ES5001 NOTES FOR FINALS PDF

WEEK 1 - LECTURES 1 & 2 - 12 AUG 2024 Topography - Earth: you can see the surface roughness, textures, bc it is more dynamic & more active than mars, applying certain forces can deform the crust of the earth, textures also show the diff loadings applied on earth’s surface, level of...

WEEK 1 - LECTURES 1 & 2 - 12 AUG 2024 Topography - Earth: you can see the surface roughness, textures, bc it is more dynamic & more active than mars, applying certain forces can deform the crust of the earth, textures also show the diff loadings applied on earth’s surface, level of activity is stronger on earth, crust of the earth is more compliant, more plastic, bc it deforms and is much rougher than on mars Why there are so many natural hazards on earth & describe the impact of human to natural disasters - Related to the EXPONENTIAL GROWTH of the global human population; human population increasing like mad, average life expectancy is increasing bc of science and technology (more medications to treat diseases, food production to be more efficient, lesser wars) - Interaction between different spheres (hydrosphere, biosphere, etc.) is creating our natural disasters - Everyday geological processes - Events are part of nature Human impact - Relates to the size and location of event - Lesser people and buildings = lesser damage - More people and buildings = more damage and catastrophic deaths - Dramatic hazards occur infrequently and in restricted areas = fewer deaths - Rare, major events (difficult to predict) = more deaths - Short-term prediction of major events is difficult due to lack of data - Trends in leisure activities and safety measures affect fatality rate - Higher fatality rate in developing countries - Cost of natural hazards increasing (larger economic loss) Compare and contrast the status of catastrophe predictions and the relationships among events Predicting catastrophe - Some natural events have predictable cycles but usually too many variables and have overlapping cycles - Prediction is possible but difficult to predict the impact on a global scale - Recurrence interval - increases linearly on a LOG SCALE and increases exponentially on a LINEAR SCALE - Magnitude is inversely proportional to frequency (bigger the event, less frequent it takes place) 1 Relationship among events - Some events are directly related to others and may overlap to reinforce each other - Past events influence future events - FEEDBACK EFFECT: Some processes result in more rapid changes Global warming → melts ice → → darker ocean water absorbs more heat energy → melts more ice - Overlapping effects: eg. high tide + storm surge @ peak = crazy high actual tide Explain general approaches in mitigating the hazards Mitigation - Land use planning Find out where disasters are likely to occur and restrict development there (-): they are often too late as the areas are already populated, might ignite political and legal opposition, restrictions are viewed as infringement of personal and property rights - Risky development - Insurance Mitigates financial impact of disasters - Role of government Research nature and behaviour of natural disasters Attempts to forecast to mitigate damage and loss of life Different agencies/organisations to take charge of different natural hazards Public education - Living with nature Cannot change natural laws Controlling nature will temporarily hinder natural processes; divert the damaging → energy to other locations; energy build up more severe damage Must learn to LIVE WITH NATURE AND NOT CONTROL IT Mitigation requires HUMAN BEHAVIOUR CHANGE Describe major natural hazards on planet earth Earthquakes Tsunamis Volcanoes Landslides Sea level rise (SLR) Extreme weathers (storms, floods) Climate change Meteorite and extreme space weather events 2  WEEK 2 - LECTURE 3 - 19 AUG 2024 Describe earth structure and explain plate tectonics theory (plate drift, sea mount production, magnetic anomalous, etc.) Earth’s structure (each layer has a unique chemical composition, physical state and can impact life on Earth’s surface) - Crust - Mantle - Outer core - Inner core Temperature increases as you move towards the centre (core) of the earth Lithosphere: the solid, outer part of the Earth - Includes crust + upper mantle - Bounded by the atmosphere above and asthenosphere below Continental Drift (1912) - Alfred Wegener - Earth’s continents have moved over geologic time relative to each other - Thus, appearing to have “drifted” across the ocean bed Plate tectonics is a scientific theory that explains how major landforms are created as a results of Earth’s lithosphere movements, which can explain many phenomena, including mountain building events, volcanoes and earthquakes Earth’s magnetic field - When a volcanic rock erupts, the particles of magnetic minerals that are contained in the rock want to align with the Earth’s magnetic field - But the magnetic particles can only move when the rock is hot - Once it cools, the particles are frozen in place - But Earth's magnetic field periodically reverses (N becomes S, S becomes N; aka magnetic reversals); hence we get some rocks with magnetic fields frozen in the current orientation and some in the reversed orientation Ocean spreading centers - Linear boundary between 2 diverging lithospheric plates on the ocean floor - 2 plates move apart from each other - Molten rock wells up from the underlying mantle into the gap between plates - Solidifies into new oceanic crust (Found at the crests of oceanic ridges) - Global seismicity delineate the plate boundary - Deep seismicity indicate the slab (old, heavier plate) has been subducted into the deeper part of the earth - Mid-ocean ridges are higher than the nearby seafloor 3 Describe three major plate boundary types and the associated hazards Divergent: where 2 plates are moving apart - The space created can also fill with new crustal material sourced from molten magma that forms below - Divergent boundaries can form within continents but will eventually open up and become ocean basins - On land, it produces rift valleys. Under the sea, it produces mid-oceanic ridges. Driving forces in plate tectonics - Convection of the earth’s (solid) mantle raises hot rocks beneath mid-ocean ridges, these rocks spread laterally, cool, and sink back into the interior of the mantle Convergent: where 2 plates are colliding - Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust - The denser plate is subducted underneath the less dense plate - The plate being forced under is eventually melted and destroyed Benioff zones: earthquakes follow the subducting slab - At continental-oceanic convergent boundaries, oceanic plate subducts because it is denser - At oceanic-oceanic convergent boundaries, the denser oceanic plate subducts - Continental-continental convergent boundaries, neither subducts under the other, instead, they push upwards and forms mountain ranges 4 Transform: where plates slide past each other - Relative motion of the plates is horizontal - Can occur underwater or on land - Crust is neither