DOCSLIB.ORG

PENEPLAINS and the GEOGRAPHICAL CYCLE1 If A

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
PENEPLAINS and the GEOGRAPHICAL CYCLE1 If A BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 33, PP. 587-598 SEPTEMBER 30, 1922 PENEPLAINS AND THE GEOGRAPHICAL CYCLE1 BY W. M. DAVIS , (Presented, before the, Society December 29, 1921) CONTENTS Page General features of a peneplain............................................................................ 587 Subsequent streams and valleys............................................................................ 589 The geographical cycle and its complications.................................................... 590 Climatic changes during a cycle of erosion........................................................ 591 Misconception of the geographical cycle as a rigid scheme.............................. 593 Essential features of the geographical cycle...................................................... 594 Induction and deduction in the scheme of the cycle........................................ 595 Deduction in the scheme of the arid cycle.......................................................... 596 Unlike use of the cycle in geology and geography........................................... 597 G e n e r a l F e a t u r e s o p a P e n e p l a i n If a landmass of whatever structure and large area be upheaved un­ equally to considerable altitudes in its interior area and if it then stand still for an indefinitely long period, it will be eventually degraded to a plain. In order to avoid the necessity of assuming so indefinitely long a period of still-stand, and in order at the same time to detain attention upon the gently undulating surface that such a region will have before it is worn down to a plain, the term peneplain was invented some thirty years ago. As no one, I believe, proposes to call the surface of ultimate degradation a “plane,” I see no sufficient reason for calling the penultimate surface a “peneplane,” as some have proposed; the original spelling, peneplain, is preferred. When the term was first proposed it was vaguely defined; and it has recently come to my knowledge that the vagueness of its definition has led some students of the physiographic evolution of the Appalachians to make for themselves a fuller definition, which I hope they will publish. In the meantime the following statement is offered of my own view.< upon the subject, as they have been gradually developed during the 1 Manuscript received by the Secretary o£ the Society January 24, 1922. XXXIX—B u l l . G e o l . S o c . A m ., V o l . 3 3 , 1 9 2 1 ( 5 8 7 ) Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/33/3/587/3414417/BUL33-0587.pdf by guest on 27 September 2021 588 W. M. DAVIS---- PENEPLAINS AND THE GEOGRAPHICAL CYCLE growth, of the many ideas that are compactly embodied in the scheme of the cycle of erosion or the geographical cycle. A peneplain developed on a large landmass of homogeneous structure should be margined along its retrograding ocean shore by sealevel delta- free valley plains, alternating with low, wave-cut bluffs on faint inter­ valley swells; and should very gradually ascend to greater altitude and greater relief at an interior divide, beyond which similar features would be repeated in reverse order to a farther ocean. The survival of large mountain-like hills along the interior divide where the initial upheaval was greatest is not inconsistent with the occurrence of a well developed peneplain—broad swells of gentle convexity between wide valley floors— over the greater part of the area between the divide and the ocean. Penck has proposed the term, mosore, for the residual hills that survive along the divide, not by reason of greater resistance, but by reason of representing a greater original mass to be consumed. Prom the mosores along the main divide, gradually dwindling trains of hills would follow the secondary divides. There is no break in the long sequence of slow changes by which the smaller hills of the secondary divides and the larger hills of the main divides are gradually reduced to so small a relief that they, too, may be regarded as part of a peneplain. The term pene­ plain should therefore be taken as especially applicable to certain advanced phases of land sculpture not sharply separated from the phases that precede and follow. If a peneplain have a breadth of 1,000 miles or more, or if a peneplain be developed in the interior of a large continent, its interior part—not merely the residual hills of fairly strong relief, but also the gently undu­ lating swells that rise but little over the broad valley floors—may have altitudes of from 1,000 to 3,000 feet or more above sealevel. Hence an evenly uplifted peneplain, now undergoing dissection, should not be ex­ pected to stand everywhere