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Earth - Coggle Diagram

- - - - Earthquakes
        
        Earthquake waves
        
        Types of Earthquake waves
        
        Body waves
        
        Body waves are generated at the focus and move in all directions traveling through the body of the earth. Body waves are of two types. p-waves and s-waves.
        
        p-Waves
        
        These waves are called the 'primary waves'.
        
        p-Waves are similar to sound waves, and they can pass through solid, liquid and gaseous materials.
        
        p-Waves are faster and are the first to arrive at the surface.
        
        Waves vibrate parallel to the direction of propagation, exerting pressure on the material in the direction of the propagation. As a result it creates density differences in the material leading to stretching and squeezing of the material.
        
        s-Waves
        
        s-Waves are the 'secondary waves'.
        
        Can only propagate through solid materials, this characteristics help scientists to understand the structure of interior the earth.
        
        The direction of vibration of s-waves are perpendicular to the direction of propagation. Hence, they create troughs and crests in the material through which they pass.
        
        Surface waves:
        
        The body waves interact with the surface rocks and generate new set of waves known as surface waves.
        
        Vibrates perpendicular to the direction of propagation.
        
        Considered to be the most damaging waves. Causes displacement of rocks, and collapse of structures.
        
        Detection of waves
        
        Reflection causes waves to rebound whereas refraction makes waves move in different directions.
        
        The variations in the direction of waves are inferred with the help of their report on seismograph
        
        Surface waves are the last to report.
        
        Shadow zone
        
        Some specific areas where the waves are not reported as known as shadow zone.
        
        Any distance within 105° from the epicentre, recorded the arrival of both p and s waves.
        
        The seismographs located beyond 145° from epicentre, record the arrival of p-waves but does not receive s-waves.
        
        The entire zone beyond 105° does not receive s-waves. Hence the shadow zone of s-waves is not only larger but covers roughly around 40% of the earth's surface.
        
        The shadow zone of p-waves appears to be a band between 105° and 145° away from the epicentre.
        
        Types of Earthquakes
        
        Tectonic earthquake: Most common type of earthquake, occurred due to sliding of rocks along a fault plane.
        
        Volcanic earthquakes: A special class of tectonic earthquake, confined to the areas of active volcanoes.
        
        Collapse earthquake: In the ares of intense mining activities, sometimes the roof of underground mines collapse causing minor tremors.
        
        Explosion eathquakes: Tremors occured due to explosion of chemical or nuclear devices.
        
        Effects of Earthquake
        
        Ground shaking
        
        Differential ground settlement
        
        Land and mud slides
        
        Soil liquefication
        
        Ground lurching
        
        Avalanches
        
        Ground displacement
        
        Floods from dam and levee failures
        
        Fires
        
        Structural collapse
        
        Falling objects
        
        Tsunami
        
        Earthquake is occurred due to release of energy along a fault.
        
        Fault is a sharp break in the crustal rocks. Rocks along a fault tend to move in the opposite directions. As the overlying rock strata presses them, the friction locks them together. However their tendency to move apart at some point of time overcomes the friction. As a result, the blocks get deformed and eventually, they slide past one another abruptly. This causes a release of energy waves travel in all directions.
        
        The point where the energy is released is called the focus or hypocentre of an earthquake.
        
        The point on the surface nearest to the focus is called epicentre. It is the first place to experience the waves
        
        All natural earthquakes take place in the lithosphere.
      - Volcanoes
        
        Classification
        
        based on nature of eruption and the form developed at the surface
        
        Composite Volcanoes:
        
        These volcanoes are characterised by eruptions of cooler and more viscous lava than basalt.
        
        These volcanoes often result in explosive eruptions.
        
        Along with lava, large quantities of pyroclastic material and ashes find their way to ground.
        
        This material accumulates in the vicinity of the vent opening s leading to formation of layers, and this makes the mounts appear as composite volcanoes.
        
        Caldera:
        
        Most explosive type of volcanoes, that they tend to collapse on themselves rather than building any tall structure.
        
        The collapsed depressions are called calderas.
        Their explosiveness indicates that the magma chamber supplying the lava is not only huge but also in close vicinity.
        
        Mid-Ocean ridge volcanoes:
        
        These volcanoes occur in the oceanic area
        where platonic divergent zones are active.
        
        These volcanoes occur over the mid oceanic ridge that spread over 70,000 Km.
        
        Shield Volcanoes:
        
        Shield volcanoes are the largest of all volcanoes on the earth.
        
        These volcanoes are mostly made up of basalt, a type of lava that is very fluids when erupted. For this reason, these volcanoes are not steep.
        