destroyed nor created - Because of friction, the plates cannot simply glide past each other - Rather, stress builds up in both plates and when it exceeds the threshold of the rocks, the energy is released, causing earthquakes - Transform boundaries are on the edges of plates - When ocean is shallow, means the ocean floor is younger - When ocean is deep, means the ocean floor is older Describe the role plate tectonics plays in the development of Earth’s landscapes Summary of plate tectonics theory - Lithosphere is broken into tectonic plates (7 or 8 major plates) - Earthquakes, volcanic activity, mountain building, and oceanic trench formation occur along the plate boundaries (or faults) - Tectonic plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, the process of subduction, or one plate moving under another, carries the edge of the lower one down into the mantle (Area of material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading). - Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography (the ridge is a topographic high) and density changes in the crust (density increases as newly-formed crust cools and moves away from the ridge). At subduction zones, the relatively cold, dense oceanic crust is “pulled” or sinks down into the mantle over the downward convecting limb of a mantle cell 5  WEEK 3 - LECTURE 4 - 26 AUG 2024 Explain how plate tectonic motions and the elastic property (elastic rebound theory) of rocks combine to cause earthquakes Causes of the earthquake: stress and strain Plastic body: won't recover to its shape Elastic body: will recover back to its shape (eg. basketball rebounding) - It is important for rocks to have elastic properties so that is will go back to their original shape(?) Elastic rebound theory: is an explanation for how energy is spread during earthquakes As earth’s crust deforms, the rocks on opposing sides of a fault are subjected to shear stress. Slowly, they deform, until the rock strength is exceeded. Then they separate with a rupture along the fault. This sudden movement releases accumulated energy, and the rocks snap back almost to their original shape. The previously solid mass is divided between the 2 slowly moving plates, the energy released through the surroundings in a seismic wave (the gradual accumulation and release of stress and strain of earthquakes) 6 Understand deformation and basic seismic waves generated by earthquakes Body waves - P wave (compression wave): particle motion in the same direction as wave propagation - S wave: particle motion PERPENDICULAR to direction of wave propagation P wave is faster (comes earlier) BUT SMALL AMPLITUDE, s wave is slower (comes later) BUT LARGER AMPLITUDE Only p waves can be propagated Surface wave slower than s wave & sometimes can have larger amplitude than s wave Speed of waves: p wave > s wave > surface wave Surface waves - Forms at the free surface - Amplitude decays exponentially with depth (deeper, lower amplitude) - Rayleigh wave - Love wave Seismic waves can also be used: - To find oil and gas - Medical scans (eg. CT scans) - Nucleation test monitoring - Building damage examination 7 Describe three different kinds of earthquake faults and recognise the fresh rupture of an earthquake fault Divergent environments - NORMAL FAULT - Opposite to convergent - Moves downwards - Eg. Nevada earthquake, USA; Sparta fault (Greece) - Produces a much clearer fault scarp Convergent environments - REVERSE/THRUST FAULT - Movement is perpendicular to fault - Eg. Chi-Chi earthquake in Taiwan Transform environments - STRIKE/SLIP FAULT - Movement is parallel to fault - Left lateral - Right lateral strike-slip event/earthquake (moves to the right of the direction u r facing?) - Eg. San Andreas fault (right lateral strike-slip fault) Can measure how the magnitude of the event by the distance the earth(?) moves This is a LEFT-lateral strike slip earthquake 8 Understand the magnitude of an earthquake and describe how the size of a fault rupture relates to an earthquake’s magnitude Some common characteristics of an earthquake: rupture size, length of rupture, width of rupture, amount of slip, dynamics, direction of rupture, impulsive or slow onset, tectonic occupation, geographic location Measuring the size of an earthquake Commonly the length, width and slip of a seismic rupture are related to each other - Shear modulus - strength of the rock aka amount of energy stored in the rock? The longer the fault, the larger the magnitude of an earthquake Some terms: - Hypocenter: the point where an earthquake or an underground explosion originates - Epicenter: the point on the Earth’s surface directly above a hypocenter or focus - Fault scarp: a planar geomorphic feature formed by offset of Earth’s surface by one or more earthquakes - Wavefront: a surface over which time of the wave have been propagated away from the hypocenter (the source) is the same 9 Why do subduction zones produce Earth’s biggest earthquakes? 10  WEEK 4 - LECTURE 5 - 2 SEP 2024 Describe different types of earthquake hazards Ground failure: fault rupture, landslides, liquefaction - Earthquakes are one of the natural disasters that caused the most casualties - 900 million people live on the Gangetic plain, near a megathrust fault Ground shaking - Eg. 1994 Northridge earthquake, California - Fault ruptures generate earthquakes, which consist of several different kinds of waves P waves - 6km/s S waves - 3.5km/s ➔ → P waves comes first followed by s waves ➔ Time between p wave and s wave is short means that the earthquake is nearby wherever you are at Surface waves (rayleigh waves & love waves) - 8 to produce tsunami - Area of rupture zone Tsunami waves cannot be generated if area of seafloor deformation is small - Rate and volume of water displaced Should be large enough - Sense of ocean floor motion Vertical deformation to produce tsunami waves - Depth of water above rupture Has to occur in deep waters Shallow waters do not have enough energy to propagate the waves and produce big tsunami waves Undersea landslides: 1958 Lituya Bay, Hawaiian Islands (Alika 2 collapse on the flanks of Mauna Loa volcano) → → - Earthquake landslide tsunami waves - A large amount of mass slides into the ocean, tsunami waves generated Undersea volcanic eruptions: 1883 Krakatau, 1628 BC Santorini, 2022 Tonga eruption - Volcanic processes can displace large volumes of waters and trigger tsunami waves When undersea volcanic eruptions are large, hot volcanic ash moves faster, hence tsunami waves Submarine volcanic explosions, gases coming out of the volcanoes, hence tsunami waves Landslides leads to collapse of volcano, hence tsunami waves - Maximum size is still unknown as these types of tsunami waves are rare - 3 possible causes Explosion beneath the seawater, explosion displaces a large quantity of seawater Underwater portions of the volcano subside quickly during the eruption, greatly disturbing the seafloor Large volumes of volcano material enter the sea and displace seawater (another fairly new cause): volcanic eruption → air pressure waves create