Term
| What are the three types of plate boundary? |
|
Definition
Conservative
Constructive
Destructive |
|
|
Term
| Describe and exemplify the occurrences at a constructive plate boundary. |
|
Definition
Can occur in two places; on land and in the oceans.
Land; GARV, where the African plate and Arabian plate are moving apart. Plumes of magma are rising, heat land and it expands and bulges to create Ethiopian Highlands and volcanoes e.g. Mount Kilamanjaro, Tanzania. Heated land strectches and creates vast lowlands called grabens, seperated by horsts. Continued activity may lead to the baslatic continental rocks thinning and falling beneath sea level, and Eastern Africa fully detaching from the rest of the continent to create a new ocean.
Oceanic; fissure created as plates move apart and magma rises to created spiralling mid oceanic ridges separated by transform faults at 90 degrees. Different rates of movement lead to shallow focus earthquakes as the stress is released, the activity can also be volcanic for example when submarine volcanoes are created. An example of this is where the North American and the Eurasian plates moved apart along the MAR. 3.5 years of eruption of lava leading to early settlement of tephra material, built up and created the volcanic island of Surtsey which is the most southern part of Iceland. Now is a UNESCO world heritage site and only 6-10 scientists are allowed to visit the island each year in order to protect the naturally high species diversity index. |
|
|
Term
Describe and exemplify the occurrences at a conservative
plate boundary. |
|
Definition
Occur anywhere where the plates are sliding alongside each other. No creation or destruction along Moho Discontinuity and so only very powerful seismic activity occurs.
Example is the San Andreas Fault system where the N Am. plate and Pacific plate are both moving north-westwards but at different rates 6cm PAC and 1cm NA. The focuses occur along the main fault and surrounding fractures through cities like Los Angeles and so create numerous earthquakes affecting San Francisco and Santa Barba regularly. |
|
|
Term
| Describe and exemplify the occurrences at a destructive plate boundary. |
|
Definition
Three types of occurrences; cont + cont, oceanic + oceanic and cont + oceanic.
Continental + oceanic is about a key process called subduction and a key example is along the Western coast of South America where the Nazca plate and S Am. are converging. The thin but dense Nazca plate is forced under the lighter continental plate and consequently the lithosphere bends downwards and frictional stresses build up creating deep focus earthquakes and even andesitic volcanic eruptions. The latter are caused when the continental plate rises, buckles and breaks to create fold mountains and the plumes of magma rises between the gaps and create explosive eruptions where the silicates melt around the Benioff zone at 100km and erupt violently. An example of this is in the Andes mountains in Chile.
Oceanic and oceanic is again about subduction, but because they're of similar densities, its hard to tell which will be subducted. The answer lies in their density or speed of movement, the denser or faster plate is subducted. The resulting land form is a deep ocean trench and a point of melting, 100km deep called the Benioff zone. The rising magma from the BZ can form island arcs or an archipelago such as the Mariana Islands along the Marianas Trench (deepest point of earths crust on earth) where the pacific plate is being subducted under the Philippines plate to create the most volcanically active convergent plate boundary in the world.
Cont + cont is where the less dense continental plates float along the asthenosphere and NO SUBDUCTION OCCURS SO NO VOLCANIC ACTIVITY. Collisions simply result in the creation of fold mountains as sediments buckle and become uplifted. Shallow focus earthquakes is all. Example would be the creation of highest mountain range in the world, Himalayas, created by the convergence of the Indo-Australian plate and the Eurasian one along the boundary of China and Nepal. |
|
|
Term
| What is the relationship between the location of both plate boundaries and seismic/ volcanic activity? |
|
Definition
| 95% of the world's earthquakes lie along the boundaries and the majority of volcanoes are too, most notably around the Pacific RING OF FIRE. Even seemingly noticeable exceptions such as the Hawaiian Islands can be partially explained by the theory of plate tectonics. |
|
|
Term
| What is the Ring of Fire? |
|
Definition
| 40,000km horseshoe shape around the Pacific plate boundary where 90% of the worlds earthquakes occur and 75% of the worlds active and dormant volcanoes lie. |
|
|
Term
|
Definition
Radioactive decay within the core has a big role to play within the creation of hot spots. Instead of the usual convection currents in the mantle, the temperatures generated are much higher and so magma shoots vertically upwards from the core. As lava builds, it gradually creates underwater mountains. These grow as more lava is deposited while ever it's located over the hot spot and surfaces above the Pacific ocean. Surface flows of aa lava and ropy pahoehoe are common. This, combined with the NW movement of the Pacific plate has created the chain of island that we know today of as the Hawaiian islands; a state of USA. The chain of islands show an important pattern, the larger islands are the newer ones; i.e. Hawaii is the largest and is only 71000 years old whereas Kauai is 5.5 million years old and is about to disappear. This link is explained by erosion, the older the island is, the more its been exposed to erosional processes of the Pacific ocean e.g. abrasion, attrition etc.
