PLATE TECTONICS

convection currents within the mantle

DIVERGENT heated mantle material expands, rises, and spreads out beneath the plates

CONVERGENT mantle material cools and sinks, pulling the plates along. slab-pull force: when the denser oceanic plate subducts beneath the less dense plate

rift valley, volcano (CC) mid-oceanic ridge (OO)

fold mountains (CC) oceanic trench (OO) volcano (OO)

TRANSFORM plates sliding past each other at transform plate boundaries forms transform faults

VOLCANOES primarily found at plate boundaries, uprising of magma through cracks and fissures

stratovolcano

shield volcano

convergent plate boundaries, subducted and melted plate has high silica content, viscous lava that traps gases easily, more violent eruptions

divergent plate boundaries, lava risen from mantle has low silica content, less viscous, gases can escape easily, less explosive eruptions

however, the extent of explosiveness can be determined by the amount of built-up pressure in the volcano as well eg. Iceland volcano 2010

highly explosive eruptions: pyroclastic flow, lahars, landslides, air pollution

fast-flowing lava: large-scale destruction at the base of the volcano

EARTHQUAKES (LOCALISED) sudden release of stored energy in rocks found along fault lines in the form of seismic waves - unexpected, little time for preparations

TSUNAMIS (REGIONAL) - underwater, offshore earthquakes, underwater volcanic eruption, landslide ; columns of water displaced, travelling in all directions as waves

on reaching shallower water, greater friction slows down the waves and thus they increase in height

  1. population density
  2. level of preparedness
  3. distance from epicentre
  4. level of development
  5. magnitude
  6. type of soil
  7. time of occcurrence
  8. depth of focus #

benefits

fertile soil - minerals that otherwise can only be extracted after millions of years when the rocks have been eroded ; especially important to countries that depend heavily on agriculture

precious stones and minerals

tourism

geothermal energy; requires technology and financial capacity, only in DCs

MEASURES

preparedness - largely dependent on financial capacity of the country and adequate knowledge among citizens

short-term responses

long-term responses

land use regulation

infrastructure

emergency drills

monitoring and warning systems

search and response - LDCs rely largely on international efforts

emergency food and medical supplies

rebuilding of infrastructure

provision of healthcare