Geomorphology (Earth Surface Processes) ES203 PDF

Geomorphology (Earth Surface Processes) ES203 [2-0-0] 17:00 – 18:00 Monday & Wednesday Javed N Malik CC201. Ph.: 7723; 8971 [email protected] ...

Geomorphology (Earth Surface Processes) ES203 [2-0-0] 17:00 – 18:00 Monday & Wednesday Javed N Malik CC201. Ph.: 7723; 8971 [email protected]  Geomorphology and its scope: Systematic study of landscapes Course content… Historical approach Structures and Process: Endogenic and Exogenic Earth as a system: Lithosphere, atmosphere, hydrosphere, biosphere and their interactions – and related landscape Surface water system: Fluvial landscape, Drainage network, basin and system, river morphology- hydrology, river dynamics Groundwater system: Role of hydrological cycle Atmospheric system: Greenhouse effect, Carbon & Nitrogen cycle 2  Theory of plate tectonics: interior of earth, plate tectonics and rock cycles Course content… Geological Time scale and stratigraphy Crustal deformation and mountain building Hazardous Earth processes: Earth processes & hazard - Internal processes: earthquakes/tsunamis Coastal, Aeolian and Glacial landforms 3  Textbooks: ◼ Ernst, W.G. (2000) Earth Systems – processes and issues. Cambridge University Press. ◼ Bloom A. L. (2012) Geomorphology. Rawat Publications. ◼ Strahler, A., Introducing Physical Geography, John Wiley & Sons, 5th edition, 2011. ◼ Skinner, B. J., and Porter, S. C., The Dynamic Earth: An Introduction to Physical Geology, John Wiley & Sons Inc., 5th edition, 2006. ◼ Keller, E, A., Environmental Geology, Prentice Hall, 9th edition, 2011. ◼ Merrits, D., Dewet, A. and Menking, K., (1998) Environmental geology; an earth system science approach, Freeman ◼ Fundamentals of Geomorphology by R. J. Huggett  Marks Distribution… Mid Semester : 35% End Semester : 40% Term Paper : 10% Lab : 10% Attendance : 05% Geomorphology and earth’s processes Geomorphology - is a study of landforms… The word geomorphology derives from three Greek words: geo (the Earth), morph (form), and logos (discourse) Three key elements of geomorphology are landform, geomorphic process, and land-surface history.  Geomorphology and earth’s processes The two complementary main brands of geomorphology are: historical geomorphology and process geomorphology Other brands include applied geomorphology, tectonic geomorphology, submarine geomorphology, planetary geomorphology, and climatic geomorphology - each climatic region creating a distinguishing suite of landforms Geomorphology and earth’s processes Geomorphology has engaged in methodological debates; we consider that the “present is the key to the past” and “the rates of Earth surface processes are operating in the same pattern under the same environmental conditions”. We study the Earth’s processes, such as: Earthquakes Volcanism Glaciation Stream-flow Rock formation First look at Planet Earth  “Big Bang” @ 12 billion yr. ago. This explosion produced atomic particles that later formed galaxies, stars and planets… Again at around 7 billion years ago another  Resources No other planet in the solar system currently has the right chemical and physical mix needed to support life. No conclusive evidence of life existing elsewhere in the universe has yet been discovered as far as we know. Earth is unique.  Some fact related to Earth Age of the Earth is 4.5-4.6 Billion years. This age was determined through radiometric dating (Uranium, Thorium) by using Mass Spectrometer (instrument). Continents ~30% and Ocean basins ~70% Sea level changes have occurred through time (Glaciers fluctuated) Prominent features of the continents are ❖ Linear mountain belts Circum-Pacific Belt & Alpine-Himalaya Belt Prominent features of in oceans are ❖ Ocean ridge systems. Continuous belt 65,000 km  Highest point on Earth? – Mt. Everest (Himalayas) 8850 m. Lowest point on Earth? – Mariana Trench -11,035 m. Deep sea trenches are subduction zones. Origin of Earth internal structure Initially the earth was cool, with uniform composition Composed of Silicon, Iron, Magnesium, aluminum, Oxygen Repeated meteoritic impacts on Earth transferred the kinetic energy into heat energy... Heating was also added by radioactive decay of materials like uranium, thorium and potassium...  Heating process started melting Iron+Nickel (heavier) and segregated in the center, whereas the lighter Si+Mg+Al floated towards the surface...  ◼Plate movements ◼Geothermal energy Earth system 20 The rock cycle, the water cycle, and their interaction: Internal & External Cycle External processes Hydrological cycle The System Concept  The System Concept A system in any portion of the universe that can be isolated from the rest of the universe for observing and measuring change. The simplest kind to understand is an isolated system. The boundary completely prevents the exchange of either matter or energy.  