        They become very explosive if somehow water gets into the vent, otherwise they are characterised by low explosivity.
        
        The upcoming lava moves int he form of a fountain and throws out the cone at the top of the vent and develops into a cinder cone.
        
        Hawaiian volcanoes are the most famous examples of shield volcanoes.
        
        Basalt flows:
        
        These volcanoes out pour highly fluid lava that flows for long distances.
        
        Some parts of the world are covered by thousands of square kilometres of thick basalt lava flows.
        
        Some flows attained thickness over 50m.
        The Deccan traps from India, is an example of landform formed due to Basalt flow.
        
        Based on volcanic activity
        
        Active
        
        Erupting: An erupting volcano is an active volcano that is having an eruption.
        
        Dormant: dormant volcano is an active volcano that is not erupting, but supposed to erupt again.
        
        An active volcano is a volcano that has had at least one eruption during the past 10,000 years. An active volcano might be erupting or dormant.
        
        Extinct: An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.
        
        A volcano is a place where gases, ashes and molten rock material -lava- escape to the ground.
        
        The molten rock materials find its way to surface from aesthenosphere.
        
        The molten material in the upper mantle portion is called magma.
        
        Once it starts moving towards the crust or it reaches the surface, it is referred to as lava.
        
        The material that reaches the ground includes lava flows, pyroclastic debris, volcanic bombs, ash and dust and gases such as nitrogen compounds, sulphur compounds, minor amounts of chlorene, hydrogen and argon.
    - - Major plates:
        
        Antarctica and surrounding oceanic plate
        
        North American plate(with western Atlantic floor separated from the South American plate along the Caribbean islands)
        
        South American plate(with western Atlantic floor separated from the North American plate along the Caribbean islands)
        
        India-Australia-New Zealand plate.
        
        Africa with the eastern Atlantic floor plate
        
        Eurasia and the adjacent oceanic plate.
      - Notable Minor plates:
        
        Cocos plate between Central America and Pacific plate
        
        Nazca plate between south America and pacific plate
        
        Arabian plate that covers the Arabian Peninsula
        
        Philippine plate between the Asiatic and Pacific plate
        
        Caroline plate between Philippine and Indian plate(North of New Guinea)
        
        Fuji plate in the North east of Australia.
      - Indian Plate
        
        The Indian plate includes peninsular India and the Australian continental portions.
        
        The subduction zone along the Himalayas forms the northern plate boundary in the form of continent-continent convergence
        8 In the east, it extends through Rakinyoma Mountains of Myanmar towards the island arc along Java Trench. The eastern margin is a spreading site lying to the east of Australia in the form of oceanic ridge in SW Pacific.
        
        The western margin follows Kirthar Mountain of Pakistan. It further extends along Makrana coast and joins the Red sea rift southeastward along Chagos archipelago.
        
        The boundary between India and the Antarctic plate is also marked by oceanic ridge running in roughly W-E direction and merging into the spreading site, a little south of New Zealand.
        
        Movement of Indian Plate
        
        India was a large island situated of Australian coast, in a vast ocean. The Tethys sea separated it from the Asian continent till about 225 million years ago. India is supposed to have started her northward journey about 200 million years ago at the time when Pangaea broke.
        
        Formation of Himalayas and Deccan plateau
        
        Himalayas formed as the result of Indian plate collided with Asian plate about 40-50 million years ago.
        
        About 140 million years before the present, the subcontinent was located as south as 50°S latitude, with Tethys sea separating Indian and Asian landmass. During the movement of the Indian plate towards the Asiatic plate, massive lava outpouring over the Indian plate, leading to the formation of Deccan traps.
        
        Himalayas started forming 40 million years after the formation of Deccan traps, and the process still continues.
    - - Plate Boundaries
        
        Types of Plate Boundaries based on movement of plates
        
        Transform Boundaries: Plate boundaries where the crust is neither destroyed nor produced as the plates slide horizontally past each other. Transform faults are the planes of separation generally perpendicualr to the mid-oceanic ridges.
        
        Divergent Boundaries: Plate boundaries where crest is generated as the plates pull away from each other. The sites where the plates move away from each other are called spreading sites.
        Eg: Mid-Atlantic Ridge where American plates are separated from Eurasian and African plates
        
        Convergent boundaries: The plate boundaries where the crust is destroyed as one plate dived under another. The location where sinking of a plate occurs is called subduction zone.
        There are three ways in which convergence can occur:
        
        Between oceanic and continental plate
        
        Between two oceanic plates
        
        Between two continental plates
      - The plates have been constantly moving over the globe throughout the history of the earth, also will keep moving on in the future as well.
        
