Hazards Flashcards
define hazard
an event which has the potential to cause harm to the environment, people, or economy
define natural disaster
an event which has the potential to cause harm caused by environmental processes
describe how a destructive plate boundary forms
convergent/subducting
- convection currents drive the plates together
- heavy oceanic plate subducts under lighter continental plate
- friction causes heat which melts the oceanic plate, forming magma
- magma rises through the cracks in the crust
- a strato-volcano forms
describe how a contstructive plate boundary forms
divergent
- convection currents causes the two plates to DIVERGE (pull apart)
- convection currents causes hot magma to rise through the crust
- cool magma either solidifies to form rock or sinks
- CONSTRUCTS (forms) a shield volcano
describe how a conservative plate boundary forms
transform
- two plates rub against eachother in opposite directions, creating friction
- friction builds up energy
- energy released in the form of seismic waves, aka earthquake
- creates fault lines
describe how a collision plate boundary forms
- two continental plates COLLIDE and create fold mountains
what anomalies are present in the distribution of volcanos and EQ’s?
- INLAND NORTHERN INDIA: many earthquakes, little volcanoes
- AFRICAN RIFT VALLEY: many volcanoes, little earthquakes
where are the most earthquakes and volcanoes clustured?
PACIFIC RING OF FIRE in the Pacific ocean: 70% of all EQ’s
which plate boundaries are earthquakes most frequent and powerful?
- Destructive (subduction)
- Conservative (rub against eachother)
describe the process of earthquake formation
- as tectonic plates move, they can get stuck
- plates try to move –> pressure builds
- plates jolt free, pressure released as energy as seismic waves
what is the focus of a volcano?
where the earthquake starts within the plate
what is the epicentre of an earthquake?
the point directly above the focus
how are earthquakes measured?
richter scale
moment magnitude scale
how does the richter scale measure earthquakes?
- seismometer measures magnitude (detects seismic waves)
- seismometer produces seismograph
- LOGRAITHMIC SCALE
- 1-2 cant feel anything and happen regularly
- 7+ very powerful, lots of destruction
how does the moment magnitude scale measure earthquakes?
- measures magnitude as energy released
- more accurate
