theme two Flashcards
volcano def
cone shaped mountained formed by eruptions of lava at the surface of the earth
crater def
a depression on the surface of a volcano, formed by volcanic activity, often circular in shape with deep sides.
vent def
the natural pipe or fissure that links the magma chamber to the crater or opening on the earths surface through which lava, ash and gases flow.
lava def
magma that has escaped from beneath the earth’s crust and has flowed onto the surface.
tectonic plates def
huge pieces of the earths crust that float and move on top of the much denser mantle below them
constructive/divergent plate boundary def
where two plates move apart, allowing magma to come to the surface as lava
magma def
molten rock found beneath the earths crust
magma chamber def
a large natural underground chamber of magma found within the surface of the earth beneath a volcano.
destructive/convergent plate boundary def
where two plates move towards each other
subduction def
when one plate sinks below another
hot spot def
a central part of the earths crust where plumes of magma rise to the earths surface
how can magma leave a volcano on to the earths crust
lava
volcanic bombs
very fine ash
what can volcanic eruptions be accompanied by
pyroclastic flows
lahars
earthquakes
composite/strato volcanoes
these are made from alternating layers of lava and ash as both come out of the vent during an eruption.
where do composite/strato volcanoes form
on destructive plate boundaries
shield volcanoes
these are made from lava. they from large volcanoes with gently sloping sides, sometimes hundreds of kilometres across before cooling and solidfying
where do shield volcanoes form
on a constructive plate boundary
dome volcanoes
these are also made from lava but the lava is acid and thicker and cools quicker. it does not flow very far before becoming solid and are steep sided and high.
active volcano
one that has recently erupted and is likely to again.
domant volcano
one that has erupted in the last 2000 years and may erupt again. hard to predict.
extinct volcano
long since finished erupting and has cooled down
earthquake def
a sudden and often violent shift in the rocks forming the earth’s crust, which is felt at the surface.
fault line def
a fracture or break in the earths surface along which rocks have moved alongside each other
focus def
the location of the actual source of an earthquake below the ground surface; also called the origin
conservative platae boundary def
where two plates are sliding alongside each other
epicentre def
location on the surface of the earth above the focus or origin of the earthquake
tsunami def
powerful, devastating waves at the coast caused by an undersea earthquake or volcanic eruption that displaces the water lying above it
seismometer def
an instrument that meaures movement of the ground, including the seismic waves generated by earthquakes and volcanic eruptions
seismic waves
waves of energy that travel through the earths layers as a result of earthquakes, volcanic eruptions, magma movements and large landslides
moment magnitude scale and richter scale def
numerical scales showing the size or magnitude of an earthwuake based on readings from a seisometer
mercalli scale def
a scale showing the effect of an earthwuake on the earths surface
aftershock def
a smaller earthquake following after the main earthquake
fold mountains def
a long, high mountain range formed by uplifting and folding of sediments
convection currents def
differences in temperature of material beneath the plates of the earth’s crust leads to the creation of currents to transfer the heat. these currents move the plants above them.
subduction zone def
the zone where one tectonic plate sinks under another
island arc def
a chain of volcaniv islands located above a subduction zone at a tectonic plate boundary
tephra def
rock fragments and particles ejected by a volcanic eruption
fumarole def
an opening in or near a volcano, through which gases, such as sulphur dioxide, are emitted
impacts of earthquakes and volcanoes on people
loss of life cutting of basic necessitites collapse of bildings infrastructure damage loss of crops fish can be killed spread of disease loss of jobs and businesses higher insurance premiums
primary effects
direct result of the earthquake or volcanic eruption
secondary effect
result of primary effects
what does the amount of damage caused by earthquakes depend on
strength depth distance from epicentre geology building construction and design space between buildings population density time of day secondary hazards like landslides contamination
opportunites granted by volcanoes
volcanic soils often fertile
geothermal power
raw materials / resources
attract tourists
how to reduce impact of volcanoes and earthquakes
improved technology
mapping high risk areas
improvind building design
ensuring emergency drills are in place
how can scientists predict volcanic eruptions
seismometers tilt meters thermometers gas sensors satellites
swash def
the movement of a sea wave up a beach after the breaking of a wave
backwash def
the movement of a sea wave down the beach after the breaking of a wave
hydraulic action
the weight and force of a wave crashing against a cliff removes particles of rockss from the cliff. also includes the process where air is trapped by a wave in a cliff and the enormous hydraulic pressure this creates opens up the clfif further.
