More Related Content


Recently uploaded(20)


Volcanoes and earthquakes education powerpoint

  1. Volcanoes
  2. What are Volcanoes? ● A volcano is a rupture of the Earth's crust which allows hot lava, poisonous gases and ash to escape from the magma chambers below the surface. ● Volcanoes occur because the Earth's crust is separated into 17 rigid tectonic plates that float around on a hotter and softer mantle below. ● This is why volcanoes are generally found around places where the plates converge and diverge. For example, as the plates move apart, a fissure opens in the ground, allowing lava to pour out onto the surface. This is called a fissure volcano. ● Scientist who study volcanoes are call Volcanologists.
  3. Volcano Phases ● Volcanoes can be in one of three phases: Active, Dormant, and Extinct. ● Active volcanoes are ones that have erupted in the pas 10,000 years, and that are likely to erupt again. An example is Mt. Saint Helens in U.S.A. ● Dormant volcanoes are ones that have not erupted in the past 10,000 years, but still have the possibility, though unlikely. An example is Mt. Rainier in the U.S.A. ● Extinct volcanoes are ones that nobody think will erupt ever again. An example is Mt. Ashitaka in Japan.
  4. Types of Volcanoes ● There are four types of Volcanoes: ● Fissure Volcanoes, ● Cinder Cone Volcanoes, ● Shield Volcanoes, ● Composite Volcanoes,
  5. Fissure Volcanoes ● Fissure volcanoes are cracks in the ground that are only a few metres wide but can be several kilometres in length. ● Fissure volcanoes are not usually explosive. Instead, the lava seeps out of the gaps in the surface of the crust.
  6. Shield Volcanoes ● Shield volcanoes are almost entirely made up out of fluid lava flows. ● Vent after vent flows out through the volcano from the centre vent. ● This builds a broad, gentle sloping cone of a flat, dome shape, similar to a warriors shield.
  7. Composite Volcanoes ● Composite volcanoes are some of the grandest on the world. ● They are typically large, steep, symmetrical cones built of alternating flows of lava ash and cinders. ● Most have a crater at the summit which contains a central vent or a clustered group of vents.
  8. Cinder Cone Volcanoes ● Cinder cone volcanoes are formed large globs of lava being launched from a single vent. ● As the gas-charged chambers explodes, lava gets launched into the air only to fall back down around the main vent as cinders in an oval or circular cone. ● Most have a bowl-shaped crater in the centre.
  9. What Causes Volcanoes? ● Volcanic activity frequently occurs on the boundaries of tectonic plates as the pressure within causes the magma below to rise up and explode or escape to the surface.
  10. The Ring of Fire! ● The Ring of Fire is a string of volcanoes that runs around the edge of the Pacific Ocean. ● The Ring of Fire is quite a circle, more like 40,000 kilometre long horseshoe. ● A string of 452 volcanoes stretches from the southern tip of South America, up along the coast of North America, across the Bering Strait, down through Japan, and into New Zealand.
  11. Measuring Volcanic Eruptions ● Volcanic eruptions are measured using the Volcanic Explosivity Index (VEI) ● Since the size and force of eruptions vary, Volcanologists take a number of factors into account when measuring volcanic eruptions, such as: ● Volume of material ejected, height of the eruptive column, duration etc. ● Each eruption is given a rating of 0-8. 0 being non-explosive and harmless, and 8 being “Run for your lives the planet is melting!” ● Each point on the scale is 10 times more powerful than the one before. This makes the most devastating eruptions that we know of thousands of times more powerful than the eruption that took off the top 400m of Mt. St Helens almost a quarter of a century ago.
  12. VEI
  13. Earthquakes
  14. What are Earthquakes? ● An earthquake is the result of a sudden release of energy in the crust that creates seismic waves. ● The seismicity of an area refers to the frequency, size, and type of earthquake experienced over a period of time.
  15. What cause Earthquakes? ● The Earth's crust is made up of several tectonic plates. These plates are always moving around on the mantle. ● Because these plates are moving, they constantly grind against one another and get stuck. ● When the rest of the plate moves far enough, one of the two plates fault, which releases large amounts of energy that was stored up by the tension. ● This causes an earthquake.
  16. Focus and Epicentre ● The focus of an earthquake is where it begins, this is where the plate slips on a fault line, usually at the plate edges. ● The Epicentre is the point directly above the Focus on the surface of the earth. This area will suffer from the most direct damage.
  17. Seismic Waves ● Seismic waves are the waves of energy caused by the breaking of rock during an earthquake. ● The main two types of waves are body waves and surface waves. ● Body waves occur in two types, primary waves (P) and secondary waves (S). ● Surface waves occur after the body waves as lower frequencies which are responsibly for most of the damage and destruction on land. ● Surface waves have two types, Love waves and Rayleigh waves.
  18. Wave Types
  19. Measuring Earthquakes ● The vibrations earthquakes produce are detected, recorded and measured by instruments called Seismographs. ● The line made by a seismograph is called a seismogram and shows the changing intensity of the earthquake by responding to motion of the ground below the instrument. ● From the data expressed in seismograms, scientists the time, the epicentre, the focal depth, the type of faulting of an earthquake and how much energy was released.
  20. The Richter Scale
  21. The Modified Mercalli Scale