Lithosphere and geomorphology. Lithosphere.
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The 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.
Rift valleys – East African Rift Valley
Mid- oceanic ridges – Mid-Atlantic ridge
Fold mountains – Himalayas
Horizontal faults – San Andreas in USA
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).
· stress was built up for a long time
· focus is near the surface
· 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
· 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.
Areas 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 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)
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
Oceanic floor - continental shelf, continental slope, abyssal plain, seamounts, mid-oceanic ridges,volcanic islands and trenches
Oceanic platforms – the biggest part of ocean’s floor, they are called basins, e.g. Brazil, Argentine – south-west part of Atlantic ocean
Oceanic 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
Igneous rock-created by crystallization of silicate minerals, water and various gases consist of magma or lava.
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
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
Many forms of it can be a disaster for people.e.g. landslides, avalanches, earthquakes, volcanoes, soil erosion, etc.
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
smallest point of certain area.
Smaller areas are parts of larger ones - riverbed - flat - valley - mountain range – continent
– Mechanical (physical) weathering
– Chemical weathering
– Biological weathering
Carbonation: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 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.
Freeze-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 pressure
transportational or any mixture of these.
waning slope (concave)
waxing slope (convex)
mass (water and sediment)
energy (re-radiated heat)
mass (water regolith)
very slow – soil creep
fast – avalanche
dry – rock fall
fluid (wet) – mud flow
- 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
-short fall - produces a straight scree
-long fall - produces a concave scree
- rockslide – schist, mica
a) downslope force > the resistance (friction and cohesion)
b) material moves downslope after a shear failure
-dry avalanche = newly fallen snow falls off older snow – mainly in winter
-wet avalanche = partially melted snow (triggered by skiing) – in spring
Many landforms are results of glacial erosion and deposition.
cold periods – glacial – ice advanced southwards
warm periods – interglacial – ice retreated northwards
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.
Precipitation, meltwater, sunlight, frost shaterring sediments
Storage of glacier ice
Meltwater, ice, rock debris, water(gas)
Zone of accumulation(inputs>outputs) – glacier is growing, snowfall>melting
Zone of abalation (outputs>inputs)- glacier is shrinking and retreating, melting>accumulation
- can be brought:
on the surface of the glacier
within the glacier
along the glacier