global hazards

• The Earth's crust is divided into different slices called tectonic plates
• Tectonic plates can move towards each other, away from each other, or side by side
• Between each tectonic plate is a plate margin
• At plate margins, mountains or volcanoes can be formed due to heat and pressure
• Living by plate margins can be dangerous, but people still live there for valuable minerals and tourism
• Continental crust is thicker but less dense, while oceanic crust is thinner but more dense
• Stuffed crust pizza is thick but less dense, while deep pan pizza is slightly thinner but more dense
• On pizza, cheese can either melt together between slices or stay on its own slice
• Just like pizza, even though we know it's not the healthiest, people still eat it for the taste
• Volcanoes are formed at plate margins or plate boundaries where tectonic plates meet
• There are three types of plate margins: destructive, constructive, and conservative
• Destructive plate margins occur when two plates collide towards each other
• Constructive plate margins occur when two plates pull apart from each other
• Volcanoes are formed at destructive and constructive plate margins
• Destructive volcanoes are formed when oceanic and continental plates collide, with the oceanic plate subducting beneath the continental plate into the mantle
• The oceanic plate is denser and sinks beneath the continental plate due to heat and pressure, melting into magma
• The magma rises back up through cracks in the crust called vents, forming destructive or composite volcanoes
• Constructive volcanoes are formed when two plates move away from each other, allowing magma to rise up and fill the gap, creating shield volcanoes
• An example of a constructive volcano is the Hawaiian Islands
• Global atmospheric circulation is the transfer of heat from the equator to the poles by the movement of air
• Air moves due to the difference in air pressure
• Wind blows from high pressure to low pressure
• High pressure is when cool air descends, low pressure is where warm air ascends
• The equator drives the whole system as it is the hottest part of the earth
• Air rises at the equator due to warming, leading to low pressure and rainfall
• Air travels North and South from the equator, becoming colder and denser, then falls creating high pressure and dry conditions at 30 degrees north and south
• Large cells of air are created due to the change in temperature and density
• The names of the cells are Hadley, Ferrel, and Polar
• Hadley cell:

  • Air rises at the equator creating low pressure
  • Air cools and forms thick cumulus clouds
  • Air moves towards the poles, cools, and sinks at 30 degrees north and south forming subtropical high pressure zones
  • Air flows back towards the equator as trade winds
• Ferrel cell:

  • Occurs between 30 and 60 degrees north and south
  • Air is pulled towards the poles forming warm winds
  • Moisture is picked up over oceans
  • Warm air meets cold air at 60 degrees north and south, causing uplift and low pressure
  • Associated with mid-latitude depressions and unstable weather conditions
• Polar cell:

  • Cold air sinks at the poles forming high pressure
  • Flows towards lower latitudes, mixing with warm air at 60 degrees north and south
  • Creates a zone of low pressure called the subpolar low
  • Polar front is the boundary between warm and cold air, causing unstable weather
• Global atmospheric circulation affects weather around the world by creating areas of high rainfall like tropical rainforests and areas of dry air like deserts
• Equator:

  • Receives a lot of solar radiation
  • Warm moist air rises and forms clouds, leading to heavy rainfall
• 30 degrees north and south:

  • Releases most of its moisture as rain
  • Few clouds and little rainfall, leading to desert conditions
• 60 degrees north:

  • Warm air rising brings cloud cover and rainfall due to westerly winds
• Earthquakes come from the Earth's outer layer, the crust, which is divided into tectonic plates
• Plate margins or plate boundaries are where the tectonic plates meet
• Tectonic plates are constantly moving, and when they get stuck and finally move, they release energy in the form of seismic waves, causing an earthquake
• Earthquakes are unpredictable because the tension can be released at any point
• Parts of an earthquake:

  • The focus is the point in the Earth where the earthquake starts, usually in the mantle where tension is released
  • The epicenter is the point directly above the focus on the Earth's surface
  • Seismic waves are vibrations from the earthquake, strongest near the epicenter and weakest further away