geography ✿ global hazards

extreme weather

weather that is unusual and can cause destruction

where is the Hadley cell located?

on the equator, 30°-40° north to south

where is the ferrel cell located?

30°-60° latitude

where is the polar cell located?

60°-90°

how are low pressure belts formed?

what do they result in?

• warm air rises, cools and condenses, creating clouds and heavy precipitation

• result in → heavy rainfall and strong winds

how are high pressure belts formed?

what do they result in?

• cool air sinks, warms up and dries out as it reaches the earth’s surface

• result in → dry and little precipitation

What type of winds are usually associated with low pressure systems?

high/ strong winds

Explain one way in which global atmospheric circulation creates a climatic zone in the subtropical and polar areas. [3]

• air sinks, causing high surface pressure

• sinking air warms up and dries out as it reaches the earth's surface, there is no condensation

• causing dry conditions and little precipitation

Identify the type of natural weather hazard shown in Fig. 1.

drought

explain one way in which global atmospheric circulation creates a climatic zone at the equator [3]

• high levels of insolation

• water evaporates, cools and condenses causing low surface pressure

• clouds are formed which causes heavy rainfall

Give two types of extreme weather associated with tropical storms

• heavy rain

• strong winds

describe how a tropical storm is formed [4]

• they form over warm oceans over 27°c, which provides energy

• water evaporates and air warm rises, creating low surface pressure

• warm air condenses forming clouds

• the earths spinning makes the storm start to spin

El Niño

• when trade winds are weakened/ reversed which causes air to sink over the western pacific, leading to high pressure and droughts

• air rises over the eastern pacific, leading to wet weather

• This occurs every 3-4 years

La Niña

• when trade winds are stronger which causes air to sink over the eastern pacific, leading to high pressure and droughts

• air rises over the western pacific, leading to wet weather

• This occurs every 2-7 years

what are 3 effects of the droughts caused by La Niña and El Niño

• crop failures

• water shortages

• increased risk of wildfires

continental crust

crust found underneath large land masses

oceanic crust

crust found underneath the oceans (ocean floor)

epicentre

the Earth's surface directly above the focus

focus

where the earthquake starts underneath the earths surface

how deep under the crust are shallow-focus EQs?

0-70km

how deep under the crust are intermediate EQs?

70-300km

how deep under the crust are deep-focus EQs?

70-700km

Describe what a hot spot is. [2]

an area of the earth’s crust where unusually high heat flow is linked to volcanic activity

constructive plates

• tectonic plates moving away from each other

• volcanic and earthquakes can occur

destructive plates

• tectonic plates move towards one another.

• forcing the oceanic crust to subduct the continental crust

conservative plates

• tectonic plates move past each other

• only earthquakes occur here

Collison plates

• two plates move towards each other

• the plates are forced upwards forming fold mountains

Convection currents

a hot current which causes tectonic plates to move

what are earthquakes caused by? [2]

• EQs occur at all plate boundaries

• EQs are caused by convection currents which cause tectonic plates to move, leading to sudden shakes

Seismic waves

Shock waves from earthquakes

what does a Richter scale measure?

the magnitude of earthquakes

what are seismometers used to detect?

seismic waves from earthquakes

what does the Mercalli scale measure?

the damage caused by earthquakes (1-10)

Explain how the movement of tectonic plates at a destructive plate boundary causes composite volcanoes to form. [4]

• the plates move towards each other and the oceanic plate is forced to subduct

• oceanic plate crust melts due to friction and creates magma

• magma rises as it is less dense and rises through the cracks in crust

• pressure in magma chamber builds up

Explain how the movement of tectonic plates at a constructive plate boundary causes sheild volcanoes to form. [4]

• the plates move away from each other

• creating a gap for the magma to rise from the mantle

• magma rises as it is less denser than rocks

• pressure builds up and magma moves through cracks in the crust

State 3 features about composite volcanoes

• found at destructive plate boundaries

• violent eruptions

• thick, heavy lava

state 3 features about shield volcanoes

• found on constructive plate boundaries

• Not as violent eruptions

• thin and runny lava

Name the process that causes the Earth’s tectonic plates to move. [1]

convection currents

what are the earth’s 4 main layers?

• Inner core

• Outer core

• Mantle

• Crust