Lecture Notes on GEOMORPHOLOGY ( shape, form

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 •Denudation occurs by erosion & mass wasting which produces sediment •Other processes : Subsidence due to physical changes in rocks below surface •All processes influenced by climate, ecology & human activity Landscape built by tectonic uplift & volcanism •Denudation occurs by erosion & mass wasting which produces sediment •Other processes : Subsidence due to physical changes in rocks below surface •All processes influenced by climate, ecology & human activity Practical applications : Measuring the effects of climate change landslide prediction river control coastal protection HISTORY

•11 cent. Chinese scholar Shen Kuo observed marine fossil shells in exposed rock. Concluded that long before it had formed along the seashore, then moved upwards. He also observed petrified bamboo preserved in a dry area today. •The first geomorphic model was the “cycle of erosion” by William Morris in the late 18th cent. According to this, a river is depicted cutting a valley deeper all the time eventually the terrain would flatten at a lower elevation. PROCESSES •Today, scientists base studies on quantitative analysis of interconnected processes, such as •The contribution of solar energy •The rates of steps of the hydrologic cycle •Plate movement rates from geophysics to compute the age & expected fate of landforms •Weathering & erosion of the land Threshold & Linkages •Threshold concept with complex response. Parameters pushed beyond equilibrium conditions •Gradual changes may reach a threshold: too much rain can lead to a landslide •Failure to consider the factor of time •Once a threshold is crossed, the system develops a new equilibrium Complex responses •During glacial times, sea level changes will affect the mouths of rivers •Long periods of time to reach a final adjustment Process Linkage •A chain reaction of responses to an altered situation •Operates on the domino principle •Example: Mt.St. Helens’ eruption led to a mudflow •Dominant responses shifted progressively downstream, into rivers, hydrology, lakes, biological influences, etc. Primary surface processes responsible for most topographic features include • Wind Waves •Weathering •Mass wasting •Groundwater •Surface water •Glaciers • Tectonism • Volcanism

RIVERS •Rivers are not only carriers of water, but also of sediment. •Water able to mobilize sediment & transport it downstream either as • bedload • suspended load • dissolved load •Rivers get bigger merging with other rivers 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. •In both terrestrial & submarine slopes GLACIAL •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 •It is field-oriented •Uses maps and photo analysis THE BASICS •The delicate balance : dynamic equilibrium (example: a glacial moraine re-adjusts to current conditions) •Exogenic process: climate •Endogenic: volcano

•Driving Forces: climate, gravity (isostasy), internal heat •Resisting: lithology, structure 2. Internal forces & climate •Changes in climate: source of instability •Take place at irregular intervals •Endogenic effect: average land=875m average ocean=3.7 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 •Isostasy •High 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 •Internal variables control type of eruption & ensuing topography •Continents : tephra, welded tuff plus gases from explosive eruptions •Oceanic volcanoes have lava flows, not explosive •Hawaii eruptions: the greatest known on Earth with 0.05 to 0.1 km3 per year •Calderas: depressions larger than 1.6 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

Eustatic changes •Isostatic movements determined by gravity •Glaciations keep water from returning into the oceans •Thus, ocean volume shrinks & sea level lowers •Melting glaciers will also result in isostatic uplift of continents Shoreline processes •In coastal regions: river terraces result when alternating cutting & filling are initiated by fluctuating sea level •Vertical movements on land result from volcanic activity, tectonic processes, uplift with faulting deformation

ALTITUDE, SPECIFIC GRAVITY, ISOSTASY Remember : Archimedes Altitudes: mean sea level = 0 m •CANADA • •Toronto : 76 m CN Tower : 553 m • •Winnipeg : 232 m -→ lowest in the Prairies • • Baldy Mt : 832 m -→ highest in Manitoba •Calgary : 1,050 m • •Montreal : 0 m