at the same altitude, and the present altitude of even its best developed parts should not be taken as necessarily giving a measnre of its uplift, as if it had previously stood at sealevel. The uplift may have been several thousand feet less than the altitude. Cvijic has emphasized this point in his discussion of the physiography of the Balkan region. Similarly, if the coastal two-thirds of a broad peneplain be flexed or faulted down near or beneath sealevel, while the inner third remain at its former altitude, the rivers there will at once proceed to in­ cise new valleys beneath their former valley floors; hence the mere occur­ rence of valleys incised in a peneplain should not be taken as evidence of uplift. Philippson has urged the importance of this interesting principle in an account of the Slate Mountains of the middle Rhine. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/33/3/587/3414417/BUL33-0587.pdf by guest on 27 September 2021 GENERAL FEATURES OF A PENEPLAIN 5 8 9 A peneplain formed in a region of varied structure will be first devel­ oped in areas of weak rocks, wherever they are situated; it will be later developed in areas of moderately resistant rocks; and by that time the weak-rock areas may be degraded to true plains. The most resistant rocks will long survive as knobs or ridges, now commonly known as monadnocks. S u b s e q u e n t S t r e a m s a n d V a l l e y s The development of subsequent streams along belts of weak structure and the corresponding diminution of consequent streams is a character­ istic feature of a well advanced cycle of erosion; and while subsequent streams are developing along belts of weak structure consequent divides will be largely replaced by subsequent divides on belts of resistant struc­ ture. But be it noted that the physiographic value of these two stream terms does not lie so much in the indications that they give of stream and valley origins as in the suggestions that they offer regarding the relation of the streams and valleys to their surroundings. A consequent stream or valley following the original slope of a body of inclined strati­ fied rocks will usually have similar rocks and similar forms on both sides; but subsequent streams and valleys are usually characterized by different rocks and by different forms on the two sides; and, further­ more, in a region of slanting structure, where a master consequent is joined by one subsequent stream, it will usually be joined also by another subsequent stream coming from the opposite direction, both subsequents being developed on the same tranverse weak belt. It is curious to note that the term subsequent, which has been proposed to name a class of streams and valleys in southern Ireland clearly described by Jukes in 1862, has not gained general acceptance among American geologists and physiographers, not even among those who adopt Powell’s trio of 1875—consequent, antecedent, and superimposed (shortened by McGee to superposed). Yet it has been pointed out that, by reason of Powell’s failure to extend the trio to a quartet by adding subsequent as a fourth member, he was led into serious errors in the inter­ pretation of the streams of the Uinta Mountains; and that Dutton made similar errors in the region of the Colorado Canyon of Arizona for the same reason. Even Gilbert referred to Powell's trio as if it contained a complete genetic classification of streams. Whether the name “subse­ quent” should be used for the fourth member of the group is unim­ portant; but that no fourth member shoujd be recognized is a serious mistake. The spontaneous development of subsequent streams in regions of tilted, strong and weak strata is an essential process in the advance Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/33/3/587/3414417/BUL33-0587.pdf by guest on 27 September 2021 590 W. M. DAVIS---- PENEPLAINS AND THE GEOGRAPHICAL CYCLE •of the cycle of erosion. The addition of three other classes of streams— insequent, obsequent, and resequent—thus enlarging the original trio to a septet, is a refinement of much less importance than the recognition of the class of subséquents. T h e geographical C y c l e a n d i t s C omplications Two of my European correspondents have lately written me that they must give up the cycle of erosion because it does not include certain facts to 'which they call attention. One group of facts is the well-opened valleys in areas of relatively weak rocks; and it is urged that these valleys were never “young” in the sense of being narrow; they were widened as well as deepened while the region was raised. I believe it is true that my own writings do not contain any explicit statement of this rather evident idea; the nearest I have come to it is to say that if a region of resistant rocks be slowly uplifted its valleys will be widened as they are deepened.
