tectonics

natural hazard

a natural event that has the potential to harm people or cause damage

two main types of hazard

tectonic hazards: earthquakes and volcanoes

meteorological hazards: tropical storms, extreme weather, heatwaves, droughts

factors affecting hazard risk

magnitude of the event

frequency of the event: the more often the hazard happens, more likely people are to be prepared, able to cope

HIC, LIC

management - prediction, protection and planning

layers of the earth

a thin crust on the outside: thin and rocky- 3 to 25 miles deep- broken up into tectonic plates

mantle- very thick mix of elements flowing very slowly- very hot

the core- hottest layer- made up of inner core and outer core

plate tectonic theory

tectonic plates move due to convection currents in the mantle, ridge push and slab pull

place where two plates meet = plate margin

oceanic and continental crust

oceanic is denser than continental crust

continental crust is older than oceanic crust

oceanic crust is formed of igneous rock where continental crust is formed of granite

continental crust is thicker than oceanic crust

oceanic crust can be renewed and destroyed; continental can’t

distribution of earthquakes and volcanoes

most tectonic hazards are on plate margins where 2 plates meet. clusters in specific places such as japan,

linear along the west coast of north and south america

earthquakes

happen when two plates are trying to move past each other

friction and pressure build up as this happens

plates will suddenly jolt and energy is released as an earthquake

conservative plate margin

plates moving past each other either in different directions or in the same direction but at different speeds. get stuck and pressure builds which suddenly jolts and energy is released as an earthquake. crust is created or destroyed

constructive plate margin

plates move apart. magma rises through the gap and cools, creating new crust. as magma forces it way to the surface, a volcano is formed. minor earthquake result

destructive plate margin

plates move towards each other. oceanic plate subducts because it is denser then melts. pressure builds up and magma pushes through the continental plate, leading to a volcanic eruption and powerful earthquakes

moment magnitude scale

measures the amount of energy released by an earthquake.

has replaced the richter scale as it is more accurate

HIC (high income country)

new zealand earthquake, 2016. 7.8 on the moment magnitude scale.

primary effects: 2 deaths, 50 injuries

secondary effects: tsunami, landslides

immediate responses: people housed in emergency shelters, power restored

long term responses: rebuilt earthquake resistant water supply

LIC (low income country)

nepal earthquake: 2015, 7.8 on moment magnitude scale.

primary effects: 8841 deaths, 16,800 injuries, 26 hospitals destroyed

secondary effects: rice seed stores destroyed led to food shortages

immediate responses: UN who distributed emergency medical supplies

long term responses: a recovery programme to increase crop production

reasons why people live in areas of tectonic hazards

feel safe- infrequent events or buildings designed to withstand earthquakes

fertile soil for farming

jobs in tourism

geo-thermal power

the 3 p’s

prediction, protection and planning

prediction

volcanic eruptions- can monitor shape of volcano, temperature, gases, earthquakes, predict an eruption

earthquakes- can’t be predicted. can be forecast by looking at historic data for patterns of where and when but cannot predict when will happen next

protection

volcanic eruptions: difficult to protect. can strengthen building so that they don't collapse under the weight of ash

earthquakes: building can be designed to withstand shaking by using reinforced concrete. only really possible in HIC

planning

volcanic eruptions: evacuation plans

earthquakes: practical drills, education, emergency supplies