Hazardous Earth: Climate Flashcards
Atmospheric Circulation/ Coriolus Effection
> Earth rotates, so air doesn’t flow in a straight line. As air moves above the Earth’s surface, planet rotates, so winds follow a curved path.
Effect of jet streams on climate
> Position of jet stream determines weather we get.
They are mostly at main circulation cells’ boundaries.
If the polar front jet is positioned north of the U.K = warmer weather.
If the polar front jet is positioned south of the U.K = colder weather.
If the polar front jet is positioned in the middle of the U.K= windier and wetter weather.
Jet stream
> A current of rapidly moving air that is usually several thousand miles long but relatively thin.
Cyclones
> A tropical storm that occurs over warm seas and oceans. Smallest type of tropical storm, but winds can still reach over 250 mph.
Occur between 20’S and 30’N of the Equator, over 27’C, 60m deep water as they take heat from oceans.
Low pressure.
Small - 650km across.
High wind speeds 300kmph as don’t use much energy.
Formed over small areas as well.
Die out over land because doesn’t get enough warm, moist air.
Cyclones formed in the Indian Ocean and South Pacific move in a westerly direction towards Asia.
Cyclones 2
> Mb = measurement of air pressure.
Lower pressure = heavy air.
Storm surge = flooding from the sea.
1. Warm air currents rise from the ocean and updrafts of rushing and rising air condense quickly into cumolonimbus clouds.
2.The cyclone tracks away from its source.
3. If it goes over landmass, it will lose mass and slowy die.
Track of cyclone = way it’s heading.
Eye of cyclone = centre of cyclone, mostly free of a storm.
Cyclone Alia
> 2009, Bangladesh.
Bangladesh (Cyclone Alia)
> Bangladesh is in Asia.
Flat country with majority of country less than 10m above sea level.
One of the poorest countries - GDP per capita = $3,600.
Flat country so floods can spread very quickly.
Build up of sediment makes sea floor rise, so floods will be more common in the future.
On average, Bangladesh receives around 2911mm of rainfall a year.
Cyclone Alia - Case Study
> Started in the Bay of Bengal, 25th May 2009.
120mm of rainfall in just a few hours.
Wind speeds reached 360km/h 120 (80km/h for cyclone to start).
Air pressure was very low (967mb), causing rise in sea level and storm surge.
Total fatalities: 339
Highest wind speed: 120 km/h
Date: 26 May 2009 – 27 May 2009
Damage: $295.6 million (2009 USD)
Category: Category 1 Hurricane (SSHWS)
3,500,000 were affected.
750,000 homes were destroyed.
200,000 still living in temporary after 1 year.
A cyclone-proof house in US$ = $1500.
45,000 cyclone warning volunteers in Bangladesh.
LEDC country longer recovery period after cyclone.
Impacts of Cyclone Alia
> SHORT-TERM IMPACTS:
-No one can work to earn money to rebuild homes + belongings.
-Humans + animals were killed.
-Flooding and no clean water, trees uprooted.
LONG-TERM IMPACTS:
-Education disrupted, government couldn’t fund repairs, 1 classroom for 200.
-People died and homes destroyed.
-Many couldn’t regrow crops because land and water was salty.
-Lack of wood as many trees were dying.
Cyclone Alia (Disaster and response)
> Oxfam, Christian Aid, Water Aid gave relief aid to victims.
Aid is vital - countries who deal with regular crisis can’t afford to keep rebuilding people + houses.
Soap, food, clothes and temporary shacks given out.
Cyclone Hazards
> HIGH WINDS:
-Cyclones can produce 250kmph winds.
-People and animals hit by flying debris.
-Trees uprooted.
STORM SURGES:
-Sea rises in low mb.
-Houses are damaged and people injured.
-Erodes beaches, damages coastal defences and flow inland and contaminate.
Intense rainfall, landslides, coastal flooding.
Hurricane Katrina
> Left $150 billion’s worth of damage.
Passed through Florida, 25th August 2005.
1836 people died and 10,000 were made homeless.
3,000,000 people were left without electricity.
53 breeches of levees and flood walls.
80% of New Orleans flooded up to 3m deep.
Homes and businesses were looted.
Roads and bridges were damaged.
Reducing the impacts
> WEATHER FORECASTING:
-Sends out weather reports and warning on TV, radio and phones.
-Allows people to prepare for storm, households with radio had a lower death rate.
-Not everyone has access to radio etc.
SATELLITE TECHNOLOGY:
-Digital images from space to see if storm is brewing.
-Warning to meteorologists to tell people to prepare.
-Expensive, but Bangladesh is developing it’s own $150 million one.
STORM SURGE DEFENCES:
-Walls built in sea to stop sea level rising and flooding land.