Load more

Recommended publications
  • Process-Form Models
    11 Process-form Models The interaction of process and landform is central to geomorphic investigations and a series of concepts have been associated with the models of landscape development suggested over the last century. Process investigations were enhanced by considering the way in which specific landscape features are related to processes, as illustrated by grade, characteristic angles, drainage density and river channel capacity. Technique developments, especially of cos- mogenic dating, have revitalised some earlier models. The complex response concept affords the reconciliation of alternative landscape histories, and a panoply of models is now becoming available offering opportunities to realize the objectives of the original qualitative approaches. Exogenic processes Microclimate and Local climate Regional climate Climatic zones meteorological events Short-term climatic change Medium-term climatic Long-term climatic Animal and plant activities Local vegetation change change (e.g. glacial– change (e.g. icehouse interglacial cycles) and hothouse states) Regional vegtation change Biological evolution Microscale landforms Mesoscale landforms Macroscale landforms Megascale landforms Area: <0.25 km2 Area: 0.25–100 km2 Area: 100–1,000,000 km2 Area: >1,000,000 km2 Lifespan: 10 years Lifespan: 1,000 years Lifespan: 10 million years Lifespan: >10 million years Exogenic examples: Fluvial Pools and riffles Meanders Large river floodplains Major drainage basins Glacial Small cirques Valley glaciers Ice caps Ice sheets and inland Aeolian Ripples
    [Show full text]
  • Critical Review of the San Juan Peneplain Southwestern Color~ Do
    Critical Review of the San Juan Peneplain Southwestern Color~ do GEOLOGICAL SURVEY PROFESSIONAL PAPER 594-I Critical Review of the San Juan Peneplain Southwestern Colorado By THOMAS A. STEVEN SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL -PAPER 594-I The volcanic and geomorphic history of the San Juan Mountains indicates no peneplain cycle of erosion between the end of ma;·or volcanism and the present time UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Albstract ----------------------------------------­ I 1 Discussion of the San Juan peneplain-Continued Introduction -------------------------------------­ 1 3. The peneplain remnants -------------------- 18 Alcknowledgments --------------------------------- 2 4. Postpeneplain deformation -------------------- 9 General geology of the San Juan region ___________ _ 2 5. Postpeneplain alluviation and volcanism ______ _ 10 The peneplain concept ----------------------------­ 4 6. Postpeneplain development of drainage_------- 12 Discussion of the San Juan peneplain -------------- 6 Possible character of the late Tertiary landscape ___ _ 13 1. Subsidence of the prevolcanism erosion surface _ 6 Summary ----·------------------------------------ 14 2. Volcanism and volcano-tectonic deformation Catalog of peneplain remnants ----------------------
    [Show full text]
  • Geographical Cycle” at the Turn of the 1960S
    TWO RE-EVALUATIONS OF DAVIS’S “GEOGRAPHICAL CYCLE” AT THE TURN OF THE 1960S DUAS REAVALIAÇÕES DO “CICLO GEOGRÁFICO” DE DAVIS NA VIRADA DA DÉCADA DE 1960 DEUX RÉÉVALUATIONS DU «CYCLE GÉOGRAPHIQUE» DE DAVIS AU TOURNANT DES ANNÉES 1960 CHRISTIAN GIUSTI1 1 Faculté des Lettres, Sorbonne Université, Paris. Laboratoire de Géographie Physique, UMR 8591 CNRS, Meudon. E-mail: [email protected] ORCID: https://ORCID.0000-0002-6531-3572 Received 15/11/2020 Sent for correction: 30/11/2020 Accepted: 15/12/2020 To Marie-Hélène Auclair, Librarian in Sorbonne (1975-1985), a most helpful friend during my early years of research. ABSTRACT Many geomorphologists today refer to Davis and his ideas without really knowing what that implies. In the second half of the 20th century, two re-evaluations of the Davisian system were carried out, which the renewed popularity of the “peneplain” concept has led us to bring back to light and discuss. Key words: Davis, geographical cycle, peneplain, Chorley, Klein. RESUMO Muitos geomorfólogos hoje se referem a Davis e suas ideias sem realmente saber o que isso implica. Na segunda metade do século XX, foram realizadas duas reavaliações do sistema Davisiano, cuja renovada popularidade do conceito de “peneplanície” nos levou a trazer de volta à luz e discutir. Palavras-chave: Davis, ciclo geográfico, peneplanície, Chorley, Klein. RÉSUMÉ De nombreux géomorphologues font aujourd'hui référence à Davis et à ses idées sans vraiment savoir ce que cela implique. Dans la seconde moitié du XXe siècle, deux réévaluations du système davisien ont été effectuées, que la popularité renouvelée du concept de «pénéplaine» nous a amenées à remettre en lumière et à discuter.