Edmonton : 668 m

WORLD •Mexico City : 2,420 m (highest capital) • •Highest N. America : St. Elias at ~ 6 km (Alaska – Yukon border) • •Highest mountain in the world : Mt. Everest at ~ 8,550 m • •Deepest trench in the world’s oceans : - 11 km Rivers in Manitoba •Source of Red River : 290 m • drop of 73 m •Source of Assiniboine river : 640 m

Mouth of Red River: 217 m Mouth at The Forks:

230 m

•

drop of

410 m

Some Manitoba elevations •Brandon airport : 409 m •Brandon at river: 363 m •Riding Mountain : 756 m •Dauphin : 304 m •Ashern : 263 m •Norway House : 217 m •Thompson : 215 m •Gillam : 145 m

Specific gravity / Archimedes principle or Law of buoyancy 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 displacement: an object immersed in water will displace a volume of water equal to the volume of that object •Water Bridge: A ship always displaces an amount of water that weighs the same as the ship Water bridge, Germany

How to measure S.G.

•Every floating object is pushed upwards by a buoyant force that is equal to the weight of the displaced fluid •The object sinks until it displaces a volume of fluid that has the same mass as the entire floating object

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 “equal standing” •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 1 km •Average depth of ocean is 3.7 km •Difference in elevation of 4.7 km !

•Average thickness of granitic crust is 30 km •Average thickness of basaltic crust is 5 km •Therefore, their densities are different •Granite is 2.6 g/cm3 •Basalt is 3.0 g/cm3 •Land sits higher because it is less dense •Both land and ocean sit with the same weight on the mantle

Conclusions •The bigger the continent, the higher the mountains •The Himalayas are in the biggest continent •The smallest mountains are in Australia •The bigger the ocean the deeper it is

•The smallest the ocean the shallower Examples of S.G. •

H2O = 1 Consider we measure Equal Volumes of all substances •Li = 0.5 • •wood • •Al = 2.6 Most rocks = 2.65 • • MnO2, Sphalerite, Chalcopyrite = 4 • • Iron ore = 4 - 5 •------------------------------------------ over 5 -------------• • •Fe, Sn, Zn, steel = 7 Galena, Cassiterite = 7 • •Mn = 7.4 • Bronze, Brass = 8 • •Cu, Ni = 9 •----------------------------------------------- over 10 • •Ag = 10 • •Pb = 11 • • • •Hg = 13.5 •--------------------------------------------- over 15 • • •W, U, Au = 19 • •Pt, Ir = 21 - 22

Physiographic provinces of Manitoba •4 distinct provinces: •The Precambrian Shield •The Hudson 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 3.5 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 150m by glacial rebound •Major element of relief: strandlines marking former beaches •Churchill & Nelson Rivers have cut through the till & bedrock. Banks up to 50m high •Sedimentary rocks below the till: layers get thicker towards center of Hudson Bay •On the shore, sediments are ~ 900 m thick •Under the bay should reach 2 km thickness •During the Paleozoic, it was under a tropical sea. Marine lives were turned into stone (fossils) 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 ~ 500 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

•The Pas Moraine •Eskers

MAP & AIR PHOTO INTERPRETATION •Latitude: use stars •Longitude: no one could figure out (12 million prize) The answer: the clock •360 degrees equals 24 hours, then 1 hour for 15 degrees of longitude •Townships created by accurate surveying Topographic maps •1:250,000 •1:50,000 •72 quadrangles (rectangles) along lines of latitude •Canada has ~ 10 million km2 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 earth’s surface •Relief: use contour lines (give you a sense of 3D •Air photographs made with a 40 % overlap. Use a stereoscope for a 3D study Stereoscope •Because people see objects with 2 eyes, they can perceive images in 3 dimensions •These 2 simultaneous images are transmitted to the brain, which combines them to produce a 3D impression of the object for depth perception •The eyes produce 3D vision by two separate movements: they focus & they converge •One needs to “see through” the paper to see in stereoscopic view •In 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: - saturation of slope material with water -freezing and thawing -- oversteepening of slopes --earthquakes

