UBC EOSC 114 exam with complete solutions

Work W = f x d The force that pushes an object times the distance the object moves Potential energy The work needed to raise an object a distance against the pull of gravity Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:02 / 0:15 Full screen Brainpower Read More Kinetic energy The energy an object has due to its motion Sensible heat Heat energy we can feel or measure Latent heat Hidden heat energy in chemical bonds Released as sensible heat Intensity vs. frequency More intense disasters occur less frequently Return period The average number of years between disaster events of the same magnitude Hazard Any event or situation that could cause human or economic harm Risk The probability that any given hazardous event might occur Crust -Top layer of the earth -Cold -Low density rocks Mantle - Middle layer of the earth - Warm - High density rocks Core - Center of the earth - Hot - Iron-nickel alloy - More dense than mantle Lithosphere Crust and upper mantle - Define as cold and rigid - Tectonic plates - Brittle Asthenosphere Mantle near melting point, and therefore ductile - Very ductile Mesosphere Lower mantle - Hotter but very high pressure - Solid -Stiff but ductile Plate tectonics are controlled by Physical properties - Composition - Density - Temperature Force - Gravity Types of deformation Elastic - Springs back, reversible Ductile - Plastic flow, permanent Brittle - Breaks, permanent Convection Plate tectonics is the upper layer of a huge, ductile convection cycle of the mantle Basal drag Friction between rigid lithosphere and the more ductile asthenosphere drags the plate along Slab pull Cold descending plate is denser than the hot mantle - Gravity pulls dense plate down Ridge push Heating as the rift raises the ridge crest - Gravity pulls the elevated plats down and apart Plate boundaries Convergent, divergent, transform Convergent - Reverse and thrust fault - Compression - Strongest - More time deforming before brittle failure - Maximum earthquake Transform - Strike-slip fault - Shear - Generally rock in shear - Moderate time before failure - Middle of earthquake size Divergent - Normal fault - Tension - Weakest boundaries - Hot rock and in tension - Least time deforming - Smallest earthquake size Basic rules (earthquakes) - Plates are in continuous motion - Rocks gradually deform - Faulting is a brittle failure in the lithosphere - Asthenosphere and mantle are too hot and ductile for brittle faulting Why is the oceanic plate always subducted Continental crust cannot be subducted because it's much less dense than mantle rock (buoyant) Body waves Travel inside materials Surface waves Travel along boundaries and between materials P wave (body wave) - Compression and extension of the solid - Particles move in the same direction as the wave propagates S wave (body wave) - Shearing distortion of the solid - Particles move perpendicular to direction wave propagates - Slower than P wave Love wave (surface wave) Horizontal movement perpendicular to wave travel direction Rayleigh wave (surface wave) Vertical and horizontal motion parallel to wave travel direction Seismic wave speeds Fastest - P waves - S waves - Surface waves Slowest Magnitude Indicates how much energy was released - Recorded by a seismometer Intensity How strong the ground motion is at the felt location - A qualitative estimate (perception) - Calculated by Modified Mercali Scale Factors that influence our perception of earthquake intensity - Magnitude - Distance from hypocenter - Structural resistance - Duration Scales to measure magnitude of the earthquake Richter - Fast but inaccurate Moment - Now the standard - Slower but more accurate *For each increase on the magnitude scale, energy release increases by 32 times **Ground motion increases by 10 Local factors and earthquake effect What material buildings are built on matters - Ground filters the frequencies of the earthquake - Affects how long the shaking continues - Influences the stability of structures - Soft ground is more problematic Structural resistance and earthquake effect - Taller buildings worse - Poorly designed buildings worse - Brick and concrete are bad - Wood, steel, reinforced concrete good Resonance All objects vibrate at characteristic frequencies - Controlled by size, composition, structure Liquefaction In soft wet soils, shaking causes the materials to liquefy - Soil loses its cohesion and flows - Loses its strength and heavy objects sink - After vibrations, sediments become firm again Earthquake prediction - Increase in seismic activity - Rapid ground deformation - Water table changes - Radon emissions - Electromagnetic disturbances - Animal behavior Geodynamic monitoring Measure the deformation of Earth's crust using satellites and ground based systems Cascadia subduction zone The recurrence interval for M9 earthquakes is about 500 years. - A convergent plate boundary that stretches from northern Vancouver Island to northern California. What are volcanoes They form where magma and gas leak out from the Earth's crust and mantle Magma A molten mixture of rock-forming substances, gases, and water from the mantle - Created by melting pre-existing rock below the Earth's surface - Extrudes as lava or explodes as pyroclastic material Lava Melted rock exposed at the Earth's surface The volcanic system Source region transport region storage region eruption region Source region Usually deep and hot - Mantle melts into magma Transport region The crust - Magma moves along cracks in the Earth's crust, forming dikes and sills - Dike: vertical - Sill: horizontal Storage region The crust