Unit 1: Global Hazards

wind can be defined as

wind can be defined as

large scale movements of air caused by differences in air pressure

warm air rises, creating a

low pressure belt

cool air sinks, creating a

high pressure belt

weather at a low pressure belt

rainy and cloudy

weather at a high pressure belt

cloudless skies/ no rainfall

trade winds are

surface winds blowing towards the equator

westerlies are

surface winds blowing towards the poles

at 60°N/S

a polar and ferrel cell meet, forming a belt of high low pressure

at 30°N/S

a hadley and ferrel cell meet, forming a belt of high pressure

at the equator

two hadley cells meet, forming a belt of low pressure

in temperate climate zones

warm summers and cool winters

in polar climate zones

very cold temperatures and receive the least amount of sunlight

in tropical climate zones

hot and humid all the time

in arid climate zones

little precipitation and hot temperatures

temperatures in high pressure areas are high because

there are few clouds so little to block the Sun's energy

the albedo effect

is the ability of a surface to reflect away solar radiation

polar ice

has a high albedo

oceans and rainforests

have a low albedo

ocean currents

move heat around the world, North Atlantic Drift

as altitude increases

air pressure decreases, so temperature decreases

the Lut desert in Iran is the hottest place because

it is covered in dark lava, with a low albedo

Antarctica is the coldest place because

98% is covered in polar ice, and it is on the North pole

katabatic winds

winds that move down a slope

jet streams

bands of high-speed winds about 10 kilometers above Earth's surface, with little to slow them down

convectional rainfall

the ground surface is heated by the sun so the air above is warmed up and rises to condense and form clouds

convectional rainfall is common at

the Equator, where temperatures are high

frontal rainfall

the mass of warm air meets the colder air and rises over it (since cold air is heavier), forming steady rain

frontal rainfall is common in

the UK, where warm air from the Tropics meets cold air from the north Pole

orographic rainfall

rainfall produced when a moving moist air mass encounters a mountain range, rises, cools, and releases condensed moisture that falls as rain

examples of places that recieve orographic rainfall

the Khasi Hills

tropical storms

a storm with winds of at least 39 miles per hour

tropical storms form between

5° N/S and 30°N/S, where the ocean is warm

the conditions for a tropical storm

sea temp above 26, depth of 60m, and several grouped thunderstorms

the coriolis effect

is the effect of the Earth's rotation which causes moving air and water to turn left in the southern hemisphere and turn right in the northern hemisphere

formation of a tropical storm

ocean water evaporates and the air rises

low pressure created, which sucks in air from trade winds

humid air from ocean moisture forms storm clouds, releasing energy

in the centre, cool air sinks creating an area of calm clear conditions, known as the eye

wind speed is measured with

anemometer

tropical storms are categorised with

the Saffir-Simpson scale

normally above the pacific ocean

trade winds move from east (South America) to west (Australia)

during La Niña

the trade winds are stronger, causing droughts in South America due to cool seawater, and flooding in Australia due to warm seawater

during El Niño

trade winds weaken or reverse, causing flooding in South America, and droughts in Australia

the crust is

earth's outermost layer, that is 10-70 km thick. divided into tectonic plates

oceanic crust (vs continential)

is thinner and denser than continential crust

the mantle

semi molten rock between the crust and core

convection currents are

circular currents in the mantle caused by the magma being heated by the core of the Earth

formation of convection currents

the lower part of the mantle is hotter than the upper parts

the hot magma becomes less dense and rises

the rising magma cools and becomes denser

the magma sinks, and the process is repeated

the core

the central part of the earth below the mantle, divided into the solid inner core and liquid outer core

destructive plate boundaries

plates are moving towards each other, and the denser oceanic crust is subducted beneath the continental crust

processes at destructive boundaries

the mantle melts the plate and mixes with seawater

the mantle becomes less dense and rises through the plate, forming volcanoes

the oceanic plate forms an ocean trench

example of destructive boundary

Andes fold mountains

Nazca plate is subducted under South American plate

collision plate boundaries

two plates made of the same crust are moving towards each other. both plates are pushed upwards creating fold mountains.

example of collision boundary

Himalays mountain range

Eurasian plate collides with Indian plate

constructive plate boundaries

plates move away from each other, and magma rises to fill the gap

the magma cools to form new ocean floor

example of constructive boundary

Mid-Atlantic Ridge, e.g. Iceland

Eurasian plate moves away from North American plate

conservative plate boundaries

plates move past each other, either in opposite directions or in the same direction at different speeds

no crust is destroyed/created

example of conservative boundary

San Andreas Fault

Pacific plate moves alongside North American plate

an earthquake

a sudden violent movement of the Earth's surface, often causing a lot of damage

formation of earthquake

tension builds up as plates get stuck

they eventually jerk past each other

seismic waves are sent out

the focus is

the point in the Earth where the earthquake starts

the epicentre is

the point on the Earth's surface directly above the focus

the mercalli scale

rates earthquakes according to their intensity and how much damage they cause at a particular place, from I to XII

a seismometer

measures horizontal or vertical motion during an earthquake

shallow focus earthquakes

have less than 70 km in depth and are formed on tectonic plates moving on/near the surface

average magnitude is 1-5

damage from shallow focus earthquakes

is widespread, as the seismic waves radiate horizontally

deep focus earthquakes

have more than 70km in depth and are caused by crust that has been subducted before

average magnitude is 6-8

damage from deep focus earthquakes

is localised, as the seismic waves radiate vertically

there is a larger distance for the waves to travel

a volcano is

a vent or fissure in the Earth's surface through which magma and gases are expelled

a hotspot is

a weak spot in the middle of a tectonic plate where a plume of magma surfaces, forming a volcano (ex: Hawaii & Yellowstone)

ash from volcanos

cover land and block the Sun

a pyroclastic flow is

a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed

composite volcanos

are formed at destructive boundaries

the lava is viscous and cools quickly

the shape is a steep sided cone

eruptions are very explosive as magma sometimes blocks vents

shield volcanoes

are formed at hotspots and constructive boundaries

the lava is runny and flows quickly

the shape is gently sloped

eruptions aren't very explosive

technological developments in LIDCs

lightweight thatch roofs

cross braced wood or bamboo frames

concrete ring to tie walls to foundations

technological developments in ACs

damper in roof reduces sway

cross bracing stops floors collapsing

shock absorbers and strong steel frame

gas pipes can flex and immediately switch off

very deep foundations

predicting earthquakes

is hard to do, however a seismic gap can be used to identify areas that haven't experienced earthquakes in a while

warning systems

smart phone warning systems

earthquake drills to educate people

having go-bags that contain survival equipment