-Stops major floods in flood-prone areas.
-If they break can’t get water back out to sea as they block it.
USA Preparation
>Weather forecasting >Satellite technology >Warning systems >Evacuation strategies >Storm surge defences
USA Preparation (Weather forecasting)
> Very reliant
Can warn millions
If inaccurate satellite recordings then the weather forecast is wrong.
USA Preparation (Satellite technology)
> There’s over 20
They aren’t perfect
They break
USA Preparation (Warning systems)
> SMS (103phones/100people)
>Poor might not be aware.
USA Preparation (Evacuation strategies)
> Evacuation.
>Some might not evacuate.
USA Preparation (Storm surge defences)
> Prevents potential flooding (levees)
Levees can break eg 700 people drowned in one small suburb when one broke.
Government spending cuts left them poorly maintained.
Saffir-Simpson Wind Scale
> Most common scale used to classify tropical cyclones.
Based on wind speeds generated by tropical cyclones.
Estimates amount of damage on property and environment.
Tropical cyclones over category 3 have potential to cause major life loss and significant damage.
Category 1
> 119-153km/h
Minimal
1.2m-1.7m storm surge.
Category 3
> 178-208km/h
Extreme
2.7-3.8m storm surge
Category 5
> 250+km/h
Catastrophic
5.4m+ storm surge.
Key events: Hurricane Katrina: August
- 23rd: Tropical depression forms off the South-eastern Bahamas.
- 24th: Upgraded to tropical storm - Katrina.
- 25th: Became hurricane, making landfall in Florida.
- 26th: Intensified to category status 2 when crossing Gulf of Mexico.
- 27th: Doubled in size, category 3, heads towards Mexico.
- 28th: Peak category 5, approaches U.S coast, 282km/h wind speed,902mb.
- 29th: Land fall eastern edge of New Orleans.
- 30th: Follows course of Mississippi downgrading to a tropical depression near Clarkesville, Tennesse.
Evidence for tectonic plates
- Study of fossils - similar fossils are found on different continents. This is evidence that these regions were once very close or joined together.
- Pattern of rocks - similar pattern of rock layers on different continents is evidence that the rocks were once joined together.
- Shape of continents - jigsaw.
Layers of the Earth
Inner core Outer core Lower Mantle Upper Mantle Oceanic Crust Continenantal crust
Lithosphere
> The uppermost layer of the Earth.
It’s cool and brittle.
It includes the very top of the upper mantle, the oceanic crust and continental crust.
Asthenosphere
> Top layer of the mantle.
35-250km.
3.4-4.4g/cm^3.
Partially molten.
Composition: peridotite.
Temp: 900-1600 degrees.
The movement of tectonic platers is evidence that there is a ‘lubricating’ layer underneath the lithosphere. This is the asthenosphere.
Geologists think the asthenosphere is partly molten rock and partly solid rock.
We need to learn more from research like that done on drilling ships.
Continental Crust
>Density: 2.7g/cm^3. >Solid, thick - 30-50km. >Lighter rocks, cannot subduct into the mantle. >Old. >Granite >Temp: Air-900 degrees.
Oceanic crust
>Density: 3.3g/cm^3. >Dense basalt, can subduct into the magma of the mantle. >Young. >Thin: 6-8km. >Temp: Air - 900degrees.
Mantle
> The mantle is the largest of the Earth’s layers by volume, and is mostly solid rock.
We know this because sometimes you can see the top of the mantle attached to an overturned piece of crust.
Upper mantle: 700km.
Lower mantle
>Density: 4.4-5.6g/cm^3. >Solid. >Composition: Peridotite. >Temp: 1600-4000 degrees. >2900km
Outer core
>Density:9.9-12.2g/cm^3. >Liquid. >Iron and nickel. >4000-5000 degrees. >5270km
Inner core
>Density: 12.6-13.0g/cm^3. >Solid. >Iron and nickel >5400 degrees. >6370km
What do earthquake waves tell us?
> Earthquake waves tell us about the physical state of the Earth.
They speed up, change direction or stop when they meet a new layer in the Earth.
Some waves travel easily through the crust, mantle and inner core, but not through the outer core. This suggests that the outer core has a different physical state and may be liquid.
Clues from space
> Evidence for Earth’s composition can come from meteorites.
Most come from the asteroid belt between Mars and Jupiter.
Metorites come in several types:
-stony meteorites,with a similar composition to basalt.
-stony-iron meteorites, containing a lot of the mineral olivine.
-iron meteorites, which are solid lumps of iron and nickel.
These meteorites may be fragments of the lithosphere, mantle and core of a shattered planet.
Iron meteorites may show that the Earth’s core is made up of iron and nickel.
Meteorite - definition
> Fragments of rock and metal that fall to Earth from space.
