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Earth Sciences
EASC 101
Cindy Hansen

Easc 101 Final Notes Feb 6 Metamorphic Rocks Chapter 9 1. Metamorphism -Metamorphism is changes to the mineralogy and texture of a pre-existing rock due to: an increase in pressure, increased temperature or chemically active fluids -Any rock type can be metamorphosed, the original (pre-existing) rock type is referred to as the parent rock (protolith), shale or mudstones are common parent rocks of slate -Solid state transforming can occur with little or no melting Foliated Metamorphic Rocks -Some metamorphic rocks show a preferred orientation to the grains (layering or alignment) of their foliation, folium is a leaf type from directed stress -Directed stress occurs due to the compressive forces acting within large regions adjacent to the convergent plate margins which is regional metamorphism (plates pushing together compressing into a mountain range) -Metamorphic grade reflects the severity of the metamorphic conditions Low slate phyllite schist gneiss High -Non-foliated metamorphic rocks are common where there is only lithostatic stress (not direct stress equal in all directions) in addition to heat from magma intrusions which is contact metamorphism -Metamorphic aureole is zones around intrusions that cause metamorphism -Intrusions are the movement of magma from within the earth's crust into spaces in the overlying strata to form igneous rock Feb 20 Geologic Resources Chapter 10 1. Geological Resources -Geologic resources are nonliving material that is mined, non-renewable (consumed faster than replenished) and divided into 2 types: mineral resources and energy resources -Mineral resources (diamonds and granite) are dimension stones which are natural stone/rock that has been selected and fabricated to a specific size or shape -They are also building stones where rock is cut from many in processing plants into thin slabs to be polished for industrial use -Mineral resources include gold (Canada is a top ten producer of gold), gold is mined using two different methods: -Hard rock mining - bedrock is mined and gold within mineral veins is separated from the waste rock - Placer mining - sediments (eroded rock) that contain appreciable amounts of gold (placer deposits) are collected and the dense gold is separated from the less dense minerals and lithic fragments (gold panning) -Flakes of gold can be collected by using a gold pan, sediment and water are swished around, poured out over a side, leaving the heavier materials behind, and gold can then be picked out by hand -They can also be collected using a sluice box, sediment and water pass over the ripples and heavier materials settle between -Diamonds are formed deep underground and are brought closer to the surface during volcanic eruptions, formed in the lithospheric zone, has to be at the right pressure and temperature, results in diamonds -Kimberlite pipe - used to service a volcano (eroded away) but below the surface there is still that pipe. magma collects diamonds as it moves up and they end up on the sides, as well as within the solidified magma of the pipe, normally in abundance in a very small area -Geologists search for the roots of ancient eroded volcanos (kimberlite pipes) to find diamonds in situ (hard rock mining) or search for sediment deposits that contain the eroded remnants of kimberlite pipes (placer mining) -Canada is number 3 producer of world’s diamonds (after botswana and russia) ,northwest territories - diavik open pit mine, most diamonds are not gem grade, used as abrasives, diavik mine was second diamond mine in Canada, after ekati mine. peak productions - 10% of world’s production -Sylvite (KCl) is an evaporite mineral that forms in ultra-saline water bodies, during the devonian period (400 MA ) the area that is now Saskatchewan was covered in shallow seaway, reefs blocked the exchange of seawater and ultra-saline conditions developed, is an important source of potassium for fertilizers -Ore metals are rock that contains concentrated minerals (such as copper and lead) is called ore, the less valuable minerals found within ore is called gangue, the ore is mined and then processed in order to separate the metals from the gangue -Crushed + water added to make a slurry, smelting is the melting and chemical reactions that strip the metallic element from the oxygen or sulphur that it is bonded to, ore metals can also be collected from placer deposits -Energy resources over the last half a century, energy consumption has increased drastically (globally), the main source for energy is fossil fuels (concentrated forms of burnable carbon) mostly petroleum, natural gas and coal. -Nuclear power is not popular, neither is bioenergy, hydro power and solar/wind/geothermal power. -Coal forms from the accumulation of partly decomposed plant matter (in swamps), the higher percentage of carbon, the higher the grade of coal, lots of different kinds - lignite, bituminous, anthracite -Canada holds close to 10 billion tonnes of the 1000 billion tonnes (1%) of global coal reserves -Petroleum (oil and gas) mainly forms from the accumulation of dead plankton on the quiet seafloor. clay/mud is also deposited in