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Deep Analysis and Research on Geomorphology which is the branch of Physical Geography
Typology: Lecture notes
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Lecture Notes on GEOMORPHOLOGY
( shape, form of land)
•Study of landforms & the processes that shape them •Why the landscapes look the way they do •Understand landform history & dynamics, so that one can predict future changes •Use field observation, physical experiment & numerical modeling
Fjord
Study of landforms & the processes that shape them
•Study of landforms & the processes that shape them •Why the landscapes look the way they do •Understand landform history & dynamics, so that one can predict future changes •Use field observation, physical experiment & numerical modeling
Landforms evolve in response to a combination of natural & man-made processes
Landscape built by tectonic uplift & volcanism
Practical applications :
Measuring the effects of climate change landslide prediction river control coastal protection
HISTORY
•Rivers are not only carriers of water , but also of sediment. •Water able to mobilize sediment & transport it downstream either as
Network of rivers
•Network of rivers forms a drainage system •Drainage systems adopt many patterns depending on topography & underlying geology
HILLSLOPE
•Soil, regolith & rock move down slope under the force of gravity via creep, slides & falls. •)n both terrestrial & submarine slopes
•Glaciers are effective agents of landscape change •Gradual movement of ice down a valley causes abrasion & plucking of the underlying rock. •Abrasion produces fine sediment, termed glacial flour. •The debris transported by the glacier, when the glacier recedes, is called a moraine. •Glacial erosion is responsible for U-shaped valleys, as opposed to V-shaped valleys of fluvial origin.
WEATHERING
•This results from mechanical wearing of rock by ice expansion, plant roots & the abrasive action of sediment •From chemical dissolution of rock •Weathering provides the source of the sediment transported by fluvial, aeolian or biotic processes. Also,it is the source of the chemicals, such as salt, dissolved in the ocean
SUBJECT
•More quantitative in recent years •)t is field-oriented •Uses maps and photo analysis
THE BASICS
•The delicate balance : dynamic equilibrium ȋexample: a glacial moraine re-adjusts to current conditions) •Exogenic process: climate •Endogenic: volcano
•Driving Forces: climate, gravity (isostasy), internal heat •Resisting: lithology, structure
•Changes in climate: source of instability •Take place at irregular intervals •Endogenic effect: average land=ͺͷm average ocean=͵. km deep •Larger continents are also taller •Bigger oceans are deeper •Continent-building=epeirogeny
Epeirogeny
•Surface topography is somehow related to the internal distribution of mass •)sostasy •(igh mountains must have low density material below •Tendency to restore equilibrium if there is an isostatic anomaly •Glacio-isostasy
Orogeny
•Deformation & plate tectonics •Tectonic geomorphology: deformation has an effect on landscapes •Active faults •Landforms used to explain the mechanics of deformation •Plate-margin analyses (California)
Volcanism
•)nternal variables control type of eruption & ensuing topography •Continents : tephra, welded tuff plus gases from explosive eruptions •Oceanic volcanoes have lava flows, not explosive •(awaii eruptions: the greatest known on Earth with 0.05 to 0.1 km3 per year •Calderas: depressions larger than ͳ. km
Climatic geomorphology
•Relationship between landforms & climate •Climates as a function of temp.-precipitation graph •Climate change & geomorphic response
Pleistocene Glaciation
•Triggering mechanisms: major volcanic event, astronomical motions, distribution of continents •Rapidity of significant climate change •Sea level fluctuation •Sea level: most important horizon in geomorphology
Some Manitoba elevations
•Brandon airport : ͶͲͻ m •Brandon at river: ͵͵ m •Riding Mountain : ͷ m •Dauphin : ͵ͲͶ m •Ashern : ʹ͵ m •Norway (ouse : 217 m •Thompson : ʹͳͷ m •Gillam : ͳͶͷ m
1.King Hieron gives a jeweller a bar of gold to make into a crown 2.When the crown was delivered, the king measured the mass. It had the same mass as the gold bar 3.The king is suspicious. He asks Archimedes. 4.A. notices that the amount of water that overflowed the tub was proportional to the amount of his body that was submerged
No one knows about density then Archimedes reasoned that 1.If the gold bar and the crown had the same mass , and 2.If both had the same volume , Then, the crown was pure gold
Density = weight in air / loss in weight when immersed in water or, weight of water displaced
Archimedes reasoned that The volume of water displaced by the crown should be the same as the volume of water displaced by the bar of gold However, the crown displaced twice the amount of water than the gold bar ( it had lower density, consisted of less dense material)
Water bridge, Germany
Lab on S.G. (GM – 1)
•Use the scale and glass tube to calculate specific gravities of a galena cube and a sample of coral limestone (typical rock on earth) •Both samples have about the same weight, but not the same volume
Isostasy
•Means Dzequal standingdz •Both land and ocean rest with equal weight on the underlying mantle of the earth •Land is made up of granite, but •Ocean floor is made up of basalt •Average elevation of land is about ͳ km •Average depth of ocean is ͵. km •Difference in elevation of 4.7 km!
