-geomorphology.pptx

Understand the landforms of us

1. Why Study Geomorphology? Understand the present Interpret the past Uniformitarianism (Present is key to the past)

2. Basic Definitions Topography refers to the elevation and relief of the Earth’s surface. Landforms are the topographic features on the Earth’s surface. Geomorphology is the study of earth surface processes and landforms. 2 The maps above represent the same area on Earth’s surface and they show three different ways we can view landforms. The image on the far left is a clip from a topographic elevation map, the image in the middle is an infrared aerial photo, and the image on the right is the geologic interpretation of surface sediments and geomorphology. This location is interesting because it contains elements of a natural and human altered physical environment. The lake in the image, (coded blue in the topographic and geology map, and black in the infrared aerial photo) was formed by artificial damming a stream the flows through this landscape.

3. Topography Topography is a term used to describe the Earth’s surface. Topography includes a variety of different features, collectively referred to as landforms. Topography is measured by the differences in elevation across the earth’s surface. Differences between high and low elevation are referred to as changes in relief. Scientist examine topography using a variety of different sources ranging from paper topographic maps to digital elevation models developed using specialized geographic information systems commonly referred to as a GIS. 3 South Carolina’s elevation relief ranges from 4,590 feet in the Blue Ridge Region to 0 feet along the Coastal Plain. The rivers dissect the topography and drain down-slope from headwaters in the mountainous Blue Ridge and Piedmont, into the alluvial valleys of the Coastal Plain before draining into the Atlantic Ocean. Blue Ridge Piedmont Coastal Plain

4. Landforms Landforms are the individual topographic features exposed on the Earth’s surface. Landforms vary in size and shape and include features such as small creeks or sand dunes, or large features. Landforms develop over a range of different time-scales. Some landforms develop rather quickly (over a few seconds, minutes, or hours), such as a landslide, while others may involve many millions of years to form, such as a mountain range. Landform development can be relatively simple and involve only a few processes, or very complex and involve a combination of multiple processes and agents. Landforms are dynamic features that are continually affected by a variety of earth-surface processes including weathering, erosion, and deposition. Earth scientists who study landforms provide decision makers with information to make natural resource, cultural management, and infrastructure decisions, that affect humans and the environment. 4 Table Rock Mountain is a metamorphosed igneous intrusion exposed by millions of years of weathering and erosion in South Carolina’s Piedmont Region. Photo Source: SCGS

5. 5 Landforms and Scale: Crustal Orders of Relief First Order of Relief: The broadest landform scale is divided into continental landmasses , which include all of the crust above sea-level (30% Earth’s surface), and ocean basins , which include the crustal areas below sea-level (70% of Earth’s surface) Second Order of Relief: The second order of relief includes regional-scale continental features such as mountain ranges, plateaus, plains, and lowlands. Examples include the Rocky Mountains, Atlantic Coastal Plain, and Tibetan Plateau. Major ocean basin features including continental shelves, slopes, abyssal plains, mid-ocean ridges, and trenches are all second-order relief landforms. Third Order of Relief: The third order of relief includes individual landform features that collectively make up the larger second-order relief landforms. Examples include individual volcanoes, glaciers, valleys, rivers, flood plains, lakes, marine terraces, beaches, and dunes. Each major landform categorized within the third order of relief may also contain many smaller features or different types of a single feature. For example, although a flood plain is an individual landform it may also contain a mosaic of smaller landforms including pointbars, oxbow lakes, and natural levees. Rivers, although a single landform, may be classified by a variety of channel types including straight, meandering, or braided.

6. 6 Crustal Orders of Relief First Order or Relief: Continental Landmasses and Ocean Basins II. Second Order of Relief: Major Continental and Ocean Landforms III. Third Order of Relief: Genetic Landform Features Images and Photos: SCGS Beaches Rivers and Flood Plains Mountains

7. Geomorphology The word “geomorphology" comes from the Greek roots "geo,“ “morph,” and “logos,” meaning “earth,” “form,” and “study,” respectively. Therefore, geomorphology is literally “the study of earth forms.” Geomorphologists are concerned primarily with earth’s surficial features, including their origin, history, composition, and impact on human activity. Geomorphology concentrates primarily on Quaternary (Pleistocene and Holocene) features. Earth’s landforms reflect the local and regional balance between hydrologic, tectonic, aeolian, glacial, atmospheric, and marine processes.

