence is considered a function of time, ignoring causality of land subsidence. 5.1.1 Extrapolation of data by naked eye No explanation of this procedure is needed except that a smooth curve with a natural trend should be obtained. 5.1.2 Application of some suitable curve: Nonlinear extrapolation 1. Fitting of quadratic function (Figure 5.1): The following function is used and the least squares method is applied: s = ax2 + bx + c, or s = ax + b,(5.1) where s = subsidence amount, x = time, and a, b, and c are constants. -
Geologic Time Scale Essential Questions: 1
Geologic Time Scale Essential Questions: 1. How does the relative and absolute age of rocks and the fossil record provide evidence to Earth’s geologic history? 2. How is Earth’s geologic history classified? 3. What are some major events in the Earth’s geologic history? Geologic Time Scale Earth Scientists • Geologist – a scientist who studies the Earth’s crust as well as the processes and history that shaped it • Paleontologist – a scientist that studies fossil remains found on the Earth’s surface in order to study primitive life forms such as: plants, animals, fungi, and bacteria Geologic Time Scale Sedimentary Rock Layers Stratigraphy • A branch of geology dealing with the arrangement of sedimentary rock layers or strata • Geologists assume the newest rock layers are on top of the older ones, unless some type of disturbance occurs. • Called the Law of Superposition © KeslerScience.om Geologic Time Scale Sedimentary Rock Layers Relative Age • The strata of sedimentary rocks is important in determining their relative age. • Relative age determines the “relative” order of past events but not the absolute age. • Like saying you’re relatively younger than your grandfather. Quick Action – Geologic Time Scale Sedimentary Rock Layers Determining Relative Age 1. Which is older sandstone or limestone? 2. Which is older mudstone or siltstone? 3. Which is the youngest rock in this strata? 4. Which is the oldest rock in this strata? Geologic Time Scale Sedimentary Rock Layers Relative Age • Strata is sometimes disturbed. • Here we see a fault (E) and an igneous intrusion (D) • See if you can determine the order of the strata in this diagram.