these quiet waters. -The organic mud is buried under more mud, and heated and squeezed, under the right heat conditions it is converted to oil or gas within the shale (source rock) the source rock is not very permeable (it holds the liquid tightly), over vast time the petroleum migrates into overlying rock where it might get trapped as the reservoir rock or it might make its way up to the surface as a seep -In order to form a trap, a low permeability rock such as shale must overly the reservoir rock, this is called a caprock, it is normally sandstone, conglomerate or lime stones, mudstone/shale are normally the caprock -Canada is the third largest producer of natural gas (methane) and second largest producer of crude oil, oil sands are loose or partly consolidated rock containing degraded oil called bitumen, subsurface collection of bitumen using SAG-D (steam assisted gravity driven) - expensive, inefficient Feb 25 Mass Wasting Chapter 18 1. -Defining mass wasting: mass wasting is defined as the downslope movement of any earth material, earth materials include bedrock, regolith(weathered bedrock), sediments, soil -Contributing factors to mass wasting: gravity has the greatest effect on steep slopes and slopes that are close to the angle of repose, angle of repose is the steepest angle a material can hold under a given set of conditions, for example, loose sand can be stacked at an angle of about 25 degrees, bedrock can be stacked at ^40 degrees, fractured bedrock is less of course, talus -Water content adds weight to slopes, can undergo freeze-thaw within fractures, causing them to widen (influence physical weathering), can act as a lubricant between grains, friction acts as a cohesion between grains, but water lubricates the grains, removing friction and thus cohesion. -Vegetation, roots act to bind grains (gives cohesion), roots also absorb water from the ground , clear-cut areas have more mass movements than vegetated areas (when tree roots break down - 5/10 years after clear-cut) -Over steepening, natural wave erosion at base of sea cliffs, man-made - building roads (we remove parts of the mountain to put a road in, we cut a portion of the mountain out, put over the other side of the mountain (cut and fill method) -Triggers are things that push an unstable slope over the edge such as earthquakes, rainstorms, in southern BC., triggers are springtime freeze-thaw events and severe rainstorms -Types of mass wasting is defined based on the type of movement, the speed and in some cases the water content -SLOW MOVEMENTS: A. Creep, imperceptible downslope movement, causes trees with bent trunks, tilted fences, everything is slowly moved downslope B. Solifluction only occurs in areas of permafrost, during the summer, you get melt of the surface layers and that move downslope as solifluction lobes, pain for building - to combat this; houses are built above ground on stilts that are drilled deep into the permafrost. -FAST MOVEMENTS: A. Flows, mudflows, debris flows, and earth flows, mudflows have greatest water content, earth flows have least, they are the flow of solid material like a liquid, lahar - volcanic mudflows, ice melt at the top of the volcano, and ash from the explosion - very deadly. -B. Rockfall - fastest of all mass movements. free fall of rock material most common in areas of freeze-thaw C. Rockslide rock material in contact with the slope as it slides down occurs along an internal plane of weakness which are not even a layer down below is less stable than layers above, dropping all the layers above it. clay layers often act as slip layers when they are wetted. sheet joints - fractures within uplifted plutonic rocks (like granite/diorite) tectonic uplift, all the material above expands, fracturing. water freeze-thaw, opening the sheet joints more. slab will break off and slide down to the highway or w/e hope slide - 1965 D. Slump material moves along a curved surface (fig. 18.7) and deposited at the base scarp is the area where material has moved from a higher location to a lower one slump deposit is the material after the slump has occurred is a rotational slide occurs with loose material E. Extraordinary large landslides portions of volcanic islands giving way in earth’s largest landslides example - mapping ocean floor of Hawaii, there’s many areas of crazy topography underwater, pieces of the island drop off into the ocean floor, causing huge tsunamis -Sea-to-sky Highway is known for rock fall and rock slides due to fractures, over steeping, freeze thaw and intense rainstorms (triggers) -To combat it we have scaling, walls and fences, wire mesh, shotcrete, drainage pipes to prevent factures and rock bolts for rock slides th March 4 Mountain Building Chapter 11 stress and strain: stress - force that is applied examples: tension compression -> crust cracks (fractures) tends to happen closer to the surface. ductile deformation -> crust bends (at depth) due to ductile deformation at depth ONLY the result of compression different from faults: faults can result from any type of stress look different depending on what kind of stress axis is line on earths surface of intersection with the axial plane imaginary line simple folds anticline (upwards