living with tectonic hazards - risk or opportunity

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living with tectonic hazards - risk or opportunity by Mind Map: living with tectonic hazards - risk or opportunity

1. natural hazards

1.1. naturally occurring event

1.2. threatens human lives

1.3. causes damage to property

1.4. of different types

1.4.1. tectonic caused by plate movements when continental crusts and ocean floors move results in earthquakes and volcanic eruptions concentrated near the coastlines of the Pacific Ocean

1.4.2. climate-related caused by severe and extreme weather and climate conditions results in floods, storms, droughts, and tropical cyclones widely distributed throughout great oceans and regions

2. internal structure of earth

2.1. lithosphere

2.1.1. crust earth's outermost layer (which we live on) is less than 1% of earth's volume range in thickness from a few km to more than 70 km

2.1.2. upper mantle lies above core (together with lower mantle) occupies 80% of earth's volume (together with lower mantle) is 2900 km thick (together with lower mantle) made up of mostly solid rock that flows under high temperature and pressure

2.1.3. is rigid and brittle

2.1.4. floats on softer asthenosphere

2.2. asthenosphere

2.2.1. lower mantle

2.2.2. core at centre of earth radius of about 3500 km composed of mostly nickel and iron inner core is solid due to extreme pressure exerted on by surrounding layers outer core a liquid layer of approximately 2100 km thick temperature estimated to be between 3000 to 5000 degrees

2.2.3. where high temperatures and pressure bring the rocks close enough to melting point to be easily deformed

3. tectonic plates

3.1. combine to form the crust

3.2. move in relation to one another

3.3. made of oceanic crust

3.3.1. beneath oceanic deeps

3.3.2. thickness between 5 to 8 km

3.3.3. consists of mainly basalt a heavy and dense rock formed form magma which has cooled quickly

3.3.4. a heavy and dense rock formed form magma which has cooled quickly

3.4. made of continental crust

3.4.1. beneath the earth's continental land masses and under shallow seas close to continents

3.4.2. thickness between 35 to 70 km

3.4.3. consists of lighter rock e.g. granite

3.4.4. wide range of rock ages - from recent to 4 billion years old

3.5. made of both

3.6. movement

3.6.1. caused by convection currents and slab-pull force

3.6.2. move few cm per year

3.6.3. noticeable over centuries because plate movements alter distribution of earth's land masses over hundred millions of years

3.7. boundaries

3.7.1. convergent where plates move away from each other where plates become faulted, folded and subducted along the north of the Pacific plate and North American plate between Philippine plate and Eurasian plate found at oceanic-oceanic plate boundaries convergence leads to denser plate subducting under other less dense plate denser subducting plate causes mantle material above to melt and form magma magma rises through crust to form volcanoes then chain or arc of islands earthquakes occur at boundary between two plates due to friction created between moving rock masses when plate subducts under another Pacific plate subducts beneath Philippine plate to form Mariana Trench and Mariana Island found at continental-continental plate boundaries two continental plates may collide and push against one another and resist subduction causes plates to break and slide along fractures in crust layers of rock on upper part of crust then compress together, fold upwards or sideways, creating fold mountains between Indian plate and Eurasian plate - formation of Himalayas found at oceanic-continental plate boundaries denser ocean plates subducts under less dense continental plate ocean trench forms at subduction zone fold mountains are formed on continental plate active volcanoes are formed on continental plate when magma below crust rises to surface earthquakes may occur on continental plate near Sumatra where Australian plate subducts under section of Eurasian plate - formation of Sunda trench

3.7.2. divergent where plates move away from each other and cause fractures where new oceanic crust forms due to magma moving upward to cool found at oceanic-oceanic plate boundaries where magma rises from mantle to form new sea floor between plates as they move apart forms a mid-oceanic ridge Mid-Atlantic Ridge in the middle of Atlantic Ocean (formed when North-American plate and Eurasian plate moved away from each other) found at continental-continental plate boundaries cause land masses to break up cause fractures to form on continental crust pulled apart crust leads to formation of rift valley East African Rift Valley

3.7.3. transform where plates move past each other movement results in formation of transformation fault process whereby tremendous stress builds up and is eventually released in the form of violent earthquakes San Andreas Fault between Pacific plate and North American plate in 1906, earthquake occurred in San Francisco, Southern California, at San Andreas Fault several hundred Kim of North American plate moved an average of 2.5 m (and almost 7 m at one point) in less than a min North Anatolian Fault between southern section of Eurasian plate and Anatolian plate Anatolian plate is considered to be a separately moving section of Eurasian plate in last 70 years, a major earthquake occurred every 10 years on average along said fault

3.7.4. developing where parts of a plate move in different directions African plate where intense earthquake and volcanic activity are likely to be present

