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Geography > Global Hazards > Flashcards

Global Hazards Flashcards

1
Q

what causes and what are the causes of high pressure?

A
  • cold air sinking
  • clear and calm weather
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2
Q

what causes and what are the causes of low pressure?

A
  • hot air rising
  • stormy, cloudy weather
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3
Q

how do high/ low pressure belts create temperate climate zones?

A

here, air rises and cools to form clouds and therefore frequent rainfall (ferrel cell)

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4
Q

how do high/ low pressure belts create tropical climate zones?

A

low pressure causes heavy rainfall and thunderstorms (hadley cells)

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5
Q

how do high/ low pressure belts create polar climate zones?

A

cold air sinks causing (high pressure) causing dry, icy and strong winds (polar cell)

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6
Q

how do high/ low pressure belts create desert climate zones?

A

sinking dry air (high pressure) causes high temperature without conditions for rainfall (between hadley and ferrel cells)

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7
Q

4 examples of extreme weather

A
  • wellington new zealand- high wind speeds 248 km/h- caused by surrounding mountains funnelling wind
  • puerto lopez (equator)- hish temp leads to rapid condensation and heavy rainfall
  • atacama, chile- andes mountains block moist warm air travelling further west causing rainfall to east but dryness to the west
  • mawsynram india- 11m rainfall per yr- reversal of air conditions/ directions from sea to land, contributing to monsoons in summer
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8
Q

why is the weather in australia so extreme?

A

it is such a huge country that it has several different climate zones causing extreme high temp in central australia and below freezing in the south-west

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9
Q

what is a tropical storm?

A

a strong storm near the equator with winds moving in a circle that feeds on energy from a warm ocean

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10
Q

how are tropical storms formed?

A
  1. sun heats ocean in summer and autumn
  2. once it reaches 27 degrees, the rising warm moist air causes low pressure
  3. this turns into a thunderstorm which causes air to be sucked in from trade winds
  4. trade winds blowing in opposite direction and rotation of earth (coriolis effect) causes thunderstorm to spin
  5. after 74mph, tropical storm is born
  6. cool air sinks in centre of storm causing calm clear conditions
  7. when storm hits land it loses energy source (ocean) and loses energy
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11
Q

what areas are prone to tropical storms?

A

between tropics of cancer and capricorn- pacific, indian and atlantic ocean

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12
Q

how does el nino lead to different weather?

A
  • usually, warm ocean currents off coast of australia cause moist warm air to rise (low pressure) and condense causing storms and rain in australia (but dry weather from high pressure in south america
  • el nino reverses this cycle
  • cool water off coast of australia reverse wind direction causing dry sinking air (high pressure) over australia causing dry hot weather (often drought) but warm wet weather (often floods) in south america
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13
Q

what is la nina?

A

the same as the normal weather pattern across the pacific ocean between australia and south america but more intense
* this causes floods in australia (very low pressure)
* and droughts in south america (very high pressure)

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14
Q

what causes drought?

A

very high pressure from cool seas making cool, dry air which sinks

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15
Q

what are trade winds?

A

winds that blow from high pressure to low pressure belts

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16
Q

what areas get drought?

A

north of africa, asia,

17
Q

what are the four types of plate boundary?

A
  • destructive
  • constructive
  • conservative
  • collision
18
Q

what happens (including hazards) at destructive plate boundaries?

A
  • plates move together and denser plate (oceanic) subducts beneath the other
  • friction causes it to melt and become molten magma
  • magma forces its way up to form a volcano
  • can also cause earthquakes
19
Q

what happens (including hazards) at constructive plate boundaries?

A
  • two plates move apart causing magma to reach surface through the gap
  • this causes volcanoes along the crack
  • also causes submarine mountain range
20
Q

what happens (including hazards) at conservative plate boundaries?

A
  • plates slide past eachother in opposite directions or same direction at diff speeds
  • this causes earthquakes
21
Q

what happens (including hazards) at collisional plate boundaries?

A
  • two continental plates collide (neither is forced under because both are continental)
  • both plates are forced up, forming fold mountains
  • can also cause shallow earthquakes
22
Q

how are earthquakes caused?

A
  • two plates become locked causing friction to build up
  • from this stress, pressure is eventually released
  • this triggers plates to move/ slip into a new position
  • this movement causes energy in the form of seismic waves to travel from the focus to epicentre
  • crust vibrates triggering an earthquake
23
Q

how does the depth of the focus of an earthquake impact the earthquake?

A
  • shallow focuses are small but common
  • the seismic waves spread and damage wide area
  • deep focuses occur on destructive plate margins
  • damage is restricted as the seismic waves travel vertically
24
Q

where are volcanoes found?

A
  • usually at destructive and constructive plate boundaries
  • most are found in a ring (bottomless) that encircles the pacific ocean (ring of fire)
25
Q

what is a hotspot volcano?

A
  • they happen away from plate boundaries
  • occur due to a plume of magma rising to eat into the plate above
  • where lava breaks through the surface, active volcanoes can occur above the hotspot
26
Q

what are the 3 types of volcano?

A
  • shield
  • composite
  • hotspot
27
Q

describe shield volcanoes and how they errupt

A
  • made of basaltic rock
  • form gently sloping cones from layers of runny lava
  • eruptions are gentle and predictable
28
Q

describe composite volcanoes and how they errupt

A
  • formed from layers of ash and lava
  • taller/ steeper slopes
  • explosive and unpredictable eruptions due to the build of pressure within the magma chamber
29
Q

evaluate the role of technology in managing tectonic hazards

A
  • warning signs of volcanic eruptions can be monitored using seismometers, thermal imaging, satellite cameras and gas samples
  • this cant stop an eruption but can give time to prepare for an eruption e.g. evacuation, creating an exclusion zone around volcano, having emergency supplies, emergency services and communication systems
  • earthquakes can’t be stopped by technology either but damage can be reduced by:
  • building earthquake resistant buildings, raising awareness, improving earthquake prediction
  • earthquakes can be predicted using things such as past seismic records, seismometers, satellite surveying, laser reflector, radon gas sensor, water table level
30
Q

what are convection currents?

A

radioactive decay in the earth’s core that cause hot circular convection currents to rise and fall causing movement of tectonic plates

31
Q

order of earth’s cells starting from 0 degrees

A
  • hadley until 30 degrees N and S
  • ferrel until 60 degrees N and S
  • polar until 90 degrees N and S
32
Q

what is lahar?

A

mud flow mixed with water, lava, ash and dust

Geography (23 decks)

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