GEOGRAPHY: UNIT 1: CHAPTER 1: GLOBAL HAZARDS

define natural hazard

processes or events that occur anturally in the environment and have the potential to cause harm to human life and property

types of natural hazards and examples

- geophysical (earthquake, volcano, tsunamis)

- hydro-meteorological (cyclones, flooding, droughts)

define earthquake

an intense shaking of the earth crust or surface which is usually caused by the movement of plate tectonics

measure earthquakes

- richter scale: strength based on seismic energy released

- mercalli scale: based on perception and damage to infrastructure

parts of an earthquake

- fault: part where plates meet

- focus: center of earthquake where sismic waves radiate outwards from

- epicenter: area directly above the focus on land

define volcano

events that occur at openings in the earths crust where magma is released at the surface

define magma

a mixture of red-hot liquid, fragments of solid rock and dissolved gases found in the Earth's crust

define lava

magma that has reached the earths surface

define tsunamis

a long high wave of water which is caused by a disturbance

types of plate boundaries

- transform / conservative

- divergent / construction

- convergent / destructive

- collision

transform plate boundaries

- plates that are sliding past each other (can be in the same or in different directions) at different speeds

- can cause earthquakes due to friction build up

divergent plate boundaries

- plates moving away from each other. as the plates move apart, there is a creation of new seafloor and the widening of the oceanic basin

- can triger tsunamis but not significant enough vertical motion for this to occur regularly

convergent plate boundaries

- plates moving towards each other. where the plates are if differnt densities and teh denser oceanic crust subducts beneath the less dense continental crust

- can cause volcanic eruptions

slope processes definition

the movement of rock soil and debris down a slope under the influence of gravity EG: landlside or avalanche - can lead to a more intense disaster scenario - can be triggered by weather or tectonic events

how can hydro-meteorological processes cause antural hazards

- heavy rainfall/ rapid snowmelt / storm surges cause flooding

- low rates of precipitation cause droughts

- strong winds and warm sea temperatures can cause cyclones

conditions needed for cyclone formation

- warm ocean (around 26 degrees)

- strong opposing winds (Corriolis effect of the Earth)

drought causes

- decrease in precipitation

- high level of reflected sunlight (ice albedo effect)

how to measure tropical storms

saffir simpson scale

- the wind speed of tropical cyclones
- categories 1-5

how to measure volcanoes

VEI

- measures teh relative explosiveness of volcanic eruptions

- 0-8 scale

disaster risk equation

risk = hazard x vulnerability

enso cycles

El Nino Southern Oscillations

el niño years

- increased rainfall and flooding in the eastern pacific

- reduced rainfall and droughts in areas such as Asutralia and Southeast Asia

la niña years

- above average rainfall and associated flooding in regions like Australia, usa and south america

- western pacific becomes warmer and experiences more convection - this can lead to heavy rainfall and storms

- development and intensification of tropcial cyclones, particularly in the Atlantic Ocean

how to measure flood

flood discharge

- total volume of water passing a particular point duringa flood event