magma chambers - Magma ponds below the Earth's surface in large chambers Eruptive region Surface volcanoes Magma viscosity Resistance to flow - Controls flow, eruption style - Depends on temperature, gas content, crystal content Chemical composition Magmas cool and crystallize to become igneous rocks - High vs low silica content - Felsic vs mafic Felsic igneous rocks Light color High viscosity (cold magma) Explosive (ash) Ex: granite and rhyolite Magic igneous rocks Dark color Low viscosity (hot magma) Non-explosive (lava) Ex: basalt and gabbro Where do igneous rocks form? Cooled at the surface - Extrusive/volcanic - Small crystals - Rapid cooling Cooled below the surface - Intrusive/plutonic - Large crystals - Slow cooling Mid-oceanic ridges - Most voluminous volcanism on Earth - Not exposed at the Earth's surface, except in Iceland - Divergent boundaries Continental volcanic arcs Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent - Contains felsic/mafic and intermediate magmas/lavas Oceanic volcanic arcs Contain mafic magmas/lavas 4 types of volcanoes - Cinder cones - Shield volcanoes - Stratovolcanoes - Calderas (supervolcanoes) Cinder cones Small, steep-sided volcanoes that erupt gas-rich, basaltic (mafic) lavas = Layers of pyroclastic ejecta Shield volcano A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions - Lava erupts from fissure, runs down gentle slopes - Erupts often - Mafic lava flows Stratovolcano Interbedded lava flows, pyroclastic flows, lahars - Usually intermediate or felsic - Frequently explosive, often viscous magma - May erupt many times Calderas (supervolcano) Created from large, explosive eruptions of felsic pyroclastic material - Caldera created when the roof of the chamber collapses - Produce the most devastating eruptions but very rare Effusive volcanoes Outpouring of molten magma from the vent lava - Passive eruptions - Lava flows (mafic intermediate) - Lava domes (felsic-intermediate) - Explosive volcanoes Gas driven violent eruptions - Pyroclastic deposits and airfall - Blocks and bombs proximal to vent Pyroclastic fall Volcanic material that falls back to earth after an explosive eruption - Eruption columns - Ash moves in the downwind direction - Blankets topography Pyroclastic flow Gas-pyroclast mixtures - Gravity-driven flows - Flow down slope, channelled in valleys - Very fast and hot Why gas matters - Magmas produce bubbles during ascent - They expand as the magma rises (power pressure) - Explosivity depend on amount of bubbles and rate of rise Explosivity of volcanoes Determined by the viscosity and gas content - Viscosity fights bubble growth - When the strength of the magma is overcome, fragmentation occurs - Pyroclastic material is produced Pyroclastic ash formation Liquid magma containing dissolvd gas is suddenly decompressed - Gas bubbles expand rapidly and blow up the liquid magma - It freezes in mid air and forms ash particles Types of eruptions Hawaiian Strombolian Vulcanian Plinean Phreatomagmatic Hawaiian explosions Low viscosity basaltic magma - Lava flows - Effusive - Fire fountaining Strombolian explosions Basaltic/andesitic magma - Mildly explosive - Bombs/lavas Vulcanian explosions Viscous itic magma - Very explosive - Sustained explosions of ash Plinian explosions Andesitic/rhyolitic ash - Violently explosive - Large, sustained column of ash - Pyroclastic flows Phreatomagmatic explosions Contact between water and magma - Water flashes to steam - Violently explosive Volcanic Explosivity Index (VEI) - Volume of as produced - Height of eruption cloud above the vent - Duration of eruption - Logarithmic scale of 0 to 8 Lava flows - Slow - Usually not dangerous - Easy to predict - Usually magic and low viscosity Ash fallout Hot ash and gas ejected from volcano - Pyroclastic material - Explosive eruptions Origins of pyroclastic flows 1 Collapse of a volcanic column 2 Explosive collapse of lava domes Lahars Volcanic debris flow - Can travel very far - Can occur without an eruption - Need lots of water and loose volcanic material Sector collapse A collapse of a weakened volcanic edifice - A debris avalanche occurs Volcanic gases Tipically highly acidic and toxic - Kills plants and animals Monitoring volcanoes - Seismology - Ground deformation - Gas emission - Thermal imaging - Satellite observation Human and economic impacts of landslides - Population density - Cost of infrastructure - Population preparedness Classification of landslides - Type of material - Type of movement - Sometimes rate of movement Type of material in landslides - Rock - Soil/Earth - Mud - Debris Type of landslide motion - Falls - Slides (rotational and translational) - Flows - Complex movements Landslide falls - Occur on very steep slopes - Material detaches because of weakness - Falls due to gravity Landslide slides - Vary from slow to fast - Usually soil, rock, debris - Material moves as coherent mass Rotational slide Surface is curved - Intermediate speed - Usually weak material - Rotation of material on a curved failure plane Translational slide If the surface is flat - Slow to fast - Usually strong material moving on weak planes - Cohesive motion Landslide flows - Very slow to very fast - Soil, mud, wet debris - Water usually very important - Chaotic fluid or plastic flow Landslide complex movements - Combinations of mass movements classification of landslides The role of gravity and landslides Usually counteracted by the internal strength of the material and friction with the slope When does a landslide occur When the force of gravity is greater than friction or the internal strength of the material See 155 more Add or remove terms