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keep it simple sciencePhotocopy Master Sheets
Years 7-8
The EarthDisk filename = “10.Earth”
Usage & copying is permitted according to theSite Licence Conditions
Year 11-12 Science CoursesBiologyPreliminary CoreLocal EcosystemPatterns in NatureLife on EarthEvolution Aust. BiotaHSC CoreMaintain. a BalanceBlueprint of LifeSearch for Better HealthOptionsCommunicationGenetics:Code Broken?
ChemistryPreliminary CoreChemical EarthMetalsWaterEnergyHSC CoreProduction of MaterialsAcidic EnvironmentChem.Monit.&MngmentOptionsShipwrecks, Corrosion...Industrial Chemistry
Earth & Envir.Science
Preliminary CorePlanet Earth...Local EnvironmentWater IssuesDynamic EarthHSC CoreTectonic ImpactsEnvirons thru TimeCaring for the CountryOptionIntroduced Species
PhysicsPreliminary CoreWorld CommunicatesElectrical Energy...Moving AboutCosmic EngineHSC CoreSpaceMotors & GeneratorsIdeas to ImplementationOptionsQuanta to QuarksAstrophysics
Year 7-8 General ScienceDisk Filename Topic Name01.Energy Energy02.Forces Forces03.Matter Solids, Liquids & Gases04.Mixtures Separating Mixtures05.Elements Elements & Compounds06.Cells Living Cells07.Life Living Things08.LifeSystems Plant & Animal Systems09.Astronomy Astronomy10.Earth The Earth11.Ecosystems Ecosystems
Year 9-10 General ScienceDisk Filename Topic Name12.Waves Wave Energy (inc. Light)13.Motion Forces & Motion14.Electricity Electricity15.Atoms Atoms & Elements16.Reactions Compounds & Reactions17.DNA Cell Division & DNA18.Evolution Evolution of Life19.Health Health & Reproduction20.Universe The Universe21.EarthScience Earth Science22.Resources Resources & Technology
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“Mind-Map” Outline of TopicThis topic is an introduction to Earth Science.
Earth Science includes studies of rocks and minerals, earthquakes and volcanoes, theweather and the oceans. Earth Science looks at the structure of the Earth itself, and how
landforms, and even oceans and continents, come and go over time.
Weathering&
Erosion
Soils&
Landscapes
The WaterCycleMinerals
The 4 “spheres”of the Earth
AirPressure
Igneous,Sedimentary,Metamorphic
Rocks
InternalStructure
Gases of theAtmosphere
GlobalWarming
&Ozone
Atmosphere, Hydrosphere &
Weather
THEEARTH
Structure ofthe Earth
TheLithosphere
TheAtmosphere
TheHydrosphere
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The Structure of the EarthYou already know that the Earth is a planet which orbits our star, the Sun.
The Earth is a ball of rock, largely covered by water, and surrounded by a layer of air.Now it is time to learn some more detail.
Inside the Solid EarthIgnoring the oceans and the air for a while, we begin with the solid Earth.
Scientists have always been interestedin earthquakes. By learning aboutearthquakes it was hoped that we mightlearn to predict them, and so avoid someof the deaths and destruction that theycause.
About 100 years ago, the study of earthquakes (called “Seismology”) became advancedenough that scientists began studyingthe way that earthquake shockwavestravel through the Earth.
From this, it became clear that the solidEarth is not totally solid, and has a layerstructure, as shown.
The LithosphereBut wait, the story gets more complicated!
Attached to the bottom of the crust is alayer of mantle rock which has “welded”itself to the crust rocks above.
This 2-part layer is called thelithosphere.
The thickness of thelithosphere varies.Under the oceans, itcan be about 5 kmthick and is mostly crust rocks withvery little mantle rock attached. Underthe continents the lithosphere is over100km thick.
Compared to the 6,400 km diameter ofthe Earth the lithosphere layer is anextremely thin shell on the outside.
Below the lithosphere is a “slipperylayer” of the mantle.
We now know that thelithosphere “floats” on the
main body of themantle, and is
broken up into largechunks of
lithosphere, calledtectonic plates.
The plates slowly move around, slidingacross the “slippery layer” of mantle rock.
In later topics you will learn about thetectonic plates and how they slowly movearound and change the continents, oceansand mountain ranges of the Earth.
The layer of gases around the Earth iscalled the a)....................................... Allour b)............................ occurs here.
We rely on the air for c)........................ tobreathe, and to shield us fromdangerous d).............................. from theSun.
