2 LithosphereThe Earth consist of the crust, the mantle and the core. Lithosphere is created by the Earth’s crust and solid mantle. It lies upon the plastic mantle rock - astenosphere. Lithosphere is studied by geology. It is the science which study the origin, structure, composition and history of the Earth.
3 Lithosphere-crust:The crust is the outer layer which is thin and rigid. It floats on the semi-molten rock mantle. It can be divided into two main types continental crust and oceanic crust.Continental crust (150 – 250 km thick) – granitic crust because it consist of SiAl(silica & aluminum)-, covers the land surface, the base of land mass, it is thicker and lighter than oceanic crustOceanic crust – basaltic crust because it consist of SiMg (silica & magnesium), granitic layer missing cover the floor of world’s ocean
4 In the core of the Earth is radioactive decay from which the convection currents escape towards the surface. They tear the crust apart and dividing it into huge fragments – tectonic plates (crustal plates) – moving away from each other(divergence) or being pushed together (convergence).Crustal plates are pushed across the Earth’s surface at 50mm/y.Continental drift – process- continents constantly changed position and size.Major tectonic plate: Eurasian, North American, South American, African, Pacific, Nazca, IndoAustalian, Antarctic, Phillipine
6 Crustal plates can converge, diverge or collide Crustal plates can converge, diverge or collide.We know 3 main types of plate boundaries according to the direction and movement of the plates.Diverging(constructive) – forced apart and new crust is created between (e.g. under the ocean – magma reaching the sea floor producing new oceanic crust) - Mid Atlantic Ridge (Europe is moving away from North America)Converging( destructive) – one plate collides with another, slides under the other (e.g. heavier oceanic plate slides below the lighter continental plate- subduction zone ) – Nazca plate sinks under the South America plateSlipping – 2 plates move horizontally ”slip” past one other – The Indian plate collide with the Eurasian plate to form the HimalayasPlate boundariesRift valleys – East African Rift ValleyMid- oceanic ridges – Mid-Atlantic ridgeFold mountains – HimalayasHorizontal faults – San Andreas in USA
11 Region where the Earth’ lithosphere forms, are typical for huge seismic and volcanic activity, tectonic movements and endogenic processes which take place within the Earth.Tectonic movements- mechanical movements of the crust caused by pressure, tension of gravitation, e.g. mountain folding
12 Tectonic forces (movements) create many crustal failures: faults and folds faulting usually occurs during an earthquakeFault - fracture in a rock which involves a movement along one side or both sides.Shift - total movementThrow - vertical displacementsHeave - horizontal displacements
13 Normal fault - result of a tension, strata are pulled apart, one side of it is thrown down - increase of land area (divergence)
14 Reverse (thrust) fault - result of a compression, one side of the fault plain is thrust over the other (convergence) - overlapping of the strata and the surface area is decreased, e.g. steep slopes are formed of more resistant rocks, gentle slopes are found on softer rocks that are thrown down (by erosion)
15 Wrench (tear) fault - movement is horizontal but the fracture is vertical, nearby plate boundaries (product of an earthquake)
16 Landforms produced by faults: Horst = upland area bounded by low ground either side (fault scarps)a) uplift of a blockb) depression of surrounding lande.g.: Harz Mts., Black ForestExtensive horst produce plateau areas (block mountains). Further Earth movements tilt the blocks = tilted blocks = they are divided by faults into subsided (wide deep basins) and elevated sections (mountains).Rift valley (graben) = reverse of a horst, it´s formed by tension, compression or parallel faults and accompanied by horsts on either side, also can be formed nearby plate boundaries where the plates are pulling apart (e.g. East African Rift Valley).