The big island is also home to 2 world record breaking volcanoes, Mauna Loa (biggest) and Kilauea (most active). |
|
|
Term
| Describe what happens over a period of time in relation to hotspots. |
|
Definition
First stage is the common eruptions of ropy pahoehoe and aa lava.
Second stage is when the movement away from the hotspot leads to the lava becoming more alkaline. Therefore cinder and spatter cones occur. E.g. on Maui
Third stage is where the eruptions become more violent and can cause pyroclastic flows. E.g. Oahu |
|
|
Term
|
Definition
| Volcanicity is or vulcanism is one of the endogenetic processes affecting the earth, i.e. one that comes from within to produce and refine landforms. The converse is exogenetic e.g. the moon causes our tides resulting in the creation of coastal landforms. Its two types are intrusive and extrusive. |
|
|
Term
| What is intrusive volcanic activity? Exemplify your answer. |
|
Definition
| Intrusive activity is volcanic activity that occurs beneath the surface, i.e. doesn't protrude through rocks. Examples of landforms caused by intrusive activity would be Dykes, Sills and batholiths. |
|
|
Term
| What is extrusive volcanic activity? Exemplify your answer. |
|
Definition
| Extrusive activity therefore occurs ON THE EARTH'S surface and is classified as major and minor. Major is the actual eruption and lava flows, minor includes hot springs, geysers and boiling mud pools. |
|
|
Term
| What are the hazards of volcanic activity? |
|
Definition
Lava flows- burn and bury crops, people and livestock.
Submarine, coastal eruptions- Tsunamis
Ash- ruins crops, air quality and transport links.
Dust emissions- air transp. inter, heavy rain- mud lahars.
Debris- blocks rivers, can cause flooding.
Pyro flows- kill and destroy.
Melting snow- causes lahars.
Dust- absorbs solar radiation and lowers atmosp, temps. |
|
|
Term
| What are the benefits of volcanic activity? |
|
Definition
Lava flows- creation of new land e.g. Hawaii
Hot rocks- geothermal power e.g. Iceland
Igneous rocks- valuable mineral deposits e.g. gold, silver, valuable building materials e.g. granite.
Sulphur released- pharmaceutical uses.
Lava and ash- fertilise soils once weathered.
Craters- good tourist locations.
Hot springs and boiling mud- geothermal. |
|
|
Term
| Describe the forms of intrusive volcanic activity. |
|
Definition
Magma within intrusive features cools, crystallises and solidifies to form igneous rock. Very slow cooling results in large crystals forming such as granite. The rocks are exposed after many years of eorision for example in Northern England and Scotland.
DYKES- solidification within a fissure surrounded by country rock. Creates low ridges a few m high or depressions if the dyke is easily eroded. E.g. Scotland (Skye and Arran)
SILLS- Solidification as layers between pre-existing rock on an incline. A few m high. E.g. Hadrians Wall on the Great Whinn Sill.
BATHOLITHS- Forcful magma bulges rock strata into dome, due to intense heat, a metamorphic aureole is created around the dome and the rocks undergo metamorphism. Creations include marble and slate. |
|
|
Term
| Describe the forms of extrusive volcanic activity. |
|
Definition
Major activity is classified by the type of volcano. The types are:
Shield volcanoes: Basaltic, HV, gentle sloping sides e.g. Mauna Loa, Hawaii.
Dome: steep-sided convex cones,HV probably rhyolite e.g. Puy region of central France.
Ash and cinder: ash, cinders and volcanic bombs ejected from the crater. The sides are steep and symmetrical, for example Paricutin, Mexico.
Composite cones are the classic pyramid-shaped volcanoes, consisting of layers of ash and lava, which is usually andesitic. Examples include Mt Etna on Sicily, and Mt Fuji in Japan.
Calderas occur when the build-up of gases becomes extreme and a huge explosion removes the summit of the cone, leaving an opening several kilometres in diameter. The caldera may become flooded by the sea, or a lake may form within it.
Minor includes geysers, hot springs and boiling mud.
GEYSERS- Hot water fills cavities, continues heating and ejects when flashes into steam. Old Faithful Geyser, Yellowstone (every 65 minutes).