The watery parts of the Earth are calledthe e)................................. This includesthe oceans, and also all the f)..................and ........................ and undergroundwater. It also includes the ice in glaciersand the polar g)...................................
The Lithosphere is a 2-part layercomprising the h).............................. andthe upper part of the i)..............................
The lithosphere “floats” on the rockunderneath. It is broken up into anumber of pieces called “j).......................plates” which can move around.
The parts of the Earth where livingthings are found is called thek)........................................ This overlapsthe other 3 “spheres”, because livingthings are found in all three.
The Atmosphere (“atmos” = vapour)The atmosphere is mainly a mixture of gases.
The clouds are made up of microscopic droplets of liquid water, and there may be some solid particles of dust in the air,
but nearly all of the atmosphere is gas.
Gases of the AtmosphereAbout 99% of dry air is made of just 2 gases:
Nitrogen (N2) Nitrogen makes up almost 4/5 of the air.We breathe it in all the time, but it doesus neither good nor harm.
Oxygen (O2)Oxygen makes up about 1/5 of the air. It is very important for living things.
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The other 1% contains a variety of gases, including:
Argon (Ar) Argon is the most common of the “inert gases”.There is also Neon (Ne), Krypton (Kr) & others.
Carbon Dioxide (CO2)CO2 makes up only about 0.04% of air,but it is vitally important to living thingsand to the Earth’s climate.
Oxygen & Carbon DioxideThese gases are so important that you need to know more about them.
OxygenOxygen makes up about 1/5 of the air.We breathe so that we can take inoxygen. Without it, a human will diewithin a few minutes.
Oxygen is a chemical element. Itschemical symbol is “O”, but it normallyexists as 2 atoms joined together, so wewrite its chemical formula as O2.
Oxygen is needed for things to burn.
Try this experiment:
Place glass jar or beakerover a lit candle.
Soon, the candle goes out.Why?Because all the oxygen in the air insidethe beaker has been used up. Withoutoxygen, the burning cannot continue.
Cellular respiration is (chemically) thesame as burning the glucose. It must
have oxygen to continue.
Carbon DioxideCarbon dioxide makes up only a tinyfraction of the air, about 0.04%. Itschemical formula is CO2, which means itis made of molecules containing 1carbon atom and 2 oxygen atoms.
CO2 can be identified by its reactionwith limewater.
Try this:Use a drinking straw togently blow bubbles througha test tube of limewater.
Soon, the limewater becomes cloudy as it reacts with the CO2 in your breath.
CO2 is the only gas which reacts withlimewater this way, so this test can beused to identify this important gas.
Air We Breathe In Air We Breathe OutOxygen 20 % 16 % Carbon Dioxide 0.04 % 4 %
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The Carbon Dioxide - Oxygen CycleYou are reminded of the processes of Photosynthesis and
Cellular Respiration in living things. Together, they connect a great cycle of nature.
Carbon Dioxide & Global Warming
Food(Glucose)
&Oxygen
CarbonDioxide
&Water
Photosynthesistraps light energy.
Cellular respiration releases energyfrom food to power all life processes.
cellularrespirationin plants
Sun What is really happening is that theenergy of the Sun is powering
all living things.
The O2 and CO2 simply get re-cycled.
Food (containing glucose) is made,destroyed and re-made over and over.
Photosynthesis makes all the food and oxygen on Earth.
The reason that CO2 levels are lowcompared to oxygen, is that the plantsare very efficient at absorbing CO2 for
photosynthesis.
Burning fossil fuels (coal, petroleum)produces huge amounts of CO2.
Measurements show that the level of CO2 inthe air has increased significantly over thepast 100 years or so.
Check your family’s latest electricity bill: it will tell you how many tonnes of CO22 have
been released to make your electricity.
As well as CO2,another “greenhousegas” called methane(CH4) is alsoincreasing in the air.
Methane is releasedwhen forests arecleared and wetlandsare drained forgrazing. Althoughonly tiny amounts ofmethane are in the air, its effect is very powerful.
The Earth absorbs the heat from the Sun,and the surface warms up. As the surfacewarms, some of the heat radiates back intospace, so the Earths cools again.
CO2 and methane “trap” some of the heatwhich would normally escape into space.This “Greenhouse Effect” is now believed tobe causing the whole world to warm up.
This “Global Warming” is causing climate
change so that weather patterns
may be disrupted and many natural
environments may bedestroyed in the
next century.
The sea ice around thenorth pole is beginningto melt. If the ice capsmelted completely, the
sea level could rise by more than 100m.
Global Warming
CO2
CH4
CO2
Heat
from
Sun
Some heat escapesback into space
Heattrapped
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OzoneOzone is a different form of oxygen, with chemical formula O3.