tsunami waves - Volcanic eruptions can lead to changes in topography/bathymetry 15 Asteroids (no modern cases): 65 million years ago K-T extinction, Eltanin impact - Average frequency of asteroid impacts is low (1km asteroid impact occurs about once every million years) - 1km asteroid falling into 5km deep ocean → → could generate 3km deep cavity cavity walls → collapse generate tsunami with immense run-up on shore - Height of fall has more effect than volume of mass that displaces water Higher height means faster speed - Speed of meteorites plays the most important role in generating tsunami Tsunami hazard mitigation - Land use zoning Limit buildings to elevations above those potentially flooded areas - Structures designed to better resist wave erosion and scour - Orientation of streets and buildings designed perpendicular to wave crest (reduces impact of tsunami waves and increases survival rate) - Well-rooted trees can be planted along potentially flooded areas to slow down water waves - Large ditch or reinforced concrete wall can be built to reduce impact of first wave As long as it can survive the big hits (first wave), the chances of survival increases - Tsunami warnings Warning systems are now perfected for far-field (far from the source tsunami) Seismic waves travel faster than tsunami waves Can give warnings of an hour to a day Pacific Ocean Tsunami Warning (PTWC) network ➔ Buoy Warning System: Buoys near anticipated sources of tsunamis detect a tsunami in its early stages and transmit it to the Pacific Tsunami Warning Center in Hawaii Tsunami hazard maps help communities with infrastructural adaptation and emergency planning - Some good infrastructure practices: Tsunami-resistant buildings Warning signs Vertical evacuation structures (eg. Tsunami Evacuation Raised Earth Parks) Elevated restaurants in Hawaii where the lower level is designed to allow waves to pass through 16  WEEK 6 - LECTURE 7 - 16 SEP 2024 Explain why some volcanic eruptions are explosive and others are not and give historical examples of each Describe and give examples of three broad categories of volcanoes Volcano types - Shield volcanoes (eg. Hawaii — Mauna Kea, Mauna Loa, Kohala, Hualalai, East Maui) Low aspect ratio because of the fluidity of lavas, commonly non-explosive eruptions FAR LARGER than stratovolcanoes (~200km) bc of the viscosity difference of magma that produces them Lavas that erupt on Hawaii are basaltic and contain about 50% silica - erupt at about 1200OC and are very fluid and pasty (viscosity increases as temperature decreases) - Stratovolcanoes (eg. Mt Vesuvius, Italy) Higher aspect ratio because of lava viscosity Both explosive and non-explosive eruptions Smaller than shield volcanoes Cinder cones Most lavas that erupt on volcanoes like Mt. St. Helens are closer to rhyolitic and are about 65 to 75% silica - erupt at about 900OC and are pretty stiff - Calderas (ultra-plinian) - eg. Toba Caldera in Sumatra Formed by very voluminous & explosive eruptions More than a hundred kilometres in scale Closest volcano eruption to Singapore 17 Describe basic types of rocks from various volcanic process Igneous rocks - Formed from the crystallisation of magma - Extrusive: fine-grained and quickly cooled eg. felsic: pumice; mafic: obsidian, basalt - Intrusive: coarse-grained and slowly cooled eg. felsic: granite; mafic: gabbro Rock cycle Classification of igneous rocks: Mineral composition, Grain size, Texture Importance of silica in magma - Magma range from about 50-75% silica - More silica, STIFFER magma, HIGHER VISCOSITY; eg. 75% silica: Rhyolite - Less silica, MORE FLUID magma, LOWER VISCOSITY; eg: 50% silica: Basalt Importance of water in magma - More water, viscosity decreases (behaves more like fluid), more explosive (especially for Rhyolite) - Explosive reaction comes from the build up of gas within bubbles - At greater depth, higher pressure, bubble rises up to the surface, pressure decreases, bubble expands, BOOM (eruption is caused by the pressure decreasing too fast) - Viscous, stress builds up easily within the bubble, when it gets to the surface of the earth, pressure is higher because magma surrounding the bubble is stiff 18 Describe a Plinian eruption column Eruption types - Shield volcanoes - Hawaiian-type eruptions Lava is very fluid and hot Bubbles can expand and escape easily Relatively gentle, low-energy eruption Magma ➔ Typically basaltic ➔ Effusive ➔ Low silica ➔ Low viscosity ➔ Very fluid Eg. Pu’u O’o eruption - Plinian-type eruptions Lava is sticky and cooler Bubbles cannot expand or escape easily Explosive Starts with glowing pyroclastic flows Forms lava domes with steep sides Key characteristics ➔ Ash and smoke columns that can extend to the stratosphere ➔ Large amounts of pumice ➔ Powerful gas blasts ➔ Large amounts of magma erupted ➔ Caldera formation possible Named after Pliny the Younger Mt. Vesuvius, Italy 19  - Calderas — Ultra-pilian type eruptions Key characteristics ➔ Caldera formation ➔ Large ejecta volumes ➔ High energy release ➔ Massive plumes ➔ Magma is rhyolitic Types of magma (temperature and mineral content of magma affect how easily it flows) - Basaltic High in iron, magnesium, calcium Low in potassium, sodium Ranges in temperature from about 1000oC - 1200oC - Andesitic Moderates amounts of minerals Ranges in temperature from about 800oC - 1000oC - Rhyolitic High in potassium, sodium Low in iron, magnesium, calcium Ranges in temperature from about 650oC - 800oC Describe three types of volcanic deposits Volcanic eruptions and products - Lava flow - Lahar (mud or debris flow) Mix of mud, water, magma - Pyroclastic flow - Lava dome - Landslide (debris avalanche) → - Eruption column Eruption cloud Ash fall Acid rain 20 Pyroclastic deposits - Pyroclastic fall (or airfall) Fallout from the Pilnian column blankets the ground with a nearly uniform mantle of fine particles Coarser grain size compared to surrounding sediments eg. Tavurvur volcano, New Britain, Papua New Guinea - Pyroclastic flow Deposits fills in the gaps in the ground Dense slurries of debris racing down the slopes of the volcano deposit, which concentrate in valleys eg. Pinatubo Volcano, the Philippines - Pyroclastic surge Clouds of debris-laden gas jetting out of the volcano and racing over the countryside forms layers of irregularly bedded ash and blocks eg. Santorini, Greece 21  WEEK 7 - LECTURE 8 - 23 SEP 2024 Describe various aspects of hazards associated with two end-member modes of volcanoes Able to understand the direct and indirect volcanoes hazards and their impact to the environment and human society - Unlike earthquakes, we often can predict volcanic eruptions, and evacuate large population centres - This requires careful monitoring, and a willingness to accept false alarms - We cannot prevent volcanic eruptions, and when they happen there will be large financial losses and human impact - Even when we successfully anticipate an eruption, we cannot always predict the style and severity Living on (or near) a volcano can lead to - Hazards (WITHOUT ERUPTION) Ground shaking