Paper 1: Hazardous Earth Flashcards
What is the lithosphere?
Upper most layer of the earth. It is cool and brittle. It includes the very top of the mantle and above this the crust.
What is the crust?
The crust forms the earths surface. It is a rock layer forming the upper part of the lithosphere. The lithosphere is split into tectonic plates.
These plates move slowly about 2-5cm each year on a layer called the asthenosphere.
How do we know about the Earths interior?
Direct evidence from the earths surface and indirect evidence such as earthquakes and materials from space.
What are the two types of crust?
Continental crust: this forms on the land, it’s made of mostly granite, which is a low density igneous rock. Lower density than the mantle basalt and therefore floats on the mantle. It is 30-50km thick.
Oceanic crust: formed under oceans. This is much thinner 6-8km thick. It is made up from igneous rock basalt same as mantle and therefore has a high density.
Properties of mantle:
It’s rocky 2900 km thick.
It has two parts the upper and lower mantle.
Upper mantle has the region the lithosphere
Lower mantle reaches outer core
It carries the crust,
Properties of the crust:
Hot rocks broke up the crust making tectonic plates.
Crust ranges between 50-70 km deep
Properties of outer core:
This is liquid and it’s temperature ranges from 4000 - 5700 degrees.
Liquid layer of of iron and nickel
Properties of inner core:
70% the size of the moon Same temperature as the surface of the sun It created the magnetic field Solid 1200 km thick.
How do we know the inside of the earth is hot?
Molten lava spewing from volcanoes
Hot springs and geysers
Why is the inside of the earth hot and what creates it?
Heat from the earth is called geothermal. The heat is produced by radioactive decay of elements such as uranium and thorium in the core and mantle. 50% the earths heat comes from radioactive decay. Radioactive decay is formed from unstable isotopes and release heat. The crust forms insolation as the earth is cooling.
How does the inner core stay solid and why?
The inner core is so deep and under huge pressure so it stays solid. The outer core is less hot and under less pressure so it liquid.
What are convection currents and how are they formed?
Heat rises from the core it creates convection currents in the liquid outer core and mantle.
These mantle conviction currents are strong enough to move the tectonic plates on the earths surface.
What are plumes?
These are a part of the convection cells where heat moves towards the surface - called plumes.
These are concentrated zones of heat. In a plume the mantle is less dense. Plumes bring magma to the surface of magma breaks through the crust it erupts as magma through volcanoes.
What is the magnetic field and what creates it?
The earth is surrounded by a huge magnetic field called the magnetosphere. This is a force field you can sometimes see known as the northern lights/Aurora.
These form when radiation from space hits the magnetosphere and lights up the sky. It also protects the earths from harmful radiation from the sun and space.
How do scientists know that Pangea once existed?
They know that the continents were joined to form Pangea once. This was because identical fossils in west Africa and eastern South America which means they were once joined.
How many tectonic plates are there?
Today’s the earths lithosphere is split into 15 large tectonic plates and 20 small ones. They move slowly on the asthenosphere
What are the three types of plate boundaries?
Divergent -formed when two plates move apart
Convergent- formed when two plates collide
Conservative- formed when two plates slide past each other.
How old is oceanic and continental crust?
Most continental crust if 3-4 billion years old. The oldest oceanic crust is 180 million years old.
Why is oceanic crust younger than continental crust?
New oceanic crust constantly forms at divergent plate boundaries. Convection currents bring magma up from the mantle and the magma is injected between the plate separating them.
As magma cools it forms a new oceanic crust plates continue to move apart allowing more magma to be injected. Old oceanic crust is destroyed by subduction at convergent plate boundaries. Continental crust is less dense so can’t be subducted and destroyed.
What is the volcanic explosively index (VEI)?
Measures the destructive power on a scale of 1-8. (Modern humans have never experienced an 8)
What are primary and secondary effects?
Primary: caused instantly by eruption. Direct link to volcano such as acid rain, lava etc.
Secondary: in hours, days or weeks after eruption caused by volcano. Causes problems such as disease, food and water shortages.
Why do volcanoes effect developing countries more than developed countries?