        The Continents are part of the plate, hence it is the plates that are moving instead of continents against the Continental drift theory proposed by Alfred Wegener.
        
        Pangaea was a result of converging of different continental masses that were parts of one or the other plates.
        
        Scientists using the palaeomagnetic data, have determined the positions held by each of the present continental landmass in different geological periods.
        
        Position of the Indian sub-continent is traced with the help of the rocks analysed from the Nagpur area.
        
        The strips of normal and reverse magnetic field that parallel the mid oceanic ridges help scientists determine the rates of plate movement.
        
        Arctic Ridge has the slowet rate with less than 2.5 cm/year. The east Pacific rise near the Easter island, in the South Pacific about 3,400 km west of Chile, has the fastest rate, with more than 15 cm/year.
      - Force for movement of Plate movement:
        
        The heat within the earth comes from two main sources: radio active decay and residual heat.
        
        The slow movement of hot, softened mantle that lies below the rigid plates is the driving force behind the plate movement.
        
        The mobile rock beneath the rigid plates is believed to be moving in a circular manner. The heated material rises to the surface, spreads and begins to cool, and then sinks back into deeper depths. This cycle is repeated over and over to generate a convection cell or convection flow
  - - - Analysis of rocks
        
        Rocks equidistant on the either sides of the crest of mid-oceanic ridges show remarkable similarities in terms of period of formation, chemical compositions and magnetic properties.Rocks closer to the mid-oceanic ridges are normal polarity and are the youngest. The age of the rocks Increases as one moves away from the crest.
        
        The ocean rocks are much younger than continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 Million years old, as compared to continental rock formations which are 3200 million years
      - Study of Sedimentary deposits
        
        Sediments on the ocean floor are unexpectedly very thin. Nowhere sediment column found to older than 200 million years.
      - Occurrence of earthquakes
        
        Deep trenches have deep-seated earthquake occurrences while in the mid-oceanic ridge areas, the quake foci have shallow depths.
      - Volcanic eruptions along mid oceanic ridges.
        
        All along the mid-oceanic ridges, volcanic eruptions are common and they bring huge amounts of lava to the surface in this area.
- - - - 1. External Crystal form:
        
        Determined by the internal arrangement of molecules.
        
        Can be cube, octahedrons, hexagonal prisms, etc..
      - 2. Cleavage:
        
        Tendency to break in given directions producing relatively plain surfaces.
        
        Result of internal arrangement of molecules
        
        May cleave in one or more directions at any angle to each other.
      - 3. Fracture:
        
        Internal molecular arrangement is so complex that there are no planes of molecules.
        
        The crystal will break in irregular manner, and not along the planes of cleavage.
      - 4. Lustre:
        
        Appearance of a material without regard to colour.
        
        Each mineral has distinctive lustre like metallic, silky, glossy, etc..
      - 5. Colour:
        
        Some minerals have characteristic colour determined by their molecular structure - Eg: malachite, azurite, chalcopyrite, etc..
        
        Some minerals are coloured by impurities, for example, quartz may be white, green, red or yellow according to the impurities contained
      - 6. Streak:
        
        Colour of the grounded powder of any mineral can be different or same as that of the mineral rock.
        
        Eg: Malachite is green and gives green streak, but fluorite is purple or green but gives white streak.
      - 7. Transparency:
        
        Transparent: Light rays pass through so that objects can be seen plainly.
        
        Translucent: Light rays pass through but will get diffused so that objects cannot be seen.
        
        Opaque: Light will not pass through at all.
      - 8. Structure:
        
        Particluar arrangement of the individual crystals.
        
        Grains: Fine, medium, coarse
        
        Fibrous: Seperable, divergent, radiating.
      - 9. Hardness:
        
        Relative resistance from being scratched.
        
        Ten minerals are selected to measure the degree of hardness from 1-10. they are:
        
        Talc
        
        Gypsum
        
        Calcite
        
        Fluorite
        
        Apatite
        
        Feldspar
        
        Quartz
        
        Topaz
        
        Corundum
        
        Diamond
      - 10. Specific gravity:
        
        The ratio between the weight of a given object and weight of an equal volume of water.
    - - Feldspar: Silicon and oxygen are common in all types of feldspar
      - Quartz: One of the most important content of sand and Granite. Consists of silica. Quartz is a hard mineral virtually insoluble in water. It is white and colorless and used in radio and radar.
      - Amphibole: Aluminum, Calcium, Silica, Iron and Magnesium are the major constituents of Amphibole. It constitute 7% of earth's crust. It is green of black in color and is used in Asbestos Industry. Hornblende is another form of Amphibole.
      - Mica: It comprises of potassium, Aluminum, Magnesium, Iron, Silica etc.. It forms 4% of earth's crust. It is commonly found in Igneous or Metamorphic rocks. It is used in electrical instruments.
      - Olivine: Magnesium, iron and silica are the major elements in Olivine. It is a greenish crystal used in jewellery, often found in basaltic rocks.
      - Pyroxene: Consists of calcium, aluminum, magnesium and silica. Pyroxene forms 10% of earth's crust. It is commonly found in meteorites. It is green or black in color.
    - - Metallic
        
        Minerals that contain metal content are categorized as Metallic minerals.
        