8. Contd. Geomorphology defines the processes and conditions that influence landform development, and the physical, morphological, and structural characteristics of landforms. Geomorphologists who study landforms often seek to answer fundamental questions that help them study landforms, such as: What is the physical form or shape of the landform? What is the elevation and topographic relief of the landform? How did the landform originate? What is the distribution of the landform and where else does it occur? Are their any patterns associated with the landform or topography? What is the significance of the landform in relation to other elements of the landscape or environment? Has the landform or geomorphology been altered by humans? Does the landform or geomorphology affect humans?

9. Uniformitarianism Uniformitarianism is a common theory held by earth scientists that states “the present is the key to the past”. Uniformitarianism implies that the processes currently shaping the Earth’s topography and landforms are the same processes as those which occurred in the past. By studying geomorphology, we are better able to interpret the origin of landforms and infer their future evolution within the landscape. Such applications are especially important for predicting, preventing, and mitigating natural hazards impact to humans, and managing our natural resources for future generations. 9 The two images below illustrate the concept of uniformitarianism. On the left is an imprint of ripple marks in sandstone, similar current ripple forms in the right image. If the present is the key to the past, we can infer that the sandstone rock formed in a low energy, fluvial environment similar to the conditions in the right image.

10. Tools of Geomorphology Maps Topographic Surface Geologic Air photos Math Models Experiments Ground Truth

11. Topics of Geomorphology Agents “that which acts or has the power to act” Water and ice, wind Subsurface Modifiers Tectonic compression, tension and shear Processes “progressive steps by which an end is attained” Weathering, erosion, transport, deposition Energy Sources Solar, geothermal, gravitational, chemical Godfrey Ridge East and Brodhead Creek, DWG, PA, , detail

12. Importance of Geomorphology • To understand geomorphological processes of various environment. To detect natural and environmental hazards efficiently, e.g. earthquake, flooding, landslide, tsunami, volcanism etc. To identify various landform features and landscapes To identify various landform features from satellite images Coastal and river research Vulnerability studies Used in Geology, Geography, Archeology, Engineering, Planning, Mining, Construction, Urbanization …

13. Rise of Geomorphic Thought Observation and hypothesis – Herodotus 450 BC Description – Hutton – 1700’s+ Explanation 1800’s Agassiz – glacial landforms Powell (1834 -1902) – fluvial/structure Gilbert (1843 -1918) – All surfaces Correlation Davis (1850 -1934) – fluvial+ Quantification and prediction – now a common goal Horn, cirque, col, rock slide, talus Geomorphology History flashcards

14. Herodotus (484 - 425 B.C.) Rocks on land in Egypt contained marine fossils. Assumed that the Nile Delta took thousands of years to form.

15. Aristotle (384 - 322 B.C.) Dry land can be submerged. Land can be raised from beneath the ocean. Described erosion by rivers, and deposition in deltas.

16. Lucretius (99-55 BC): Recognized weathering processes on rocks. Seneca (3-65 AD): Observed erosion of valleys by running water. Ibn-Sina (980-1037 AD): Concluded that mountains could be uplifted, and later eroded.

17. Renaissance Period Leonardo DaVinci (1452-1519) found marine fossils on land G. Bauer [“Agricola”] (1494-1555) hypothesized that mountains were sculpted by weathering and mass movements Steno (1638-87) regarded water as the most significant agent of erosion

18. Landscape Creation vs. Landscape Development Biblical interpretations hindered the proliferation of non-catastrophic landform evolution theories. Werner (1749-1817) theorized that all mountains formed under water as layers of sediment, , and were ultimately sculpted by rapidly receding oceans.

19. Catastrophic Theories Georges Cuvier: Great catastrophic floods produced unconformities, and carved Earth’s landscape.