Fractures/Fissures ➔ Eg. Mammoth mountain, California Outgassing ➔ Volcanoes often leak gas ➔ Gas may stay in the soil or percolate into the air ➔ CO2 is denser than air so it sits near the ground level ➔ Animals (including people) can suffocate due to the concentrations of this odourless gas ➔ High concentrations of CO2 in the soil kill plants by denying their roots of O2 and by interfering with nutrient uptake ➔ Although the leaves of plants produce oxygen and absorb CO2 during photosynthesis, their roots need to absorb oxygen directly. High CO2 concentrations in the soil kill plants by denying their roots oxygen and by interfering with nutrient uptake. ➔ Eg. Mammoth Mountain, California: trees on the south side of the volcano began dying from high concentrations of CO2 gas in the soil Acid lakes ➔ Crater lakes can have pH values as low as 0.1 (strong acid); this is the result of gases from magma, like CO2, SO2, HS, HCI, HF dissolving in water Lahars & landslides ➔ Lahar: volcanic mudslide — a mixture of water, rock fragments, soil, etc. flowing down a volcanic slope or a river valley on or near a volcano ➔ Lahars grow as they flow and erode material on the volcanic slope ➔ Lahars can be triggered by eruption, or by heavy rain; move at tens of metres per second and destroy communities ➔ Eg. The city of Puyallup, Washington, is built on top of an old lahar deposit. Many communities are at risk. 22 - Direct hazards (WITH ERUPTION) Most types of volcanic deposits can pose hazards Lava flows ➔ Least hazardous of all processes in volcanic eruptions ➔ Rate and distance depend on temperature, silica content, extrusion rate and slope of land ➔ Cold lava flows (flows with high silica content) will not travel far due to high viscosity ➔ Biggest hazard is to property ➔ Eg. Hawaii; Mt. Etna, Sicily; Holuhraun eruption Bardarbunda volcanic complex, Iceland Pyroclastic flows ➔ Pyro (fire); clastic (broken) ➔ High-density mixtures of hot, dry rock fragments and hot gases moving away from an eruption vent ➔ Destroys almost everything in their path ➔ Moves faster than 80km/h, temperatures 200-700oC ➔ Can block streams and create temporary dams, that will later overtop and cause sudden flooding downstream ➔ Eg. Mount Pinatubo; Mayon Volcano, Philippines Pyroclastic falls (ash fall) ➔ Volcanic ash is composed of very small fragments of rock ➔ Ash can cover wide areas and travel downwind from the erupting volcano ➔ Effects: reduces visibility, blocks sunlight, damages engines, dense - can collapse roofs, disrupts power generation/transmission/distribution, clogs water supplies, causes breath difficulty, damages crops, etc. Ground shaking Fissuring Outgassing Lahars & landslides - Indirect hazards (WITH ERUPTION) Air travel effects ➔ Eg. KLM Flight 867: flew into a thick cloud of volcanic ash from Mount Redoubt, captain used backup power to restart the engines ➔ Eg. Eyjafjallajokull eruption: commercial aircraft were unable to reach altitudes of 40,000ft. without passing through the ash cloud ➔ Damage to jet engine — possible engine failure, Abrasion to cockpit windows, Penetration of air conditioning system, Contamination of electrical, hydraulic and fuel systems ➔ Cancelled flights — business and leisure travel delayed/cancelled, perishable goods lost, industrial plants suspended production Climate change ➔ → Volcanic ashes can physically block sunlight Drop in global temperatures ➔ Led to famines and epidemics of typhus and cholera ➔ Global climate change: hotter summers 23 Worst case scenario for volcanoes — Supervolcano - Volcano capable of producing a volcanic eruption with an ejecta volume greater than 1000km3 (240 cu mi) - Taupo volcanic zone, New Zealand – 26,500 and 254,000 years ago - Toba, Sumatra – 74,000 years ago - Yellowstone – 640,000; 2,100,000; 4,500,000; 6,000,000 years ago - Cerro Galan, Argentina – 2,500,000 years ago - Pacana, Chile – 4,000,000 years ago Able to describe basic scientific monitoring of volcanoes Volcanic Monitoring - Volcanic tremor - seismic signals indicating magma movement - Ground deformation (GPS, InSAR, Tiltmeter) InSAR (Synthetic Aperture Radar interferometry): mapping the surface displacement from space - Gas Monitoring Gas samples are collected from fumaroles and active vents Gas levels may also be monitored by remote sensing techniques Heat and hydrothermal activity - Hydrothermal activity: demonstrates the presence of magma, not necessarily magma movement - Thermal features: can be monitored by Night aerial observations Thermal (infrared imaging) Direct temperature measurements Infrasound - Picks up the vibration of air pressure that can propagate away from a volcanic eruption - Locating the source of something :) Eg. Pinatubo prediction - Different government agencies worked to convince local inhabitants of the severity of the threat - 3 evacuation zones and 5 stages of alerts; daily alerts announced in major and local news sources - ~ 60,000 people evacuated before the major eruption Eg. Mt. St. Helens prediction - USGS scientists convinced local authorities to close the volcano to the public based on observations of ground deformation and tremors - A landslide on the north face of the volcano exposed the magma chamber, producing a sideways eruption - 57 people were killed, including a geologist 24  WEEK 8 - LECTURE 9 - 7 OCT 2024 What is a landslide Landslide: the movement of a mass of rock, debris, or earth and/or mud down a slope - Sliding takes place from a few metres to a few tenths of metres per second → - Rocks can slide or roll downhill rockfall - May occur when large volume of material moves downslope quickly → rotational/translational landslide → - May be wet (rain) debris flow → - May occur gradually creep (very slow; a few centimetres per day) - Downslope ground movement is a natural part of landscape evolution (gravity!!!!!!!!!) → - Landslides can cause tsunamis eg. Hawaii - eg. Near San Salvador, El Salvador, 2001 ; Palu Bay area landslide, 2018 ; Shimla, Himachal, India 2017 Mount Kinabalu Earthquake, June 2015 - Magnitude 6.2 earthquake - Earthquake caused rockfall - Singaporean teachers and students were killed by rockfalls and landslides Rotational slides - Moves downward and outward above curved slip surface, with movement rotational about an axis parallel to slope - Head moves downward and rotates backward - Toe moves upward on top of landscape - Move short distances Translational slides - Moves faster and farther than rotational slides - Move on planar slip surface such as fault, joint, clay-rich layer - Move as long as on downward-inclined surface, and driving mass exists - Underlying material fails so overlying material slides - Different behaviours Remain coherent as block Deform and disintegrate to form debris slide 25 How, where and why do landslides occur Physical processes What causes landslides - Driving force Gravity pulls down on material → External forces contribute eg. earthquakes, eruptions - Resisting force Holds material in place Strength of material and amount fo friction - Factors contributing to slope failure