HOT SPRINGS- constant heating of the groundwater beneath surface by hot rocks (never boils and ejects).
BOILING MUD POOLS- steam and gas rise under rain ponds, acidity produces clay, clay mixes with hot water to produce boiling mud. Common in New Zealand. |
|
|
Term
| How are volcanoes classfied? |
|
Definition
Refers to level of violence of the eruption. This depends on the amount of pressure, and also the amount of gas or silica in the magma.
Ranges from QUIET with basaltic lava (Icelandic of Hawaiian) to MODERATE with andesitic (Vesuvian) and then to VIOLENT with rhiolytic lava (Krakatoan eruptions). |
|
|
Term
| When do natural events become natural disasters/ hazards? |
|
Definition
Volcanic effects become a hazard when they impact upon the human and
built environments, killing and injuring people, burying and collapsing
buildings, destroying the infrastructure and bringing agricultural activities to
a halt. |
|
|
Term
| What are the primary effects of most volcanic eruptions? |
|
Definition
TEPHRA- solid material of varying size from volcanic bombs to ash particles.
PYROCLASTIC FLOWS- very hot (800 degrees) gaseous and tephra filled flows moving at high velocity down the slopes.
LAVA FLOWS
VOLCANIC GASES- CO CO2 H2S and SO2 |
|
|
Term
| What are the secondary effects of most volcanic eruptions? |
|
Definition
• Lahars - volcanic mud flows such as those that devastated the
Colombian town of Armero after the eruption of Nevado del Ruiz in
November 1985
• Flooding - melting of glaciers and ice caps such as the Grimsvotn
glacial burst on Iceland in November 1996
• Tsunamis - giant sea waves generated after violent caldera-forming
events such as that which occurred on Krakatoa in 1883
• Volcanic landslides
• Climatic change - the ejection of vast amounts of volcanic debris into
the atmosphere can reduce global temperatures and is believed to
have been an agent in past climatic change. |
|
|
Term
| What are the four ares that are to be considered inrelation to management of natural hazards? |
|
Definition
Prediction
Protection
Planning
Foreign Aid |
|
|
Term
| GIve two examples of recent volcanic events that you've studied in two contrasting ares of the world. |
|
Definition
CHANCES PEAK VOLCANO 18/07/95 and 25/07/97- Montserrat, British Territory but located in the Caribbean Island arc (Lesser Antilles) where the Atlantic Plate is being subducted under the Caribbean.
MOUNT ETNA 15/12/91 till 31/03/93- Sicily, Island off the Southern point of Italy. (GDP of $20,000) Where the african and eurasian plates are thought to be moving apart causing the process of rifting, similar to the GARV. |
|
|
Term
| Describe the eruption and its nature of an LEDC eruption. |
|
Definition
CHANCES PEAK,
18/07/95- ash and dust began to flow so scientists began to monitor gases, microquakes and changes in the volcano's shape and so it was only dormant, not extinct. 01/04/96- population was forced to evacuate the capital city of plymouth for fear that the eruption would consume the whole of the southern island.
25/07/97 erupted violently as a Vulcanian eruption, all 3 with a dome building, collapsing and then 5 million cubic metres of lava and pyroclastic flows falling down the Soufrierre Hills as ash, dust and mud up to 200m/s. Fertilises soil to enable cash crops to be grown such as Sea Island Cotton. |
|
|
Term
| Describe the nature and eruption of the MEDC volcanic eruption you've studied. |
|
Definition
Etna is a nest of composite volcanoes with many collapsed calderas, similar to the structure of a set of russian dolls. It causes a regular natural hazard as over 25% of Sicily's population live on the flanks of Etna. Its eruptions are usually
dominated by effusive activity (Hawaiian) and sometimes mild Strombolia (frequent, explosive, tephra filled, few lava flows).
15/12/91- Hawaiian coming from a fissure on the South East crater, lasted for over a year.
08/11/090 Strombolian from same crater but combined with a 4.4 magnitude earthquake. |
|
|
Term
| Describe the effects of the LEDC volcanic eruption you have studied. |
|
Definition
SHORT TERM
Soc-19 people killed, over 400 burn related and breathing problems reported. 2/3 land evacuated and called the exclusion zone.
His-
Eco- 3/4 infrastructure destroyed, 2/3 housing.
Env- farmland for sea island cotton destroyed and 5000 livestock killed.
Pol- all entitled to UK residency
LONG TERM
Soc-Top heavy pop pyramid created as youths see no future.