20. James Hutton (1726-97) Granites form through heat & fusion deep underground, and are later uplifted and exhumed. Landforms are produced by slow, continuous processes. Uniformatarianism

21. Hutton (continued) Sediments are eroded from landforms, only to be deposited and later lithified into new rocks. There is neither an apparent beginning nor end to landform development.

22. Hutton’s Proponents John Playfair (1748-1819) – Illustrations of the Huttonian Theory of the Earth (1802). – Streams carve their own drainage systems. – Stream reaches and maintains equilibrium, adjusted to local gradient. CONCEPT OF “GRADED STREAM” – The Earth is very ancient; ongoing processes continue to change it. Charles Lyell (1797 - 1875) The Principles of Geology (1833 - 1875) A strong promoter of Uniformitarian theory A vehement opponent of Catastrophism

23. Other Nineteenth Century European Contributions Venetz, and Bernardhi: Moraines and erratics prove glaciations extended from polal regions(1832) Louis Agassiz : Recognized glacial landforms in Europe & N. Am.- introduced the concept of Ice Ages (1837)

24. Charles Darwin Recorded his observations during the voyage of “the Beagle.” Suggested an origin for atolls

25. William Morris Davis 1850 -1934 Davis' Cycle of erosion An example from an arid climate. Davis' idea of a peneplain

26. Grove Karl Gilbert Process Geomorphology (1890) Recognized some Utah landscapes were formed by Pleistocene Lake Bonneville. Great Salt Lake and Bonneville salt flats are remnants, contributed to the understanding of river incision, Identified lunar craters as caused by impacts, and carried out early impact - cratering experiments Landforms are a balance between resisting framework and the forces acting to alter the landscape Implies that time is one component of many that affect the appearance of the Earth Inferred that the landscape was in equilibrium between driving forces and resisting forces

27. Davisian Geomorphology & TIME Davisian Geomorphology & TIME as the dominant factor dominated the scientific literature until the 1960’s John Hack proposed landscape development occurred similarly to the way Gilbert had espoused, recognizing considerable variability in most geomorphic systems Most were in Dynamic Equilibrium 1930-1965 Rise of Quantitative Approaches to Geomorphology Quantitative trends continue (computers, satellite, other remotely sensed data, numerical methods, improved dating techniques,…)

28. Concepts of Equilibrium Equilibrium means balance. In geomorphology, it refers to no net change, usually in terms of a balance between deposition and erosion, uplift and downcutting, or soil production and removal. In short, Erosion, transportation and deposition Equilibrium is strived for but seldom achieved. A change in one part of a system affects all others.

29. Fluvial Equilibrium Recent uplift in excess of erosional rates results in a system that is out of equilibrium. Weathering and erosion dominate headland areas with removed material being transported to a depositional basin. As headlands recede, both erosional and depositional rates decrease. If the region remains stable for an extended period, equilibrium, where erosional and depositional rates are equal, might be achieved.

30. Base Level Base level is the level below which erosion cannot occur and above which deposition does not take place. Sea level is the ultimate base level Lakes and reservoirs provide temporary base levels Changes in sea level can be eustatic or relative Changes in base level create and destroy accommodation space

31. Evolutionary Geomorphology William Morris Davis (1850-1934) Based on Darwinian Evolutionary Theory Landscapes evolve throughout time Stage of evolution can be determined by examining the characteristics of the landscape Implies that TIME is the critical factor in determining what the landscape looks like Structure Process Resulting Time Landform

32. Concepts in Geomorphology Systems “an assemblage of parts forming a whole” Fluvial, glacial, coastal, foreland basin, collisional mountains Climate Determines dominant agents Time Reshaping = "Evolution" of landforms/landscapes Systems can dominate large areas. Regions summarized as Physiography Maps

33. Concepts in Geomorphology Concept 1: ‘ The same physical processes and laws that operate today operated throughout geologic time (present is key to the past), although not necessarily always with the same intensity as now ’ (Thornbury 1969).

34. Concept 2: ‘ Geologic structure is a dominant control factor in the evolution of landforms and is reflected in them ’ (Thornbury 1969).

35. Concept 3: ‘ Geomorphic processes leave their distinctive imprints upon landforms and each geomorphic process develops its own characteristic assemblage of land forms ’ (Thornbury 1969).

