tectonic hazards and processes

volcanic hot spots

Volcanoes found away from the plate boundary, due to a magma plume closer to the surface, situated among the centre of plates, which is a localised area of the lithosphere which has an unusually high temperature due to the upwelling of hot molten material. E.g the ring of fire.

OFZ (oceanic fracture zone)

A belt of activity through the oceans along the mid-ocean ridges through Africa, The read sea and the dead sea.

CFZ (continental fracture zone)

a belt of activity along the mountain ranges from Spain through the Alps to the Middle east and the Himalayas.

the crust

known as the lithosphere, the uppermost layer of the earth which is the thinnest, least dense and the lightest. oceanic crust is only 7km thick, whereas continental can be up to 70km thick.

the mantle

may also be called the asthenosphere largely composed of silicate rocks, rich in iron and magnesium. the mantle is semi-molten and a temperature gradient generates convection currents. this causes the circulation of the mantle and may contribute to the lithospheres plate tectonic movement. the mantle is at a depth from 700km to 1890km thick.

outer core

dense, semi molten rocks containing iron and nickel alloys, at a depth of 2890km to 5150km below earth surface.

inner core

similar composition to the outer core, its over 510km below the earths crust. the inner core is a solid due to the extreme pressures it experiences. The cores high temp is a result of primordial heat left over from the earths formation, radiogenetic heat produced from radioactive decay.

how does the earths internal structure explain plate movement

the earths mantle has a temperature gradient. the highest temps occur where the mantle material is in contact with heat producing core so there is a steady increase of temperature with depth. rocks in the upper mantle cool and brittle, rocks in the lower mantle are hot and plastic. rocks in the upper mantle can break under stress and cause and earthquake. heat that is derived from the earths core rises within the mantle to drive convection currents which drive plate movements. these operate as cells and the type of movement of plates translates into particular hazard risk. Importance of convection currents is disputed as subduction occurs due to gravity.

what are intra plate processes and how do they create hazards

intra plates-earthquakes can occur at the middle of plates, the causes are not fully understood but it is assumed that plates have pre existing weaknesses which become reactivated, forming seismic waves.

-associated with smaller magnitude earthquakes but may fracture the crust well away from the plate boundary, which may yield a large magnitude earthquake.

plate tectonic theory

as the denser, oceanic crust is subducted beneath the continental crust, there is friction stress. as the two surfaces are not smooth, the two plates can become locked together. both friction and locking create a build up of tectonic strain which stores elastic potential energy. when the pressure exceeds the strength of the fault, the rock fractures, which produces a sudden release of energy, creating seismic waves which radiate away. the brittle crust rebounds either side of the fracture which is the ground shaking in an earthquake.

p waves

p waves: arrive first, fast, moves through solid rock and fluids, pushes and pulls- compresses in the direction of travel.

s waves: slower, only moves through solid rock, up and down movement.

s waves

rayleigh waves: only travels through surface in rolling motion, the ground is moved up and down and side to side, responsible for most of the shaking.

rayleigh waves

love waves: only travels through the surface of the crust, fastest of the surface waves and moves side to side as it moves outward.

love waves

landslides

landslides are a result of violent shaking, especially in 'young' mountain ranges.

liquefaction is where the ground is made of loose sediment and during the shaking they loose their binds and water moves into these spaces, causing buildings to sink.

liquefaction

Christchurch: the quake was centres 10km south east of the city at a depth of 5km. 185 dead. 164 seriously injured. liquefaction was a key issue which amplified the effects.

christchurch

explain the formation of a tsunami

a sequence of waves with deep troughs in between, because water is drawn upwards into each wave. Tsunamis are created by water column displacement, mostly by under sea plate movement where part of the sea bed is thrust up. an earthquake under the sea/ocean, rebounding plate, displacement of water column.

how do volcanoes erupt

partial melting of the mantle- the origin of magma, rises and then may stall and accumulate, magma then rises into storage regions, which can then stagnate. volcanic eruptions of tephra, or lava flows. volcanic gases can mix with the atmosphere. large composite volcanoes are found at destructive plate margins.

types of lava and their characteristics

basaltic: hottest, 10000-2000oC, low silica content, high co2, low gas content, formed by melting of mantle minerals, thin and runny, gentle eruption, formed at ocean hot spots and mid ocean ridges.

andesitic: 800-1000oC, intermediate silica 60%, high water content, gas content is 3-4%, formed by subducted oceanic plate melts with and mixes with sea water, slow flow, formed at composite cone volcanoes.

rhyolitic: coolest, 650-800oC, high silica, low iron and magnesium, 4-6% gas content, formed by the melting of lithospheric mantle and slabs, thick and stiff, very violent eruptions, formed at supervolcanos.