Slope steepness (slope angle, α) ➔ There needs to be a slope (tilting of land) for a landslide to occur ➔ Steeper slope, greater driving force, greater likelihood of slope failure ➔ Angle of repose (critical angle): steepest angle at which any loose material is stable; depends on angularity and size of grains and moisture content Material weight Moisture content ➔ Moisture content increases, friction decreases - Mass will slide (or slope will fail) when force, F exceeds frictional resistance, f - Reduction in friction increases the likelihood of slope failure - Max. friction = Normal force * friction coefficient Sources of weakness for planar internal surfaces - Layers in sedimentary rock - Fractures in any kind of rock - Contacts between rocks of different strength - Faults, or slip surfaces of old landslides 26 Cohesion adding to frictional resistance - Frictional resistance depends on: slope angle α, load, cohesion - Cohesion: important force for holding soil grains together due to surface tension of water (or other glue material) between loose grains - Cohesion is overcome when driving force is large enough - Increase in pore fluid pressure (deeper underground) reduces friction and facilitates landslide Impacts Rockfall → - Very fast 1m/s - 100m/s - Short runout bc the speed is very fast - Patchy impact - eg. taiwan 27 Debris flow → - Fast 1cm/s - 10m/s - Long runout (can be > 50km) - Impact through burial, boulders and dynamic forces - Level of impact related to sediment concentration, debris content, velocity and depth Translational landslide → - Fast 1cm/s - 10m/s - Long runout (can be > 50km) - Complete impact through burial and dynamic forces - Can transform into debris avalanche Creep → - Slow 0.3mm/year - 3.1cm/year - Short runout - Damage to brittle structures through ground movement Cascading impacts - Flood A landslide dam on Sichuan Dadu River, created by an earthquake 10 days earlier, burst and caused a flood that > 1400km downstream and killed 100,000 Vajont Dam, Italy: during the initial filling, a massive landslide into the lake displaced 50 million m3 of water, a wave of 250m high overtopped the dam and completely destroyed villages and towns downstream Monitoring A lot of monitoring comes from the mining industry bc landslides occur a lot in the mining industry. - Landslide potential index → - Remote sensing geologists can identify risks Mitigation - Soil nails - Retaining walls - Gabion wall 28  WEEK 9 - LECTURE 10 - 14 OCT 2024 What hazards face delta regions - A lot of cities are located in the delta region (eg. shanghai, bangkok, new orleans, etc.) - Why are people living in delta regions? → Delta regions are relatively flat easy to travel around → Deltas are one of the most fertilised land important for high crop production Deltas have sufficient fresh water because they are located along major rivers - Deltas: a low-lying, landform created by deposition of sediment that is carried by a river as it enters slower-moving or stagnant water; usually where a river enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment Ganges-Brahmaputra delta in Bangladesh - 400km wide (greatest delta in the world) - Comprises numerous distributary rivers which changes from time to time - Most active distributary rivers are on the right - Distributary rivers in the centre and on the left are less clearly connected and were more active when the main river was directly connected to them As deltas grow seaward - Debris builds out into the sea and the river profile lengthens - River bed at each point along its course has to RISE (grade has to adjust to the increasing length) - The city gets lower relative to the river 29 What causes sea level rise - Sea level rise & rising temperatures threaten deltas Global sea level changes are caused by - Tectonics Local issue for much of Southeast Asia Uplifted coasts (eg. Kaikoura Uplift, New Zealand) - Uplifted coasts - Subsidence eg. Jakarta Because of the extraction of underground water and additional loading by structures Much more uncertainty, hence requires action - Melting ice and warming oceans Rising global temperatures, thermal expansion — as seawater warms, volume increases ⅓ of glacial loss and melting ice sheets in the last 25 years Recent ice sheet loss ~40% in the 21st century eg. 2018 iceberg A-68 broke off the Larsen C Ice Shelf in the western Antarctic — Approx. 500m thick & >1 trillion tonnes (>8 times of Singapore) How do we monitor subsidence and sea level rise - Track with satellite technology - Monitoring groundwater-related subsidence Why is sea level rise important - Sea level rise can lead to higher storm surges Storm surge - Storm surge/storm flood/tidal surge/storm tide: A coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems - Include tropical and extra-tropical cyclones - Measured as the rise in water level above the normal tidal level, and does not include waves - Much more uncertainty hence required innovation - Track storm surges with reflected GPS 30 What is compound flooding Definition of compound events - IPCC: Two or more extreme events occurring simultaneously or successively Combinations of extreme events with underlying conditions that amplify the impact of the events Combinations of events that are not themselves extremes but lead to an extreme event or impact when combined; the contributing events can be of similar (clustered multiple events) or different types - A compound event is an extreme impact that depends on multiple statistically dependent variables or events - The combination of multiple drivers and/or hazards that contributes to societal or environmental impacts Storms surges and tsunamis Other lecture Mitigation eg. New Orleans, 2005 Hurricane Katrina (from geology to a storm surge) - Damage was exacerbated by engineering and poor land-use planning - Older parts of the delta have sunk - primarily due to compaction of sand and mud and oxidation of organic material in the sediments - As the delta grows seaward, the city gets lower relative to the river Options for the future - RETREAT Move to places with higher elevation Minimises loses and maximises the cost-effectiveness of the operation - ACCOMMODATE/ADAPT Let natural system effects occur Accommodate rises and minimise human impacts For many Asian countries, adaptation is the immediate priority to respond to sea-level rise - DEFEND Soft or hard engineering Coastal protection measures, eg. building a seawall, etc. eg. The “Great Garuda” Jakarta seawall, Dutch floodgates: Maeslantkering 31  WEEK 10 - LECTURE 11 - 21 OCT 2024 What is a cyclone How, where and why do cyclones occur? Cyclone: from the Greek “kuklos” = circle - Everywhere else in the right condition - There are no cyclones along the equator because the Coriolis force is zero Hurricane: from “Hurican” = the Caribbean god of evil - Caribbean Western - Atlantic NE Pacific Typhoon: from the Greek “tuphon” = whirlwhind, reinforced by the chinese “tai fun” = big wind - Northwest Pacific (but they are all basically the same thing) What causes a cyclone - Warm water to