- often built in risky areas because there’s no where else affordable to live.
- can’t afford safe, well built houses so building often collapsed
- they don’t have insurance
- their governments don’t have money and resources to provide aid
- communications are poor so warnings and evacuation may not happen.
What is an earthquake?
This is a sudden release of energy. Underground tectonic plates try to push each other along fractures building up tension which is suddenly released sending out pulses of energy.
What are tsunamis?
Earthquakes under the sea can be generated by tsunamis. Tsunamis are waves that travel up to 900km/h and wavelengths over 200km.
What happens when a tsunami hits?
It causes a very powerful flood, pushing several km inland destroying homes, bridges and infrastructure. Warning systems in the ocean can detect tsunamis and set of sirens and alarms but this is only useful if the epicentre is some distance from the coast.
What is the asthenosphere?
It is part of the earths mantle. It is a hot semi molten layer that lies beneath the tectonic plates. It is the top layer of the mantle.
This acts as a lubricating layer under the lithosphere to help move the tectonic plates.
What is the mantle?
The middle layer of the earth. It lies beneath the crust and the core and is about 2900km thick. It’s an outer layer is the asthenosphere. Below the asthenosphere is mainly rock.
Explain one difference between the lithosphere and the asthenosphere?
The lithosphere is the upmost layer of the earth which is split into tectonic plates, while the asthenosphere underneath it is composed of the uppermost part of the mantle. As we move from the lithosphere to the asthenosphere the temperature increase. This increase in temperature as well as extreme pressure causes the rocks to become plastic. In time these semi-molten rocks will flow. This is caused by convection currents.
Explain one difference between oceanic and continental crust.
One difference between oceanic and continental crust is that continental crust is made u of thick granite which is impermeable so therefore it has a low density and can float on the mantle as the mantle is made up of basalt which is a denser rock.
In contrast to this the oceanic crust is made up of basalt and is more dense. However this is still slightly less dense than basalt so also floats on the mantle. The oceanic crust is much thinner than the continental crust.
How do meteorites help geologists to work out what our inner earth is made up of?
Meteorites are fragments of earth and metal that fall to earth from space. Most come from the asteroid belt between Mars and Jupiter.
These meteorites can be fragments of the lithosphere, mantle and core of a shattered planet. So for example iron meteorites may show that the earths core is made up of iron and nickel.
What types of meteorites are there?
- 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.
How is the heat distributed globally?
In two ways:
- by air movements caused by pressure differences
- ocean currents
Why is wind important in order to keep temperatures at a safe level?
The angle of the suns rays makes solar energy very intense at the equator but disperse over wider areas at the poles. Wind plays an important part in making the Earth habitable by redistributing heat. Without wind the equator would be unbearably hot while the poles would be even colder.
How do areas of low pressure and high pressure form over land masses and the sea in the summer?
When the sun heats the land it also heats the air above it. So the air expands, becomes lighter and rises. This forms low pressure over areas of over landmasses in the summer.
In summer air over the sea remains cooler and denser over the sea as the sun takes longer to heat up the sea. This forms areas of high pressure.
How do land and sea heat up differently?
On land, dark surfaces (e.g soil and forest) absorb sunlight, which is converted to heat. Land heats up quickly in the summer but only at the surface so cools quickly in the winter.
The sea behaves differently. Some sunlight is reflected from the surface while some is absorbed to 30m deep. It therefore takes longer to heat so so longer to cool.
How is wind formed and how does it move?
Differences in air pressure cause air to move - from high to low pressure, creating wind. It moves in a circular way because of the Earths rotation.
What is the Gulf Stream?
This is a warm ocean current that can causes temperature differences in areas.
Where does the Gulf Stream begin and end?
It is driven by westerly winds and begins in the Gulf of Mexico, blowing northwest where a branch of it heads towards Europe to become the North Atlantic drift. The Atlantic drift keeps January sea temperatures at a warm 11°c. Around Greenland and Northern Canada the current cools turns south and forms the cold ‘Labrador Current’, which chills Newfoundland.
How is the Gulf Stream convection current formed?
- in the North Atlantic Cold, salty water is heavy so sinks.
