Lithosphere and geomorphology

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Lithosphere and geomorphology
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Lithosphere

• The Earth consist of the crust, the mantle and
  the core. Lithosphere is created by the Earths
  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.

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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
  crust
• Oceanic crust basaltic crust because it consist
  of SiMg (silica magnesium), granitic layer
  missing cover the floor of worlds ocean

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• 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 Earths
  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

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Map of tectonic plate
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• 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 plate
• Slipping 2 plates move horizontally slip past
  one other The Indian plate collide with the
  Eurasian plate to form the Himalayas
• Plate boundaries
• Rift valleys East African Rift Valley
• Mid- oceanic ridges Mid-Atlantic ridge
• Fold mountains Himalayas
• Horizontal faults San Andreas in USA

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Tectonic plate
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Diverging, converging and slipping boundaries
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East African Rift Valley and Mid-Atlantic Ridge
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Himalayas and San Andreas in USA
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• 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

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Tectonic forces (movements) create many crustal
failures faults and folds

• faulting usually occurs during an earthquake
• Fault - fracture in a rock which involves a
  movement along one side or both sides.
• Shift - total movement
• Throw - vertical displacements
• Heave - horizontal displacements

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• Normal fault - result of a tension, strata are
  pulled apart, one side of it is thrown down -
  increase of land area (divergence)

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• 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)

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• Wrench (tear) fault - movement is horizontal but
  the fracture is vertical, nearby plate boundaries
  (product of an earthquake)

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Landforms produced by faults

• Horst upland area bounded by low ground either
  side (fault scarps)
• a) uplift of a block
• b) depression of surrounding land
• e.g. Harz Mts., Black Forest
• Extensive 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, its
  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).

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• folding occurs when layers of rock are distorted
  but not fractured
• Fold - distorted layers of rock
• Simple fold - anticline syncline
• Recumbent fold - crumpled several times
• Asymmetric fold
• Over fold

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Earthquakes seismic activity

• - tremors or ground movements caused by shock
  waves gt 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 Earths crust.
• Actual movement few cms but the sudden release
  of seismic (earthquake) energy can be enormous
• focus - 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 Earths surface
  above the focus
• More powerful earthquake is when
• stress was built up for a long time
• focus is near the surface

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• Each year - thousands of earthquakes gt 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
  off
• Primary 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) gt great
  damages to coastal areas.
• Geomorphological effects land movements,
  tsunami, landslides, avalanches.

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Volcanoes volcanic activity

• Geothermal heat is released from the Earths 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 Hawaii
• Geothermal activity
• Areas with geothermal activity crust is thin
  and magma is present at quite shallow depth-
• magma heats rocks above it (350C at a depth of
  less than 5 km). Percolating groundwater is
  heated and then driven upwards by convection
  through cracks in the crust. Superheated water
• begins 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)

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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 ages
• Land mass
• Shields - cores of the land mass, e.g. old
  Scandinavian, Canadian, African, Australian
  shield created by old igneous (granite) and
  metamorphic (marble) rocks
• Tables - 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 activity
• Ocean
• Oceanic floor - continental shelf, continental
  slope, abyssal plain, seamounts, mid-oceanic
  ridges,volcanic islands and trenches
• Oceanic platforms the biggest part of oceans
  floor, they are called basins, e.g. Brazil,
  Argentine south-west part of Atlantic ocean

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Rocks

• In 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 mica
• rocks - composition of minerals or organic
  remains
• igneous rocks
• sedimentary rocks
• metamorphic rocks
• Metamorphic rocks - is formed by pressure and
  extreme heat applied to existing rocks within the
  earths crust causing them to change their
  mineral structure and texture. E.g marble, gneiss

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• 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,

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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 organisms
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
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Metamorphic rocks - is formed by pressure and
extreme heat applied to existing rocks within the
earths crust causing them to change their
mineral structure and texture. E.g marble, gneiss
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Geomorphology

• - is science about the Earths 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
  atmosphere
• Relief (Georelief) - complex of shapes of the
  Earths 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, etc
• Many 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 insolation
• crest line line joining places of a crest,
  places of the highest altitude upon a crest
• valley line line joining places of a valley,
  places of the lowest altitude within a valley
• Vertical segmentation of relief - vertical
  difference (meters) between the highest and the
• smallest point of certain area.
• Horizontal segmentation of relief - the number of
  valley lines
• Hierarchy of relief forms