provide energy More than 26oC to at least 50m depth (generally 5-20 degrees N and S of the Equator) Strong latitudinal control on temperature Western parts of the basins are warmer Ocean currents ➔ Cold currents inhibit the development of cyclones ➔ Water has the largest heat capacity (latent heat) ➔ Ocean water becomes the largest energy pool hence it is very difficult to change the temperature of ocean water ➔ Ocean currents circulate both horizontally and vertically 32 - A favourable atmospheric profile (wind speed has to be stable along the atmospheric layer) Warm, supersaturated air up to 6km above sea level (latent heat from condensation leads to warm air) ➔ Condensation RELEASES heat/energy → energy is used to supply the atmosphere uprising Low variation in wind speed with height < 10m/s Cool air at height to prevent warm air from continually rising - A strong Coriolis force Most cyclones move from EAST to WEST because of the spinning of the Earth Northern hemisphere - anticlockwise rotation (Singapore) ➔ Path of cyclone deviates to the right Southern hemisphere - clockwise rotation ➔ Path of cyclone deviates to the left - An initial disturbance (aka a little bit of spinning to start it) Tropical disturbance: towering thunderstorms with maximum sustained winds < 40km/h Tropical depression: inward flowing of air starts to rotate under Coriolis for defined surface circulation (centre of cyclone has to be LOW PRESSURE centre, so that surrounding water vapours will move into the centre); maximum sustained winds < 63km/h Tropical storms (wind 60-120 km/h) Cyclone (air descends into the storm centre where rotation is weakest, warms, thus evaporating cloud and forming the “eye”; winds speed > 120km/h) 33 Physical processes - Diameters: range from 300 to > 1500 km - Air pressure: > 1000 hPa near the edge, as long as 950 hPa or less in the central eye. Minimum recorded eye pressure was 870 hPa. Pressure is important for storm surge - Wind speed: ~30km/h near the edge. At the edge of the eye, winds may be consistently faster than 240km/h. In the eye itself, winds might be light and variable. - Speed of forward motion: generally < 40km/h. They are faster in more temperate climates where other air systems are moving faster. The nearer the equator, the slower their forward speed Hazards - Strong winds Wind strength is dependent on pressure - Storm surge Piling up of water from onshore winds → Low pressure elevated ocean surface (eg. 870 hPa can produce an additional 6.6m rise in sea level) → Bathymetry shallowing water increases wave height Greatest storm surge associated with cyclones can be > 9m Storm surges flood low-lying terrain and provides a base for high waves to move further inland Level of storm surge depends on: ➔ Size of storm: larger wind field = bigger storm surge ➔ Forward speed: slower storms = bigger storm surge inland; faster storms = bigger storm surge on open coast ➔ Angle of approach (geometry): perpendicular to coast = more storm surge - Poorer informal communities that are the most vulnerable - Often, people will rebuild straight back in the same place after a cyclone (eg. Cyclone Ketsana, Philippines, 2009) Cyclone Impacts - Strong winds impact property (eg. Ketsana, Philippines, 2009; Hurricane Irma, Caribbean, 2017) Water inundation results in greatest loss of property Wind-borne missiles (eg. a piece of wood piercing through a tree branch) Damages to ships 34  - People Drownings (90% of cyclone-related fatalities) Building damage Wind-blown debris Landslides - Global costs related to cyclones have dramatically increased Rapidly growing populations along the coast More expensive buildings - Number of deaths has decreased Improved ability to predict landfall locations Coordinated ability to evacuate populations at risk Warning/Monitoring Since tropical cyclones move relatively slowly (compared to seismic waves), and are so large, satellite and ship-borne platforms can monitor their path - Cyclone warning system Provides information on location, intensity and movement up to 5 days ahead Analysis and forecasts with lead times of up to 24 hours are usually updated every 3 hours When a tropical cyclone moves within the vicinity of a region, analysis information is issued hourly and more detailed forecasts with 3-hourly information covering the period up to 24 hours ahead are issued to advise the public of possible impending disaster conditions Mitigation eg. Hurricane Rita, USA, 2005: Just three weeks after Hurricane Katrina devastated the northern Gulf Coast, the threat of yet another major hurricane prompted mass evacuations in coastal Texas. An estimated 2.5 – 3.7 million people fled prior to Rita's landfall, making it the largest evacuation in United States' history. - Mangroves, dune systems & coral reefs protect communities from storm surges and waves - Boarding up windows to defend against wind damage 35 Is Singapore safe from cyclones? — Not really Thunderstorms and Lightning Thunderstorms - Most common in latitudes near the equator (eg. Singapore) - Form as unstable, warm and moist air rapidly rises into colder air and condenses, releasing heat and causing updraft - Water droplets freeze in anvil-shaped cumulonimbus clouds - Cold air pushing under warm air along cold front is common triggering mechanism - Lightning strikes can kill people, while strong winds knock down trees, power lines and buildings. Thunderstorms can also cause wildfires, hail and tornadoes *tornadoes are smaller forms of cyclones, but they are NOT the same Lightning - Lightning is an electric discharge, or spark, that occurs in thunderstorms - (usually) 80% occurs within clouds, 20% occurs between cloud and ground - Lightning is ubiquitous, with more than 6000+ ground strikes per minute from 40000 thunderstorms per day worldwide How lightning is formed - Results from the strong separation of charge that builds up between top and bottom of cumulonimbus cloud - Charge separation increases as water droplets and ice particles are carried in droplets and collide with downward-moving ice particles or hail Lightning only occurs in cold clouds with super cooled droplets and temps below -15oC, hence ice crystal processes responsible for precipitation in cold clouds is likely to play a critical role in charge separation - The top cloud carries a strong positive charge (+), bottom cloud carries strong negative charge (-) - Negative charges near bottom of clouds attract positive charges toward ground surface, especially to tall objects - Eventually, electrical resistance in the air cannot keep opposite charges apart - Negatively charged step leaders angle their way toward theground - Leaders generally fork as they find different paths to ground - Positive leaders reach upward toward them from elevated objects on ground - When one of pairs of leaders connects, massive negative charge follows the conductive path of leader stroke from cloud to ground - Followed by return stroke moving back toward the cloud along established connection - Instantly heats air to temperatures about 28,000oC - Accompanying