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
- population density
- level of preparedness
- distance from epicentre
- level of development
- magnitude
- type of soil
- time of occcurrence
- 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