•Average thickness of granitic crust is ͵Ͳ km •Average thickness of basaltic crust is ͷ km •Therefore, their densities are different •Granite is ʹ. g/cm͵ •Basalt is ͵.Ͳ g/cm͵ •Land sits higher because it is less dense •Both land and ocean sit with the same weight on the mantle
•The smallest the ocean the shallower
Examples of S.G.
•Mn = .Ͷ
•Cu, Ni = ͻ
•(g = ͳ͵.ͷ
•Pt, )r = ʹͳ - 22
•Ͷ distinct provinces: •The Precambrian Shield •The (udson Bay Lowlands
•The Manitoba Lowlands •The Southern Uplands •Pleistocene Glaciation: the last major surface-shaping event
The Precambrian Shield
•Flat, hummocky terrain with lots of rock outcrops •Rocks formed from ͵.ͷ b.y. ago •Started with volcanic islands over rift valleys with black smokers & associated metal deposits (Flin Flon, Snow Lake, Lynn Lake)
•Later, collision of continents resulted in the formation of mountains •Magma below the mountains precipitated deposits of titanium, lithium, cesium & tantalum •Where ancient continents collided lavas poured out from great depth bringing up deposits of nickel found along the Thompson Belt
Hudson Bay Lowlands
•Low elevation, undulating plain •Elevated up to ͳͷͲm by glacial rebound •Major element of relief: strandlines marking former beaches •Churchill & Nelson Rivers have cut through the till & bedrock. Banks up to ͷͲm high
•Sedimentary rocks below the till: layers get thicker towards center of Hudson Bay •On the shore, sediments are ~ ͻͲͲ m thick •Under the bay should reach ʹ km thickness
•During the Paleozoic, it was under a tropical sea. Marine lives were turned into stone ȋfossilsȌ which is now limestone (Tyndall Stone) •When sea dried up, deposits of halite, gypsum & potash formed
Manitoba Lowlands
•We are within this area •Western edge is the Manitoba Escarpment - up at least 8 m
Southwest Uplands
•A plateau ~ ͷͲͲ m higher than the Lowlands •Debris left over after glaciers melted •Dauphin & Swan river valleys dug in afterwards
Pleistocene Glaciation: plenty of evidence to see
•Unusual flatness of Manitoba & Canada in general •Polished rock surfaces with scratch marks •Glacial till •Erratics
•Latitude: use stars •Longitude: no one could figure out ȋͳʹ million prizeȌ The answer: the clock •͵Ͳ degrees equals ʹͶ hours, then ͳ hour for ͳͷ degrees of longitude •Townships created by accurate surveying
Topographic maps
•ͳ:ʹͷͲ,ͲͲͲ •ͳ:ͷͲ,ͲͲͲ •ʹ quadrangles ȋrectanglesȌ along lines of latitude •Canada has ~ ͳͲ million kmʹ area •Modern topographic maps compiled from aerial photographs •Surveyed by triangulation
•Photogrammetric map plotter •Map scale: relationship between a measured distance on the map and the actual distance on the earthǯs surface •Relief: use contour lines ȋgive you a sense of ͵D •Air photographs made with a ͶͲ % overlap. Use a stereoscope for a ͵D study
Stereoscope
•Because people see objects with 2 eyes, they can perceive images in 3 dimensions •These ʹ simultaneous images are transmitted to the brain, which combines them to produce a ͵D impression of the object for depth perception •The eyes produce ͵D vision by two separate movements: they focus & they converge •One needs to Dzsee throughdz the paper to see in stereoscopic view
•)n order to have a stereoscopic effect, one need two pictures of the same location taken from two points of view •There is an exaggerated height or depth
MASS MOVEMENT
•Surface features •Role of mass movement in the evolution of slope processes
Main concept
•A universal erosional process •Factors affecting are:
