Topic 1- Natural Hazards

• A natural hazard is a natural event that threatens to cause harm to people and the environment. They can have physical and/or human causes
• Some natural hazards with human causes are: earthquakes, landslides and flooding. Whereas, some natural hazards with environmental causes include: tornado, tsunami and hurricanes. Wildfires, sandstorms and droughts can be caused by both.
• There are many things that affect the impact or seriousness of a hazard:

  • proximity to people
  • Time of day
  • Preparation done
  • Amount of warning and defences in place
• The mantle is the 2nd layer of the Earth and is to 3000 degrees Celsius. It is made of hot melted rock called magma, is 2800km thick and the widest section of the earth. Huge heat and pressure causes the mantle to be made up of 15-30 foot high crystals.
• The crust is the outermost layer of the Earth and is made up of solid rock eg: granite. It is generally 3km-50km thick and is up to 6000 degrees Celsius.
• The outer core is 2100km thick and a liquid metal shell for the section beneath it. It is up to 4000 degrees Celsius.
• The inner core is the hottest section at around 5000 degrees Celsius and is 1340km thick. It is made up of solid heavy metals like iron and nickel.
• Volcanoes and earthquakes are found in the same areas of the world, on the edges of the earths tectonic plates especially around the pacific plate-know as the ring of fire. They sit on tectonic plate boundaries.
• Volcanoes and earthquakes are found in the same areas of the world, on the edges of the earths tectonic plates especially around the pacific plate-know as the ring of fire. They sit on tectonic plate boundaries.
• There are two different types of tectonic plates: oceanic and continental. Oceanic plates are thinner, more dense crust, around 3-6 miles thick and are floating. They can also sink. Continental plates are thicker, less dense crust, 20-40 miles thick and are attached to the mantle. They do not sink and are the upper thickness and at mountain ranges.
• Destructive plates margins are when an oceanic and continental player collide. The denser oceanic plate sub ducts under the continental plate. As the oceanic plate moves into the mantle it melts, creating magma which rises through the crust to form a volcano. Eruptions at these boundaries are violent and explosive. Friction between the plates also forms earthquakes. An example of a destructive plate margin is when the Nazca plate sub-ducted under the South American plate forming the Andes.
• Constructive plate margins are where two oceanic plates are moving apart. Magma forces it’s way through the cracks in the surface. As it breaks through the crust it causes earthquakes and forms shield volcanoes. An example of a constructive plate margin is when the North American and Eurasian plates move apart to create the mid Atlantic ridge. Iceland is an island along it.
• Conservative plate margins are where two plates slide past each other at different speed or from different directions. Friction causes the two plates to stick together and pressure builds up. When friction is overcome the sudden movement creates an earthquake. The plates can be oceanic or continental. No volcanoes are formed as no crust is created or destroyed. An example of a conservative plate margin is when the North American plate and pacific plate move side by side forming the San Andreas fault.
• Collision plate margins occurs when two continental plates meet. When the plates collide the crust becomes crumpled and uplifted to form high mountain plates. The pressure pushing them together can cause severe earthquakes but not volcanoes. am example of a collision plate boundary is when the Indian and Eurasian plate collide forming the Himalayas.
• Secondary vent- a smaller vent in the side of a volcano
• Magma chamber- an area deep in the earths crust that contains magma that can rise to the surface
• Ash cloud- cloud of ash that is usually erupted from composite volcanoes sometimes as high as 60km
• Crater- a funnel shaped hollow at the top of a volcanic cone
• Crust- the earths outermost layer made up of continental and oceanic sections
• Main vent- the main pipe in a volcano through which volcanic material erupts and lava travels up from the magma chamber
• Lava flow- molten rock that flows out of erupting volcanoes, called magma inside the crust or mantle
• Shield volcanoes have gently sloping sides and runny lava that covers a wide area. Gases escape very easily from shield volcanoes. Mauna toa in Hawaii is a shield volcano.
• Composite volcanoes are steep sided and cone shaped made up of layers odd ash and lava and containing sticky lava that doesn’t flow very far. Mount Etna in Italy is an example.
• Why do people still live near volcanoes?

  • of they think the volcano is dormant (low risk)
  • fertile soil (good farming)
  • Cultural or religious reasons/native land
  • money from tourism
  • Resources in the area
  • Good spice of geothermal energy
  • Scientific studies
• Causes of mt st helens eruption:

  • The volcano sits on a destructive plate margin (the juan de fuca plate moving towards the north american plate)
  • It had been dormant for 123 years
  • The melting of the juan de fuca plate creates more magma and puts pressure on the magma chamber
  • Earthquakes from the friction of the plates moving together were detected
• Effects of mt St Helens eruption:

  • towns in Washington, 250 miles away were covered in ash, stopping traffic and closing business
  • Over 200 homes and cabins were destroyed, leaving many people homeless
  • 57 people lost their lives
  • 11 million animals were killed and 4 billion feet of timber were destroyed. The total cost of the eruption stood at $1.1 billion
• Mt St Helens is a composite volcano located in the state of Washington on the west coast of the USA
• What initiated the timeline of the Mt. St. Helens eruption?

  Small earthquakes started off small eruptions of steam and gas.
• What geological process contributed to the increase in pressure on the magma chamber at Mt. St. Helens?

  The Juan de Fuca plate dives into the mantle and melts.
• What was the result of the pressure build-up in the magma chamber?

  A huge bulge, known as cryptome, formed on the north side of the volcano.
• At what rate did the bulge on the north side of Mt. St. Helens grow?

  The bulge grew at a rate of 5 feet per day.
• What magnitude earthquake occurred on the morning of May 18th that triggered the eruption?

  An earthquake measuring 5.1 on the Richter scale.
• What was the impact of the magma eruption from Mt. St. Helens?

  It destroyed everything in a 370-mile radius and killed 57 people.
• What significant geological event occurred as a result of one side of the volcano blowing away?

  The world's largest landslide occurred.
• What happened to Mt. St. Helens after the eruption?

  It calmed down, and its shape completely changed.
• Deducting the risk of volcanoes:

  • Predict- trying to forecast when an eruption will happen. This can allow for protection and evacuation
  • Protect- making sure buildings and local areas are able to withstand an eruption
  • Prepare- this involves bothe inhabitants and emergency services being ready for an eruption
• What can be done to predict when a volcano will erupt?

  • Monitor the shape of the volcano
  • Monitor small earthquakes
  • Monitor has changes around the volcano
• What can be done to protect for a volcano?

  • Buildings have smooth slanted roofs to prevent ash build up and collapse
  • Open areas between building to prevent the spread of fire (fire breaks)
  • Buildings made from non-flammable materials
  • Block windows, chimneys, doors and vents to prevent ash from getting in
• What can be done to prepare for a volcano?

  • people can be evacuated from exclusion zones to reduce impacts
  • Emergency supplies of food and water ready
  • Local emergency services prepared and trained
• Physicists, geologists and signal theorists have developed a machine learning based algorithm to predict when mount St Helen’s will next errupt