geo

• Flash Flooding


  When lots of water suddenly flows into a river, causing it to overflow its banks. Often caused by a short period of heavy rainfall.
• Boscastle Flash Flood


  • Occurred on 16th August 2004
  • In the village of Boscastle on the north coast of Cornwall
  • Caused by a flash flood
• Causes of the Boscastle Flash Flood


  • 75 mm of rain (the amount that would normally fall in a month) fell in just two hours
  • A low press system brought warm, moist air from the Atlantic Ocean
  • The air mass cooled as it rose above the land, causing thunderstorms with intense rainfall
  • Lots of rain over the previous weeks meant that the ground was wetter than normal, and could not absorb the water
  • Boscastle is in a steep-sided valley close to the confluence of three rivers
  • The steep valley sides meant that surface water ran into the river channels very quickly
  • The confluences meant that about two billion litres of water were funnelled down the river valleys into Boscastle
  • The old bridge in the village had a low arch over a very narrow river channel
  • Flooding was made worse because trees and vehicles in the flood water became trapped under the bridge, forming a dam
• Consequences of the Boscastle Flash Flood


  • 58 properties, 4 businesses, roads and bridges were destroyed or damaged
  • The flood was so sudden that people couldn't evacuate or move belongings to safer places
  • About 50 cars were washed out into sea, causing some environmental pollution
  • After the floods, the number of tourists dropped significantly, as the village is a popular tourist destination and 90% of the local economy relies on tourism
  • One person was seriously injured, and some residents suffered mental health problems after the flood due to stress relating to the floods and insurance claims
• Responses to the Boscastle Flash Flood


  • Emergency services quickly responded to save people in Boscastle, with around 100 people having to be airlifted to safety by seven helicopters
  • Residents and tourists that were flooded out of their accommodation were looked after in local accommodation and the village hall
  • Homes, businesses and roads were eventually rebuilt
  • The bridge was rebuilt with a higher arch, so that debris is less likely to dam the river
  • A £10 million new flood defence scheme was opened in 2008, which included widening and deepening the river to improve its flow
• KNOWLEDGE ORIGANDER Unit 1 Pcal Paper) Global Hazards-Weather
• The core consists of two parts - an inner solid core and an outer liquid core.

  
• The mantle is the thickest layer beneath the crust, composed mainly of magma (molten rock).
• The Earth's crust is the outermost layer, made up of solid rock.
• The mantle is divided into two layers - the upper part being rigid and the lower part being semi-molten.
• The Earth’s atmosphere is divided into five layers based on temperature and altitude.
• The crust is composed mainly of silicate rocks and has both oceanic and continental components.
• Troposphere – The lowest atmospheric layer where most weather occurs.
• Plate tectonics theory explains how the Earth’s lithospheric plates interact at plate boundaries.
• Stratosphere – A region between 10 km and 50 km above the earth’s surface.
• Tectonic plates are large pieces of the lithosphere that float on top of the asthenosphere.
• The inner solid core has a radius of about 75% of the total radius of the Earth.
• The core is divided into two parts - the inner solid core and the outer liquid core.
• The outer liquid core extends from the inner solid core to the boundary between the core and the mantle.
• Plate boundaries occur where tectonic plates meet and interact.
• There are three types of plate boundaries: divergent, convergent, and transform.
• Troposphere – The lowest atmospheric layer where weather occurs; air temperature decreases with increasing height.
• Stratosphere – Layer above troposphere where ozone concentration increases with height.
• The lithosphere is the rigid outer shell of the earth that includes the crust and uppermost portion of the mantle.
• The asthenosphere is located below the lithosphere and is less dense than the rest of the mantle.
• Mesosphere – Above stratosphere where temperatures decrease rapidly with height.
• The asthenosphere is located below the lithosphere and is less dense than the rest of the mantle.
• Stratosphere – A region above the troposphere that contains ozone gas which absorbs UV radiation from the sun.
• The mesosphere is the second layer from the top and contains most of the mass of the planet.
• Stratosphere – A region above the troposphere that contains ozone gas which absorbs UV radiation from the sun.
• Mesosphere – An area between the stratosphere and thermosphere with very low temperatures.
• Stratosphere – A region above the troposphere that contains ozone gas which absorbs UV radiation from the sun.
• Mesosphere – Above the stratosphere, this layer is very cold (-80°C).
• Stratosphere – A region above the troposphere that contains ozone (O3) which absorbs UV radiation from the sun.
• Ionosphere – This layer reflects radio waves back to earth allowing long distance communication.
• Thermosphere – A thin layer near space where satellites orbit.
• Mesosphere – An upper-atmospheric layer extending from about 80 to 96 kilometers (km) above the Earth's surface.
• Mesosphere – A region between 50 km and 80 km above the earth’s surface.
• Mesosphere – An upper-atmospheric layer extending from about 80 to 96 kilometers (km) above the Earth's surface.
• Continents are large land masses that float on top of the asthenosphere, while oceans are deep bodies of water covering about three quarters of the Earth's surface.