        Precious metals: Gold, Silver, Platinum, etc..
        
        Ferrous metals: Iron and other metals often mixed with iron to form various kinds of steel.
        
        Non-ferrous metals: This include metals like copper, lead, zinc, tin, aluminium, etc..
      - Non-Metallic: These minerals do not contain metal content. Sulfur, phosphates and nitrates are examples of non-metallic minerals. Cement is a mixture of non-metallic minerals.
    - - Classification based on formation
        
        Sedimentary rocks: Rocks(Igneous, sedimentary and metamorphic) of the earth's surface are exposed to denudation agents, and are broken to various sizes of fragments. Such fragments are transported by different exogenous agencies and deposited. These deposits through compaction turn into rocks. This process is called lithification.
        Layers of deposits retain their characteristics even after lithification. Hence, a number of layers of varying thickness can be seen in sedimentary rocks like sandstone, shale, etc..
        Depending on the mode of formation, sedimentary rocks can be classified into three major groups:
        
        Mechanically formed: Sandstone, Conglomerate, Limestone, Shale, Loess, etc..
        
        Organically formed: Geyserite, Chalk, Limestone, Coal, etc..
        
        Chemically formed: Chert, Limestone, Halite, Potash etc..
        
        Igneous rocks: Igneous rocks form from magma cools and solidifies, they are known as primary rocks. The process of cooling and solidifying can happen in the earth's crust or on the surface of the earth.
        Igneous rocks are classified based on texture. Texture depends upon size and arrangement of grains or other physical condition of the materials.
        
        If the molten material is cooled slowly at great depths, mineral grains may be very large.
        
        Sudden cooling at the surface results in smooth and tiny grains.
        
        Intermediate conditions of cooling would results in intermediate sizes of grains making up igneous rocks.
        
        Eg: Granite, Gabbro, Pegmatite, Basalt, Volcanic breccia, Tuff, etc..
        
        Metamorphic rocks
        
        Rocks form under the act of Pressure, Volume and Temperature variations are called metamorphic rocks.
        
        Metamorphism occurs when rocks are forced down to lower levels of tectonic processes or when molten magma through the crust comes in contact with the crustal rocks or the underlying rocks are subjected to great amount of pressure by overlying rocks.
        
        Metamorphism is a process by which already consolidated rocks undergo crystallization and reorganization of materials within the original rocks.
        
        Two types of metamorphism
        
        Thermal Metamorphism
        
        Materials of the rocks chemically alter and recrystallize is called Thermal metamorphism
        
        Contact metamorphism: In contact metamorphism, the rocks come in contact with hot intruding magma and lava, and the rock materials crystallize under high temperatures.
        Quite often, new materials formed out of magma/lava are added to the rocks.
        
        Regional metamorphism: In regional metamorphism, rocks undergo re-crystallization due to deformation caused by tectonic shearing together with high temperature or pressure or both.
        
        Dynamic metamorphism: Mechanical disruption and reorganization of the original materials within the rocks due to breaking and crushing without any appreciable chemical changes is called dynamic metamorphism.
        
        Structural features
        
        Foliation/Lineation: Arrangement of minerals or grains in lines or fragments in metamorphic rocks are called foliation or lineation.
        
        Banding: Arrangement of minerals or materials into alternating thin and thick layers appearing in light and dark shades are called banding, and such rocks are called banded rocks.
        
        Eg: Gneissoid, Granite, Syenite, Slate, Schist, Marble, Quartzite etc..
      - Rock Cycle
        
        Igneous rocks are the primary rocks and other rocks are formed from the primary rocks.
        
        Igneous rocks can go metamorphism and change into metamorphic rocks. The fragments from Igneous and Metamorphic rocks can form into sedimentary rocks.
        
        Sedimentary rocks can themselves turn into fragments and the fragments can be the source of formation of new sedimentary rocks.
        