    [Show full text]
  • A Geographical Pilgrimage from Ireland to Italy Author(S): W
    A Geographical Pilgrimage from Ireland to Italy Author(s): W. M. Davis Source: Annals of the Association of American Geographers, Vol. 2 (1912), pp. 73-100 Published by: Taylor & Francis, Ltd. on behalf of the Association of American Geographers Stable URL: http://www.jstor.org/stable/2560643 Accessed: 27-06-2016 03:32 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Taylor & Francis, Ltd., Association of American Geographers are collaborating with JSTOR to digitize, preserve and extend access to Annals of the Association of American Geographers This content downloaded from 128.163.2.206 on Mon, 27 Jun 2016 03:32:37 UTC All use subject to http://about.jstor.org/terms ANNALS OF THE ASSOCIATION OF AMERICAN GEOGRAPHERS Volume II, pp. 73-100. A GEOGRAPHICAL PILGRIMAGE FROM IRELAND TO ITALY W. M. DAVIS CONTENTS Page The pilgrimage of 1911 and its members.. 73 Five days in Ireland ................................... 75 A concise description of southwestern Ireland ... 76 A week in Wales ................................... 78 The even upland at Lands End.80 Marine denurdation and subaerial degradation. 81 The sea cliffs of Cornwall ................................... 82 A round-about-explanation. 83 The uplands of Devonshire-Cornwall ................................. 84 The rarity of cliffs of decreasing height .................
    [Show full text]
  • The Basics of Geomorphology: Key Concepts
    THE BASICS OF GEOMORPHOLOGY: KEY CONCEPTS Supporting Website Material This website provides material to supplement the text and is organized by chapter with the complete reference list given at the end. Diagrams and tables that are essential for understanding the text are contained in the book. For each chapter the synopsis is given together with additional material, which includes figures and tables, compiled to amplify the dis- cussion in the text, relevant articles in Progress in Physical Geography, which is an excellent resource to pursue particular themes, and a list of the concepts given in bold from the index (together with the references cited in each chapter). The complete reference list is given at the end. 1 Introduction: Concepts and Geomorphology Any discipline has concepts that are key for its progress. For geomorphol- ogy these need to be explicitly stated and consistently understood for what they are. We set them within the evolving history of geomorphology and the changing techniques and understanding that have been involved. This demonstrates the fashioning surges that have characterized the discipline and which complicate identification of those concepts which endure and which remain basic to the present and future study of geomorphology. Figure 1.1 Grand Canyon (from near Powell Memorial) Table 1.1 Some developments in constructing geomorphology (years in italics refer to use of the word ‘geomorphology’) Year Contribution 1674 Pierre Perrault’s (1608–1680) published book on De l’origine des fontaines, showing precipitation sufficient to sustain the flow of rivers in the Seine basin: probably a foundation for understanding of the hydrological cycle.