17 folding occurs when layers of rock are distorted but not fractured Fold - distorted layers of rockSimple fold - anticline + synclineRecumbent fold - crumpled several timesAsymmetric foldOver fold
18 Earthquakes – seismic activity - tremors or ground movements caused by shock waves => occur normally at plate boundaries. Plate movement causes stress to build up within the crustal rocks until the rocks break along the line of a fault or cracks in the Earth´s crust.Actual movement = few cms but the sudden release of seismic (earthquake) energy can be enormousfocus - the point at which the rocks break within the crust. This may be some distance below the surface and the seismic energy emitted from the focus travels in all directions as seismic waves.epicentre.- the point on the Earth´s surface above the focusMore powerful earthquake is when:· stress was built up for a long time· focus is near the surface
19 Each year - thousands of earthquakes => few are centred near populated areas and strong enough to cause loss of lives - primary effects (from the violent shaking of the ground during an earthquake), e.g.· buildings may collapse killing people inside them,· shattered window glass may shower on to the streets below· huge cracks may open in the ground· roads may be damaged· water pipes and (electricity) mains may be cut offPrimary effects can generate secondary effects, e.g.· deaths because of food and water shortage· fires _ gas or oil leaking from fractured pipes· diseases _ lack of medical care and clean drinking water· tsunamis _ huge waves caused when earthquake occurs under the sea (1000 kph in open water, 65kph close to land + 15 m high). Created by displacing of the seabed (seafloor) => great damages to coastal areas.Geomorphological effects = land movements, tsunami, landslides, avalanches.
22 Volcanoes – volcanic activity Geothermal heat is released from the Earth´s core at the surface mainly through volcanoes.Magma pours onto the surface as lava – acid & basic.Acid lava volcano - mainly steep-sided, common along destructive plate boundaries, Magma - melting of basaltic oceanic crust and marine sediments, (e.g. volcanoes of Phillipines)Basic lava volcano - common along constructive plate boundaries, magma - basalt arising directly from the mantle, e.g. Mauna Loa in HawaiiGeothermal activityAreas with geothermal activity = crust is thin and magma is present at quite shallow depth-magma heats rocks above it (350°C at a depth of less than 5 km). Percolating groundwater is heated and then driven upwards by convection through cracks in the crust. Superheated waterbegins to boil closer to the surface and then is emitted onto the surface -· fumerole (superheated water turned to steam because of the sudden drop in pressure)· mudpool (bubbling pool of mud – liquefied soil where steam condenses near surface)· hot spring (superheated water + cold groundwater = hot spring at the surface)· geyser (regular eruption of hot water and steam, e.g. geysers in New Zealand)
26 Endogenic processes processes within the Earth Platforms - shields and tables - basic building elements of all the continents - The older the platform,the smaller the relief!Mobile orogenic zones- fold (range) mountains from Paleozoic, Mesozoic and Tertiary agesLand massShields - cores of the land mass, e.g. old Scandinavian, Canadian, African, Australian shield created by old igneous (granite) and metamorphic (marble) rocksTables - parts of platforms where older fold parentn rock was covered by younger (sedimentary) rocks - plains (East-European)Orogenic zones = determined by faults, originated in platform rims or in between them -mountain folding activityOceanOceanic floor - continental shelf, continental slope, abyssal plain, seamounts, mid-oceanic ridges,volcanic islands and trenchesOceanic platforms – the biggest part of ocean’s floor, they are called basins, e.g. Brazil, Argentine – south-west part of Atlantic oceanOceanic mobile zones - midoceanic ridges, long and narrow mountain ranges, somewhere occurring above the sea level as islands (Pacific Ocean), their length is about 45 000 km e.g. Mid-Atlantic Ridge
