Causes of earthquakes

• The Restless Earth, Earthquakes, Volcanoes, Folding & faulting, Rocks, Weathering, Karst, Rivers (fluvial processes), Coastal processes (sea), Glacial processes (ice), Mass movement, Isostacy & fluvial adjustment, Human interaction with surface processes, Weather & weather maps
• Regional introduction, Peripheral Irish region (B.M.W.), Core Irish region (South & East), Peripheral European region (Mezzogiorno), Core European region (Paris Basin), Continental/sub-continental (S.W. USA), Continental/sub-continental (India), Types & complexities of regions
• Maps and aerial photograph skills for short questions, Maps and aerial photograph skills for long questions, Graphs, charts and satellite imagery
• Population Change, Overpopulation, Migration, Settlement, Urban Settlement, Problems with urbanisation
• Introduction, Economic development, Levels of development change over time, Globalisation & multinational companies, Ireland & the European Union, Environmental impacts
• The Theory of Continental Drift proposes that the original land surface of the earth fractured and drifted for over 200 million years across the earth’s surface, forming the continents
• The Theory of Thermal Convection explains the process of Global Crustal Plate Movement
• Plates move through the Theory of Thermal Convection, where hot rock rises from within the earth to the surface, cools, flows sideways, and sinks, dragging the lithosphere with it
• Alfred Wegner proposed the Theory of Continental Drift in 1915, noting evidence like matching fossils, continental fit, and matching rocks and mountain ranges
• Pangaea, the supercontinent, broke into Laurasia and Gondwanaland, which drifted across the earth’s surface before breaking up into the continental landmasses we have today
• The Theory of Continental Drift was accepted in 1963 with the discovery of the Mid Atlantic Ridge, proving that the oceans were spreading and pushing the continents around the globe
• At convergent plate boundaries, plates collide, with the heavier plate being pulled downwards along the Benioff Zone beneath the other in a process called subduction
• Convergent plate boundaries can be Oceanic Plate to Oceanic Plate, Oceanic Plate to Continental Plate, or Continental Plate to Continental Plate, resulting in various landforms like oceanic trenches, volcanic mountains, and fold mountains
• Causes of earthquakes:

  • Along Convergent Plate Boundaries:
  • Subduction occurs when plates collide, with earthquakes as deep as 750km below the surface
  • Examples: Kobe earthquake in Japan in 1995, San Francisco earthquake in October 1989
  • Along Divergent Plate Boundaries:
  • Plates move apart, process of sea floor spreading
  • Example: Mid-Atlantic Ridge formed by Eurasian and North American Plates separating
  • Along Transform Faults:
  • Plates slide past each other without crust destruction or creation
  • Example: San Andreas Fault in California
  • In the interior of plates:
  • Tensional forces cause land to sink between parallel faults, forming Rift Valleys
  • Example: Great Rift Valley in East Africa
• Types of damage caused by earthquakes:

  1. Ground vibrations:

  • Shaking causes buildings to fall
  • Example: Izmit earthquake in Turkey in 1999

  1. Liquefaction:

  • Saturated soil becomes a thick liquid, removing buildings and bridges
  • Example: Mexico City built on a lakebed

  1. Avalanches & landslides caused by earthquakes
  2. Fire:

  • Often more dangerous than the earthquake itself
  • Example: Great San Francisco earthquake in 1906
• Earthquake prediction:

  • Read the answer in the workbook on pages 19 and 20
• Indian Ocean tsunami:

  • Read the answer in the workbook on pages 23 & 24
• Volcanoes occur in the Pacific Ring of Fire where plates converge and diverge, and at hot spots

  • Divergent Plate Boundaries: plates separate, theory of Sea Floor Spreading
  • Convergent Plate Boundaries: heavier plate sinks beneath the other, subduction
  • Hot Spots: warm areas deep within the earth’s mantle where plumes of hot magma rise to the surface forming volcanoes
• Mauna Loa, a shield volcano (4170m) on the island of Hawaii, is the world's largest active volcano
• The Hawaiian Islands are the tops of volcanoes that formed above a hot spot in the earth's interior
• As the volcanoes grew, they moved away from the hot spot as the Pacific Plate moves northwestwards at 3.5 inches per year
• Hot spots also lie under Yellowstone National Forest Park and the islands of Iceland and Reunion
• Shield volcanoes are associated with basic lava flows, low in silica, not explosive, and usually found at constructive plate boundaries
• Shield volcanoes have a broad base, not steep sides, and resemble a warrior's shield with the outer side facing the sky
• Lava plateaux are associated with basic lava flows, elevated areas associated with divergent plate boundaries
• Dome volcanoes are associated with acidic lava flows, high in silica, thick or viscous, highly explosive, and usually found at destructive plate boundaries
• Composite volcanoes are associated with acid lava flows producing explosive eruptions, composed of alternating layers of pyroclastic material and lava, often found at convergent plate boundaries
• Volcanic intrusive landforms result from magma cooling within the earth's crust, forming intrusive igneous rocks or plutons
• Plutonic structures like batholiths, dykes, and sills eventually reach the surface due to weathering and erosion
• Batholiths are dome-shaped masses of igneous rocks mainly granite formed by intrusion of magma into cavities as it forces its way upwards into the crust
• Sills are horizontal sheets of igneous rocks formed when magma forced its way upwards and settled between two layers of sedimentary rock where it cooled and solidified
• Advantages of volcanoes include fertile soils, formation of precious stones and minerals, geothermal energy, and tourism
• Disadvantages of volcanoes include loss of life, damage to property, and environmental damage
• The eruption of Krakatoa in 1883 caused a column of pyroclastic material to travel 40 kms across the sea, destroying coastal communities in Sumatra and killing more than 36,000 people
• In AD79, Vesuvius erupted, destroying Pompeii and Herculaneum, burying Pompeii under 3m of materials that fossilised both inhabitants and buildings
• The eruption of Mount Pinatubo in 1991 had major effects on the environment, darkening the sky for many days and reducing global temperatures by 5°C
• Caledonian Foldings occurred 450 million years ago when the North American & Eurasian Plates converged during the Silurian geological period
• Magma intruded into the upfolds during the Caledonian Foldings to form granite
• The name "Caledonian" comes from Caledonia, the Roman name for Scotland
• Caledonian Foldings were higher than today’s Alps but have been reduced by weathering and erosion