36. Concept 4: ‘ As the different erosional agents act upon the earth ’ s surface there is produced an orderly sequence of landforms having distinctive characteristics at the successive stages of their development ’ (Thornbury 1969).

37. Concept 5: ‘ Geomorphic scale is a significant parameter in the interpretation of landform development and landform characteristics of geomorphic systems. Landscape is function of time and space ’ (Singh Savindra 2007).

38. Concept 6: A simple geomorphological equation may be envisaged as a vehicle for the explanation of landform as follows F= f (PM) dt (Gregory 1977).

39. Concept 7: Complexity of geomorphic evolution is more common than simplicity (Thornbury 1969).

40. Concept 8 : ‘ Little of the earth ’ s topography is older than Tertiary and most of it no older than Pleistocene ’ (Thornbury 1969).

41. Concept 9 : ‘ An appreciation of world climates is necessary to a proper understanding of the varying importance of the different geomorphic processes ’ (Thornbury 1969).

42. I. Overview B. Process Geomorphology: 1. concept of process ….the action involved when a force induces a change (either chemical or physical) in the materials or forms at the earth’s surface. 2. Loose definition: ”The study of landforms and the methods by which the landforms were(are) created”

43. II. The Basics of Process Geomorphology A delicate balance or equilibrium exists between landforms and process. 1. Geomorphic Systems The balance between form and process is best demonstrated by considering both factors as systems or component of systems. A system is a collection of related components

44. II. The Basics of Process Geomorphology A delicate balance or equilibrium exists between landforms and process. 1. G.K. Gilbert – “dynamic adjustment” Landforms reflect the interaction between the dominant process and the local geology

45. II. The Basics of Process Geomorphology A delicate balance or equilibrium exists between landforms and process. 2. William Morris Davis “cycles of erosion”

46. II. The Basics of Process Geomorphology A delicate balance or equilibrium exists between landforms and process. 3. John Hack “dynamic equilibrium”

47. II. The Basics of Process Geomorphology A delicate balance or equilibrium exists between landforms and process. 2. Defining Equilibrium and Time Scales Schumm (1977)

48. II. The Basics of Process Geomorphology B. The perceived balance between process and form is created by the interaction of energy, force, and resistance. Process : (def) The action involved when a force induces a change in the materials or landforms at the Earth’s surface. OR The method by which one thing may be produced from something else.

49. Agent, Process & products Agents of Geomorphic Processes River -Humid Geomorphic Environment Wind - Arid Environment Glacier/ice - Polar Environments Wave - Coastal Environment Geomorphic processes Erosion Transportation Deposition Geomorphic products Erosional landform features Transportation Depositional landform features

50. Constructive and Destructive Processes Constructive processes build landforms through tectonic and depositional processes. Tectonic processes include movements at plate boundaries, earthquakes, orogeny , deformation, and volcanic activity. Deposition is the accumulation or accretion of weathered and eroded materials. Destructive processes break down landforms through weathering, erosion, and mass wasting. Weathering is the disintegration of rocks by mechanical, chemical, and biological agents. Erosion is the removal and transportation of weathered material by water, wind, ice, or gravity. Mass wasting is the rapid down-slope movement of materials by gravity. Other Agents and Processes that Affect Landform Development Climate : temperature, precipitation, water cycle, atmospheric conditions Time : fast and slow rates of change People: influences on natural resources and earth surface processes

51. Constructive Processes 52 Constructive processes are responsible for physically building or constructing certain landforms. Constructive processes include tectonic and depositional processes and their landforms. Tectonic Landforms are created by massive earth movements due to tectonic and volcanic activity, and include landforms such as: mountains, rift valleys, volcanoes, and intrusive igneous landforms Depositional Landforms are produced from the deposition of weathered and eroded surface materials. Depositional landforms include features such as: beaches, barrier islands, spits, deltas, flood plains, dunes, alluvial fans, and glacial moraines. Floodplain deposits at the confluence of Mississippi and Arkansas Rivers. The Stromboli Volcano erupting off the coast of Sicily in the Mediterranean Sea. Source: wikimedia commons Copyright ©Google Earth 200

