natural hazards Flashcards
what is a natural hazard?
natural event that has the potential to cause harm to people, property, or the environment
what factors affect risk?
poverty-in poorer parts of world poverty might force people to live in areas of risk
farming-when river floods it deposits fertile silt on its floodplain (good for farming) but people who live there may be at risk from these floods in low lying countryside many live on floodplains
climate change-may cause some parts of world to be wetter and increase flood risk, others drier and prone drought
urbanisation-more densely populated areas at larger earthquake risk
what is the plate tectonics theory?
the earths lithosphere is divided into large, rigid plates that float on the semi-fluid asthenosphere beneath them, these plates move and interact at their boundaries, causing earthquakes, volcanic activity, mountain building, and ocean trench forming
what is the distribution of earthquakes and volcanoes?
both earthquakes and volcanoes occur in long belts that follow the plate margins e.g. around the edge of the pacific ocean
what is a constructive plate margin?
where two plates are moving apart
what is a destructive plate margin?
where two plates are moving towards one another
what is a conservative plate margin?
where two plates are sliding alongside eachother
what are the main features of an earthquake?
epicentre-the point on the earths surface directly above where the earthquake originates, known as the focus or hypocentre usually where strongest shake is felt
focus-the location within the earth where the earthquake starts, typically along a fault line, where stress is released in the form of seismic waves
seismic waves-the energy released during an earthquake travels as seismic waves
aftershocks-smaller tremors that occur following the main earthquake event, these happen as earths crust adjusts to the changes caused by the main earthquake
what are the two different ways of measuring earthquakes?
richter scale and seismometer
why do tectonic hazards happen in chile and nepal?
because they are located along tectonic plate boundaries
what are the primary affects of the earthquake in chile?
-around 500 killed and 12000 injured, 800000 affected
-220000 homes, 4500 schools, 53 ports, 56 hospital and other public buildings destroyed
-port of Talcahuanao and Santiago airport badly damaged
-much of chile lost power, water supplies and communications
-cost of earthquake $30 billion
what are the secondary affects of the earthquake in chile?
-150km roads damaged, mainly by landslides, remote communities cut off for days
-several coastal towns devastated by tsunami waves
-several pacific countries struck by tsunami waves, warnings prevented loss of life
-fire at chemical plant near satiago, area had to be evacuated
what are the primary affects of the earthquake in nepal?
-9000 died, 20000 injured, over 8 million affected
-3 million left homeless
-electricity and water supplies, sanitation and communications affected
-1.4 million needed food, water and shelter in the days and weeks after the earthquake
-7000 schools destroyed and hospitals overwhelmed
-international airport became congested as aid arrived
-50% shops destroyed, affecting food supplies and people’s livelihoods
-cost $5 billion
what are the secondary affects of the earthquake in nepal?
-groud shaking triggered landslides and avalanches, blocking roads and hampering relief efforts
-avalanches on mount everest killed atleast 19 people
-avalanche in Langtang region left 250 people missing
-landslide blocked the Kali Gandki River l, 140km north west of capital (Kathmandu), many evacuated incase of flooding
-earthquake occurred on land no tsunami
what were the immediate responses after the earthquake in chile?
-emergency services acted swiftly, international help needed to supply field hospitals, satellite phones and floating bridges
-temp repairs made to important route 5 north-south highway within 24 hours, enabling aid to be transported from Satiago to affected areas
-power and water restored to 90% of homes within 10 days
-national appeal raised $60 million, enough to build 30 000 small emergency shelters
what were the long-term responses after the earthquake in chile?
-month after chile’s government launched a housing reconstruction plan to help nearly 200000 households affected by the earthquake
-chiles strong economy, based on copper exports could be rebuilt without the need for much foreign aid
-the president announced it could take four years for chile to recover fully from the damage to buildings and ports
what were the immediate responses after the earthquake in nepal?
-search and rescue teams, water and medical support arrived quick from counties like UK, India and China
-helicopters rescued many people caught in avalanches on mount everest and delivered supplies to villages cut off by landslides
-half a million tents needed to provide shelter for homeless
-financial aid pledged from many countries
-field hospitals set up to support overcrowded main hospitals
-300000 people migrated from Kathmandu to seek shelter and support with family and friends
-social media widely used in search and rescue operations and satelites mapped damaged areas
what were the long-term responses after the earthquake in nepal?
-roads repaired and landslides cleared. Lakes, formed by landslides damming river valleys, needed to be emptied to avoid flooding
-thousands of homeless people to be re-housed, and damaged homes repaired. Over 7000 schools to be re-built or repaired
-stricter controls on building codes
-in june 2015 nepal hosted an international conference to discuss reconstruction and seek technical and financial support from other countries
-tourism, major income source, to be boosted-by july 2015 some heritage sites re-opened and tourists were starting to return
-repairs to everest base camp and trekking routes - by august 2015 new routes had been established and the mountain re-opened for climbers
-in late 2015 a blockade at the indian border badly affected supplies of fuels, medicines and construction materials.
why do earthquakes cause more loss of life in poor than rich countries
because buildings are often poorly constructed and lack earthquake-resistant features. Poorer nations also have limited resources for disaster preparedness, early warning systems, and emergency response. Additionally, infrastructure and medical services may be insufficient, making recovery difficult. In contrast, wealthier countries have stronger buildings, better preparedness, and quicker recovery systems, which help reduce the impact of earthquakes.
why do people live in places at risk of tectonic hazard?