3.8. areas of deformation and active earthquake fractures are present

4. landforms

4.1. found at different plate boundaries

4.2. movement of plates at different plate boundaries results in formation of various landforms

4.3. fold mountains

4.3.1. formed at convergent plate boundaries where plates move towards each other and collide resultant compressional force creates immense pressure which causes layers of rocks to buckle and fold process known as folding at most basic level, folding involves compression of rock layers into wave-like structures known as folds in a folded rock layer when compressional force on one limb of hold increases, rocks may buckle until a fracture forms limb then moves forward to ride over the other folding is common in sedimentary rocks as said rocks are more flexible than igneous rocks or metamorphic rocks

4.3.2. Rocky Mountains located in North America formed from almost complete subduction of Juan de Fuca plate beneath North America plate considered geologically young since less than 100 million years old

4.3.3. Himalayas formed millions of years ago when Indian plate and Eurasian plate collided span across Southern Asia considered geologically young since less than 100 million years old

4.3.4. Andes

4.3.5. Tibetan Plateau tallest and largest on earth formed millions of years ago when Indian plate and Eurasian plate collided

4.3.6. Appalachian Mountains located in USA old and formed about 270 to 400 million years ago

4.3.7. Ural Mountains located in Russia Federation old and formed about 270 to 400 million years ago

4.4. rift valleys

4.4.1. formed at divergent plate boundaries where plates are pulled apart and giving rise to faults a fault is a fracture in rocks along which the rocks are displaced tensional forces from these movements result in parts of crust being fractured process is called faulting sections of crust extend along these faults tensional forces cause central block of land to subside between pair of parallel lines to form a rift valley tensional forces cause land masses surrounding block of land to subside to form a block mountain between pair of parallel faults rift valleys and block mountains may occur in isolation but multiple rift valleys and block mountains can sometimes be found in the same area Basin and Range Province of North America

4.4.2. valleys with steep sides

4.4.3. East African Rift Valley formed due to divergent movement of Somalian boundary of African plate and Nubian boundary of African plate

4.4.4. Hutt Valley of New Zealand formed due to divergent movement of Australian plate and Pacific plate

4.5. block mountains

4.5.1. formed at divergent plate boundaries

4.5.2. blocks of land with steep slopes left standing higher than surrounding land

4.5.3. Vosges in France separated from Black Forest by Rhine Valley formed from divergence of Eurasian plate and North American plate

4.5.4. Black Forest in Germany separated from Vosges by Rhine Valley formed from divergence of Eurasian plate and North American plate

4.6. volcanoes

4.6.1. formed by magma ejected from mantle onto earth's surface magma is molten rock found below earth's surface and builds up within crust to form a magma chamber magma chamber - reservoir of molten rock beneath earth's crust

4.6.2. formed at convergent and divergent plate boundaries where there is subduction

4.6.3. mantle material melts at subduction zone to form magma

4.6.4. magma rises as it is less dense than surrounding rock and accumulates in magma chamber

4.6.5. pressure in magma chamber builds up until magma forces its way onto earth's surfaces through vents vents are openings in earth's surface with pipe leading into magma chamber magma ejected onto earth's surface is known as lava upward movement of magma both into earth's crust and surface is known as vulcanicity

4.6.6. lava builds up around vent to form volcanos

4.6.7. types stratovolcanoes as more magma seeps into magma chamber, amount of pressure builds up and gives rise to volcanic eruption eruption releases pyroclasts new eruption of lava covers pyroclasts (to prevent erosion) and builds up volcano lava builds up around the vent and solidify to form small volcanic cone vent may become blocked during formation of volcano forces magma to find new exit route to surface secondary cone of newer volcanic material will then develop successive eruptions build a high volcano with a slightly concave profile summit of volcano may be blown off during an explosion eruption sides of crater then collapse inwards due to lack of structural support results in large depression known as caldera formed Mount Pinatubo in the Philippines Mount Mayon in the Philippines Mount Merapi in the Indonesia shield volcanoes have gently sloping sides have broad summit formed where low-silica lava has been ejected low-silica lava flows easily and spreads out over large area before solidifying eruptions are usually not explosive due to nature of lava successive eruptions allows base of volcano to increase in size as lava accumulates common near divergent plate boundaries where magma can rise directly from mantle Mount Washington in USA

4.6.8. vary in shapes and sizes due to characteristics of lava low-silica lava low viscosity allows for gases to escape easily flows more easily through vent before reaching surface outer layer of cooling lava forms thin crust once on earth's surface high-silica lava high viscosity traps air more easily as magma moves towards earth's surface ejection ejects lava, ash, rock fragments and gases into surrounding environment viscosity - refers to the stickiness of the lava grits resistance to flow