Types of mass movement •Rock falls •Debris flows •Landslides •Rock glaciers KARST •Limestone & gypsum affected •Not easily observed, because much of geomorphic work is below surface •No surface drainage (streams, rivers) •Underground drainage •Most likely to occur in temperate or tropical climates (need water)

Terminology •Multilingual,first described in Jugoslavia •Doline = sinkhole •Calcite, rarely dolomite (aragonite) •Also, gypsum and halite (100 X faster) •Porosity & permeability important •Presence of faults, fractures, joints increases permeability The Solution Process (CO2) •Calcium ion & bicarbonate ion dissolved in water

•Carbon dioxide is soluble in water •Colder water will dissolve more CO2 •Biogenic CO2 goes into solution, from plant roots respiration, also microbial action Equations •CO2 in water •forms carbonic acid •forms bicarbonate ion •calcium carbonate soluble in acidic water •CaCO3 dissolves & precipitates again into stalactites & stalagmites Solution Rates: the controlling factors •The most karst landforms in tropical climates with lush vegetation •Karst encourages growth of plants & enhances microbial activity that adds extra CO2 to the system •Runoff the most significant parameter controlling calcite dissolution, then the P of CO2, then water temperature •As water percolates from the surface downwards through fractures, the solution rates decrease with flow distance •70 % of limestone corrosion occurs within the first 10 m of the ground surface •Slow corrosion until fractures reach 1 cm in diameter (breakthrough). After that dissolution rates increase dramatically •The time required to reach breakthrough are very long (10,000 to a few million) Karst Hydrology & Drainage •Karst landforms are superimposed on a former fluvial landscape •Rivers lose water when some of the flow descends into swallow holes •Large part of the flow may follow a subsurface route •Mean annual floods in carbonate basins are considerably lower than in other rocks Karst Aquifers •Tracing of water with dyes •The underground system is a collection of conduits functioning like a 3-dimensional rivers Surface & Groundwater •Flow through conduits is the unique characteristic of karst hydrology •Karst water has a high hardness (rich in calcium +- magnesium) •Karst drainage is well organized Closed depressions:Dolines

•Sink or sinkhole •Can be tiny to huge depressions •From 10 m to 1 km in diameter •Depths of 2 m to 500 m •Circular or elliptical in plan view •No external drainage (only underground) •On surface, strongly pitted appearance •Densities may exceed 2,500 per km2 •Average 1 to 9 per km2 •Dolines are the fundamental element of karst Formation of solution sinkholes •Factors most conductive to the solutional dolines are: •Slope •Lithology & structure, such as joints •Vegetation & cover (the CO2 factor) Collapse dolines •Depressions initiated by solution that occurs beneath the surface •Growth of cavities particularly during floods & heavy rains •Rapid lowering of the water table •Lowering of the water table by human activities (mining) Doline morphometry •Karst originally thought to be controlled by climate alone •Also, by rock type •Studies show dependent on: •Groundwater recharge, permeability, regolith thickness & hydraulic gradient •Time is also a factor & joints in rock “Blind & Dry Valleys” •river eventually sink into the underground system •Rivers terminating at the cliff face occupy blind valleys Tower Karst •Steep-sided, cone-shaped residual hills •Pitted landscape •Towers called pepinos, haystack, mogotes •Asymmetric mogotes •The plains between towers rest near the water table •Many theories on tower karst formation