27 RocksIn the upper part of lithosphere we can find all the chemical elements. There are mostly silicate minerals which are combination of oxide, silicon and some other metals – micarocks - composition of minerals or organic remainsigneous rockssedimentary rocksmetamorphic rocksMetamorphic rocks - is formed by pressure and extreme heat applied to existing rocks within the earth’s crust causing them to change their mineral structure and texture. E.g marble, gneiss
28 Igneous rock-created by crystallization of silicate minerals, water and various gases consist of magma or lava.According to the presence of SiO2, rocks are divided into:- acid, e.g. granite,- neutral, e.g. andesite,- basic, e.g. basalt,
29 Sedimentary rocks -is formed by deposition of rock particles that have been eroded. Mechanical and chemical disruption of rocks is called weathering.- Mechanical weathering = disintegration of rocks by the influence of different temperatures, frost or organism´s activity.- Chemical weathering = rocks are decomposited by air and water (by chemical processes) and changed into rocks of different nature compared to the previous ones. e.g sandstone, limestone, dolomite
30 Metamorphic rocks - is formed by pressure and extreme heat applied to existing rocks within the earth’s crust causing them to change their mineral structure and texture. E.g marble, gneiss
31 Geomorphology- is science about the Earth’s relief. It studies the formation, evolution and character of relief and its forms.-it is a landmark between solid lithosphere + pedosphere and liquid hydrosphere + gaseous atmosphereRelief (Georelief) - complex of shapes of the Earth’s surface, it is created by geomorphological processes – many forms of georelief e.g. slopes, valley, mountains, basins, lowlands, plateaux, plains, etc. Relief also influences other parts of the Earth e.g. flora, fauna, climate, construction of buildings, agriculture, etcMany forms of it can be a disaster for people.e.g. landslides, avalanches, earthquakes, volcanoes, soil erosion, etc.The most basic feature of the relief is – altitude. Also there are many others:descend (slope) line – a line perpendicular to countours (contour lines)aspect – orientation to points of the compass (cardinal points) e.g. southern aspect receives more insolationcrest line – line joining places of a crest, places of the highest altitude upon a crestvalley line – line joining places of a valley, places of the lowest altitude within a valleyVertical segmentation of relief - vertical difference (meters) between the highest and thesmallest point of certain area.Horizontal segmentation of relief - the number of valley linesHierarchy of relief formsSmaller areas are parts of larger ones - riverbed - flat - valley - mountain range – continent
32 Weathering- decomposition and disintegration of rocks in situ (in the same place)- breaking down of rock into smaller components at or near the Earth´s surface3 types of weathering:– Mechanical (physical) weathering– Chemical weathering– Biological weatheringChemical weathering = decomposition of a rock, rocks are broken down by chemical reactions e.g. kaoliniteCarbonation:Rainwater absorbs carbon dioxide (CO2) as it falls through the air and soaks through the soil. This makes is acidic. It will attack rocks composed of calcium carbonate (CaCO3) e.g limestoneOxidation: Metals and metallic minerals (Fe) in rocks combine with oxygen (O2) from the air to form another substance. Rocks which contained of iron are especially weathered by this process.Hydrolysis: Some rock minerals combine with rainwater and break down into other chemical forms. This process of hydrolysis is important in producing sand and clay when water (H2O) combines granite.Mechanical (physical) weathering - disintegration of a rock, rocks break up due to stress e.g. screeFreeze-thaw (ice crystal growth or frost shattering) – water expands by 1/10 when it freezes (below 0°C) – ice crystals in a rock grow and then a rock is splitted as a result of the pressureBiological weathering (biotic forces) - mechanical + chemical weathering e.g plants´ roots, animals, etc.
33 Slope processes Slope - any part of the solid land surface. Slope - an inclined surface or hillslope- an angle of inclination or slope angleSurfaces can be:sub-aerial (exposed)sub-marine (underwater)aggradational (depositional)degradational (erosional)transportational or any mixture of these.Geography (geomorphology) studies the hillslope = area between the watershed and the baseSlope form = the shape of the slope in cross-sectionSlope processes = activities acting on the slopesSlope evolution = development of slopes with timeEndogenic processes occur within the Earth (tectonic forces)
34 Exogenic processes operate at/near the Earth´s surface (weathering/erosion, mass movements) large-scale movement of the Earth’s surface without a moving agent(river, glacier) e.g. rockfall, landslide, mudflow, avalancheThe simplest model of slope form:waning slope (concave)scree slopecliffwaxing slope (convex)Slopes - an open system - „active“ processes that shape „passive“ materials:Inputs:energy (insolation)mass (water and sediment)Outputs:energy (re-radiated heat)mass (water regolith)
35 Mass movements- large-scale movement of the Earth’s surface without a moving agent(river, glacier, ocean wave), type of exogenic processesMass movement:very slow – soil creepfast – avalanchedry – rock fallfluid (wet) – mud flowMass movement on the slope is determined by:1. gravity- it can move the material down slope - slide component- it holds the particle to the slope - stick component2. slope angle – the downslope movement is proportional to the weight of the particle and to the slope angle3. pore pressure – water fills the spaces between the particles, lubricates them and pushes them apart under pressure, very important in movement of wet material on low-angle slopes
36 Types of mass movementSurface wash – takes place when soil’s infiltration capacity has been exceeded,in particular when the ground is frozen or heavily saturated, on the other hand, it might take place also in semi-arid and arid regions where particles’ size prevent percolationSheetwash – unchannelled flow of water over a soil surface, is capable of transporting material dislodged by rainsplacsh. On most slopes it breaks into areas of high velocity and areas of lower velocity.Throughflow – takes place when water moves down through the soil. It is chennelled into natural pipes in the soil, it gives the sufficient energy to transport material of considerable volume.Heave/creep – small – scale movement occurring mostly in winter.Talus creep – slow movement of fragments on a scree slopeRainsplash erosion – erosive effect of raindrops on hillslopeFalls - on steep slopes (>70°) weathered rocks are detached and fall due to gravity-short fall - produces a straight scree-long fall - produces a concave screeSlides - when the whole mass of material moves along a slip plane- rockslide – schist, mica- landslidea) downslope force > the resistance (friction and cohesion)b) material moves downslope after a shear failureSlumps - rotational slides on softer rocks (claystone) along a curved plane.Flows - continuous, fluent movements of fine, deeply weathered clay, saturated with water=> highly fluid, no cohesionAvalanches - rapid movements of snow and ice, rock and soil (debris avalanche) down a slope, very common in mountain areas.-dry avalanche = newly fallen snow falls off older snow – mainly in winter-wet avalanche = partially melted snow (triggered by skiing) – in spring
38 Glaciation– is formation of glaciers in certain areasMany landforms are results of glacial erosion and deposition.2 main phases:cold periods – glacial – ice advanced southwardswarm periods – interglacial – ice retreated northwardsAccumulation of ice – when a mass of ice is formed in a valley – formation of a glacierIt can flow slowly downhill because of influence of gravity. E.g largest glaciers – in the Himalayas, Rocky mountains and the AlpsContinuous mass of ice covering a large land surface – ice sheet.
39 Glacier as a systemInputs:Precipitation, meltwater, sunlight, frost shaterring sedimentsProcesses:Storage of glacier iceOutput:Meltwater, ice, rock debris, water(gas)A glacier moves into warmer areas where the ice is melt – 2 parts:Zone of accumulation(inputs>outputs) – glacier is growing, snowfall>meltingZone of abalation (outputs>inputs)- glacier is shrinking and retreating, melting>accumulation
40 Glacial erosion and transport Cold polar glaciers - move very slowlyWarm, temperate glaciers – move faster because meltwater helps to reduce the frictional forceGlaciers can transport large amounts of rock debris – moraine- can be brought:on the surface of the glacierwithin the glacieralong the glacierCorrie – semi-circular, steep-side basin cut into the side of a mountain or at the head of a valley.Corrie lake(tarn)- glacier that has come into valley and interglacial period it melted – only water remained – glacial lakesPyramid peak – 3-4 corries cutting back on each otherU-shaped valley – created by a glacier moving downslopesHanging valley – tributary glaciers flow into the main larger one. After malting these glaciers leave the valley hanging above them
41 LandformsDrumlins – egg-shaped hills, formed under the glacuier by ice that has moulded boulder clayu into this distinctive shapeEskers – long ridges of deposited material, formed by deposition from meltwater streams which flow under the ice.Erratics – boulders transported over a long distance and deposited by glaciers.Kames – small mounds of debris within ice, after thawing that dropped on the groundKettle holes – detached blocks of ice, after melting water5 is in a hollow and could be lost by evaporation an infiltrationOutwash plains – as meltwater streams flow away from the glacier, they begin to sort out material and deposit their load.