expansion of air at supersonic speed is thunder (this is why we hear the sound of thunder) - Lightning strikes most frequently in the Democratic Republic of the Congo Thunder: lightning rapidly heats air → intense heating causes the air to expand rapidly → expanding air cools, then contracts rapidly and generates sound waves 36 Lightning in Singapore - Singapore has about 185 lightning days per year - Highest incidence of lightning activity typically occurs in November followed by April and May; these are the inter-monsoon months when the predominantly light and variable winds favour the development of localised and intense thunderstorms - On average, the inter-monsoon months account for more than 50% of the lightning strokes in a year Downbursts and other hazards associated with thunderstorms - Small areas of rapidly descending air can develop in strong thunderstorms - As fast as 200 km/hr - Accompanied by a descending mass of cold air, sometimes rain - Cause wind shear, which can cause planes to plummet to the ground as they lose lift from under wings - Damage sometimes mistaken for tornado, but evidence will show straight-line winds, rather than rotational damage from tornadoes Waterspouts and other weird stormy things Hail - Causes $US2.9 billion in annual damages to cars, roofs, crops and livestock in the USA - Hailstones appear when warm and humid air in thunderstorms rises rapidly into upper atmosphere and freezes - Upward and downward movement accumulates layers of ice until heavy enough to overcome updrafts and fall to ground - Largest hailstones can be larger than a baseball Twisters and waterspouts - A waterspout is an intense columnar vortex (usually appearing as a funnel-shaped cloud) that occurs over a body of water and is connected to a cloud (usually a cumuliform cloud) - While it is often weaker than most of its land counterparts, stronger versions do occur - Waterspouts do not suck up water; the water seen in the main funnel cloud is actually water droplets formed by condensation - Waterspouts are a very localised phenomenon 37  WEEK 11 / 12 - LECTURE 12 - 28 OCT 2024 / 4 NOV 2024 What is climate change How, where and why does it occur Climate change: A change in global or regional climate patterns Climate → weather across a broad area averaged over a long period of time (usually at least 30 years) - Due to global warming, the average temperature has increased by about 4oC - Temperatures at higher latitudes (i.e. Antarctica) are lower Climate: long term atmospheric conditions in a region - Earth’s climate includes interactions of: atmospheres, hydrosphere, geosphere, biosphere, cryosphere - Climate system: exchanges of energy and moisture between these spheres Climate system interacts with all the spheres Majority of the energy in the climate system comes from the sun - Energy is mainly stored and sequestered in the atmosphere, ocean, land and ice *ocean is the largest energy pool due to its huge mass and latent heat Earth’s atmosphere: 1st layer to meet when sun energy comes to earth - Atmospheric layers: Ionosphere - above these layers Mesosphere - up to 90km Stratosphere - up to 50km Troposphere - 0 to 18km - Atmospheric content: 78% N 21% O Less than 1% Ar, CO2 and other trace gases Water vapour 1-4% on average *the earth would be -19oC without atmosphere; clouds also have a greenhouse effect 38 Slide 12 - When there is huge amounts of ice, temperatures is lower - In the last 20,000 years, global temperatures is very stable - If global temperature changes by 2oC, it will be disastrous for human life - Most life on earth concentrates on a latitude of 30-40o, hence further North/South will be too cold for living things to thrive What naturally changes the climate? - Possible explanation for ice ages: variation in Earth’s orbit and rotation - Orbital changes called Milankovitch cycles (these correspond well with at least 20 ice ages) - Orbital changes convert to energy supply changes 39 Milankovitch theories - Eccentricity of Earth’s orbit - Obliquity of Earth’s axis - Precession of Earth’s axis Due to the wobble of the axis Impact due to elliptical nature of orbit What else naturally changes the climate? - Volcanic eruptions Volcanic ejecta (sulfur dioxide) may block sunlight Needs many eruptions in a short time period Not observed in recent history 40 The Earth’s energy balance - Energy from the sun must be balanced by energy lost back into space - If not, will have radiative forcing (RF): difference in energy between top of troposphere and energy below it +ve RF: more incoming than outgoing radiation; warms Earth -ve: RF: cools Earth Physical processes The carbon cycle - CO2 from human activities MORE THAN CO2 plants and oceans can uptake - Greenhouse gases prevent long-wave heat radiation escaping, and also reflect short-wave radiation back to space - “Natural” greenhouse gases Water vapor mostly evaporated from oceans CO2 and CH4 emitted by erupting volcanoes, animals, decaying vegetation, and forest fires NOx generated during lightning storms - Greenhouse gases are also by-products of human activities, such as burning fossil fuels - Pollution: major source of atmospheric particles, particularly affecting developing countries - Positive feedback loop: even if human-caused CO2 emissions stopped today, amount added to oceans would slowly release back, preventing significant atmospheric temperature drop for at least 1000 years 41 Impacts Consequences of climate change - Sea-level rise Coastal areas flood Salt water contaminates freshwater aquifers Low levees overtopped during floods Coastal populations displaced eg. Bangladesh would lose more than 17% of its land with 1m of SLR; annual flood affect 20% of land today; raising levees would be cost-prohibitive - Changes to global oceanic circulation Ocean salinity changes (from melting glaciers and ice sheets) could alter path and strength of Gulf Stream Resulting in cooling in western Europe - More extreme and severe weather Most of Earth’s near-surface heat is concentrated in the oceans ➔ Warmer oceans lead to greater evaporation and more rainfall Ocean heat contributes significantly to the energy that drives storms ➔ Warmer seas will cause stronger, more frequent storms ➔ Changes in circulation patterns may mean storms extend father to the N & S - Glacial melt Himalayan glaciers are important for providing freshwater flow for immense downstream populations in dry seasons Loss of glaciers threatens rice and wheat crops As glaciers melt, they expose surrounding dark rocks that soak up more heat; feedback effect causes more melting Albedo: property of a surface indicating how much sunlight is reflected ➔ High-albedo surfaces: snow and ice reflect much of sun’s energy ➔ Low-albedo surfaces: water and dark land absorb energy and lead to more warming ➔ Can lead to feedback loop: melting ice exposes dark surface of ocean, reflects less energy, heats water, melts more ice Impacts on plants and animals - Plants, animals and humans adapt to climate change, migrate or become extinct - Terrestrial plants and