how does location and physical processes affect the eruption of volcanoes

variation is due to plate boundaries. destructive lead to subduction zones so volcanoes created are strato/composite. These produce acidic lavas due to the lava type, eruptions can be less frequent and lava can become stuck in the main vent building.

what is a jokulhalup

a type of glacial outburst flood that occurs when a lake fed by glacial meltwater breaches its dam, releasing large volumes of water, debris, and ice. These floods are often triggered by geothermal heating, subglacial volcanic eruptions, or the bursting of a dam. Jökulhlaups can cause significant flooding and landform modification, making them a hazard to infrastructure and people

what is a pyroclastic flow

a fast-moving current of hot gas and volcanic matter (tephra) that flows along the ground away from a volcano during an explosive eruption. It consists of a fluidized mixture of hot rock fragments, gases, and entrapped air, moving at high speeds, Pyroclastic flows are extremely dangerous to any living thing in their path due to their high temperature and speed

what is a lahar

destructive volcanic mudflows composed of a mixture of water, volcanic ash, and debris, which can flow rapidly down the slopes of a volcano, posing significant hazards to nearby areas.

destructive (convergent) plate boundary

locations where one plate is subducted beneath another mantle convection pulls oceanic plates apart creating fracture zones, and convection pulls oceanic plates towards subduction zones. due to elevated altitude at mid ocean ridges there is a slop down which creates gravitational sliding, ridge push. colder, denser oceanic plate is subducted beneath less dense continental plate (slab pull). the movement can become locked for many years which can build up the stress where it is released suddenly which energy radiating out from the hypocentre, this can occur between 10-400km. This zone is known as the benioff zone. The descending plate begins to melt at a depth by a process called wet partial melting. This generates magma with a high gas and silica content, which can erupt with explosive force.

destructive (convergent) plate boundaries

subduction of denser oceanic crust, due to slab pull, unstable molten magma rises to the surface causing a change of rock type, plus seawater, the crust pushes up and convection occurs in the mantle, typically the pacific and oceanic plate.

constructive (divergent) plate boundary

undersea valley gap is filled by lava flowing from fissures on the seafloor, parallel to plate boundaries to create new crust. submarine volcanoes may become island. convections in the mantle and decompressions in the asthenosphere due to a gap between the plates

collision (convergent) plate boundary

faulting leads to wide, shallow earthquake zones. a small section of oceanic crust is scraped off during the collisions. remains of old oceanic crusts are broken off and descend into the asthenosphere.

degg model and risk

hazards should not be confused with natural disasters. a disaster will only occur when a vulnerable population- one that will be significantly disrupted and damaged- is exposed to a hazard. deggs model is a good representation is this concept. if the population is not vulnerable, the hazard will not have a significant effect, thus the event will not be disastrous.

how is risk explained in the degg model (equation)

risk= hazards x vulnerability/ capacity to cope

how does the richter scale measure events and how was it been advanced

uses the arrival of P and S waves as well as the amplitude of the S wave. the moment magnitude scale is more accurate as it uses energy released by shockwaves as well as the area of rupture and movement.

how does the mercalli scale measure events

it uses the amount of damage by the earthquake waves. it is qualitative and uses descriptions of damage and human perception, observing the effects on people, buildings and the environment.

how does the volcanic explosiveness scale measure events

it is based off the amount of tephra- ejected material- from the volcano. the larger the amount, the bigger the explosivity according to the index. it is useful to compare the amount of energy released and the type of eruption.

explain the pressure and release model

used in disaster risk reduction and management that helps to explain the causes and dynamics of disasters. the model suggests that disasters are the results of two factors: pressures and vulnerability.

how can risk be reduced

prediction/monitoring and preparation by educating the public. building defences to reduce impact and providing aid and support systems such as services to minimize the dangerous effects and reduce the amount of deaths.

what do hazard profiles suggest

there are similarities in physical processes and a difference in impact linked to levels of development. higher financial costs in developed countries, but even small costs mean a lot of people in different situations

the influence of development and governance on the effects of disasters

increasing losses due to natural hazards around the worlds is a result of increasing vulnerability, not always in financial poverty but as an overall disadvantage due to physical, political, social, cultural and economic factors. By 2050, 66.4% of the worlds population will be urban, the world risk index considers measures of exposure, susceptibility, coping capacity and adaptive capacity. insurance companies are concerned about the increase risks and losses, especially in multiple hazard zones.

what is effective governance

the process by which a country is run, an established national government, keeping people safe healthy and getting people educated.