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Weathering

• - decomposition and disintegration of rocks in
  situ (in the same place)
• - breaking down of rock into smaller components
  at or near the Earths surface
• 3 types of weathering
• Mechanical (physical) weathering
• Chemical weathering
• Biological weathering
• Chemical weathering decomposition of a rock,
  rocks are broken down by chemical reactions e.g.
  kaolinite
• CarbonationRainwater 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 limestone
• Oxidation 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. scree
• Freeze-thaw (ice crystal growth or frost
  shattering) water expands by 1/10 when it
  freezes (below 0C) ice crystals in a rock grow
  and then a rock is splitted as a result of the
  pressure
• Biological weathering (biotic forces) -
  mechanical chemical weathering e.g plants
  roots, animals, etc.

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Slope processes

• Slope - any part of the solid land surface.
• Slope - an inclined surface or hillslope
• - an angle of inclination or slope
  angle
• Surfaces 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 base
• Slope form the shape of the slope in
  cross-section
• Slope processes activities acting on the slopes
• Slope evolution development of slopes with time

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• Exogenic processes operate at/near the Earths
  surface (weathering/erosion, mass movements)
  large-scale movement of the Earths surface
  without a moving agent(river, glacier) e.g.
  rockfall, landslide, mudflow, avalanche
• The simplest model of slope form
• waning slope (concave)
• scree slope
• cliff
• waxing 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)

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Mass movements

• - large-scale movement of the Earths surface
  without a moving agent(river, glacier, ocean
  wave), type of exogenic processes
• Mass movement
• very slow soil creep
• fast avalanche
• dry rock fall
• fluid (wet) mud flow
• Mass 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
  component
• 2. slope angle the downslope movement is
  proportional to the weight of the particle and to
  the slope angle
• 3. 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

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Types of mass movement

• Surface wash takes place when soils
  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 percolation
• Sheetwash 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 slope
• Rainsplash erosion erosive effect of raindrops
  on hillslope
• Falls - on steep slopes (gt70) weathered rocks
  are detached and fall due to gravity
• -short fall - produces a straight scree
• -long fall - produces a concave scree
• Slides - when the whole mass of material moves
  along a slip plane
• - rockslide schist, mica
• - landslide

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Glaciation

• is formation of glaciers in certain areas
• Many landforms are results of glacial erosion
  and deposition.
• 2 main phases
• cold periods glacial ice advanced southwards
• warm periods interglacial ice retreated
  northwards
• Accumulation of ice when a mass of ice is
  formed in a valley formation of a glacier
• It can flow slowly downhill because of influence
  of gravity. E.g largest glaciers in the
  Himalayas, Rocky mountains and the Alps
• Continuous mass of ice covering a large land
  surface ice sheet.

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Glacier as a system

• Inputs
• Precipitation, meltwater, sunlight, frost
  shaterring sediments
• Processes
• Storage of glacier ice
• Output
• Meltwater, ice, rock debris, water(gas)
• A glacier moves into warmer areas where the ice
  is melt 2 parts
• Zone of accumulation(inputsgtoutputs) glacier
  is growing, snowfallgtmelting
• Zone of abalation (outputsgtinputs)- glacier is
  shrinking and retreating, meltinggtaccumulation

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Glacial erosion and transport

• Cold polar glaciers - move very slowly
• Warm, temperate glaciers move faster because
  meltwater helps to reduce the frictional force
• Glaciers can transport large amounts of rock
  debris moraine
• - can be brought
• on the surface of the glacier
• within the glacier
• along the glacier
• Corrie 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 lakes
• Pyramid peak 3-4 corries cutting back on each
  other
• U-shaped valley created by a glacier moving
  downslopes
• Hanging valley tributary glaciers flow into the
  main larger one. After malting these glaciers
  leave the valley hanging above them

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Landforms

• Drumlins egg-shaped hills, formed under the
  glacuier by ice that has moulded boulder clayu
  into this distinctive shape
• Eskers 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 ground
• Kettle holes detached blocks of ice, after
  melting water5 is in a hollow and could be lost
  by evaporation an infiltration
• Outwash plains as meltwater streams flow away
  from the glacier, they begin to sort out material
  and deposit their load.