        The Crustal rocks(Igneous, Sedimentary and Metamorphic) once formed may be carried down into the mantle through subduction process and the same melt down due to increase in temperature in the interior and turn into molten magma, the original source of Igneous rocks.
      - A rock is an aggregate of one or more minerals. Rock may be hard or soft of varied colors. Rocks do not have definite mineral constituents or composition.
  - - - Exogenic Process
        
        Weathering
        
        Types of Weathering
        
        Physical Weathering
        
        Physical or mechanical weathering depends on some applied forces.
        
        Forces behind Physical weathering
        
        Gravitational force Influences through pressure, load shearing and stress.
        
        Expansion forces due to temperature, Crystal Growth and animal activity.
        
        Water pressure controlled by drying and wetting cycles
        
        Some physical weathering processes:
        
        Unloading and expansion:
        
        Removal of overlying rock load because of continued erosion causes vertical pressure release which results in expansion of upper layers of rocks producing disintegration of rock masses called exfoliation.
        
        Large smooth exfoliation domes are the result of this process.
        
        Temperature changes and expansion:
        
        Various materials have their own thermal properties causing expansion and contraction.
        
        This process is more effective in dry climates and high elevations where diurnal temperature changes are drastic. Surface layers expands more than the layers at the depth, and this leads to formation of stress within the rock resulting in heaving and fracturing parallel to the surface.
        
        Due to differential heating and resulting expansion and contraction of surface layer and their subsequent exfoliation from the surface results in smooth rounded surfaces in rocks.
        
        Rocks like granite, with smooth surfaces and rounded small to big boulders called tors, form due to such exfoliation
        
        Frost weathering/Frost Wedging:
        
        Frost weathering/wedging occurs due to growth of ice within pores and cracks of rocks during repeated cycles of freezing and melting.
        
        Rapid freezing of water causes its sudden expansion and high pressure. The resulting expansion affects joints and cracks and small inter granular fractures to become wider and wider till rocks break apart.
        
        This process is most effective at high elevations in mid-latitudes where freezing and melting is often repeated.
        
        Glacial areas are subject to frost wedging daily.
        
        Salt Weathering:
        
        Salt in rocks expand due to thermal action, hydration and Crystallization.
        
        Salts like calcium, sodium, magnesium, potassium, barium etc., have a tendency to expand. Expansion of these salts depends on temperature and their thermal properties. High temperature range between 30°C and 50°C of surface temperatures in deserts favor salt expansion.
        
        Salt Crystals near surface pores cause splitting of individual grains within rocks, which eventually fall off. This process results in granular disintegration or granular foliation.
        
        Salt Crystallisation is the most effective of all salt weathering process. In areas with alternating wetting and drying conditions salt crystal growth is favoured and the neighbouring grains are pushed aside. Sodium Chloride and gypsum crystals in desert areas heave up overlying layers of materials and with result polygonal cracks develop all over the heaved surface. With salt growth, chalk breaks down, followed by limestone, sandstone, shale, gneiss, granite, etc.,
        
        Biological Weathering
        
        Biological weathering is the contribution to or removal of minerals and ions from the weathering environment and physical changes due to growth or movement of organisms.
        
        Examples of Biological Weathering:
        
        Burrowing and wedging by organisms like earthworms, termites, rodents, etc., help in exposing new surfaces to chemical attack and assists in the penetration of moisture and air.
        
        Human beings by disturbing vegetation, ploughing and cultivating soils, also help in mixing and creating new contact between air, water and minerals in earth materials.
        
        Decaying plant and animal matter help in the production of humic, carbonic and other acids, which enhance decay and solubility of some elements.
        
        Algae utilise mineral nutrients for growth and help in concentration of iron and manganese oxides.
        
        Plant roots exerts a tremendous pressure on the earth materials mechanically breaking them apart.
        
        Chemical Weathering
        
        A group of processes; solution, carbonation, hydration, oxidation and reduction act on the earth materials to decompose, dissolve or reduce them to a fine state through chemical reactions by oxygen, surface or ground water and other acids.
        
        Types of chemical weathering
        
        Solution: When a mineral is dissolved in water or acid, the water or acid with dissolved content is called solution. The process involves removal of solids in solution and depends upon the solubility of the mineral in water or weak acid.
        
        Rock minerals like nitrates, sulphates, potassium etc.,
        
        Minerals like calcium carbonate, calicium magnesium bicarbonate present in limestone are soluble in water containing carbonic acids.
        
        Carbonation: Carbonation is the reaction of carbonates and bicarbonates with minerals and is a common process in helping the breaking down of feldspar and other carbonate minerals.
        
        Carbon dioxide from the atmosphere and air is absorbed by the water, to form carbonic acid that act as a weak acid. Calcium carbonate and magnesium carbonates dissolved in carbonic acid and are removed in a solution without leaving any residue resulting in cave formation.
        