how does the world risk report decide risk and which countries or regions are more at risk and why

in 2014 they commented that the urban governments of rapidly growing cities faced the major challenges of established planning measures to reduce vulnerability. the world risk index considered measures of exposure susceptibility coping capacity and adaptive capacity.

how can volcanoes be predicted and monitored?

gravity sensors to rock magma patterns gradually changes from a magma buildup to gas being released before the eruption Volcano monitoring should include many observations such as earthquakes, ground movement volcanic gas rock, chemistry, and remote satellite analysis on a continuous or near real time basis

how can tsunami be predicted and monitored?

an earthquake occurred in the ocean water column uplifted the NOAA uses the DART system, which is the deep ocean assessment and reporting of tsunamis.

how can earthquakes be predicted in a monitored?

rising levels of radon changes in electromagnetic field near fault lines animals such as toads

The dilation theory is based on the principal that where seismic activity is likely to occur next to this area will be under pressure which causes cracks and rocks to expand and dilate.

dilation theory

what could influence a places abilities make accurate and reliable predictions?

level of development could prevent prediction as some areas don't have funding or money to do scientific research and can't afford technology

what are the factors of the disaster management cycle and what do they include?

The immediate response is the immediate help in the form of saving lives and aid to keep people alive

The long-term response is rehab rehabilitation which is rebuilding infrastructure and services rehabilitating injury and peoples lives.

The protection stage is prevent prevention which is acting to reduce the scale of the next disaster.

what are the stages of the park model?

stage one is response and is taking place in hours and days after the event it includes modifying the cause and the event and shows the quality of life that is normal

Stage two is reconstruction and happens within days and weeks it's where the hazard occur occurs and quality of life is normal level

Stage three is the mitigation which is months two years the event has happened and search and rescue is underway. The quality of life drops at this stage and stays low for several days.

what are some strengths and limitations of the park model?

some strengths include is that it is useful to analyse the types of response, compare and contrast hazards, can help deepen the understanding of responses and pinpoint different types of response is needed.

some limitations include that some places take much longer to reach the stages. It's too general and not about magnitude and there's no account of inequality of development. Some countries are in need of outside help.

define multi hazard zone and why they're such a challenge

places where a number of physical hazards combined with an increase level of risk for the country

they are a challenge due to frequency of events, both tectonic and meteorological which can lead to damages to infrastructure, lack of protection and a vulnerable population

why is identification important?

without identification people are more risk. Identification can include management development, investment disaster preparedness loss prevention, protection and international aid.

what includes modifying the event and explain the type and advantages and disadvantages

land you signing which can prevent building on low line coast close to volcanoes and areas of high ground shaking and liquefaction risk. They are low-cost and remove people from high risk areas but prevent economic development on some high value land and requires strict enforced planning rules.

Asemic buildings our buildings with deep foundations and sloped roofs so that ash doesn't build and create pressure. They can help prevent collapsing buildings and protect people and property but they can be high cost for larger buildings and low income. Families can't afford this.

Tsunami defences such as seagulls that stopped waves travelling inland. They can reduce damage and provide security but are very high cost and don't look nice.

Lava diversion of barriers and water cooling to divert and slow down lava flows. They divert Lara away and have a low cost but only work for low-level lava.

what includes modify the vulnerability and what are the advantages and disadvantages

High tech scientific monitoring used to monitor volcano behaviour and predict eruptions. In most cases predicting corruption is possible and warning and evacuation can save lives. However, it is costly so not all developing world volcanoes are monitored and it doesn't prevent property damage.

Community preparedness and education earthquakes in preparation days and educational schools. These are low costs and often implemented by NGOs they can save lives through small action. However, they don't prevent properly damage and a harder to implement in isolated rural areas.

Adaptation is moving out of harms way and relocating to a safe area. These help save lives and property however high population densities preventer disrupts peoples traditional homes and traditions.

what includes modifying the loss and what are the advantages and disadvantages?

short-term emergency aid search and rescue followed by emergency food, water and shelter. Reduces death hole by saving lives and keeping people alive longer until longer-term help arrives. However, can be high cost and technical difficulties in isolated areas emergency services are limited and poorly equipped in developing countries.

Insurance compensation given to people to replace their losses. Allows people to recover economically for paying reconstruction. However, doesn't help save lives not many LIC's have insurance.

how do developing, developed and emerging countries compare for impacts?

developing countries have higher displaying costs but good recovery and more resilient buildings but damage is also more costly

Developing countries have high deaf tolls widespread displacement and recovery can be long but public services are also damaged

emerging countries are faced by overcrowding high displacement costs and pressure to rebuild

Are tectonic disasters happening more frequently?

they stay at relatively stable rates due to the constant movement of the Earth tectonic plates the reported events have increased because of population growth, urbanisation, global communication and reporting