His-Loss of culture as over half of 11000 pop went to Antigua
Env-Sea Island Cotton thrived after initial wipeout from highly fertilised soils created as the silicates and manganese absorbed into the soil.
Eco- WH Bramble airport closed for 2 weeks while ash cloud dissipated.
Pol- New government base created in Brades, the new capital, around the docklands of Little Bay. |
|
|
Term
| Describe the effects of the MEDC volcanic eruption you have studied. |
|
Definition
SHORT TERM
Soc-NO DEATHS, 8000 no water in Zafferana
His-
Env-250 million cubic metres of AND and RHY lava, low effusion rate so didn't threaten humans.
Eco-7 million Lira in cost of insurance claims for land and housing.
Pol-
LONG TERM
Soc-Tourist industry boomed.
His- loss of traditional methods of making livelihood
Env-
Eco-money used for response schemes and regeneration of ski resort (Piano Battaglia)
Pol- |
|
|
Term
| Compare the management strategies put in place for two contrasting volcanic events. |
|
Definition
CHANCES PEAK, MONTSERRAT
Immediate: Montserrat Volcano Observatory set up in 95, predicted 97 successfully.
NGOs like Red Cross sent aid.
£17 million from UK Government sent.
Long term: 3 year redevelopment
Tourists returning in numbers as features in national geogrpahic magazine.
MT ETNA
Immediate: US army, 2 tonnes of concrete to make barriers. Airport closed. £5.6 million of aid.
Long term: Prediciton- NASA-MODIS use satellites to monitor ash clouds. Gas samples taken by Sicilian Vulcanolgy centre to test for high sulfur and CO.
Planning: emergency rations, exclusion zones, evacuation, communication. |
|
|
Term
| What are the four ares that are to be considered inrelation to management of natural hazards? |
|
Definition
Prediction
Protection
Planning
Foreign Aid |
|
|
Term
|
Definition
| Study of shaking ground. 95% of time, seismic acitivity occurs around plate margins. |
|
|
Term
| How is an earthquake created? |
|
Definition
| Movement of plates isn't always smooth, at times, they 'stick' and friction builds stress within the lithosphere. Sudden release results in fractures called faults, the point of fracture is called the focus. The epicentre is therefore the point on earth directly above the focus, i.e. its geographical location. |
|
|
Term
| How is an earthquake created? |
|
Definition
| Movement of plates isn't always smooth, at times, they 'stick' and friction builds stress within the lithosphere. Sudden release results in fractures called faults, the point of fracture is called the focus. The epicentre is therefore the point on earth directly above the focus, i.e. its geographical location. |
|
|
Term
| How long do eartghquakes last? |
|
Definition
| The initial release of pressure lasts for minutes at most within the lithosphere, but humans experience the afterschocks which can last for several weeks while the crust settles again. |
|
|
Term
| Identify the different types of shockwaves. |
|
Definition
Body waves:
P (primary waves)
S (secondary)
Surface waves:
L (surface love)
R (Rayleigh) |
|
|
Term
|
Definition
| Primary or push waves send compressions through the crust, mantle and core. They're the fastest and so hit first with the highest frequency, similar to sound waves. |
|
|
Term
|
Definition
| Secondary or shear waves are half as fast a P waves and so arrive second in movement similar to the wriggle of a skipping rope, i.e. vertically. The can't travel through solids and so won't be felt on the opposite side of the earth to the focus because they haven't travelled through the core. |
|
|
Term
|
Definition
| Love waves are the slowest and shake the ground from side to side, causing the most damage on land. |
|
|
Term
|
Definition
| Rayleigh waves radiate from the epicentre and occur in complicated low-frequency rolling motions in a vertical movement. |
|
|
Term
| How are earthquakes measured? |
|
Definition
Seismometers record the amount of energy released during an earthquake, i.e. the magnitude. They also record the direction (horizontal/ vertical)of the vibrations.
Seismic records have been built up over time and so can now be used in order to predict when the next earthquakes will occur. |
|
|
Term
| What are the scales for measuring earthquakes? |
|
Definition
Magnitude is measured by Richter!
Logarithmic, so a M2 is ten times as powerful as an M1. Anythign of M6 is considered destructive, with the highest value ever recorded being a 9.5 in Chile in 1960.