Limestone caves •Undergound features •Entrances or openings are called shafts or chimneys. Maybe more than 100m deep & 15 m wide •Caves terminate downwards •A spring maybe the termination point Passage morphology •Narrow, vertical slits called canyons or elliptical tubes •Canyons develop above water table, while tubes below the water table •Stalactites are made up of travertine. This is where calcite precipitates out of solution •Branch-work or maze pattern Origin of limestone caves •Highly complex mechanics •Depends of rock structure & changes in lithology •Some caves along rock contacts •Along flow routes of least resistance •Passages above, along or below water table •Also, the time factor Karst : summary •Requirements for karst: crystalline, high in calcite, intensely fractured •Humid & humid-tropical climates •Biogenic CO2 •Water diverted into the underground system •Flow controlled by orientation of fractures & interconnected cavities Karst landforms: summary •Most common: depressions (sinkholes) •In tropical karst: hills •In temperate karst: depressions •Caves may form above, below or along the water table Karst Chemistry •Acid water that dissolves limestone becomes so enriched in calcium and bicarbonate that it turns alkaline (the opposite of acid) and may actually begin precipitating calcite (to form stalactites & stalagmites) •Calcite + carbonic acid= Ca 2+ + HCO3 bicarbonate •A karst spring: source of a river Carlsbad Caverns,NM

•A World Heritage Site today •Was known as a small 27m - entrance pit which led to a dead-end passage (120 m long) •Cavers heard a wind coming out of the floor of the cave •Started digging in 1984 •Breakthrough into large passages was in 1986 •Over 160 km of passages •Depth of 450 m •5th largest in the world CENOTE •Sinkhole with water •In Yucatan peninsula, Mexico •Like rounded pools with clear water •May be linked to caves underneath •Not connected to underground rivers

Manitoba caves •Manitoba Speleological (cave) Society •Started surveying in 1987 •Over 250 caves located •A new park (N of Grand Rapids) proposed •Little Limestone Lake: azure-blue color British Columbia caves •Rocky Mountains: contain the most extensive areas of soluble rock in the province •Canada’s longest (20 km) & deepest (540 m) documented caves •Due to extreme weather, not studied well •Those on Vancouver Island: very abundant due to its association with temperate rain forest

Glacial Processes/Landforms •Most spectacular landscapes •Snow accumulates & metamorphoses into ice, then it moves •Snow has very low density & delicate hexagonal crystals •Freezing & remelting forms high-density ice (granular, or firn) •Anywhere from 13 to 80 m is needed to change snow into ice •The only air remaining in ice is trapped as air bubbles within the crystal (Remaining air makes snow/ice look white, if no air, then it is colorless) GLACIERS : EXTRAORDINARY LANDSCAPE – MAKERS Most important – powerful : Ice, 2 – 3 km thick glaciers

Last Ice Age devastated the pre-existing scenery of Canada Bulldozed the country taking away the hills flattening the mountains & digging up trenches over softer rock formations How did they do that? With only ice, much softer than rock When ice moves, it can only scratch the rock below if rocks stick at the bottom of the ice pile THE answer is : abrasion, plucking: ice melts into water that goes into cracks and freezes by expanding and breaking the solid bedrock around it, little by little into pieces that are incorporated into the moving mass of ice ALPINE – MOUNTAINS Horn, pyramid-like Cirques Arêtes Tarns Crevasses Hanging valleys with waterfalls

CONTINENTAL flat topography polished & scratched bedrock surface erratics roche moutonnee parallel lake boundaries (depressions, softer rock) Moraines – hills of glacial till Drumlins in groups from previous glaciations Eskers , kames , kame terraces ( all stratified) Lake Agassiz : 80,000 square miles Largest known fresh water lake

Temperate v. polar glaciers •Temperate glaciers: more active, some melting & refreezing •They move faster, erode more & carry greater load •Polar glaciers: less active •They move slow, erode less The mass balance -→ at the lower reaches of glaciers: •Ablation: processes that remove snow & ice, such as melting, evaporation, wind erosion, sublimation & the breaking off of large blocks of ice into bodies of standing water (culving) -→At the higher reaches of glaciers: •Accumulation: from snowfall, rain & the freeze-on of meltwater at the base Movement of glaciers •Two independent processes: •Internal deformation of the ice, called creep •Sliding of the glacier along its base and sides Fjord: most spectacular scenery •Preikestolen (Pulpit Rock), Norway