-natural hazards dont happen that often
-people in poverty have bigger issues like food, money and security
-better building design can withstand earthquakes
-monitoring can give warnings when need to evacuate
-fault lines let water reach surface important in desert areas
-favourable areas like coasts have ports where plate margins happen to be
-some arnt aware of risks
-volcanoes have fertile soils, rocks to build, rich mineral deposits and hot water
how can monitoring reduce tectonic hazard effects?
using scientific equipment to detect warning signs of events such as volcanic erruption
remote sensing-satelites detect heat and changes to shape of volcano
seismicity-seismographs record earthquakes
ground deformation-changes to shaoe of the volcano are measured with laser beams
geophysical measurements-detect changes in gravity as magma rises
hydrology-measurements of gasses dissolved in water
how can prediction reduce tectonic hazard effects?
using historical eevidenc e and monitoring, scientists can make predictions about when and where a tectonic hazard may happen
the prediction of a volcanic eruption is based on scientific monitoring, in 2010 an increase in earthquakae activity beneathe Eyjafjallajokull ice cap let scientists predics erruptions that took place in march and april that year
it is impossible to make accurate prediction s about earthquakes due to lack of clear warning signs however scientists studying historical records of earthquakes at plate margins have identified locations that they belikeve are at greatest risk.
how can protection reduce tectonic hazard effects?
designing buildings that will withstand tectonic hazards
use earth embankments or explosives to divert lava flows away from property when volcanoes erupt, e.g. mount etna in italy
earthquakes, protection is main way reducing risk for example in chile: new buildings reinforced concrete columns strengthened by a steel frame, regular drills help people stay alert and be prepared
construct tsunami walls to protect people and important buildings like nuclear power stations
how can planning reduce tectonic hazard effects?
identifying and avoiding places most at risk
hazard maps produced for many of worlds most dangerous volcanoes, restrict certain land uses or identify which areas should be evacuated when eruption is about to happen
maps produced to show effects of an earthquake or identify areas most at risk of damage , high-value land like hospitals, reservoirs and office blocks can be protected in these vulnerable areas
what is global atmospheric circulation?
the cruising altitude of an aeroplane is about 10km above the ground surface. at this altitude vast majority of atmospheres mass is below you . the atmosphere - the air above our heads - is a highly complex swirling mass of gases, liquids and solids. including water droplets, water vapour, ash, carbon dioxide and oxygen
how does global atmospheric circulation work?
see image of atmospheric circulation model
-air sinking towards ground surface forms areas of high pressure , winds on ground move outwards from these areas
-air rising from ground surface forms areas of low pressure on ground winds on ground move towards areas of low pressure
-winds on ground distorted by earths rotation, curve as move from areas of high to low pressure
-surface winds important in transferring heat and moisture from one place to another
-patterns of pressure belts and winds are affected by seasonal changes, tilt and rotation of earth causes relative changes in position of overhead sun. seasonal changes cause pressure belts and winds to move north in summer and south in winter.
how does global atmospheric circulation affect the world’s weather?
cloudy and wet in the uk:
55 degrees north just below 60 degrees N line of latitude puts the uk close to boundary of cold polar air moving down from the north and warm sub-tropical air moving up from the south, boundary between these two air masses is unstable here there is rising air and low-pressure belts (the sub-polar low) on the ground, rising air cools and condenses to form clouds and rain.
Surface winds in these mid-latitudes vome from the south-west these winds bring warm & wet conditions to the uk. but sometimes the cold polar air from the north moves down over the uk bringing snow and cold winter weather
how does global atmospheric circulation affect the world’s weather?
hot and dry in the dessert:
most of worlds desrts 30 degrees north and south of the equator, air is sinking, making a belt of high pressure, no air rising so little clouds and rainfall , hot in day and cold at night as no clouds mean heat is quickly lost from the ground
how does global atmospheric circulation affect the world’s weather?
hot and sweaty at the equator:
air is rising and there is another low pressure belt , very hot with sun directly overhead. equatorial regions like central africa and south-east asia, experience hot, humid conditions. often cloudy with high rainfall , tropical rainforests are found here.
how are tropical storms distributed?
as patterns of sea surface temperatures change , they may affect distribution of tropical storms, in future tropical storms may affect areas outside the hazard zone like south atlantic and parts of the sub-tropics, hurricanes may also become more powerful
Tropical storms, including hurricanes, typhoons, and cyclones, form in tropical and subtropical oceans where sea surface temperatures are at least 26.5°C.
In the Atlantic, hurricanes affect the Caribbean, Gulf of Mexico, and the U.S. east coast. In the Eastern Pacific, hurricanes form off the western coasts of North and Central America. Typhoons occur in the Western Pacific, impacting countries like the Philippines, Japan, and China. Cyclones develop in the Bay of Bengal and the Arabian Sea, affecting India, Bangladesh, and surrounding areas.
Tropical storms do not form within 5 degrees of the equator due to the weak Coriolis effect, and they generally occur between the Tropics of Cancer and Capricorn.
what causes a tropical storm and how do they form?
- on reaching land the storms energy supply is cut off , friction with the land slows it down and it begins to weaken , if the storm reaches warm seas after crossing the land it may pick up strength again
- as storm carried across ocean by prevailing winds it gathers strength
- sorm now develops an eye at its centre where air decends rapidly, the outer edge of the eye is the eyewall where the most intense weather conditions (strong winds and heavy rain) are felt
- several smaller thunderstorms join together to form a giant spinning storm. when the surface winds reach an average of 120km per hour the storm officially becomes a tropical storm
- as the air condenses it releases heat which powers the storm and draws up more and more water from the ocean
- this evaporated air cools as it rises and condenses to form towering thunderstorm clouds
- a strong upward movement of air draws water vapour up from the warm ocean surface.