4.6.9. distribution close correlation between distribution of major active volcanoes and location of plate boundaries regions / places Pacific Ring of Fire diverging tectonic plates

4.6.10. volcanic eruptions state of volcanoes active - refers to volcanoes which are currently erupting or are expected to in near future dormant - refers to volcanoes which are currently inactive but may erupt in near future extinct - refers to volcanoes without current seismic activity with no geological evidence of eruptions for past thousands of years risks of living near volcanic areas subduction zones of Pacific Ring of Fire massive destruction by volcanic materials such materials: lava, pyroclasts (consist of ash, rock fragments, and volcanic bombs) lava has high temperatures of between 500 degrees and 1400 degrees and burns ares it flows through low-silica lava moves rapidly and flows over a long distance to cause damage to larger areas pyroclastic flows can destroy everything in its path with hot rock fragments ranging from ash to boulders travelling at speeds greater than 200 m/s inhaling said hot ash and gases can result in serious injury or death volcanic bombs of heated rocks can fall in areas surrounding volcanoes and cause damage to property such volcanic bombs can range in length from several centimetres to sizes of cars landslides eruption of Nevada del Ruiz in Andes mountains of South America, in 1985 pollution benefits of living near volcanic areas fertile soil precious stones and minerals building materials tourism geothermal energy

5. earthquakes

5.1. is a vibration in the earth's crust caused by the sudden release of stored energy in the rocks found along the fault lines

5.2. occur when there is plate movement along plate boundaries

5.3. plate movements cause the slow build-up of stress on rocks found on either side of fault

5.4. when rocks can no longer withstand increasing stress, they slip many metres suddenly and cause an earthquake

5.5. releases energy in the form of seismic waves

5.6. focus

5.6.1. where seismic waves radiate out from of sudden release

5.7. epicentre

5.7.1. on the earth's surface directly above the focus

5.8. most energy released by earthquakes travels along surface of earth and cause ground to vibrate violently

5.9. after earthquakes

5.9.1. stress from the ground within earth's crust may cause many smaller earthquakes - called aftershocks - to occur along fault line

5.9.2. series of aftershocks may occur for several months after initial earthquake

5.9.3. some aftershocks can be nearly as powerful as original earthquake

5.10. depth of earthquakes' focus within earth's crust can have great impact on the land

5.11. types of earthquake

5.11.1. location of focus deep-focus earthquake occurs between 70 and 700 kilometres below the earth's surface shallow-focus earthquake occurs in upper 70 kilometres of the earth's crust

5.11.2. impact on land deep-focus earthquake smaller impact on the land as vibrations or seismic waves take a longer time to reach surface and would have lost most of their energy by then shallow-focus earthquake greater impact on the land as vibrations or seismic waves reach the land surface more quickly

5.12. extent of earthquake

5.12.1. magnitudes of earthquakes amount of energy released different earthquakes have different magnitudes measured using Richter Scale for each increasing magnitude on Richter Scale, impact of earthquake becomes 10 times greater in magnitude than previous one magnitude and impact on land strongest earthquake ever recorded: Valdvia, Chile / in 1960 / measured 9.5 on scale greater magnitudes may not always equate to more extensive damage and destruction an earthquake of 9.0 magnitude in Tokyo, in 2011, had a death toll of 28,000 people an earthquake of 7.0 earthquake in Haiti, in 2010, ha d a death toll of more than 300,000 people

5.12.2. population density number of people living in the affected area sparsely populated areas - likely to affect fewer people densely populated areas - likely to affect more people earthquake in city can cause more casualties and damage than one in countryside

5.12.3. level of preparedness amount of preparedness taken by authorities and citizens preparations include having evacuations plans, trained rescue workers and ranges of action plans damage caused by earthquake is more manageable than areas further away from city

5.12.4. distance from epicentre damaged caused by earthquake is more severe when area is closer to epicentre of earthquake during the earthquake in Christchurch, New Zealand, in 2011, the epicentre was in a town a few kilometres away from city centre the city suffered more damage than areas further away from the city

5.12.5. time of occurrence time of day during which earthquakes occur determines where people are and what they are doing affects people's chance of survival in earthquakes if earthquakes occur when most most people are sleeping - higher chance of people being trapped in their houses and more deaths may occur an earthquake in Sun Moon Lake Region in Taiwan, in 1999 - more than 2400 people died

5.12.6. type of soil seismic waves are amplified in places where sediments are loose and unconsolidated results in greater damage when earthquakes occur structures built on saturated and unconsolidated sediments can be affected by liquefaction liquefaction is when the ground becomes unstable and saturated soil flows like a liquid in Christchurch, New Zealand, in 2011 - many houses and buildings had to be abandoned because of liquefaction after the earthquake