Normal Oxygen Ozone
O22 O33
Importance of OzoneOzone is much more chemically reactive thanoxygen, and is very dangerous if breathed in.At ground level, ozone is a nasty, dangerousair pollutant.
However, in the upper atmosphere it serves avital function for land-living plants andanimals... it absorbs dangerous ultra-violet(UV) radiation from the Sun.
UV radiation damages living cells and cancause deadly skin cancers. Plants cannotgrow properly if exposed to excessive UV.
Without the “ozone layer”, UV radiation wouldmake life on land virtually impossible.
So What’s the Problem?In the second half of the 20th century,our industries produced a number ofchemical gases called “CFC’s”. Theseare very useful substances used inrefrigerators, some fire extinguishers,aerosol cans, plastics manufacture, andmuch more.
By the 1970’s scientists began tomeasure higher levels of UV radiationreaching the Earth’s surface becausethe ozone levels were getting less.
Research revealed that the ozone wasbeing destroyed by CFC’s released intothe air. CFC chemicals cause ozone tobe destroyed faster than it is made.
CFC’s are very long-lasting and cancontinue destroying ozone for 30-50years.
Problem Solved?Scientists quickly searched foralternative chemicals to replace CFC’swhich would not harm the ozone layer.
By 1995 most countries in the world hadstopped using CFC’s.
The CFC released 30 years ago is stillcausing a loss of ozone, but the rate ofloss is slowing down.
Scientists believe that ozone levels willstart to increase again and eventuallyget back to normal.
Impacts of ScienceThe Science and Technology of electricity has been one of the most important
things to have happened to human society in the past 100 years or so.The impacts of this on society have been almost entirely beneficial,
while the impacts on the environment have been entirely detrimental.
Science and Economics
Benefits to SocietyLarge scale use of electricity has givenhumans many benefits and has becomeessential to our economy, jobs,communications, leisure and lifestyle.
Our factories rely on electricity to makeall our machines, clothing,appliances, medicines, etc.
Our business & financesystems run on computers andcommunications powered byelectricity.
We enjoy a comfortable, safe andentertaining lifestyle with electricallights, TV, air-con, appliances, phonesand all the convenient gadgets.
Starting in the 1970’s, some scientistsbegan to warn us about some seriousproblems that were emerging.
Two of the most important problemsconcerned changes to the atmosphere.
Ozone Problem Solved?This problem was described previously.
After alerting the world to the problem,scientists were able to suggest solutions,in the form of alternative chemicals toreplace the destructive CFC’s.
The suggested replacement chemicalswere also economically suitable,because they caused little change tocosts, jobs and production methods.
Since there was no conflict between thescientific advice and the economy,governments quickly followed theadvice and passed appropriate laws.Industry rapidly complied.
Greenhouse Problem Continues?Scientists have also warned us aboutrising CO2 levels and the dangers ofGlobal Warming. They have alsosuggested many solutions, such asswitching to alternative energy supplieslike solar and wind power.
Unfortunately, the solutions do not fiteasily into our global economy. Toimmediately follow the scientific advicewould cause massive changes toindustries, jobs, finances andeverybody’s lifestyle.
That’s why governments hestitate totake decisive action. The scientificadvice is in conflict with the economy.
People Make DecisionsIt is NOT up to scientists to make the decisionsneeded. It is up to every citizen to vote forleaders who will act to solve problems. Goodcitizens need to know about both the Scienceand the economic necessities. In a democracy,people get the government they deserve.
Damage to the EnvironmentLarge amounts of our electricity isgenerated from the burning of fossilfuels, such as coal. In the early days,this created a lot of pollution andproblems such as “acid-rain”.
Many problems havebeen cleaned-up, but
one HUGE problemremains... burning coal
releases CO2 gas intothe atmosphere.
The levels of CO2 haverisen significantly and there is no longerany doubt about the effect: GlobalWarming due to a “Greenhouse Effect”.
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Air PressureRemember that in agas the particlesare constantlyflying everywhereat high speed.
They frequently collide with each other,and with the walls of their container.Each collision pushes on the inside ofthe container, or on each other. Thismeans there is a constant push, orforce, acting within the gas.
Pressure is measured as the amount offorce pushing per unit of area.
The unit ofpressure usedmost often inscience is thekilopascal (kPa)
1 kPa = 1,000 N force per square metre.
Some examples of pressure valuesNormal air pressure (sea level) ≅≅ 100 kPa
Inflated car tyre ≅≅ 200 kPaInside a scuba airtank ≅≅ 800kPa
The “pascal” unit is namedin honour of the greatFrench scientist and
mathematician Blaise Pascal (1623-662).