    [Show full text]
  • Contributions to the History of Geomorphology and Quaternary Geology: an Introduction
    Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 Contributions to the history of geomorphology and Quaternary geology: an introduction DAVID R. OLDROYD1 & RODNEY H. GRAPES2 1School of History and Philosophy, The University of New South Wales, Sydney, NSW 2052, Australia (e-mail: [email protected]) 2Department of Earth and Environmental Sciences, Korea University, Seoul, 136-701, Korea (e-mail: [email protected]) This Special Publication deals with various aspects the Baltic States in 2006, where a great deal of of the histories of geomorphology and Quaternary what the geologist sees consists of Quaternary geology in different parts of the world. Geomor- sediments. However, much of the Earth’s surface phology is the study of landforms and the processes is not formed of these sediments but of older that shape them, past and present. Quaternary rocks exposed at the surface by erosion and struc- geology studies the sediments and associated tural displacement. Here, geomorphology can seek materials that have come to mantle much of answers to questions regarding the past histories of Earth’s surface during the relatively recent Pleisto- these rocks, their subsequent erosion, and present cene and Holocene epochs. Geomorphology, with location and form. Geomorphology also raises its concern for Earth’s surface features and pro- questions, and may provide answers, regarding tec- cesses, deals with information that is much more tonic issues, for example from deformed marine amenable to observation and measurement than is terraces and offset fault systems. In all these the case for most geological work. Quaternary instances, the history of geological and geomor- geology focuses mostly, but not exclusively, on phological investigations can serve to illustrate the Earth’s surficial sedimentary cover, which is both the progress and pitfalls involved in the scien- usually more accessible than the harder rocks of tific understanding of the Earth’s surface and the deeper past.
    [Show full text]
  • Alphabetical Glossary of Geomorphology
    International Association of Geomorphologists Association Internationale des Géomorphologues ALPHABETICAL GLOSSARY OF GEOMORPHOLOGY Version 1.0 Prepared for the IAG by Andrew Goudie, July 2014 Suggestions for corrections and additions should be sent to [email protected] Abime A vertical shaft in karstic (limestone) areas Ablation The wasting and removal of material from a rock surface by weathering and erosion, or more specifically from a glacier surface by melting, erosion or calving Ablation till Glacial debris deposited when a glacier melts away Abrasion The mechanical wearing down, scraping, or grinding away of a rock surface by friction, ensuing from collision between particles during their transport in wind, ice, running water, waves or gravity. It is sometimes termed corrosion Abrasion notch An elongated cliff-base hollow (typically 1-2 m high and up to 3m recessed) cut out by abrasion, usually where breaking waves are armed with rock fragments Abrasion platform A smooth, seaward-sloping surface formed by abrasion, extending across a rocky shore and often continuing below low tide level as a broad, very gently sloping surface (plain of marine erosion) formed by long-continued abrasion Abrasion ramp A smooth, seaward-sloping segment formed by abrasion on a rocky shore, usually a few meters wide, close to the cliff base Abyss Either a deep part of the ocean or a ravine or deep gorge Abyssal hill A small hill that rises from the floor of an abyssal plain. They are the most abundant geomorphic structures on the planet Earth, covering more than 30% of the ocean floors Abyssal plain An underwater plain on the deep ocean floor, usually found at depths between 3000 and 6000 m.
    [Show full text]
  • Peneplains and Related Land Forms
    No. 3622, APRIL 1, 1939 NATURE 569 while they are attending classes ! The corridor floors Dr. Lowery again, "it is our desire that the College are covered with grey mottled rubber to render the shall become one great educational and recreational movement of students as silent as possible, and community centre where men and women may meet supplementary to the main staircases, passenger lifts in their leisure time for the purpose of engaging in have been installed. matters of common interest, thereby securing the It was John Ruskin who wrote, many years ago, fullest opportunity for self-expression". "The entire object of true education is to make The material building of this huge college has been people not merely do the right things but enjoy the very efficiently carried out by the general contractors, right things". Yet, the pioneers of technical educa­ Messrs. F. R. Hipperson and Son, Ltd., of London, tion were mainly concerned with providing a training to the plans of Mr. J. Stuart, the architect, but an which was severely utilitarian. But, as Dr. H. even greater work will now be undertaken by the Lowery, the principal of the College, aptly points out, principal and his large staff in laying the foundations "A new problem . has arisen-it becomes of another edifice which will undoubtedly reveal necessary to provide training for leisure as well as itself in the trained mind, skilled craftsmanship, for vocation". Here then is a new function implying cultured recreation and, what is most important of heavy responsibilities for the modern college. It is all, trustworthiness and reliability of character.