        Hydration: Hydration is the chemical addition of water. minerals take up water and expands; this expansion causes increase in volume of the mineral or the rock. The process is reversible and long continuation of the process may lead to cause fatigue in the rocks further leads to disintegration. Thus the volumes changes in minerals due to hydration also causes physical weathering through exfoliation and granular disintegration.
        
        Calcium sulphate absorbs water to turn into Gypsum.
        
        Oxidation: Oxidation means combination of oxygen with minerals to form oxides or hydroxides. Oxidation occurs when there is ready access to atmosphere and oxygenated waters.
        
        Rocks breakdown due to disturbances caused by oxidation.
        
        Minerals most affected are iron, magnesium, sulphur, etc.,
        
        Reduction: When oxidized minerals are placed in an environment where oxygen in absent, reduction takes place. Happens usually below water table, in areas of stagnant water and waterlogged ground.
        
        Red color of oxidized iron turns into greenish or bluish grey when subjected to reduction.
        
        Significance of weathering:
        
        Weathering causes breaking down of rocks into fragments which results in erosion and mass movements.
        
        Forest and vegetation depends upon depth of weathering mantle.
        
        Weathering of rocks and deposits helps in enrichment and concentration of certain valuable ores such as iron, manganese, aluminum, copper, etc., which are great importance to national economy.
        
        Weathering is an important process in the formation of soil.
        
        Weathering is the action of weather and climate over earth materials. It is defined as the mechanical disintegration and chemical decomposition of rocks through actions of various elements of climate and weather.
        
        Mass Movements
        
        Grouped under three major types
        
        Rapid movements
        
        Some rapid movements:
        
        Landslides
        
        2 more items...
        
        Earthflow: Movement of water-saturated clayey or silty earth materials down low-angle terraces or hillsides is known as earthflow. Quite often, the materials slump making step like terraces and leaving arcuate scarps at their heads and an accumulation bulge at their toe. When the slopes are steeper, even the bedrock especially soft sedimentary rocks like shale or deeply weathered igneous rock may slide downslope.
        
        Mudflow: Mudflow happens in the absence of vegetation cover and with heavy rainfall, thick layers of weathered materials get saturated with water and either slowly or rapidly flow down along definite channels. It looks like a stream of mud within a valley.
        
        Debris Avalanche: Debris avalanche is a characteristic of humid regions with or without vegetation cover and occurs in narrow tracks on steep slopes. this debris avalanche can be much faster than the mudflow.
        
        These movements are prevalent to humid climatic regions and occur over gentle to steep slopes.
        
        Slow movements
        
        Some slow movements
        
        Solifluction: Slow down slope flow of soil mass or fine grained rock debris saturated or lubricated with water. This process is quite common in moist-temperate areas where surface melting of deeply frozen ground and long continued rain, occur frequently. When the upper portions get saturated and when the lower parts are impervious to water percolation, flowing occurs in the upper parts.
        
        Creep: Movement of material is extremely slow and only perceptible through extended observation. Materials involved can be soil or rock debris. Leaning of Telephone poles, trees, etc., down slope is due to the effect of creep. Depending on type of material there are different kind of creeps such as; soil creep, talus creep, rock creep, rock-glacier creep, etc.,
        
        These are movements that are extremely slow and takes years to see a perceptible effect on the surface.
        
        Causes:
        
        Removal of support from below to materials above through artificial or natural processes.
        
        Increase in gradient and height of slopes.
        
        Overloading through addition of materials through natural or artificial filling.
        
        Overloading through heavy rainfall, saturation and lubrication of slope of materials.
        
        Removal of material or load from over original slope surface.
        
        Occurrence of earthquake, explosions or machinery.
        
        Excessive natural seepage.
        
        Heavy draw down of waters from rivers, lakes, reservoirs etc., leading to slow outflow of water from under the slope of riverbanks.
        
        Indiscriminate removal of natural vegetation.
        
        Three forms of Mass movements
        
        Heave
        
        Flow
        
        Slide
        
        Mass movements is the movement of surface materials due to the influence of Gravity. Mass movements are very active over weathered slopes, rather than unweathered materials. Mass movements are aided by gravity and no geomorphic agents like running water, glaciers, wind, currents, etc., participate in mass movements.
        
        Erosion and Deposition
        
        Erosion
        
        Erosion involves acquisition and transportation of rock debris. When massive rocks breaks into small fragments through weathering and any other process, erosional agents remove and transport it to other places depending upon the dynamics of these agents. Abrasion by rock debris carried by these geomorphic agents also aids greatly in erosion.
        