52. Destructive Processes 53 Destructive processes create landforms through weathering and erosion of surface materials facilitated by water, wind, ice, and gravity. Mass-wasting events occur in areas where weathering and erosion is accelerated. Weathering is the disintegration and decomposition of rock at or near the Earth’s surface by mechanical, chemical, or biological weathering processes. Erosion is the removal and transportation of weathered or unweathered materials by water, wind, ice, and gravity . Mass-Wasting is a rapid period of weathering and erosion that removes and transports materials very quickly and is often triggered by an environmental stimuli. Mass wasting includes rock falls, landslides, debris and mud flows, slumps, and creep . Landforms formed by destructive processes include river and stream valleys, waterfalls, glacial valleys, karst landscapes, coastal cliffs, and wave-cut scarps.

53. Geomorphic Processes: Physical processes which create and modify landforms on the surface of the earth Endogenous (Endogenic) vs. Exogenous (Exogenic) Processes Rock Cycle 

54. A. Endogenous Processes Endogenous Processes are large-scale landform building and transforming processes – they create relief . 1. Igneous Processes Volcanism: Volcanic eruptions  Volcanoes Plutonism : Igneous intrusions Tectonic Processes ( Also called Diastrophism) Folding: anticlines, synclines, mountains Faulting: rift valleys, graben , escarpments Lateral Faulting: strike-slip faults Earthquakes  evidence of present-day tectonic activity

55. The forces coming from within the earth are called as endogenetic forces which cause two types of movements in the earth, viz, (i) Horizontal movements, and (ii) Vertical movements. Endogenetic forces introduce various types of vertical irregularities which give birth to many kinds of relief features on the earth's surface, eg., mountains, plateaus, plains, lakes, faults, folds, etc.

56. On an average, the origin of endogenetic forces is related to thermal conditions of the interior of earth. Generally, the endogenetic forces and related horizontal and vertical movements are caused due to contraction and expansion of rocks' because of varying thermal conditions and temperature changes inside the earth. The endogenetic forces and movements are divided, on the basis of intensity, into two major categories as in following chart: Diastrophic forces (ii) Sudden forces

57. Diastrophic Forces and Sudden Forces take place mainly along the plate boundaries, which are the zones that are not stable. Endogenetic processes cause many major landform features.

58. B. Exogenous Processes Also called Gradational Processes , they comprise degradation and aggradation – they modify relief a continuum of processes – Weathering  Mass Wasting  Erosion  Transportation  Deposition these processes are carried through by Geomorphic Agents: gravity, flowing water (rivers), moving ice (glaciers), waves and tides (oceans and lakes), wind, plants, organisms, animals and humans 1. Degradation Processes  Also called Denudation Processes a. Weathering , b. Mass Wasting and c. Erosion and Transportation Aggradation Processes a. Deposition – fluvial, eolian , glacial, coastal

59. Sudden Forces EARTH'S MOVEMENT OR FORCE Endogenetic Forces Diastrophic Forces Epeirogenetic Forces Orogenetic Forces Exogenetic Forces Upward Movement (Emergence) Downward Movement (Submergence) Tensional Forces Compressional Forces Crustal Fracture Crustal Bending Cracking Faulting Warping Folding (Faults) (Folds) Down warping Up warping

60. Diastrophic Forces These forces include both vertical and horizontal movements which are caused due to forces deep within the earth. These diastrophic forces operate very slowly and their effects become discernable after thousands and millions of years. These forces also termed as constructive forces, affect larger areas of the globe and Produce meso -level reliefs, for example, mountains, plateau, plains, lakes, big faults, etc. These diastrophic forces are further subdivided into two groups, namely, epeirogenetic movements and orogenetic movements.

61.  ii) Sudden forces Sudden forces are the result of long period preparation deep within the earth. Only their cumulative effects on the earth's surface are quick and sudden. Geologically, these sudden forces are termed as 'constructive forces' because these create certain relief features on the earth's surface.