abrasion
where rocks and sand are picekd up by a wave and thrown against the cliff
solution
some minerals are put into solution by weak acids found in seawater
attrition
rocks on the beach are rolled up and down the beach by swash and backwash. as this happens they collide with each other and become smaller and rounder as a result
longshore drift def
the movement of material along a beach transported by wave action
spits def
ridges of sand or shingle attached to the land but ending in open sea
bars def
ridges of sand or shingle acrss the entrance of a bay or river mouth
tombolos def
spits connecting an island to the mainland
groynes def
wooden, stone or concrete barriers built perpendicular to the coast in order to break waves and reduce the movement of sediment along the beach
constructive wave action
swash stronger than backwash so more sand and shingle will travel up the beach
destructive wave action
swash weaker than backwash so more sand and shingle will be moved down offshore
salt marsh def
an area of mudflats formed when sediment is deposited in the low wave energy area behind a spit
cliff notch def
a small overhang formed at the base of a cliff by wave action
wave cut platform def
a wide, flat area of rock at the bottom of cliffs seen at low tide
headlands def
areas ofmore resistant rock jutting out from the coast into the sea
cave def
a hollow at the base of a cliff which has been eroded by rocks
arch def
a rock bridge formed at a headland that has been partly broken through by the sea
stack def
an isolated column of rock at the end of a headland formed after a stack has collapsed
bay def
a broad coastal inlet, often curved and with a beach, between two headlands
what will happen if the coastline alternates between soft and hard rock
differntial erosion will take place resulting in a disconcordant coastline
wherer do salt marshes form
sheltered bays and estuaries in the protected area behind a spit or tombolo
coral reef def
a ridge of rock near the surface of the sea, formed by frowth and deposit of coral
types of coral reef
barrier
fringe
atoll
conditions for coral reefs to form
temp has to be 23-25 degrees depth of water had to be less than 25cm water has be clear for lots of sunlight low salinaty low sediment high energy wave action for freshly oxygenated water exposure to air
where are mangerove swamps found
along coastliens between 30 north and 30 south of the equator.
magrove swamps def
tidal swamps that are dominated by mangroves (shrubs or small trees with numerous tangled roots that grow above ground
adaptations of mangroves
low oxygen conditions low salt intake in tree low water loss aerial roots to absorb nutrients the seeds float
roles of mangroves
coastal protection
breeding ground
source of food, medicine and raw materials
managing impacts of coastal erosion
sea walls
revetment
gabions
rock armour
groynes
beach nourishment
assessments on how to defend a coast:
cost-benefit analysis
environmental impact assements
shoreline management plan
tropical storm def
areas of very low pressure in low latitudes, with strong winds and heavy rains
ICZM def
integrated coastal zone management
the management of the coast using an integraed approach, taking into account all aspects of the coastal zone, including geographical and political boundaries
littoral cell def
a length/section of the coast that is isolated from adjacent sections of coast and has its own sources
weather def
the state of the atmosphere at any paticular moment in time
climate def
a description of the averages and extremes of weather variables of an area over an extended period of time
stevenson screen def
a container in which weather/meteorological instruments are placed
isohyet def
a line on a map joining places of equal rainfall
how is weather data collected
stevenson screen rain gauge maximum minimum thermometer wet and dry bulb thermometer barometer anemometer wind vanes cloud cover sunshine recorder
diurnal range def
the daily range of temperature
relative humidity def
the amount of water vapour (moisture) in the air, expressed as a percentage of the maximum amount of water vapour that the air could hold at a given time