        Agents of erosion
        
        The denudational process of erosion and transportation is controlled by Kinetic energy. These are brought by wind, glaciers, running water, waves, and ground water; which are known as agents of erosion. Of these, first three are controlled by climatic conditions.
        
        Wind: Being in the gaseous state is the least effective agent of erosion mostly favours in the arid regions.
        
        Glaciers: Glaciers move at very low velocity due to tremendous mass and are more effective as an agent of erosion.
        
        Running water: Mostly contributed by rivers and streams by carrying sediments due to weathering from upward regions and deposits at the low lying valleys.
        
        Ground water: The work of ground water is determined more by lithological character of the region. If the rocks are permeable and soluble, and if the water is available only then karst topography develops.
        
        Waves: In case of waves, it is the location along the interface of lithosphere and hydrosphere - coastal region - that will determine the work of waves.
        
        Deposition: Deposition is a consequence of erosion. The erosional agents loose their velocity and hence energy on gentler slopes and the materials carried by them start to settle themselves. In other words, deposition is not actually work of any agent. The coarser materials get deposited first and finer ones later. By deposition depressions get filled up. The same erosional agents also acts as depositional agents.
        
        Exogenic geomorphic processes derive their energy from atmosphere, determined by ultimate energy from the sun, and also the gradients created by tectonic factors.
        All the exogenic geomorphic processes are covered under a general term; denudation
      - Endogenic Process
        
        Volcanism
        
        Diastrophism
        
        Epeirogenic processes: Processes involving uplift or warping of large parts of earth's crust.
        
        Earthquakes: Local, relatively minor movements.
        
        Plate Tectonic movements: Horizontal movement of crustal plates.
        
        Orogenic processes: Processes involving mountain building through severe folding and affecting long and narrow belts of the earth's crust.
        
        Definition: All processes that move, build up portions of earth's crust comes under diastrophism.
        
        Definition: Endogenic Processes are caused due to endogenic forces; i.e. the energy emanating from within the earth due to radio activity, rotation, tidal friction and primordial heat from the origin of earth.
    - - Soil is a dynamic medium in which many chemical, physical and biological activities go on constantly. soil is a result of decay, it is also the medium of growth. It is a changing and developing body. It has many characteristics that fluctuate with seasons. Soil becomes adjusted to conditions of climate, landform and vegetation and will change internally when these controlling conditions change.
      - Process of soil formation or Pedogenesis:
        The weathered material or transported deposits are colonised by bacteria, and other inferior plant bodies like mosses and lichens. Also, several minor organisms may take shelter within the mantle and deposits. The dead remains of organisms and plants help in humus accumulation. Minor grasses and ferns may grow, later bushes and trees will start growing through seeds brought in by birds and wind. Plant roots penetrate down, burrowing animals bring up particles, mass of material becomes porous and sponge like with a capacity to retain water and to permit the passage of air and finally a mature soil, a complex mixture of mineral and organic product forms.
      - Soil forming factors.
        
        Parent material:
        
        Parent material is a passive control factor in soil formation.
        
        It can be in-situ or on site weathered rock debris or transported deposits. Soil formation depends upon the texture and structure(deposition of individual grains/particle debris) as well as the mineral and chemical composition of rock debris/deposits.
        
        Nature, rate of weathering and depth of weathering are important consideration under parent material.
        
        When soil are young and have not matured, these show strong links with the type of parent rock.
        
        In case of limestone ares, where the weathering process are specific and peculiar, soil will show clear relation with the parent rock.
        
        Topography:
        
        Another passive control factor like parent material.
        
        The influence of topography is felt through the amount of exposure of a surface covered by parent materials to sunlight and the amount of surface and sub-surface drainage over and through the parent materials.
        
        Soil will be thin on steep slopes and thick over flat upland areas.
        
        Over gentle slopes where erosion is slow and percolation of water is good soil formation is very favourable.
        
        Soil over flat areas may develop a thick layer of clay with good accumulation of organic matter giving the soil dark colour.
        
        In the middle latitudes of northern hemisphere, the south facing slopes exposed to sunlight have different conditions of vegetation, and soil, compared to the north facing slopes with cool moist conditions have different soil and vegetation.
        
        Biological activity
        
        The vegetative cover and organisms that occupy the parent materials from the beginning and also at later stages help in adding organic matter, moisture retention, nitrogen, etc..
        
        Dead plants provide humus, the finely divided organic matter of the soil.
        
        Organic acids which form during humification aid in decomposing the minerals of the soil parent materials.
        