62. (A)Epeirogenetic movements: Epeirogenetic word consists of two words, viz: 'epiros' (meaning thereby continent) and 'genesis' (meaning thereby original). Epeirogenetic movement causes upliftment and subsidence of continental masses through upward movements are, infact, vertical movements. These forces and resultant movements affect larger parts of the continents. These are further divided into two types: upward movement and downward movement.

63. (B) Orogenetic movement : The word orogenetic has been derived from two Greek words, ‘oros' (meaning thereby mountain) and 'genesis' (meaning thereby origin or formation). Orogenetic movement is caused due to endogenetic forces working in horizontal movements. Horizontal forces and movements are also called as tangential forces. Orogenetic or horizontal forces work in two ways, namely, (i) in opposite direction, and (ii) towards each other. This is called 'tensional force' when it operates in opposite directions. Such type of forces and movements are also called as divergent forces.

64. Thus, tensional forces create rupture, cracks, fracture and faults in the crustal parts of the earth. The-force when operates face to face, is called compression force or convergent force. Compressional force causes crustal bending leading to the formation of fields or crustal warping leading to local rise or subsidence of crustal parts. Crustal bending: When horizontal forces work face to face, the crustal rocks are bent due to resistant compressional and tangential forces.

65. It is in two ways: (i) warping, and (ii) folding. The process of crustal warping affects larger areas of the crust wherein the crustal parts are either warped (raised),upward or downward. The upward rise of the crustal part due to compressive force resulting from convergent horizontal movement is called upwarping. While the bending of the crustal part downward in the form of a basin or depression is called down warping.

66. Folding Folding is one of the endogenetic processes. When two forces push towards each other from opposite sides, the rock layers will bend into folds. The process by which folds are formed are due to compressional forces known as folding. There are large-scale and small-scale folds. Large-scale folds are found mainly along destructive plate boundaries.

67. Faulting Faulting is the fracturing and displacement of more brittle rock strata along a fault plane either caused by tension or compression. A break in rock along which a vertical or horizontal rock movement has occurred is called a fault. The process of forming a fault is faulting. The line of fault which appears on land surface is known as fault line. These lines are often lines of weakness which allow molten rock to rise up onto the earth surface when there is active volcanic activity nearby. There are three types of fault which are caused by different endogenetic forces: - Normal fault: Compressional force from the plate - Reverse fault: Tensional Force from the Plate - Tear fault: Diagonal Compressional force from the Plate Faulting forms two major landforms - block mountains and rift valleys.

68. Sudden Forces Sudden movements, caused by sudden endogenetic forces coming from deep within the earth, cause sudden and rapid events that these cause massive distructions at and below the earth’s surfaces. Such events, like volcanic eruptions and earthquakes, are called extreme events and become disastrous hazards when they occur in densely populated localities. These forces work very quickly and their results are seen within minutes. It is important to note that these forces are the result of long-period cumulative effects on the earth’s surface are quick and sudden. Geologically, these forces are termed as constructive forces because these create certain relief features on the earth’s surface. For example, volcanic eruptions result in the formation of volcanic cones and mountains while fissure flows of lavas form extensive lava plateaux, such as Deccan plateau of India and Columbia plateau of USA. Similarly, it forms the lava plains. Earthquakes create faults, fractures, lakes, etc.

69. Earthquake An earthquake is a vibration or oscillation of the surface of the earth caused by sudden release of enormous pressure.

70. Vulcanicity Vulcanicity (also known as volcanic activity or igneous activity) is one of the endogenetic processes. Magma beneath the crust is under very great pressure. When folding and faulting occur, cracks or fractures which are lines of weakness. When these lines of weakness develop downward in the crust and reach the magma, they will release the pressure in the magma. This allows magma to rise up along the lines of weakness and intrude into the crust. Some magma may even reach the earth's surface. There are two types of vulcanicity: intrusive vulcanicity and extrusive vulcanicity.

71. In the end, it can be concluded that the plates are responsible for the endogenetic processes and landforms, and glacier, river, wind, atmospheric happenings, etc. are responsible for the exogenetic process and landforms.