    [Show full text]
  • Geography Semester - I (Cbcs)
    M.A. GEOGRAPHY SEMESTER - I (CBCS) GEOGRAPHY PAPER - 101 PRINCIPLES OF GEOGRAPHY © UNIVERSITY OF MUMBAI Prof. Suhas Pednekar Vice-Chancellor, University of Mumbai, Prof. Ravindra D. Kulkarni Prof. Prakash Mahanwar Pro Vice-Chancellor, Director, University of Mumbai, IDOL, University of Mumbai, Programme Co-ordinator : Mr.Anil Bankar Associate Professor of History and Head Faculty of Arts, IDOL, University of Mumbai Course Co-ordinator : Mr.Ajit Gopichand Patil Asst. Professor, IDOL, University of Mumbai, Mumbai Course Writers : Dr. Prakash Dongre Associate Professor, N. K. College, Malad, Mumbai : Dr. H. M. Pednekar Retd. Ex-Principal Ondhe College, Vikramgad : Dr.Sardar Patil Associate Professor & Head, ASP College, Devrukh, Dist. Ratnagiri July 2021, Print - I Published by : Director Institute of Distance and Open Learning , University of Mumbai, Vidyanagari, Mumbai - 400 098. ipin Enterprises Tantia Jogani Industrial Estate, Unit No. 2, Ground Floor, Sitaram Mill Compound, DTP Composed and : Mumbai UniversityPress Printed by Vidyanagari,J.R. Boricha Santacruz Marg, Mumbai (E), Mumbai - 400 - 400098 011 GEOGRAPHY M. A. Part – I ; Semester I 101: Principles of Geomorphology No. of Credits: 4; Teaching Hours 60 + Notional Hours 60= Total hours 120 1. Unit - I (15 hours) 1.1 Nature, scope and content of Geomorphology 1.2 Geological Evolution of Earth and Geological time scale 1.3 Development of geomorphic thought, Catastrophism, Uniformitarianism, Neocatastrophism 2. Unit - II (15 hours) 2.1 Constitution of the earth’s interior 2.2 Continental Drift Theory - Sea floor spreading - Plate Tectonics 2.3 Geosynclines: Geosynclinal Theory of Kobber, Holmes’ Convection Current Theory , Theories of Isostasy 2.4 Endogenetic movements- types, consequences (earthquakes and volcanoes) and landforms 3.
    [Show full text]
  • The Paradox of Equivalence of the Davisian End-Peneplain and Penckian Primary Peneplain
    Concepts and Modelling in Geomorphology: International Perspectives, Eds. I. S. Evans, R. Dikau, E. Tokunaga, H. Ohmori and M. Hirano, pp. 3–32. © by TERRAPUB, Tokyo, 2003. The Paradox of Equivalence of the Davisian End-Peneplain and Penckian Primary Peneplain Hiroo OHMORI Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bukyo-ku, Tokyo 113-0033, Japan e-mail: [email protected] Abstract. The Davisian model elucidates landscape development through an orogeny by denudation processes, postulating prolonged still-stand of a landmass following rapid tectonic uplift, ultimately resulting in a peneplain. The Penckian model emphasizes that landscape is shaped by concurrent tectonics and denudation, and includes the primary peneplain as an antithesis against the Davisian end-peneplain by assuming a steady state between tectonic uplift and denudation from the beginning of orogenesis. Every ordinary landscape development through an orogeny has been expected to follow a course located between the two distinctive courses of landscape development. On the basis of the relationships between mountain altitude, local relief and denudation rate observed in Japan, denudation rate increases with local relief and the local relief increases with mountain altitude. A mountain range is considerably denuded even during the uplift phase. As denudation rate approaches tectonic uplift rate with an increase in mountain altitude by tectonic uplift, a steady state between denudation and uplift appears, and the mountain range attains a critical altitude that remains constant, in spite of continuous tectonic uplift. If tectonic uplift ceases, the mountain range is lowered by denudation, resulting in a subdued low relief landscape, ultimately a peneplain.