- this sets up a convention current which drags surface water down.
- the current draws warm salty water over the ocean surface from areas near the equator such as The Gulf of Mexico.
- This cools and sinks in the Labrador and Greenland seas and flows south towards the equator where it is warmed again.
What is the global circulation model?
A theory that explains how the atmosphere operates in a series of 3 cells on each side of the equator.
What is meant by atmospheric circulation?
The movement of air around the Earth to try and balance the temperature.
What is the ITCZ?
Inter-Tropical Convergence Zone. This is an area of low pressure which brings rain. It stretches around the Earth, moving North in June when the sun is over head the Tropic of Cancer. By December the over head sun moves south towards the tropical of Capricorn taking the ITCZ with it.
In Mali why does rain normally arrive in May and why does Mali have a short rainy season?
Malis rainy season is in May because this is when ITCZ is over Mali. But by December the overhead sun moves south towards the Tropic of Capricorn taking the ITCZ with it so:
- Mali has a short rain season
- it rains in Kano (Nigeria, near Mali) a few weeks earliest and lasts longer.
- in Lagos, Nigeria the rain stays longer still and rains every month.
How does the ITCZ form?
The ITCZ forms within tropics, when two masses of air meet - or converge. It is parts of a movement of the atmosphere known as the global circulation model.
What causes the convection cells in the global circulation model?
The cells are cured by heating and cooling, and between them create the worlds high and low pressure systems.
What are the three global circulation cells?
Polar cell
Ferrel cell
Hadley cell
The Hadley cells is the biggest.
What is a high pressure?
When the Earths atmosphere is pushing really hard in the Earths surface, meaning air cannot rise. This results in very little or no precipitation in areas of high pressure.
What is low pressure?
When there is very little pressure pushing down on earths surface. This results in lots of rain.
Suggest two ways that Global circulation patterns affect rainfall distribution in West Africa (4 marks):
One way Global circulation patterns can affect rainfall distribution is that in the summer the air heats up, expands becomes lighter so rises. This forms areas of low pressure so much rain will occur here.
Another way global circulation patterns affect rainfall over West Africa is that winds blow from high to low pressure, towards West Africa and Southern Sahara. These are known as trade winds and carry moisture inland. These winds and the moisture they contain, cause a lot of rain over West Africa.
What causes Mali’s rainy season in the Northern hemisphere in the summer?
The Hadley cell.
What causes trade winds?
The Earth spinning (the Coriolis effect) creates three types of wind:
Westerly trade winds
North east trade winds
South east trade winds
After bringing rain to Mali in June the Hadley cell moves south due to the chains position of the sun. By January the latter has reversed how has this happened and what are the effects of this?
- the northern hemisphere winter creates a cool, dense high pressure area over North Africa.
- the sun is now overhead at the Tropic of Capricorn, warming the Southern Hemisphere, and forming a new low pressure area.
- Trade Winds blow from high to low pressure, drawing dry air from the Sahara across Mali and causing its dry season.
- these trade winds meet others from the Southern Hemisphere to create the ITCZ, which has shifted southwards. It brings rain to Southern Africa.
- to complete the Hadley cell, rising air from the ITCZ cools high in the atmosphere and becomes denser. Fed by air below, it spreads out until it subsides as high pressure air.
- the Hadley cells is just one part of the global atmosphere. There are two Hadley cells. The ITCZ forms when trade winds from each one meet.
Where can the Hadley, Ferrell and Polar cell be located?
Hadley: 0°-30° N and S
Ferrel: 30°-60° N and S
Polar: 60°-90°N and S
Which cell brings a front of rain to the UK?
The winds that drive the Gulf Stream from part of the Hadley cell collect moisture over the oceans and meet cold dense air from the polar cell between 50°-60°N and S. This creates front brining high rainfall which causes much of the UK’s rainfall.
What is one impact of how the global circulation model affects climate around the world?
One impact is that it leaves some tropical areas with little rain.
Why are deserts dry either little rain all year round?
E.g:
-in June the rains brought by the ITCZ never reach the Sahara, so it remains dry. In January, a high pressure area brings cooler, clear, dry air which means that the Sahara is dry too.