72. Diastrophism Diastrophism is also called tectonism, large-scale deformation of earth’s crust by natural processes, which leads to the formation of continents and ocean basins, mountain systems, plateaus, rift valleys, and other features by mechanisms such as plate movement, volcanic loading, or folding. Internal forces active here

73. Metamorphism Metamorphism is the change in rock structure, minerals or geologic structure. It is a process of change in the physical structure of rock as a result of long-term heat, pressure and introduction of chemically active fluids, especially a change that increases the rock's hardness and crystalline structure. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids.

74. Types of Exogenetic / Exogenous Processes Weathering Erosion/ Degradation Transportation Deposition/Aggradation Mass movement

75. Denudation It means to make the things exposed. The processes by which the rocks on the earth’s surface are broken into pieces through the application of external physical forces and the debris are transported elsewhere is known as denudation. This denudation work is performed through three processes such as weathering, erosion and transportation. Denudation= Weathering + Erosion + Transportation

76. Weathering The weathering is a process by which the rocks on the surface of the earth is broken mechanically into pieces due to snow or frost, the variation of temperature and pressure or due to chemical (dissolution) action on the materials. Even the rocks are dislodged by the animals. But the rocks weathered this way, are not transported elsewhere.

77. Erosion Erosion and transportation are accomplished together. The process by which the rocks of the earth’s crust are eroded by the river, wind, glacier, ocean currents etc. are transported elsewhere is known as erosion.

78. Degradation Degradation is the lowering of a bottomland surface through the process of erosion; Conceptually it is the opposite of the vertical component of aggradation and is most frequently applied to sediment removed from a channel bed or other low-lying parts of a stream channel.

79. Deposition Deposition is the constructive process of accumulation into beds or irregular masses of loose sediment or other rock material by any natural agent;

80. Aggradation Aggradation is the raising or elevating of a bottomland surface through the process of alluvial deposition; Conceptually it is the vertical component of accretion and is most frequently applied to sediment deposition on a channel bed, bar or other near-channel surfaces, flood plain, or, less often, low-lying alluvial terrace.

81. Sedimentation Sedimentation is the process by which sediment is mechanically deposited from suspension within a fluid, generally water, or ice, thereby accumulating as layers of sediment that are segregated owing to differences in size, shape, and composition of the sediment particles.

82. Mass movement/Mass Wasting Mass movement is any downslope transfer, through gravitational and generally water-facilitated (viscous) processes, of near-surface soil and rock material; which includes a wide range of ground movements, such as rock fall, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments. Rates of mass movement range from very slow creep to nearly instantaneous slope failure.

83. Modification of landforms results from the application of energy. Landforms represent the interaction between driving forces and resistance.   Driving Forces: Climate, Gravity, Forces generated inside the earth Resistance: Provided by the geologic framework The link between these two components here is PROCESS

84. Bank Stability – The Factor of Safety Resisting Forces Driving Forces If F s is greater than 1, bank is stable. If F s is less than 1 bank will fail. (We usually add a safety margin – F s >1.3 is stable.) Resisting Forces Driving Forces (gravity) soil strength bank angle vegetation weight of bank reinforcement water in bank Factor of Safety (F s ) =

85. Force and Resistance (Or what it takes to initiate movement (erosion) of material) Think in terms of SPECIFIC PROCESSES On the stream bed Force/resistance On the stream banks Force/resistance

86. II. The Basics of Process Geomorphology C. Changes in the balance between driving and resisting forces may destabilize the system. The system may cross a threshold, and may initiate a new pattern of equilibrium.

87. 1. Thresholds Changes in the geomorphic system when the limits of equilibrium are exceeded a. Extrinsic Thresholds : caused by external controlling factors b. Intrinsic Threshold : usually caused by internal factors.

88. Genetic Landform Classification The genetic landform classification system groups landforms by the dominant set of geomorphic processes responsible for their formation. This includes the following processes and associated landforms: Tectonic Landforms Extrusive Igneous Landforms Intrusive Igneous Landforms Fluvial Landforms Karst Landforms Aeolian Landforms Coastal Landforms Ocean Floor Topography Glacial Landforms Within each of these genetic classifications, the resulting landforms are a product of either constructive and destructive processes or a combination of both. Landforms are also influenced by other agents or processes including time, climate, and human activity. 89