    [Show full text]
  • Component-I (A)- Personal Detail Role Name Affiliation Principal Investigator Prof
    Component-I (A)- Personal Detail Role Name Affiliation Principal Investigator Prof. Masood Ahsan Department of Siddiqui Geography, Jamia Millia Islamia, New Delhi Paper Coordinator Dr.Sayed Zaheen Alam Dyal Singh College, University of Delhi, New Delhi Content Writer Dr. Karuna Shree Department of Geography, Kirori Mal College, University of Delhi, Delhi Content Reviewer Dr. Anshu Department of Geography, Kirori Mal College, University of Delhi, Delhi Language Editor Component-I (B) Description of Module Items Description of Module Subject Name Geography Paper Name Geomorphology Module Name/Title Interruptions of the Cycle of Erosion (Tectonics, Climatic and Base Level Changes) Module Id GEO-18 Pre-requisites Slope Elements, Models of Slope Development Objectives Keywords Monadnocks, Rejuvenation, Base Level, Peneplanation, Eustatic Rejuvenation, Static Rejuvenation, Glacio Eustatism, Climatic Accidents, Knick Points Interruptions of the Cycle of Erosion (Tectonics, Climatic and Base Level Changes) Dr. Karuna Shree, Assistant Professor, Department of Geography, Kirori Mal College, University of Delhi, Delhi The objectives of present module are as follows: 1 Fluvial system 2 Cycle of Erosion 3 Davisian cycle of erosion 4 Rejuvenation: 4.1 Base level Change 4.1.1 Dynamic rejuvenation 4.1.2 Eustatic Rejuvenation 4.1.3 Climatic interruptions to the cycle of erosion 5 Rejuvenated landforms 1. Fluvial system Fluvial system may be divides into following three zones: Zone 1 primarily watershed basin and from here the sediments are collected (primarily the zone of sediment collection). Zone 2 is the primarily involved in transformation of sediments from zone 1 to zone 2. So this is transportation zone. Zone 3 is where these sediments finally sink and gets deposited so this id primarily zone of deposition.
    [Show full text]
  • Growing Topography Due to Contrasting Rock Types in a Tectonically Dead Landscape Daniel Peifer1,2, Cristina Persano1, Martin D
    https://doi.org/10.5194/esurf-2020-68 Preprint. Discussion started: 25 August 2020 c Author(s) 2020. CC BY 4.0 License. Growing topography due to contrasting rock types in a tectonically dead landscape Daniel Peifer1,2, Cristina Persano1, Martin D. Hurst1, Paul Bishop1, Derek Fabel3 1School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, UK 5 2CAPES Foundation, Ministry of Education of Brazil, Brasilia - DF 70040-020, Brazil 3Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF, UK Correspondence to: Daniel Peifer ([email protected]) Abstract. Many mountain ranges survive in a phase of erosional decay for millions of years (Myr) following the cessation of tectonic activity. Landscape dynamics in these post-orogenic settings have long puzzled geologists due to the expectation that 10 topographic relief should decline with time. Our understanding of how denudation rates, crustal dynamics, bedrock erodibility, climate, and mantle-driven processes interact to dictate the persistence of relief in the absence of ongoing tectonics is incomplete. Here we explore how lateral variations in rock type, ranging from resistant quartzites to less-resistant schists and phyllites and up to the least-resistant gneisses and granitic rocks, have affected rates and patterns of denudation and topographic forms in a humid semitropical, high-relief, post-orogenic landscape in Brazil where active tectonics ended hundreds of Myr 15 ago. We show that denudation rates are negatively correlated to topographic relief, channel steepness and modern precipitation rates. Denudation instead correlates with inferred bedrock strength, with resistant rocks denuding more slowly relative to more erodible rock units, and suggest that the efficiency of fluvial erosion varies primarily due to these bedrock differences.
    [Show full text]