Air Pressure and Your BodyNormal air pressure at sea level is about 100 kPa. Over the area of your wholebody this is like having a100kg mass pressing onyou.
How come you don’t feel squashed?
Simply because your body has the same amount ofpressure inside, pushingoutwards.
Air pressure decreases with altitude. If you goup in an aircraft, or drive up a high mountain,the outside air pressure gets less. You will feelthe pressure difference in your ears, until itequalizes again.
Astronauts in space or on the Moon,where there is no air, need pressuresuits to breathe, and also to protectthem from the zero pressure aroundthem. Their own “body pressure”pushing outwards would cause fataldamage without the suit.
Atmosphere v. SpaceThe pressure of the atmosphere is dueto the weight of all the air abovepressing down.
As you go higher up, there is lessand less air above you, so the airgets “thinner” and the pressuregets less.
So how high up can you go beforethere is no air, and you are in outerspace?There is no simple answer to that!
The air gets thinner and thinner, butthere are a few atoms and molecules ofgas even as far up as 500km.
However, even just 3-4km up you mayhave some difficulty breathing.
By 20km up you’d need apressure suit (like an
astronaut’s space suit) tobreathe and survive the
low pressure.
By 50km up there isvirtually no air pressure,
and by 100km you can saythat you are in space.
Technically, there are still a few gasmolecules, but the pressure is effectivelyzero. You are in the vacuum of space.
Almost 4/5 of the air is made up of thegas a)...................................... Most of theremainder is b)............................ gas,which we breathe in, to use for cellularc)...................................
The last 1% of the air is a mixture ofmany gases including d)...........................(the most abundant of the minor gases)
Although it makes up only 0.04% of air,the gas e)............................................... isvery important to living things. It isabsorbed by plants for f)..........................by which they make food. This processreleases g).......................... gas, so thesegases are recycled over and over.
Carbon dioxide is important for worldclimate. It traps some of the h)................which would normally radiate intospace. This is called the“i).................................... Effect”.
Humans have increased the amount ofCO2 in the air, mainly by the burning ofj)....................... fuels such as k)..............and ..................................... As CO2 levelsrise, the world is warming up. This iscalled “l)....................... Warming”.
Ozone is a form of m)........................ gas.It forms in the high atmosphere, where itabsorbs dangerous n)...............................rays from the Sun. For many yearshumans were using chemicals calledo).................... (abbreviation) whichdestroy ozone.
Gases push in all directions. This force(per unit of area) is called p).....................Air pressure q)........................... as yougo upwards in the atmosphere. Aboveabout 3-4km you may have difficultyr)................................. By about 20km up,you’ll need a s)...................... suit, and byabout 100km up you are in t)....................
The data table shows the air pressure atincreasing heights above the Earth’ssurface.
Graph the data on the grid as a series of points, then join them with an even curve.
Questions1. What does “kPa” stand for?........................................................................2. Some people have breathing difficulties if air pressure drops belowabout 70 kPa. About what altitude will this happen? .........................
3. What is the air pressure on Mt Everest, almost 9km high? ......................
This diagram represents one of thecycles of nature, with the treerepresenting all plants and the elephantrepresenting all animals.
1. Fill in the names of the processes,and the substances, in the spacesaround the diagram.
2. Which of the gases in the diagram isinvolved in “Global Warming”?
........................................................3. Another human-caused factor in“Global Warming” is that forests arebeing cleared in many places, to create
more farming & grazing land.
Suggest how this mightcontribute to Global Warming.
Atmosphere, Hydrosphere & WeatherThe day-to-day weather, and the long-term climate, are controlled by
both atmosphere and hydrosphere.
Air Pressure and WeatherMost of our winds, storms and weatherpatterns are due to air pressure effects in theatmosphere.
In some places, a huge “bubble” of the air(maybe 1,000 km across) can warm up. This“bubble” expands so that the air particlesbecome further apart and the air pressurebecomes lower than the surrounding air.This is a “low pressure cell”.
Meanwhile, in another place the air is coolingand contracting. The air particles are forcedcloser together, so the pressure rises... a“high pressure cell”.
Both pressure systems begin to rotatebecause of the spin of the Earth, so circularwinds blow around each “cell”.
Low pressure cells often bring stormsand rain (and cyclones) while “highs”tend to bring fine, dry weather. Bothcreate the winds that blow around them,and from one to the other.