Convection currents
> Convection currents contribute to plate movement:
- The core heats the molten rock in the mantle to create a convection current.
- Heated rock from the mantle rises to the Earth’s surface.
- At the surface the convection current moves the tectonic plates in the crust.
- Molten rock cools and flows back to the core to be reheated.
Where does the earth get its heat from?
- Primordial heat: created during the great bombardment, meteorites hit the Earth and this kinetic energy was transferred to heat. Which is still keeping the planet warm today.
- Radioactive Decay: the process by which an unstable atom loses energy by emitting particles of radiation and heats the planet.
Magnetic field
> The Earth is surrounded by a huge, invisible magnetic field called the magnetosphere.
This is a force field which you can sometimes see, better known as the northern lights or aurora boreails.
These form when radiation from space hits the magnetosphere and lights up the sky.
The magnetosphere protects the Earth from harmful radiation from the space and sun.
The Earth’s magnetic field is made by the outer core. As liquid iron in the outer core flows, it works like an electrical dynamo. This produces the magnetic field.
Hot rocks
> Inside the Earth is hot. We know this because of:
-molten lava spewing from active volcanoes.
-hot springs and geysers.
Heat from inside the Earth is called geothermal.
The heat is produced by the radioactive decay of elements such as uranium and thorium in the core and mantle.
This raises the core’s temp to over 5000 degrees.
Geothermal- definition
> Heat from inside the Earth.
Radioactive decay - definition
> Atoms of unstable elements release particles from their nuclei and give off heat.
Plumes - definition
> The parts of convection cells where heat moves towards the surface.
These are concentrated zones of heat.
Plumes
> In a plume, the mantle is less dense.
Plumes bring the magma to the surface.
If magma breaks through the crust, it erupts as lava in a volcano:
-some plumes rise like long sheets of heat. These form divergent plate boundaries at the surface.
-other plums are like columns of heat. These form hot spots. Hot spots can be in the middle of a tectonic plate, like in Hawaii and Yellowstone in the USA.
Moving plates
> Today, the Earth’s lithosphere is split into 15 large tectonic plates and 20 small ones.
The plates move very slowly on the asthenosphere.
Where 2 plates meet there’s a plate boundary.
There’s 3 types of plate boundary.
Most earthquakes and volcanoes are found on plate boundaries.
The 3 types of plate boundary
- Divergent plate boundaries - formed when 2 plates move apart.
- Convergent plate boundaries - formed when 2 plates collide.
- Conservative plate boundaries - formed when 2 plates slide past each other.
>Also collision zones
Conservative Plate Boundary
> Here the two plates are sliding past each other. When the plates stick it causes tension to build up. When this is released an earthquake occurs.
An example of this is on the San Andreas fault line in Los Angeles.
Here crust is neither created nor destroyed.
Rare, but destructive, because they are shallow.
Destructive earthquakes up to magnitude 8.5 with small tremors alsmost daily.
No volcanoes.
Pacific and North American Plates.
Collision Zone
> Here, 2 plates are moving towards each other.
As both plates are continental neither of them can be subducted.
Therefore the crust is crumpled upwards to form fold mountains.
An example of these would be the Himalayas, where the Indian plate has collided with the Eurasian plate.
Destructive earthquakes up to magnitude 9. Landslides are triggered too.
Volcanoes are very rare.
Earthquakes happen on faults in collision zones, e.g. 2015 earthquake in Nepal.
Divergent Plate Boundary
> Here, two plates are moving apart from each other.
This causes the magma to rise up from the mantle and form new oceanic crust.
This process normally occurs under oceans, and results in the formation of underwater volcanoes.
Some of these become so large they appear above sea level such as Iceland. Iceland on North Atlantic Ridge, Eurasian and North American plates are moving apart.
Small earthquakes up to 5.0-6.0.
Not very explosive or dangerous volcanoes, they occur in fissures, erupt basalt lava at 1200 degrees, which is very hot and runny.
It forms lava flows and shallow sided volcanoes.
Small earthquakes due to friction as plates tear apart.
Convergent plate boundary
> Here the 2 plates are moving towards each other.
However the oceanic crust is being pushed underneath the continental plate as it’s far denser.
This forms a deep sea trench.
Oceanic crust is melted into magma by the mantle.
This then rises along the fault lines to form volcanoes.
Very destructive earthquakes up to 9.5, tsunami can form.
Very explosive, destructive volcanoes, steep sided, cone-shaped, erupt andesite lava at 900-1000 degrees.
Andes Mountains in Peru and Chile.
As plates push together, oceanic plate is subducted. As it sinks, it melts and creates magma called andesite.
Fissure - definition
Cracks in the crust
Active volcano
liable to erupt e.g. Mt Etna
