Global Hazards Flashcards
What are the 3 cells of air?
Hadley, Ferrel, Polar
What do the circulations of air do?
they transport heat from the equator to the poles
What happens at the ferrel cell?
air joins the sinking air of the Hadley cell and travels at low heights to mid latitudes where it rises along the border of the polar cell.
the air then flows back towards lower latitudes, in the direction of the equator.
What happens at the Hadley cell?
Trade winds blow from the tropical regions to wards the euator, when they meet they rise and thunderstorms are created.
From the top of theses storms the air circulates to higher latitudes as it cool and sinks.
What happens at the polar cell?
The warm air rises along the broder of the ferrel cell and circulates towards the poles. The air cools and sinks and travels back toward lower latitudes.
What is the troposphere?
An area of the atmosphere about 10-15 km high, where the Earth’s weather takes place
Where are each of the cells located?
hadley - equator to 30-40o
ferrel - edge of hadley to 60-70o
polar - edge of ferrel to poles
Which is the largest and smallest cell?
hadley and polar
What causes high pressure?
cold air sinking
Where can you find high pressure?
the air sinking at 30 north and south of the equator
What causes low pressure?
warm air rising
Where can you find low pressure
at the equator
What does the climate tend to look like at low pressure?
high winds and warm rising air. lots of precipitation.
What does the climate tend to look like at high pressure?
cold sinking air, subject to warming. usually associated with clear skies and dry, calm weather
what are 4 types of climate?
temperate, tropical, sub-tropical, polar
What does temperate climate look like?
low pressure, rising air, causes lots of precipitation.
What does tropical climate look like?
low pressure, heavy rainfall and thunderstorms
What does sub-tropical climate look like?
desert conditions, with very high temps during the day and very low temps during the night due to lack of cloud cover
What does polar climate look like?
high pressure, dry and icy winds. very cold, windy and dry.
What is El Nino
it is a weather phenomenon in which the water and air currents reverse between Australia and south America
What are normal conditions between australia and south america?
trade winds blow towards australia from south america causing warm surface water by the coast of australia. Strong surface currents towards australia cause cold deep water by the coast of south america.
What happens during El Nino?
trade winds weaken, stop or even reverse. Warm water around australia goes back towards to south america, increasing the sea level. water becomes 6-8 celsius warmer by peru. Peru experiences more rainfall and australia experiences drier conditions.
What happens during la nina?
la nina is a more exaggerated version of normal conditions in the south pacific. Australia will have warmer waters with more chances of flooding, whereas south america will have colder waters with more chances of drought.
What is a tropical storm?
starts as a low pressure system originating in the tropics known as a tropical depression, which can develop into a hurricane.
When does a storm become a hurricane?
when its wind speeds become faster than 119 km/h
Where are tropical storms found?
between the tropics
what is the most dangerous part of the storm?
the eyewall
Which months do tropical storms occur in?
june to november in the northern hemisphere, and november to april in the southern hemisphere.
How frequently do storms occur?
approximately 80 storms annually
energy released by the average hurricane has _____ by __% in the past 30 years.
increased, 70
What is a drought?
a period of below average rainfall with abnormally dry weather leading to a shortage of water.
What are some of the causes of drought?
disturbed weather patterns
global temperature increase
intertropical convergence zone
What is the intertropical convergence zone?
the ITCZ is a low pressure belt which circles the globe around the equator.
What are 3 human activities that have made droughts worse?
excessive irrigation
dam building
over-grazing
over-farming
soil erosion
deforestation
What was the big dry?
the driest period in Australia since 125 years between 2002-2009
Why does Australia not get much rainfall?
it is located in a sub-tropical part of the world that experiences dry, sinking air leading to clear skies and little rain
How did El Nino play a part in causing the Big Dry?
when el nino is present, the country becomes drier and the chances of rainfall decrease. The reversal of the trade winds leads to the water cool and less evaporation for precipitation.
How did overpopulation play a part in causing the Big Dry?
cannot maintain current population to growth in relation to access to water.
What is a super typhoon and give an example?
a typhoon that has sustained wind speeds of over 150mph for over a minute.
typhoon haiyan
What are the 4 layers of the Earth?
inner core, outer core, mantle, crust
What is magma?
hot, dense, liquid rock that churns around
What are the 2 types of tectonic plates?
oceanic and continental
What is an example of an oceanic plate?
pacific plate
What causes the magma to move?
convection currents
How to convection currents move the magma?
the magma closest to the core gets heated up and rises as it is less dense. Once it reaches the crust, it cools and sinks as it is more dense again. This process continuously repeats.
What are the differences between the 2 types of tectonic plates?
oceanic found beneath ocean, continental found beneath land
oceanic 5-15km and continental 25-100km
What is an example of a continental plate?
North American plate
What are the 3 plate margins and what happens in them?
destructive - denser plate subducts under the other plate. Volcanoes (composite) and earthquakes
Constructive - two plates moves apart and magma fills the gap. Shield volcanoes form
Conservative - two plates slide past each other causing earthquakes
What is subduction?
the sinking of the denser plate under the other plate at destructive plate margins
What are the 2 types of volcanoes?
shield and composite
What are characteristics of shield volcanoes?
made of basaltic rock
form gently sloping cones from layers of runny lava
gentle and predictable eruptions
What are characteristics of composite volcanoes?
most common type found on land
created by alternating layers of ash and lava
explosive and unpredictable eruptions
What is a volcanic case study?
E-16 Icelandic eruption 2010
What are causes of earthquakes?
when 2 plates get locked causing friction to build up. from this stress, the pressure eventually gets released, triggering the plates to move into new positions. the movement causes seismic waves and an earthquake
What is epicentre and focus of an earthquake?
epicentre - the point directly above the focus (seismic waves reach first)
focus - the point at which pressure is released
What are the differences between shallow and deep focuses?
shallow:
usually small and common
seismic waves spread and damage wide area
deep:
occur on destructive plate margins
damage is localised
How do we measure Earthquakes?
Mercalli scale
Richter scale
What are characteristics of the Mercalli scale?
measure how much damage is done by observation
instrument, weak, extreme, cataclysmic
limitation is that it is subjective
What are the characteristics of the Richter scale?
scientific measurement of energy released
measured by seismometer from 1-10
each point up the scale is 10 times greater
What are the 5 volcanic hazards?
ash cloud, gas, lahar, pyroclastic flow, volcanic bomb
What is ash cloud?
small pieces of pulverised rock and glass which are thrown into the atmosphere
What is volcanic gas?
sulphur dioxide, water vapour and carbon dioxide (greenhouse gases)
What is lahar?
a volcanic mudflow which runs down a volcano
What is pyroclastic flow?
a fast moving current of super-heated gas and ash moving at 450mph
What is a volcanic bomb?
a thick lava fragment that is ejected from the volcano
How do you predict volcanic eruptions?
small earthquakes are caused
temperature around the volcano increases as activity increases
when volcano is close to erupting it starts releasing gases
What are some preparations for volcanic eruptions?
creating exclusion zone around the volcano
being ready and able to evacuate residents
having emergency supply of provisions
trained emergency services
How do you predict earthquakes?
satellite surveying
laser reflector (surveys movement across fault lines)
seismometer
seismic record to predict
How do you protect against earthquakes?
building earthquake resistant infrastructure
raising public awareness
improving earthquake prediction
