Earthquakes, tsunamis, volcanoes

• Earthquakes are a sudden movement or trembling of Earths crust
• Earthquakes occur when plates collide or slide past each other (destructive plate boundary and transform plate boundary)
• The focus is the point deep underground where the earthquake originates
• Shock waves or tremors spread out from the focus
• The epicentre is the area on the surface directly above the focus, this is where the tremors are strongest
• Seismograph detects the size of the tremors of an earthquake
• Richter scale measures magnitude of earthquake (10 units)
• Case study: Nepal Earthquake: focus was in the Himalayas, it occurred in April 2015, 7.9 on Richter scale and aftershocks of 6.7
• A tsunami is a huge wave or a series of waves that result from an underwater earthquake or volcano
• Case Study: Japan tsunami: occurred during 2011, 9.0 on Richter Scale, caused by underwater earthquake that lasted 6 mins causing a tsunami, epicentre under Pacific Ocean
• Japan tsunami results: towns destroyed, roads and bridges washed away, 18000 killed
• Negative impacts from Nepal earthquake: 8,000 people died, 20,000 were injured and 3.5 million were left homeless. Avalanches and ice falls occurred in many of the climbing regions
• Volcanoes release gas, steam, rocks and lava from the crater
• Volcanoes are formed when plates separate and collide
• Volcanoes are an opening in the Earths crust through which lava, volcanic ash and gases escape
• Example of an active volcano is Mt Etna is Italy
• Example of dormant volcano is Mount St Helens in the Cascade Range of the USA
• Positive impacts from volcanoes is that it boosts economy because it increases tourism, and minerals in lava can benefit the soil
• Negative impacts from volcanoes is destruction of homes and habitats, death, flights delayed and destruction of nature
• Case Study: Mount St Helens eruption: 200 homes were destroyed, 57 people died due to its poisonous gas, 12million farmed fish were killed, 7,000 large animals were killed in the blast