Tectonic Hazards Flashcards
Tectonic plate
A large piece of earths crust
Plate boundary
Where 2 tectonic plates meet
Constructive/divergent plate boundary
Oceanic plates move apart, sea floor spreads and mid-ocean ridges are made as magma rises to fill the gap, underwater volcanoes formed, where 2 continental plates diverge rift valleys are formed
Destructive plate boundary
Oceanic and continental plates move together, heavier oceanic plate sinks under continental and melts, it rises and breaks though the continental to make volcanoes and violent earthquakes, it is the most dangerous margin
Collision plate boundary
Continental plates move together, too light to sink, buckle and fold to make fold mountains and earthquakes
Conservative plate boundary
Plates moving different directions or speeds, lock together by friction, pressure builds, pressure released making earthquakes
Characteristics of continental crust
Thicker, lighter, forms continents, granite
Characteristics of oceanic crusts
Thinner, heavier, forms ocean bed, basalt
Shield volcanoes
Formed in oceans(often constructive), rise from ocean floor, gentle upper slopes and steep lower slopes, made of lava flows built over a central vent, shield shaped
Stratovolcanoes
Steeper slopes and narrower, steep slopes made of la a flows that don’t travel far, alternating layers of ash and lava, more explosive because of long dormant times, first explosive to open vent and then lava flows out
Parts of a volcano
Conduit-where lava flows
Magma chamber-contains magma deep in earths crust
Side vent-vent on side of volcano
Primary impacts of volcanoes
Lava, ash, pyroclastic flow, volcanic bombs
Secondary impacts of volcanoes
Fire, lahars, landslides, trunamis
How can impacts of eruptions be reduced
Diversion of lava flow with excavators, spray lava with water to solidify, build walls across valleys to stop mudflows, stronger buildings so they don’t collapse, monitor earthquakes or gas emissions, ban passage to hazard areas
Hot spot
Volcano forms middle of a plate under the ocean, magma rises. In the middle of a plate, plate moves and another volcano in formed, string of islands
What is an earthquake
Shaking and vibration of the ground caused by movements in the crust
What is the focus of an earthquake
Point underground where shockwaves start
What is the epicentre of an earthquake
Pint aboce ground right above focus where vibration is highest
What is the richter scale
Scale that measures size of an earthquake, each point is 10x bigger than the last
What is a seismograph
Apparatus than measures size of an earthquake and records it on a seismogram
What affects the damage of an earthquake
The magnitude, the depth of focus, the population density, the time of day, the time it lasts
Reducing the risk of earthquakes
Monitoring with tilt meters, costly methods that provide only few seconds warning, prepare disaster plans, educate people, organise emergency supplies, efficient warning centre, specially trained dogs to locate survivors, prepare buildings VS earthquakes