L
L
H
H
Reading the Weather MapThe curved lines are “isobars”. They connect places with the sameair pressure, and surround High andLow pressure areas with circularpatterns.Winds blow clockwise around lows,and anti-cclockwise around highs.
When isobars are tightlytogether, winds arestronger.
When far apart,conditions are calm.
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wweeaatthheerr
TThhiiss ssyymmbbooll mmeeaannss aa ““ccoolldd ffrroonntt””.. AA mmaassss ooff ccoollddaaiirr iiss mmoovviinngg aaccrroossss TTaassmmaanniiaa..
Oceans and ClimateOcean currents can have a huge impact onclimate.
On opposite sides of the North Atlantic Oceanthe climates are very different. In north-eastCanada the climate is so cold that agricultureis very limited. At the same latitude in Europeit is cold in winter, but summer is mild andmany crops are grown.
The difference is the warm ocean currentwhich warms the climate of Europe. Frigidcold currents chill coastal Canada.
In the Pacific Ocean, warm currents nearSouth America cause wind patterns whichbring prolonged droughts to Australia. This iscalled “El Nino”. In most years there are coldcurrents instead, and these bring rain andcyclones to the Australian coast.
Most of the water in the “Hydrosphere”is in the a)................................ Some of itis frozen in the ice caps and inb)................................. The remainder isin lakes and rivers or it is c)......................................
The “water cycle” is powered by theheat of the d)....................... This causeswater e).................................., or turnfrom f)....................... to ........................
Water also enters the atmosphere byg)......................................., which isevaporation from plants. This moves alot of water from soil to the air.
As the water vapour rises, it cools andh)............................. back to liquid. Thetiny droplets remain suspended in theair, forming i)..............................
If the droplets grow large enough theywill fall down as j)......................, or (iffrozen) they will fall as k).......................or ........................... All these things arecollectively called “l)..............................”
The cycle is completed when the waterdrains back to the m)..................... byflowing down n)........................ orseeping underground.
Weather and climate are controlled byboth o)....................................... and....................................................
A lot of day-to-day weather is caused byhigh and low p)............................... cellsin the air. These cells rotate so thatq)......................... blows around them,bringing moist air, clouds, storms, etc.
The oceans have a big influence onr)........................ For example, periods ofdrought in Australia are caused by warmcurrents in the s)........................ ocean.This is called an t)“.........................” event.(Spanish name)
Worksheet 8Air, Water & Weather Student Name.............................................
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Process P
Ocean
Land
Process Q
Process R
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The Lithosphere (“lithos” = rock)The solid, rocky outside layer of the Earth is a very thin “skin”
compared to the size of the Earth itself.To study the lithosphere, the first step is to learn what it is made from.
Rocks are Made from MineralsWhat is a rock?
Most rocks are mixtures of a variety of crystalline chemicals called “minerals”.Each mineral forms crystals of a particular shape, colour and “hardness”.
Quartz (or Silica)The most common mineral on Earth is aglass-like substance called quartz.
(It’s not surprising that it’s “glass-like”... quartz is the main ingredient for making glass!)
Many smallfragments ofquartz is whatwe call sand.
If you hold arock in sun-light and it“sparkles”,that’s probably because it has smallcrystals of quartz in it.
CalciteAnother common mineral is calcite.
Rocks containing calcite can be easilyidentified by placing a drop or two ofacid on them. (A drop of vinegar will do)
If calcite is present, the acid will “fizz”with little bubbles. Acid reactschemicallywith calciteto make CO2gas. That’swhat makesthe bubbles.
Silicate MineralsThe “silicates” are a large family of minerals which are all related to quartz.
(Quartz is also known as “silica”) 95% of rocks contain silicates.Each particular silicate mineral is quartz with various chemical elements embedded
in its crystal structure. This changes its colour, hardness and crystal shape. The elements embedded in silicates are (most commonly)
aluminium, calcium, magnesium, iron and potassium.
Some Silicate Minerals
The rock in limestone caves is mainly calcite.
Olivine
Most silicates occur mixed together in common rocks.When they occur in pure crystals they are “gems”,
and “semi-pprecious stones”
OrthoclaseFeldspar
TalcMica
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The Rocks of the LithosphereRocks can be mixtures of many different minerals combined in any proportions.
This means that thousands of different kinds of rock are possible.However, all rocks can be classified into just 3 groups,
according to how the rock was formed.
Igneous RocksIgneous rocks are formed from molten minerals that have cooled and solidified.
These rocks are associated with volcanic activity.
Some Common Igneous Rocks
Magma & LavaIn many parts of the world, heat and movements in thelithosphere cause the rocks to melt deep below thesurface.