Also: Hanging valley

Other landforms: Esker, from sand in a river under glacier

Drumlin, usually in groups: “basket of eggs” topography

Kame Terrace: sand/gravel on top of glacier

Internal Motion •Ice behaves as a viscous liquid •Ice deforms as a plastic substance •The continuous deformation is the creep process that allows glacial ice to flow steadily under its own weight •Speed on ice surface is much higher than at depth •Velocity is highest along the central axis •In ablation zones, velocity decrease downglacier •In accumulation zones, velocity increases gownglacier Sliding •Sometimes high velocity at the sides of glaciers •Water can be present at the glacier bottom •Linked cavity system with water circulating Ice structures •Stratification •Crevasses develop perpendicular to direction of max. elongation of the ice - result of tension or flow over surface irregularities Summary •Snow accumulates & gets transformed by compaction, recrystallization, melting & re-freezing •When thickness reaches a critical size, it begins to move •Volumes of accumulation & ablation determine level of glacial activity

•Internal movement (creep) or sliding due to the presence of water Glacial landforms •Louis Agassiz : 1807 - 1873 •Father of Glaciology. Glacier = “God’s great plough” •Gave mostly French names to glacial phenomena. Also, America’s leading scientist •First person to realize Swiss landscape formed by glaciers. Came to Canada and confirmed that glaciers covered it as well •Lake Agassiz: named in 1879 Glaciers •e or mountain glaciers •Continental glaciers - Greenland, Antarctica today, throughout Canada during the last Ice Age •Each has its own characteristic processes & landforms Alpine glaciers •In BC, Alaska & Baffin & Arctic Islands The Pas Moraine •For thousands of years it served as a natural land bridge connecting central province with the west •End moraine: 330 km long, 6 km wide, 27 m high. North slope is gentle, southern is steep •Formed around 10,000 years ago •Northern limit of Lake Agassiz Expedition to the Sulfur Springs of Ellesmere Island Sheep rock (roche moutonnee) •Rock exposure shaped by ice flowing over it •Gentle slope from where ice came from •Steep, irregular slope down ice Moraines •Hills made up of till, not stratified •Manitoba’s Southwest Uplands are made up of till when glacier stopped •Hills (mountains) have no solid rock underneath Eskers •Pure sand that is layered •Must have formed by a river that flowed underneath the glacier •Now a wavy, continuous ridge made up of sand + - gravel (no clay or boulders) •Ideal for roads in the Precambrian Shield •Have been used as roadways for thousands of years. Also, for shelter and graveyards

Till or glacial till •Material carried by glacier •Dumped where glacier stopped moving and melted •Assortment of rocks of all sizes, not stratified Kame & Kame Terraces •Made up of sand +- gravel that is stratified •Must have formed from rivers that flowed above the glacier •When glacier melted the sand / gravel collapsed onto the ground and created hills Outwash Terraces Glacial Erratics •Large rounded boulders with scratch marks on them •Only a glacier could move such huge rocks Drumlins •Basket of eggs topography: usually in groups of many •Elongated hills •Made up of glacial till, not stratified •Steep slope up-ice, gentle slope down-ice Kettle hole

Palsa

Hanging valley •Waterfall where many contours are close together Manitoba digital elevation model PERIGLACIAL •Extremely cold climates •In cold climates, even glaciers are not present •Frozen ground processes- permafrost •Intense frost action, ground surface free of snow part of the year •Includes high elevation mountains Patterned ground

Pingo

Rock glacier

People have lived there for long •Inuit •Now development for oil, gas •Nightmare for construction with broken pipes, collapsing buildings, etc •Cold climate research conducted in N.America & Russia •Frost action & mass movements form the core of most periglacial processes •Accelerated freeze-thaw & frost weathering processes •Both in high latitudes and high altitudes Permafrost & Ground Ice •The ice can exist as a cement between soil particles or as larger masses of pure ice •Ice masses may also fill cracks (wedges) •Overlain by a thin layer (