The System Concept (2) The nearest thing to an isolated system in the real world is a closed system: i.e., such system has a boundary that permits the exchange of energy with its surroundings, but not matter.  1. Electromagnetic Radiation 26 The wavelength (λ) is given in μm (10-6 m) or nm (10-9 m).  The Earth System (1) Earth is only approximately a closed system because: Because meteorites coming from space and fall on Earth, causes slight escape of gases into space Moreover, Earth is comprised of four open systems.  The Earth System (1) The Earth system is composed of: The geosphere (rocks). The atmosphere (air). The hydrosphere (water). The biosphere (life in all its forms). Energy and materials (like water, carbon, and minerals) are transferred from one system to another. To a close approximation, Earth is a closed system. open system An open system can exchange both energy and matter across its boundary. An open system can exchange both energy (sunlight) and matter across its boundary, e.g., Drainage Basins are internal Open Systems  Open system The geosphere (rocks). The atmosphere (air). The hydrosphere (water). The biosphere (life in all its forms). Sub-systems of Earth Lithosphere Hydrosphere Atmosphere Biosphere Five Fundamental Concepts of Geomorphology and Environmental Geology ▪ Human population growth ▪ Sustainability ▪ Earth as a system ▪ Hazardous Earth processes ▪ Scientific knowledge and values  Human Influences We human are influencing Earth’s external geologic processes. – More than 7 billion people.  Concept One: Human Population Growth The number one environmental problem - is rapid increase in world human population Population Bomb : Exponential growth of the human population results in an explosive increase in the number of people ❑ The causes of rapid population growth o Increases in food production and distribution o Improvement in public health (water and sanitation) o Medical technology (vaccines and antibiotics) o Gain in education and standards of living within many developing nations ❑ How Many People Can Earth Comfortably Support? o Not an easy answer to the population problem o The ability to feed people does not solve the problems of limited space available to people and maintenance or improvement of their quality of life. o Some studies suggest that the present population is already above a comfortable carrying capacity for the planet o So far, Earth is our only suitable habitat ??? World Population Growth  Case Study: Population growth Flooding and Sustainability in Bangladesh  Case Study: Population growth Flooding and Sustainability in Bangladesh ▪ Bangladesh is vulnerable to catastrophic flooding from river as well as tropical storms. ▪ 20-30% of country flooded each year ▪ Half of the Population: Lives at elevation < 8 m ▪ 17 Million People: Lives at elevation < 1 m from MSL. ▪ It is estimated that global mean sea- level would rise to 1.5 m by 2100 (IPCC 2001a; Sweet et al. 2017). ▪ It has been estimated that by 2100 around 600 million people will be living in coastal floodplains (Nicholls and Mimura 1998). ▪ IPCC (2001b) had already warned that about 1 m rise in sea level could displace nearly 7 million people from Intergovernmental Panel on Climate Change (IPCC) coastal India.  Case Study: Population growth Flooding and Sustainability in Bangladesh ▪ Flooding mainly due to: Excess rainfall and snow melting in foothills of Himalaya Simultaneous peak flooding in all main rivers High-tides in Bay of Bengal ▪ Change in Flood Potential due to change in land-use pattern : Deforestation of Himalayan region Excessive sediment deposition in rivers Western style development ▪ Floods become catastrophic when high tides coincide with tropical storms since half of the land is within 8 m of sea-level.  Concept Two : Sustainability Sustainability is the environmental ❑ Life Expectancy of an American: objective According to the Mineral Information Institute in Golden, Colorado, the ❑ Development whichborn average American ensures in 2004 that has a future generations will have equal life expectancy of 77.3 years and will access to the resources that our planet need: offers. ❑❑ 16,20,000 Refers kg of to types of minerals, developmentmetals and that arefuels to sustainviable, economically his or do hernot standards harm theofenvironment, living overand a society. lifetime. Which means an average of 20,886 kg of mineral and ❑ Long-term energy concept, resourcesthat something per year for happens overevery man,orwoman, decades and even over hundreds child in of theyears. United States. ▪ Are We in an Environmental Crisis? ▪ Demands made on diminishing resources by a growing human population and the ever-increasing production of human waste have produced what is popularly referred to as the Environmental Crisis ▪ Result of overpopulation, urbanization and industrialization, combined with too little ethical regard for our land and inadequate institutions to cope with environmental stress ▪ Political and social pressures ❑ Environmental Crisis Occupied by French colonies While leaving cut a lot of trees Haiti for timber and took away Deforestation continued after Dominican the independence also Republic  Concept Three: Earth as a System Impact on the landscape and environment ▪ Understanding Earth’s systems and their changes is critical towards solving environmental problems ▪ System – is the defined part of the universe selected for the study ▪ Examples - Planet, Volcano, Ocean basin, River… ▪ Components of the system mutually adjust to function as a whole with changes in one component bringing about changes in other components. ▪ For example, water, land, atmosphere and life mutually adjust to keep the entire Earth system operating… i.e., mutual adjustment & balance…  Input – Output Analysis of a System Net change depends on the relative rates of the input and output  Input – Output Analysis of a System ▪ Where the input into the system is equal to the output, a rough steady state is established and no net change occurs ▪ e.g., Our planet is a roughly steady-state system with respect to energy. Incoming solar radiation is roughly balanced by outgoing radiation from Earth. ▪ Where the input into the system is less than the output ▪ e.g., use of resources, such as fossil fuels or groundwater. Extreme condition of this case will lead to extinction ▪ Where the input exceeds output the stock of whatever is being measured will increase. ▪ e.g., Build up of heavy metals in lakes from industrial pollution or the pollution of soil and water.  How Can We Evaluate Change? ▪ The average residence time is a measure of the time it takes for the total stock or supply of the material to be cycled through a system ▪ To compute the average residence time (T), assuming constant size of the system and constant rate of transfer, we take the total size of the stock (S) and divide it by the average rate of transfer (F) through the system T = S/F  Process: Uniformitarianism ▪ The geomorphic processes varies enormously, it may be as slow as a few centimetre per thousand years to 50 m/s. ▪ These processes depends upon the region, climate, vegetation, altitude, depth etc. ▪ It has been suggested that “geomorphic features are similar to all chemical and physical processes. Under same set of environmental conditions, they have acted in the past, will act in the same pattern in future and are observed as same today – known as Hutton’s principle of uniformity of process - called Uniformitarianism ▪ The present is the key to the past, called Uniformitarianism  Process: Uniformitarianism ▪ Present Human Activity is Part of the Key to Understanding the Future ▪ In making inferences about geologic events, we must consider the effects of human activity on the Earth system and natural Earth processes. ▪ For example, rivers flood regardless of human activities, but human activities, such as ▪ paving the ground in cities, increase runoff and the magnitude and frequency of flooding. ▪ After the paving, floods of a particular size are more frequent, and a particular rainstorm can produce a larger flood as compared to that was experienced before the paving ▪ The principle of environmental unity, which states that one action causes others in a chain of actions, is an important principle in the prediction of changes in the Earth system. ▪ Example: Change in local environment after construction of dam on a river  2. Geology as a Science Process comparison: slow versus rapid The most recent layer of sediment The explosive impact of a meteorite is about 250 million years old. created this 1.2-km-wide crater in just a few seconds. The rocks at the bottom of the Grand Canyon are 1.7–2.0 billion years old.  Concept Four: Hazardous Earth Processes ▪ There have always been Earth processes that are hazardous to people. ▪ These natural hazards must be recognized and avoided when possible, and their threat to human life and property must be minimized ▪ Earlier, losses from hazardous Earth processes were not significant ❑ Lesser number of people ❑ Lesser Population Density ▪ Due to ever increasing population, natural hazards that produce disasters are becoming super disasters called catastrophes ▪ In past 20 years, ❑ Annual human loss of 150,000 people ❑ Financial damages of $20 billion ▪ Human population increase has forced more people to live in hazardous areas, such as in floodplains, on steep slopes and near volcanoes ▪ Land-use transformations, including urbanization and deforestation resulting greater damage Geohazards  Concept Five: Scientific Knowledge and Values ▪ The results of scientific inquiry to solve a particular environmental problem often provide a series of potential solutions consistent with the scientific findings. The chosen solution is a reflection of our value system ▪ Knowledge, Imagination and Critical Thinking are important in order to understand and analyze any process The Steps in the Scientific Method Earth’s environmental systems The Earth’s environment has a complex networks of systems interlinked with one another… Systems show several defining properties System = a network of relationships among parts, elements, or components They interact and influence one another They exchange energy, matter, or information Systems receive inputs in form of energy, matter, or information They utilize these inputs and produce outputs Feedback loop = a circular process in which a system’s output serves as input to that same system Negative and positive feedback loops do not mean bad and good  NEGATIVE AND POSITIVE FEEDBACK Negative feedback is when a change in a system leads a sequence of changes that eventually neutralize the effect of original change, resulting in stabilizing the system. Accelerates Increased Slope erosion Stream bedload + - + Steepening of Increased Valley-side slope Channel + Erosion  +ve feedback As Earth warms: Ice cover melts, exposing soil or water Albedo decreases (Albedo = reflectivity) More energy is absorbed by Earth’s surface Global temperature rises More ice melts  Positive (+ve) feedback loop Positive feedback loop = instead of stabilizing a system, it drives it further toward one extreme or another – Exponential growth in human population, erosion, melting sea ice Rare in nature – But is common in natural systems altered by humans  Negative (-ve) feedback Carbon dioxide levels increases in the atmosphere – causes rise in temperature of the Earth As Earth warms: The rate of photosynthesis in plants increases More carbon dioxide is therefore removed from the atmosphere by plants Reducing the greenhouse effect and reducing global temperature… The Aral Sea is dying because of diverting water for irrigation  THE EARTH’S SURFACE IN ACTION: MOUNTAIN UPLIFT AND GLOBAL COOLING The geomorphic system: Implication to environmental/climate change Active mountain building process is linked to global climatic change Through airflow modification and in part through weathering. Young mountains weather and erode quickly. Weathering processes remove carbon-dioxide from the atmosphere by converting it to soluble carbonates. The carbonates are carried to the oceans, where they are deposited and buried. It is possible that the growth of the Himalaya scrubbed enough carbon- dioxide from the atmosphere to cause a global climatic cooling that culminated in the Quaternary ice ages (Raymo and Ruddiman 1992; Ruddiman 1997).  Human Influences (2) Our daily activities are having measurable effects on: Rainfall Climate Air Water quality Erosion  Earth processes and landscape Thus, to have proper understanding of the earth’s processes and related landscape (geomorphology) it is essential to know various natural process related to the Earth and its Environment: Internal processes External processes  Physical vs Historical Geomorphology Historical geomorphology Historical geomorphology is the study of landform evolution or changes in landforms over medium and long timescales. Usually timescales well beyond the span of an individual human’s experience – centuries, millennia, millions and hundreds of millions of years. Chronology of events, both physical and biological, that have occurred in the past. The past is the biggest clue to the present. Physical geomorphology Concerned with understanding the processes and the materials.  The components of historical explanation needed to account for geomorphic events of increasing size and age. The top right of the diagram contains purely historical explanations, while the bottom left contains purely modern explanations. The two explanations overlap in the middle zone, the top curve showing the maximum extent of modern explanations and the lower curve showing the maximum extent of historical explanations. Source: After Schumm (1985b; 1991, 53)