This is the same for tropical deserts north of the equator e.g Arabian and the same process occurs south of the equator, such as in the Great Sandy Desert in Australia.
This is how all the words tropical deserts originate.
How is the polar desert of Antarctica and the Arctic formed?
The cooler Ferrel cell (which contains less moisture because it’s cooler) takes mild sun tropical winds as far as 50°-60°N and S, where they meet colder winds from the Polar Cell forms a front which brings a front of rain, which when cold enough turns to snow. The dry dense air at the poles creates the polar desert of Antarctica and the Arctic sheet.
What causes low air pressure?
Rising air leads to low pressure at the Earths surface.
- as air rises and cools it forms clouds of precipitation.
- with low pressure, wind circulated rapidly inwards and upwards.
- storms are deep areas of low pressure that bring string winds and heavy rain.
What causes high pressure and where is air pressure the highest?
Sinking air leads to high pressure at the Earths surface. Pressure is highest at sea level.
Why is pressure important?
Pressure determines our weather.
How is wind created?
Air naturally wants to flow from high to pressure. Combined with the rotation of the Earth, areas of different pressure create our flow of wind.
When air rises (in areas of low pressure) air immediately rushes to take its place in the Earths surface (this air is from areas of high pressure) and the movement of this creates wind.
What type of weather is caused by high pressure?
With high pressure, descending air suppresses weather development. This leads to calm sunny conditions or often fog.
What is a climatologist?
A scientist who is an expert in climate and climate change.
What is the stratosphere?
A layer of air 10-50km above the Earths surface. It is above the cloudy layer we live in, the troposphere.
What do volcanic eruptions produce?
- ash
- sulphur dioxide
What are some of the causes of natural climate change?
- volcanoes (the eruption theory)
- asteroid collisions
- solar activity (the sunspot theory)
How can large volcanic eruptions cause temporary climate change?
If ash and gas rise high enough from a large eruption, they will be spread around the Earth in the stratosphere by high-level winds. The blanket of ash and gas will stop some sunlight reaching the Earths surface. Instead the sunlight is reflected of the ash and gas back into space. This cools the planet and lowers the average temperature.
When did Mount Pinatubo in the Philippines erupt and what were the affects of the eruption?
- erupted in 1991
- released 17 million tonnes of sulphur dioxide. This was enough to reduce global sunlight by 10%, cooling the o,a net by 0.5°c for a year.
- this caused colder temperatures, which affected crops as they died meaning a poor harvest.
When did the eruption of Tambora in Indonesia take place and what affects did it cause?
- the eruption occurred in 1815.
- it is the biggest eruption in human history
- in 1816 temperatures around the Earth were so cold that it was called ‘year without summer’
- up to 200,000 people dies in Europe as Harvests failed.
- the effect lasted 4-5 years. In general volcanoes only affect the climate for a few years.
What is the asteroid collision theory?
Asteroid collisions can alter Earths climate by they need to be big.
1km sized asteroid strike the Earth every 500,000 years. An impact if this size would blast millions of tonnes of ash and dust into the atmosphere. This would cool the climate at the dust and ash blocking incoming sunlight. It would be similar in impact to a large volcanic eruption and its affects could last 5-10 years.
Give an example of an asteroid collision that altered Earths climate:
- in 1908 an asteroid with a diameter of 100m exploded in the air 5km above Tunguska, Russia.
- the blast flattened 80 million trees, but was not large enough to alter the climate.
What is a sunspot and what is the sunspot theory?
These are black areas on the suns surface. Sometime the sun has many spots, at other times they disappear. They tell us that the sun is more active than usual. Lots of spots mean more solar energy being fired out from the sun towards Earth.
Give two examples of how sunspots have affected our atmosphere in the past:
cooler periods such as the ‘Little Ice Age’ and warmer periods such as the ‘Medieval Warm Period’, Amy have been caused by sunspot activity.
However, some people thick there were more volcanic eruptions during the ‘Little Ice Age’ which caused cooler temperatures.
But climate change in timescales of a few hundred years cannot be explained by volcanic eruptions- but it could be explained by the sunspot theory.