        Intensity of bacterial activity shows up differences between soils of cold and warm climates.
        
        Humus accumulates in cold climates as bacterial growth is slow. With undecomposed organic matter because of low bacterial activity, layers of peat develop in sub arctic and tundra climate.
        
        In humid tropical and equatorial climates, bacterial growth and action is intense and dead vegetation is rapidly oxidised leaving very low humus content in soil.
        
        Bacteria and other soil organisms take gaseous nitrogen from the air and convert it into a chemical form that can be used by plants. This process is known as nitrogen fixation, which is mostly done by Rhizobium bacterias which are present in the root nodules of leguminous plants, which are beneficial to host plant and other plants.
        
        Influence of large animals like ants, termites, earthworms, rodents etc., is mechanical, but it is nevertheless important in soil formation as they rework the soil up and down. In case of earthworms, as they feed on soil, the texture and chemistry of soil that comes of their body changes.
        
        Time
        
        The duration of time the soil forming processes operate, determines the maturation of soil and profile development. A soil becomes mature when all soil forming processes act for a sufficiently long time developing the soil profile.
        
        Soil developing from recently deposited alluvium or glacial till, are considered young and they exhibit no horizons or poorly developed horizons.
        
        No specific duration of time in absolute terms can be fixed for soil to develop and mature.
        
        Climate
        
        Climate is an active factor is soil formation.
        
        Two climatic elements involved in soil formation
        
        Moisture -In terms of its intensity, frequency and duration of precipitation, evaporation and humidity.
        
        Precipitation gives soil moisture content which makes the chemical and biological activities possible.
        
        Excess of water helps in the downward transportation of soil components through the soil(eluviation) and deposits the same down below(illuviation).
        
        In climates like wet equatorial rainy areas with high rainfall, not only calcium, sodium, magnesium, potassium, but also major part of silica is removed from the soil. The removal of silica from the soil is known as desilication.
        
        In dry climates, because of high temperature, evaporation exceeds precipitation and hence ground water is brought up to the surface by capillary action and in the process water evaporates leaving behind salts in the soil. Such salts form in a crust in the soil known as hardpans.
        
        In tropical climates and in areas with intermediate precipitation conditions, calcium carbonate nodules are formed.
        
        Temperature -in terms of seasonal and diurnal variations.
        
        Temperature act in two ways -Increasing or reducing chemical and biological activity.
        
        Chemical activity is increased in higher temperatures, reduced in cooler temperatures(with an exception of carbonation) and stops in freezing conditions. That is why, tropical soils with higher temperatures show deeper profiles and in the frozen tundra regions soils contain largely mechanically broken materials.
  - - - Running water.
        
        Erosional Landforms
        
        Depositional Landforms
- - - - Knowing total thickness of the earth, scientists have estimated the values of temperature, pressure and the density of the materials at different depths.
      - Meteors: The material and the structure observed in the meteors are similar to that of the earth. They are solid bodies developed out of materials same as, or similar to, our planet. hence, this becomes yet another source of information about the interior of the earth.
      - Gravity Anomaly: Acceleration due to gravity 'g' varies according to the uneven distribution of mass of material within the earth.
      - Magnetic Surveys: Determining the Earth's magnetic field intensity distribution in the crustal portion can provide information about the distribution of materials.
      - Seismic Activities: Seismic activites can provide information about the interior of the earth.
    - - Ocean drilling
        
        Deep Ocean Drilling Project: The Deep Sea Drilling Project (DSDP) was an ocean drilling project operated from 1968 to 1983. DSDP provided crucial data to support the seafloor spreading hypothesis and helped to prove the theory of plate tectonics. DSDP was the first of three international scientific ocean drilling programs that have operated over more than 40 years. It was followed by the Ocean Drilling Program (ODP) in 1985, the Integrated Ocean Drilling Program in 2004 and the present International Ocean Discovery Program in 2013
        
        The International Ocean Discovery Program (IODP) is an international marine research collaboration dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The research enabled by IODP samples and data improves scientific understanding of changing climate and ocean conditions, the origins of ancient life, risks posed by geohazards, and the structure and processes of Earth's tectonic plates and uppermost mantle.
        
        Integrated Ocean Drilling Project: The Integrated Ocean Drilling Program (IODP) was an international marine research program. The program used heavy drilling equipment mounted aboard ships to monitor and sample sub-seafloor environments. With this research, the IODP documented environmental change, Earth processes and effects, the biosphere, solid earth cycles, and geodynamics.
      - Observing through surface rocks and rocks gathered from mining or drilling
      - Molten material thrown onto earth's surface during volcanic eruption forms another source of obtaining direct information