Zusammenfassung der Ressource
Restless Earth
- Volcanoes - Destructive & Constructive
- destructive - oceanic plates goes under continental - more dense (= ocean trench)
- oceanic plate - into mantle = melted & destroyed
- pool of magma
- magma rises through cracks in crust - vents
- magma erupts (lava) = volcano
- constructive margins - magma rises up through gap (from plates moving) = volcano
- Plates pull apart - convection currents - mantle
- Gap created - plugged by rising magma
- Cools to form lava
- Again & Again = layers build up = volcano under the ocean
- hotspots = really hot parts - of mantle
- Composite volcanoes
- made from ash & lava - cooled and hardened - layers
- lava = thick & flows slowly - hardens quickly = steep-sided volcano
- Shield volcanoes
- made from only lava
- runny lava - flows quickly - spreads over wide area = low flat volcano
- Dome volcanoes
- made from only lava
- thick lava - flows slowly & hardens quickly = steep-sided volcano
- Predicting Eruptions = important - minimise damage & save lives
- monitor signs before eruption
- tiny earthquakes, escaping gas, shape (bulges) = likely eruption
- Earthquakes = All Plate Margins
- Destructive - tension builds up when 1 plate gets stuck
- Constructive - tension builds - cracks within plates
- Conservative - plates grinding get stuck
- Plates = jerk past each other - shock waves - earthquake
- spread out from focus - point where earthquakes starts - near focus = more stronger/more damage
- epicentre = point directly above focus on Earth's surface
- Richter Scale = energy released - magnitude
- magnitude measured with seismometer
- logarithmic = ten times more powerful after every no.
- major earthquake = above 5
- Mercalli scale - measures effects - from observations (words/photos) - scale of 1 to 12
- Fold Mountains
- plates collide - sedimentary rocks = folded & forced upwards
- destructive plate boundaries
- continental plate & oceanic e.g. Andes
- 2 continental plates e.g. Himalayas
- high mountains - rocky, steep slops - snow
& glaciers in high bits - lakes in valleys
- FARMING: higher slopes = graze animals
lower = grow crops - cut terraces = easier to growing crops
- MINING: metal ores - steep
slopes = mining access - difficult
- zig-zag roads carved on sides for access
- HYDRO-ELECTRIC POWER (HEP): steep-sided mountains &
high lakes - ideal for generating HEP
- FORESTRY: grow some tree types (conifer)
- fuel, building materials, paper & furniture
- TOURISM: great scenery - winter = skiing, snowboarding
& ice climbing - summer = walkers - tunnels in mountains
- straight, fast roads - improves communications
- Tectonic Plates
- continental crust = thicker & less dense
oceanic crust = thinner & denser
- plates move as mantle move - conveyor belt
- Destructive Margin - move towards
- oceanic + continental = denser oceanic forced down into
mantle - destroyed - creates volcanoes & ocean trenches
- 2 continental plates - smash together - no crust destroyed
- Constructive Margin - move apart
- magma rises from mantle to fill gap & cools - creates new crust
- Conservative Margin - slide past
- same direction - different speeds - no crust created/destroyed
- Supervolcanoes = massive
- destructive plate boundaries/hot parts of mantle - hotspots
- magma rises up through cracks = magma basin - pressure = bulge - several km wide
- bulge cracks = vents for lava to escape - lava erupts = earthquakes & ash & rock
- magma basin empties - bulge - no longer supported = collapses - more lava spewed
- after - big crater (caldera) - left where bulge collapsed -
filled with water = large lake e.g. Lake Toba - Indonesia
- Flat (-unlike normals - mountains)
- Cover large area
- Caldera (no crater)
- Global Consequences
- only few - no eruption - tens of thousands of years
- thousands of cubic km of rock, ash & lava
- cloud of super-heated gas & ash - flow at high speed - killing, burning, burying everything it touches - within 10 miles = destroyed
- ash - kilometres into air - block out all daylight - continents = trigger mini ice ages (less heat reaching)
- ash = settle over hundreds of square kilometres - burying fields & buildings
- Yellowstone - Wyoming - 55 by 72km - geysers mud pots, lakes, waterfalls - attractions
- destroys everything in 100km radius - buildings, forests, farmland, 30 000 lives
- poisonous gases - contaminates water & rainfall
- ash = breathing difficulty
- Thousands of lives killed
- Forest Fires = air pollution & acid rain - affects nearby countries
- Weather Patterns = change
- Temp. - drop by 30°C - block sunlight
- could trigger ice age lasting many years = massive famine