This molten material is called “magma”. Sometimes itcan force its way to the surface and a volcanic eruptionoccurs. The molten rock that erupts at the surface iscalled “lava”.
Granite forms from slow-cooling magma.
You can see the separatemineral crystals, including
a lot of quartz.
This is a rock that floats!Pumice is like the “froth” on
lava from volcanic gasesforming bubbles.
This is basalt from a recent lava flow.You can still see the flow patterns from
when it was liquid. Basalt is dark-coloured with microscopic crystals.
Granite
Surface lava flow
Magma chambermay be many km
underground.
Layers oflava rockand ash
Basalt Pumice
As the magma or lava cools down, the moltenminerals solidify and form solid crystals. Thisforms igneous rocks.
Magma cools slowly, deep underground. Thisallows the mineral crystals to grow larger and beclearly visible in the rock. Lava cools quickly atthe surface, and the crystals are too small to see.
The colours vary, too. Igneous rocks with largeamounts of quartz are pale in colour. If there isless quartz and more silicate minerals, the colouris usually darker.
Sedimentary RocksSedimentsRocks are worn down and carried away bywater, wind and ice. Erosion of rocksproduces gravel and sand and silt, or mud.
Eventually, these eroded fragmentssettle to the bottom of a lake or ocean.These are called sediments.
As more and more sedimentsaccumulate on top, the layers arecompressed by huge forces. Any wateris squeezed out. The grains becomecemented together and the whole massbecomes a hard rock. (Although it’susually not as hard as igneous rock)
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The Rocks of the LithosphereRocks can be mixtures of many different minerals combined in any proportions.
This means that thousands of different kinds of rock are possible.However, all rocks can be classified into just 3 groups,
according to how the rock was formed.
During erosion, the pebbles, mud, sand,etc. are often sorted out and separatedfrom each other. Sediments are oftenmade of particles all the same size.
Common Sedimentary Rocks
FossilsSome sedimentary rocks contain the
remains and traces of ancient living things that were buried
in the sediments.
This fish lived 150 million years ago.Its body was trapped in silt which later
became shale rock.
This entire mountain range is made ofsedimentary rocks which have been uplifted from
the ancient seafloor by earth movements.You can clearly see the sedimentary layers.
A Mountain of LimestoneLimestone is mostly calcite mineral
ShaleThis rock formsfrom layers of silt or mud.
Colours vary, but itis fine-ggrained.You can see the
sedimentary layersin this sample.
SandstoneForms from
sand particlescompressed and
cemented together.This piece has
been cut to make adecorative wall.
ConglomerateYou can see thatthis rock is made
from gravelcemented with a dark mud.
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Metamorphic RocksThese are rocks that are formed when a previous igneous or sedimentary rock is
changed by extreme heat and/or pressure within the lithosphere.
Heat & Pressure Causes Changes
The extreme heat near a chamber ofmolten magma can cause changes tosurrounding sedimentary rocks.
For example, thesand particles insedimentarysandstone canpartly melt so theyall fuse together toform a mass ofglassy quartziterock.
Perhaps the best known metamorphicrock is marble. It is formed fromlimestone, a sedimentary rockcontaining a lot of calcite mineral.
Under great heat and pressure, thecalcite is re-crystallised and the rockbecomes much harder. Beautifulcolours and patterns may develop dueto small amounts of otherminerals in it.
People have been usingmarble for statues anddecorative structures forthousands of years.
Just like the limestone fromwhich it came, marble will“fizz” if a few drops of acid areplaced on it.
The Rocks of the LithosphereRocks can be mixtures of many different minerals combined in any proportions.
This means that thousands of different kinds of rock are possible.However, all rocks can be classified into just 3 groups,
according to how the rock was formed.
Flat slabs ofSlate
formed fromcompressedshale rock
Quartzite
The massive movements of thelithosphere that slowly push thecontinents around and lift up entiremountain ranges generate enormous,relentless forces.
These forces can squeeze rock so muchthat its structure changes. Slate is ahard metamorphic rock formed fromshale that has been pressurised.
It splits into thin slabs that make ituseful for roof and floor tiles.
A decorative use of marble
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MineralsMost rocks are mixtures of variousa)................................, each with its ownb)........................ shape, colour andhardness.
The most common mineral on Earth isc)................................ which is hard andd)...................-like.
Another common mineral is calcite,which is easily identified by placing adrop of e)....................... on a rocksample. If calcite is present, it willf).....................
95% of rocks contain one or more of themany types of g)..............................minerals. These are based on quartz,but have various metals embedded inthe h)............................ structure. Thischanges the colour, crystal shape andi)..............................
Igneous RocksIgneous rocks form from j).......................minerals and are associated withk).................................. activity.
Molten rock deep in the Earth is calledl)................................ If it cools deepunderground, it will cool m).....................and mineral crystals have time to grow.A common rock of this type isn)............................. in which you caneasily see different o)................................
If the molten rock erupts at the surface itis called p).......................... This coolsq)..............................., so the crystals arevery r)............................. A common rockof this type is s)..............................
Sedimentary RocksRocks and soil are worn down andcarried away by water, wind, etc. This iscalled t)........................... Eventually thesand, clay or silt is deposited on a lakeor sea floor as u)................................More and more layers accumulate,v).................................. the layers below,until the sediments become rock. Often,some mineral in the sediments acts likew).............................. and helps hold therock together.
Sometimes the body or traces of livingthings are trapped in the sediments andare preserved as x)...............................
Two common sedimentary rocks areshale, made from y)............................sediments, and z)...................................from sand.
Metamorphic RocksThese are made when an existing rock ischanged by aa).............................. and/or...............................
The heat from nearby ab)..........................activity can change sandstone intoac)........................................
The huge ad)............................... thatoccur when mountain ranges are beingformed can squeeze shale into a newstructure called ae)...............................
Rocks containing a lot of calcite, suchas af).................................... can be re-crystallised by heat and pressure tobecome ag)..................................... Thisbeautiful rock has been used for statuesfor thousands of years.
Weathering of RocksMost rocks are pretty hard, but they’re not indestructable.Rocks are gradually “broken down” into smaller pieces,
and chemically changed into new substances.This breaking-down of rock is called weathering.
There are 2 quite different weathering processes that occur.
Physical WeatheringThis means the physical breaking ofrock into smaller particles, withoutchanging it chemically.
The classic example is when quartzcrystals are broken into small fragmentsto form sand grains. It’s still quartz, butthe grains are smaller.
What causes physical weathering?
One of the main causes is temperaturechange. On a hot day the outside of arock becomes hot and expands slightly.At night it gets cold and contracts.
This cycle of expanding and contractingcracks the surface and small fragmentsfall off. On a cold night in themountains, you can often hear theclatter of small rock fragments tumblingdown the cliffs and gorges.
If it getscoldenoughto freezewaterthisprocessspeedsup. Waterseepsinto cracks in the rock. When it freezes,it expands and cracks the rock furtheruntil pieces break off.
Another major process of physicalweathering is the tumbling of stones ina fast-flowing river, or by the waves nearthe coast. Sand and rocks are tossedand tumbled together so they are firstrounded, and then worn down intosmaller and smaller pieces.
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Chemical WeatheringThis is when the minerals in a rock arechemically changed by reaction withoxygen and natural acid chemicals inthe environment.
The crystal structure of the mineralchanges to a new, softer substance, andthe rock softens and falls apart.
Quartz does not change chemically, (itonly breaks physically into sand grains)but many of the silcate minerals changeinto what we might call “clay”.
Rocks containingthe mineral calciteare especially easyto weather. As youknow, calcite reactschemically withacids. If water withsome dissolved acidseeps throughcalcite rocks, therock slowlydissolves away. Thisis how limestonecaves develop.
So, where do the acids come from?
Carbon dioxide (CO2) gas from the airdissolves in water to form a (very weak)acid solution. Living things in the soilproduce natural acids, and the rotting ofdead vegetation releases natural acids.
ErosionOnce rocks have been weathered, another process becomes possible.Erosion is the movement of rock and soil from one place to another.
The main things which cause erosion are flowing water or ice, and the wind.
Wind ErosionIn deserts and along beaches, the windoften moves loose dust and sand. Sandis often piled up to form “sand dunes”.
These can slowly “migrate” as sand isblown up and over the top, andcascades down the other side.
Erosion by IceThere are no glaciers in Australia, but inmany colder climate areas, they are oneof the most important agents of erosion.
A glacier is nature’s bulldozer. The slow,relentless movement of billions oftonnes of ice gouges out the rock,weathering and eroding in one step.
This chunk of ice has broken off a glacier and hasfloated across a melt-wwater lake. Notice the load ofbroken rock it is carrying. This ice must have beenat the base or side of the glacier and gouged the
rock from the mountains visible in the background.When the ice melts, the rock will be deposited,
then washed away again by flowing water.
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Erosion by WaterMoving water is a major cause oferosion.