fold) syncline (downwards fold) symmetrical anticline + synclines axial plane is vertical, each limb is symmetrical asymmetrical anticline + synclines axial plane is inclined, limbs are not mirror images. monocline a single limb bends in rock formed by reactivation of old buried faults complex folds overturned anticlines + synclines axial plane becomes even more inclined both limbs now point in the same direction recumbent fold folds become stacked each fold has an axial plane axial planes are horizontal (near horizontal) March 6 Mountain Building Chapter 11 Folds the entire fold is tilted (plunged) along the hinge. Hence these are anticlines and synclines that have been deformed further by later tilting. when plunging anticlines and synclines are uplifted and eroded, a V pattern is revealed on the earth’s surface. figure 11.16a rule of V for uplifted and eroded plunging folds > V’s point in the same direction as tilt for a plunging anticline. >V’s point in the OPPOSITE direction as tilt for plunging synclines. an example: wyoming adding geologic map symbols domes and basins rock is deformed upwards (domes) or downwards (basins) in all directions uplifted and eroded domes and basins show circular patterns. domes: the oldest rock is at the center of an eroded dome. basins: the oldest rock is at the edges of an eroded basin. Faults fault plane - the surface of rupture half arrows shown in cross section view to indicate relative displacement footwall block - the block that sits below the fault plane hanging wall block - the block that sits above the fault plane look at figure 11.8 fault plane is the DIAGONAL LINE not the surface of the earth. normal faults: if the hanging wall goes DOWN with respect to the footwall then it is called a normal fault caused by tension (fig 11.9) reverse fault/thrust fault if the hanging wall goes UP with respect to the footwall then it is called a reverse or thrust fault and is caused by COMPRESSION. thrust fault is if dip angle is LESS THAN 20* strike-slip fault if neither the hanging wall nor the foot wall moves relative to each other, and instead the motion is lateral, then it is called a strike-slip fault and is caused by shear stress. oblique slip faults more than one type of stress - we get both lateral and vertical displacement (don’t need to know for lab) orogenisis - the building of mountain faults three types volcanic mountains formed through volcanism (ex Hawaiian islands) volcanic arcs are formed this way. fault block mountains tension results in horsts (parallel hills) and grabens. (ex basin and range province in idaho, nevada, utah) horsts are when the middle bit rises up grabens are when the middle bit goes down fig 11.26 fold and thrust mountains compression results in folding and thrusting at or near convergent plate margins. (ex rocky mountains) uplifting folding and thrust faulting of the rocky mountains inboard as island arcs accreted to the western coasting adjacent to the uplifted mountain belt was a downwards compressed basic (western Canada interior seaway inundated this basin. (Alberta’s source of oil and gas) March 11 Geologic Time & Earth’s History Chapter 13+14 1. Uniformitarianism: Jame Hutton father of geology, mountains can rise and be warn away -Relative Age dating is determining the sequence of geologic events for an area by applying basic stratigraphic principles -Seven Stratigraphic principles, strata is any material laid down on the Earth’s surface as layers which includes all sediments, lava flows and ash beds 1. Superposition is the principle that states that, in undisturbed strata, newer layers will be deposited over older layers; thus, in a core sample, those samples of earth and rock nearest the surface will be newer in age than those beneath them, not the case for overturned -Recumbent is the older on top of younger 2. Original Horizontality: All strata are deposited as horizontal layers so if you find them otherwise, then deformation must have occurred 3. Original Lateral Continuity: Strata extends in all directions until it reaches a barrier, it then thins to a zero edge or it grades into a different sediment type 4. Cross-Cutting relationship: Rock units that cut across other rock units must be younger than what they cut, applied to intrusions and faults 5. Inclusions: are pieces of rock found within other rocks, are always older than what they are included in 6. Fossil Succession: Life has evolved over time; certain periods of time can be recognized by the fossil content of the strata 7. Unconformities: are surfaces of erosion that separates much younger rock above from much older rock below Types of Unconformities -An unconformity is a contact between two rock units in which the upper unit is usually much younger than the lower unit. Unconformities are typically buried erosional surfaces that can represent a break in the geologic record of hundreds of millions of years or more. -Disconformities are usually erosional contacts that are parallel to the bedding planes of the upper and lower rock units. Since disconformities are hard to recognize in a layered sedimentary rock sequence, they are often discovered when the fossils in the
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