animals are migrating toward poles Higher temperatures in northern climates may improve agricultural production there 42 Warnings/Monitoring Indirect record of climate conditions - Ice cores Scientists can analyse the temperatures of these cores - Tree rings → → Summer more sun and rain lighter rings → → Winter less run and rain darker rings - Sediments (which forms over long periods of time) 43 Nick Shackleton figured out a way to measure changes in the amount of ice on Earth over long periods of time — A “proxy” for ice volume - Where Milankovich used physics to theorise multiple ice ages, Shackleton used chemistry to characterise the ice ages and physics to date them - That proxy used the oxygen isotopic composition of ancient ocean water to tell how much ice existed Oceans are enriched in 18O over 16O when conditions are cooler (as 18O is locked up in ice). Reflected in marine organism shells. Evaporation favours 16O & Precipitation favours 18O 18O is heavier than 16O, but 18O doesn't evaporate easily, so rainwater is actually lighter than the seawater If this lighter rainfall does not return to the sea but is instead deposited in large glaciers, as the ice accumulates, the water in the sea becomes more and more rich in 18 O → Foraminifera they use oxygen in the sea-water to make their shells If the water molecules in the ocean are richer in 18O when they form their shells (like during an ice age), the forams’ shells will also have a greater concentration of 18 O. So, their tiny shells are chemical records of the waxing and waning of Earth’s great ice sheets. We geologists call this chemical record a “proxy.” Record of temperature from the Antarctic ice sheet - Variations in the ratio of lighter and heavier isotopes of oxygen and hydrogen record changes in temperature when the snow fell - One basic observation is that the past ten thousand years is by no means normal; In fact, it appears to be the longest stable time of the past 400,000 years! Dansgaard-Oeschger and Heinrich events are events indicating the high and low temperatures in the last 100,000 years Glacier length as a proxy - Glacier length can be related to temperature through some basic physics → more glaciers, temperature is lower; less glaciers, temperature is higher - Based on the proxy, global average temperatures has risen by 0.6oC over the past 200 years 44 Temperatures of the past 2000 years - Little ice age: global temperatures is much lower than the previous ice age eg. Thames River freezes over 24 times in London / eruption of Tambora Impact to human civilisation: More highly variable weather → Growing seasons in England were shortened by 15-20% → crop failures affecting crop/agriculture production → Great fluctuations in grain prices →led to → significant economic problems led to social and political unrest Another proxy: Rainfall records → Cave deposits - The rain that falls on the Chinese coast is actually isotopically “heavier” than water that falls a couple of days later, farther inland. - Water drips from the top of the cave. The water contains calcite, then when water evaporates, and leaves calcite behind, it forms stalagmites that rise from the floor of the cave - A stalagmite grows when the weather is very rainy and doesn’t grow when the weather is not very rainy. Climate change can impact - Political stability - Food security - Water security - Human progress 45 Climate change impact at relatively SHORT time scale — Walker Circulation Cell - Air pressure across equatorial Pacific is higher in eastern Pacific - Strong southeast trade winds - Pacific warm pool on western side of ocean - Thermocline deeper on western side - Upwelling off the coast of Peru 46 El Nino Southern Oscillation (ENSO) - red part as shown above (THE WARM PHASE) - Walker cell disrupted - High pressure in the eastern Pacific weakens - Weaker trade winds (more warm water remains in the eastern part of the Pacific) - Warm pool migrates eastward - More rainfall in the eastern areas of the Earth - Thermocline deeper in eastern Pacific (less warm water moving out, hence less cool water can supply to the surface of the ocean) - Downwelling - Lower biological productivity (Peruvian fishing suffers) - Some impacts Droughts (in Australia, Africa, Brazil, Indonesia) Floods (in Peru, Southern USA) 47 La Nina - blue part as shown above (ENSO COOL PHASE) - Increased pressure difference across equatorial Pacific - Stronger trade winds - Stronger upwelling in eastern Pacific - Shallower thermocline - Cooler than normal seawater - Higher biological productivity Occurrence of ENSO events - El Nino warm phase occurs about every 2-10 years - Highly irregular - Phases usually last 12-18 months - 10,000-year sediment record of events - ENSO may be part of Pacific Decadal Oscillation (PDO) Long-term natural climate cycle Lasts 20-30 years 48 Mitigation - Need to reduce sources of greenhouse gases - Consume power more efficiently - Act quickly - Change perspective from reacting to short-term threats to recognising the long-term threat The simplest, most effective strategies - Lower transportation-related energy use (eg. use of bicycles, etc.) - Use less fuel to heat or cool homes and buildings (eg. use less air-conditioner) - Use energy-efficient light bulbs, appliances and insulation - Use alternative energy sources (eg. solar, wind) - Minimise deforestation and soil degradation Carbon Sequestration: Artificial - Carbon sequestration: CO2 is removed from the atmosphere and held in solid/liquid form - Artificial carbon sequestration involves the removal of CO2 from a fossil-fuel-burning power plant, transporting it to a disposal site, and storing it permanently underground - Is it possible to conduct carbon sequestration in Singapore? Yes, it has been an option for consideration for years, because porous geological units at anticlines (eg. at St. John’s Island in SG) could be used for CO2 sequestration. Seal layer has low permeability so that carbon dioxide won’t leak out easily. Or carbon dioxide captured in Singapore can be transported to Malaysia/Indonesia’s oil and gas fields. *oil and gas fields are the best for CCS Carbon Sequestration: Natural - Plants (especially forests) store most of the world’s carbon in leaves, branches, stems and roots - Remains in the plant until it decays or is burned 49 Geoenginering solutions Case study - USA - Earth’s atmospheric temperature has been rising since industrial revolution - Climate system in SOUTHERN hemisphere is much more stable because majority of the places are covered by the ocean, which is the largest heat pool - While in the NORTHERN hemisphere, majority are our Continents, hence we see a larger fluctuation of temperatures - Increase in concentration of greenhouse gases will increase the temperature of Earth - IPCC Conclusion: Human influence is the dominating cause for climate change!!!!!!!! - If all Antarctic ice are melted, sea level will rise by 60m, almost all of Singapore will be gone except maybe NTU Student Service Centre - Largest temperature increase is in the NORTHERN hemisphere 50