Scale of damage is the Modified Mercalli! Goes on observational characteristics from I (Imperceptable) to XII (catastrophic). I can't be felt by humans, 3 is moderate and rattles doors, 8 is destructive and chimneys will fall and then 12 is castastrophic and complete devastation will be incurred. |
|
|
Term
| Give two examples from contrasting areas of the world for seismic events that you have studied. |
|
Definition
MEDC- L'Aquila, Italy 06/04/09
LEDC- Port au prince, Haiti 12/01/10 |
|
|
Term
| Why are the effects of natural hazards more severe in LEDCs? |
|
Definition
| Volcanic eruptions; Montserrat more severe than Mt Etna because far fewer management strategies in place. Little attention given as Chances Peak was thought to be dormant. No plans created for if an eruption occured. Key infrastructure built there in the 90s so effects were felt worse. |
|
|
Term
| Describe the full case study of a seismic event in an MEDC. |
|
Definition
L'Aqiula, 06/04/09
CAUSES
African plate pushing into eurasion plate at 3cm/ year. Caused the young fold mountain range of the alps and makes Italy one of the most seismically active countries in Europe. L'Aquila was probaby caused from stresses built up along the line of the Apennine mountain range. Was most destructive because its focus was only 10km deep. Struck in early hours, 7km north of L'Aquila as a 6.3 on richterscale.
EFFECTS
SOC- Collapse of homes caused the majorit of the 305 deaths.
300 aftershocks hampered most rescue efforts, destroying transport links.
Looting occured meaning people wanted to remain in their homes or businesses.
34000 lived in temporary tents as they were homeless.
HIS- 10,000 buildings damaged in L'Aquila including cathedral of historical importance.
ENV- landslides, disrupted 15000km of land used for farming.
RESPONSES AND MANAGEMENT
Initially: red cross food garden, 10,000 meals per day organised by italian government.
train companies turned free and gave up carriages as tewmporary accomo.
Long term: government repaying whole cost inc 2.4 billion euro hardship grants.
creation of new cities to stimulate economic growth.
People still living in the emergency accomo provided even after President Burlusconi claimded L'aquila would become focus of his development.
PREPERATION- They now eartquak-proof the buildings by following the EMSC guidelines. |
|
|
Term
| Describe fully the case study for an LEDC seismic event. |
|
Definition
Haiti, Jan 2012.
Same magnitude on richter scale as san fran one (7) but 1/4 million lives lost compared to 63. Largely due to the lack of control the government has over the way people live their lives.
CAUSES
The caribbean islands sit on the strike-slip fault which is similar to the san andreas. The C and the NA plates in an EW direction then catch, 2008, then ping 2010. Magnitude 7. Epicentre was 15 miles from PAP but energy equivalent to atomic bonb was transmitted in the waves skaing the entire country.
EFFECTS
SOC- 250,000 killed, PAP des. in 20 sec
HIS-50% buildings bes, inc gov.
ENV-corals pushed north into unfamiliar habitats where some died.
ECO-
POL-
SOC-aftershock of 6.1 killed more and 7 died from tsunami.
HIS-
ENV-
ECO-$7.9 billion cost
POL-civil servants lost, gov crippled, country lost order. |
|
|
Term
|
Definition
| Often mistakenly termed tidal wave, they are the result of seismic activity. The wave differs from your typical because it is the cause of wind or tide, and the wave height is low out to see (1m) and high to land (<25m) and the length long 100km to 1000km. |
|
|
Term
| What are the typical characteristics of Tsunamis? |
|
Definition
-Long wavelength (dist between crests) from 100km to 1000km.
-Low waveheight out to sea (1m) and and high on shore (25m).
-Wave period is very long (time between) can range from 10-60 minutes.
-Usually a series of waves, with first not always being biggest.
-Often, when funneled into an inelt, the waves build up and break as one wave wall onto the shoreline.
-Speed of the waves ranges from 400-600MPH. |
|
|
Term
| What factors affect the destructivity of a tsunami? |
|
Definition
-Whether there are warning systems in place or not e.g. Pacific Tsunami Warning System, Hawaii.
- In Pacific oceanor not; 90% of Tsunamis occur here as its bordered by the ring of fire (most active collective boundary on earth also 90% earthquakes and 75% of volcanoes).
-Land use
-Land relief
-Population density |
|
|
Term
| Example and summarised case study of a Tsunami. |
|
Definition
BOXING DAY DISASTER, INDIAN OCEAN (2004)
Indo australian pushing north, being subducted by the south east moving eurasion. Sudden drop of 15m. Started a chain of tsunamis. SHALLOW FOCUS MADE EVERYTHING MORE DEADLY, was already SECOND WORST EVER RECORDED at 9.3 on Richter.
EFFECTS
Soc-
His-
Env-
Eco-
Pol-
Soc-
His-
Env-
Eco-
Pol- |
|
|