5.12.7. locations of earthquakes convergent, divergent and transform plate boundaries most commonly at convergent plate boundaries (because more stress builds up when a plate subducts beneath another in Tōhoku, Japan, in 2011 (caused by convergence of plates) in Indian Ocean, in 2004 (caused by convergence of plates) around three-quarters of earthquakes which occur each year are found along the Pacific Ring of Fire some may occur some distance away from plate boundaries in Sichuan, China, in 2008

5.12.8. measurements of earthquakes seismograph records seismic waves released by an earthquake spring-mounted weight in seismograph moves up and down when tremors are detected ink maker then records motions of ground by making vertical markings on piece of graph paper attached to rotating drum distance that a location shifts as a result of an earthquake is closely related to the magnitude of an earthquake measurement of how far location shifts allows scientists to calculate magnitude of earthquake that has occurred measurement of how far a location shifts can be found out using the Global Positioning System

5.13. risks of living in earthquakes zones

5.13.1. (threat of) tsunamis one of the most damaging hazards associated with earthquakes refers to unusually large sea wave can be formed by movement of sea floor during a large earthquake at subduction zone explosive underwater volcanic eruption landslide above sea level which causes materials to plunge into the water - such landslides may be due to earthquakes and volcanic eruptions formation starts when seismic energy from an offshore earthquake forces out a mass of sea water tsunami waves may start at height of less than 1 metre, with wave lengths of 100 to 150 km, at speeds of 800 km/h and may pass undetected on reaching shallower water tsunami waves could be travelling at 30 to 50 km/h and may reach heights of around 15 m can travel long distances and cause widespread destruction at coastal areas when swept inland earthquake in Indian Ocean, in 2004, magnitude 9.2 triggered tsunami with waves that spread throughout Indian Ocean tsunami caused damage to coastal communities in 12 countries most damaged experienced in low-lying costa areas of western Sumatra, Indonesia, including city of Banda Aceh tsunami waves were between 4 to 39 m high and went as far inland as 10 km houses were swept inland or out to sea

5.13.2. (threat of) fires

5.13.3. (threat of) landslides shaking of ground during earthquakes can weaken slopes of hills and mountains instability may then result in landslides landslides are rapid downslope movements of soil, rock, and vegetation debris from a slope can range from several metres to several kilometres in both length and width mudflows may also occur when there is heavy rainfall which saturates the soil, causing the mixed soil debris to flow down the slope mudflows are often experienced in Indonesia and the Philippines where heavy rainfall is common earthquake off the coast of Peru, in 1970 said earthquake destabilised slopes of Mount Huascarán and triggered landslide said landslide travelled at more than 160 kilometres per hour completely flattened town of Ranrahirca within seconds death toll was more than 18,00 and only 200 people survived it

5.13.4. disruption of services such as electricity, gas, and water (communication services) such as television broadcasts and telephone connections vibrations on ground can snap pipes and break cables which may cause outbreak of fires earthquake in Kobe, Japan, in 2004, damaged pipes and transmission lines, disrupting electricity, gas and water supplies to about a million of Kobe's 1.4 million residents

5.13.5. destruction of properties people maybe be without homes after disaster and reside at temporary shelters while their homes are being rebuilt earthquake in Tōhoku Japan, in 2011 caused a tsunami which travelled up to 10 km inland extensive structural damage resulted in hundreds of thousands of people being forced from their homes severe shortage of housings and concerns about long-term consequences on health of people

5.13.6. destruction of infrastructure earthquakes may cause cracks to form in infrastructure such as roads an bridges transportation can be disrupted as it is unsafe to use damaged roads earthquake in Kobe, Japan, in 1995 - many places in the city became inaccessible or difficult to reach

5.13.7. loss of lives earthquakes and associated hazards often threaten lives of those living in earthquake zones

5.14. examples (location, date, magnitude on Richter Scale, estimated number of deaths, impact)

5.14.1. Tohoku, Japan March 2011 9.0 28,000 (upper estimate) 155, 000 homes lost powerful tsunami crippled nuclear power plant estimated damage: US $300 billion

5.14.2. Christchurch, New Zealand February 2011 6.3 180 central city area largely destroyed

5.14.3. Chile February 2010 8.8 600 estimated damage: US $15 to 30 billion

5.14.4. Haiti January 2010 7.0 300, 000 1.3 million people homeless

5.14.5. Sichuan, China May 2008 7.9 100, 000 374, 000 people injured 15 million people had to be evacuated 5.36 million building collapsed major landslides occurred

5.14.6. Northern Pakistan October 2005 7.6 86, 000 estimated 3.5 million people homeless entire districts destroyed

5.14.7. Aceh-Andaman, Indonesia December 2004 9.2 228, 000 1.7 million people homeless