As rivers flow, they carry tonnes of finesand and “silt” down to the sea.Eventually these solid particles willsettle to form sediments. They may formsand-bars, or beaches, or simply beburied to become new sedimentaryrocks millions of years later.
In steep mountain creeks, the fastflowing water can transport pebbles andboulders. The tumbling stones help cutthrough the bed-rock and gouge outcanyons and valleys.
The action of waves at the coast is apowerful agent of erosion.
Waves“undercut”the rock atsea level.Then therock abovecollapses,leavingverticalcliffs.
At water level, a flat rock platform shows where thebase of the cliff used to be, before erosion.
These sea cliffs are at “The Gap”,Watsons Bay, Sydney.
Quartz forms sandgrains. Chemicalweathering turnssilicates into clay.
The plants and rottinghumus produce acids
which seep downthrough the subsoil.
This causes thechemical weathering.
“Topsoil” is usuallydarker than subsoilbecause it contains
“humus”.This is rotted plant
material which changesthe texture of the soil,
helps hold moisture andfertilizes plant roots.
The topsoil is theessential, fertile layer.Fine-grained
sand and clay “subsoil”
River FloodplainDeposition Soils
Many soils are formed by erosion anddeposition, rather than weathering of thebedrock. The soil in this photo has beendeposited as alluvial sediments duringfloods.
Floodplains are flat and ideal for farmingand each flood deposits another silt layer,so the soil stays fertile.
Tree rootsgrowing
through rock.
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Landscapes Formed by Erosion & DepositionMany landscapes, both ordinary and spectacular, are the result of the weathering
and erosion of rock, or the deposition of sediments.
Wind ErosionThis rock formation in WesternAustralia is called “Wave Rock”. Ithas been eroded into this shapeby wind-blown sand.
Ice ErosionA glacier once filled this valley
and gouged out all the rock. The U-shape is typical
of erosion by ice. (Mountain valleys eroded by water are V-shaped)
Erosion by RainThe softvolcanicash ofthis partofTurkeywashesaway inrain,exceptwhere it is “capped” by harder, darkerrock. Erosion has produced thesestrange “fairy chimneys”. Local peoplehollow them out to use as homes.
U-sshaped
River Erosion & DepositionOnce they’re down out of the mountains, riversmeander sideways and erode a wider and widervalley. Seasonal flooding deposits sediments toform a flat floodplain.
Flood waters cut new channels creatingislands, and river meanders get cut-off to formbillabongs , or “ox-bow lakes”.
Coastal DepositionThis sand spit and beaches have
formed from sand deposited by tidesrushing in and out of this coastal bay.
PPhhoottoo bbyy PPaatt BBrriiddee
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1. Explain the difference between physicalweathering and chemical weathering bycompleting these sentences.
Physical weathering breaks rock intoa)..............................................., but doesnot change it into b)...................................
Chemical weathering changes rocksand minerals into c)................................................................................
2.a) Describe 2 things which causephysical weathering of rock.
5.Complete the sentences to describe theways that soil can form.
Soil can form from the underlyingbedrock by a)................................. of therock. The rock is b)...........................broken into smaller particles, and alsoc).................................. changed intosubstances such as clay.
Good d)“...........................” alwayscontains a lot of e)“..................................”which is rotted plant material
Some soils are formed by f)......................of eroded silt. On a river g)..............plain,every flood deposits h).............................
6. Give one example of a landscapecreated by:
a) wave erosion at a coastline .........................................
b) deposition of sedimentson a coastline.........................................
c) river erosion andseasonal flooding ..................................
Answer SectionWorksheet 1a) Crust b) Mantlec) Outer Core d) Inner Coree) Seismology: study of earthquake wavesf) Outer coreg) iron & nickel metalsh) It is made up of the crust rocks withsome mantle rock attached.
Worksheet 101.a) smaller piecesb) a new substancec) new chemical substances2.a) temperature change, flowing water tumbling rocksb) acid or oxygen3.a) breaksb) new substancesc) moves or transportsd) new location, different place4.Moving water, wind, ice (glaciers)5.a) weathering b) physicallyc) chemically d) topsoile) humus f) depositiong) flood h) a new layer of silt6.a) sea cliffs b) beach, sand barc) floodplain7.Wind erosionWave erosion
Topic Test1. a) F b) T c) F d) T e) Ff) F g) F h) F i) T j) T
2.a) Magma is molten rock deepunderground, while lava is molten rock atthe surface.b) Evaporation is liquid gas.Condensation is gas liquid.c) Weathering breaks rock down, erosionmoves it to a new location.
3.a) I b) D c) G d) D e) Kf) A g) C h) F i) L j) E