The Restless Earth

The Changing World

Tectonic plates

• The crust is made of about twelve platesplates.• These are like big rafts floating on the semi-molten

mantle.• Convection currents within the mantle cause the

plates to move.• Although they only move about 2 cm/year this can

have huge effects over long periods of time.

Sea floor spreading

When two oceanic plates move apart molten rock rises to the surface.

magma rising

sea floor spreading

oceanic plate

Pangaea

Continental Drift

• On average, the plates only drift about 2cm/year. However 2cm multiplied by a million is a long way!

• Scientists think the continents were originally all together in a super-continent called Pangaea.

• Over millions of years they have drifted to their present positions on the floating tectonic plates.

Millions of years

Continental Drift

Evidence for Continental Drift

The theory is supported by several pieces of evidence. For example, if we consider Africa and South America there is:

– The “jig-saw fit” – The similarities in the rock layers

from Africa and South America.– Similarities in the type and age of

fossils.– Evidence of related species that

definitely did not swim the Atlantic Ocean!

Jig Saw fit

Similar rocks and fossils

• How do convection currents actually work?

• Place potassium permanganate crystals at bottom of beaker of water

• Start to heat water with bunsen

• Diagram in book of what happens

How does it work?

Plate boundaries

• Constructive plate boundary – new ocean floor is created

• Destructive plate boundary – oceanic plates slide under continental plates – subduction

• Conservative plate boundary – plates slide past each other - Earthquakes

What happens when plates meet

Effects at Plate Boundaries

volcanoes result from the rising magma (melted oceanic plate)

volcano

continental plate

oceanic plate

magma rising

When a continental plate and an oceanic plate meet, the effects include:

plates juddering past each other producing earthquakes

the continental plate buckles upwards whilst the oceanic plate subducts (goes underground)

• Find the words and write a sentence about how each one has something to do with plate tectonics.

– Drift– Earthquake– Fossil– Jigsaw– Magma– Pangaea– Plates– Subduct– Volcano

K G F N Z P D C L EL F O Q A P C X K EE M S V O L C A N OI X S U B D U C T AD R I F T Q J S M WM K L Q H S I A W FP L A T E S G K E NZ V R Q A M S P F XP A N G A E A P V AE V R A D G W L I S

Activity

Rocks

Types of rocks

There are three main types of rocks:

1.1.IgneousIgneous - formed when molten rock cools.

2.2.SedimentarySedimentary – formed by the “cementing together” of small grains of sediment.

3.3.MetamorphicMetamorphic – rocks changed by the effect of heat and pressure.

All of these are involved in a continuous flow of rock from the surface underground only to emerge again later as part of the on-going rock cycle.

Igneous rocks

• These are rocks formed by the cooling of molten rock (magma.)

magma

volcanoMagma cools and solidifies forming igneous rocks.

Types of igneous rocks

Igneous rocks divide into two main groups:– Intrusive igneous– Extrusive igneous.

• Intrusive igneous rocks, like granite, are formed when magma solidifies within the ground.

• Extrusive igneous rocks, like basalt, are formed when magma solidifies above the ground.

Igneous rocks and crystal size

The more slowly a rock changes from liquid to solid the bigger the crystals grow.

Intrusive igneous rocks, like granite, usually have clearly visible crystals.

Extrusive igneous rocks, like basalt, have crystals that are usually small.

Intrusive igneous rocks that cool really slowly can have very big crystals.

Extrusive igneous rocks that cool really quickly can have a glassy appearance.

Chemical and Physical Weathering

• Surface rocks seem to be gradually reduced in size by weathering processes.

• Chemical weathering is when chemicals, such as those in acid rain, ‘eat’ away certain rocks.

• Physical weathering is to do with the rocks being broken down by the action of wind, rain and sun. For example, during the freezing and thawing of water in the cracks of rocks, the expansion of water makes the rocks splinter.

• The small broken fragments wash into rivers and, eventually, reach the sea where they settle as sediment.

Sedimentary Rocks are rocks formed when particles of sediment build up and are “cemented together” by the effect of pressure and minerals.

sea

Fragments washed to the sea

Sedimentary rocks

Rocks are brokenup by the actionof weather

Sedimentary rocks

Sedimentary Rocks tend to have visible grains of sediment.

Sometimes they contain fossils.

They are usually softer than igneous rocks.

Examples of sedimentary rocks are sandstone and mudstone.

Gettin

g o

lder

Sandstone is formed from the cementing together of grains of sand.

Sedimentary rocks

Magma

metamorphicrock

forminghere

Metamorphic rocks are formed by the effect of heat and pressure on existing rocks.This can greatly affect the hardness, texture or layer patterns of the rocks.

heat

Pressure from surface rocks

Metamorphic rocks

Marble, slate and schist are metamorphic.

– Limestone is a rock often formed from the sediment of shells. Temperature and pressure cause the rock to reform as small crystals that are much harder. It is used as a hard and decorative stone in buildings, sculptures etc.

– Slate is formed when pressure squeezes mudstone into plate like grey sheets. It is used in roofing.

– Schist and mica are formed when mudstone is subjected to very high temperatures as well as pressure. Again they contain layers which is typical of many (not all) metamorphic rocks.

Metamorphic rocks

Match the rock with the correct description.Give an example of this type of rock.

Rock typeRock type DescriptionDescription

intrusive igneous

Large crystals, hard rock

metamorphic Sandy texture, soft rock

extrusive igneous

Small crystals, hard rock

sedimentary Wavy layers of crystals

Activity

The rock cycle

Crack the code! What should this really say?

• (Giant hewer) leads to fragments collecting in the sea and forming (am seen dirty) rocks such as chalk, (sum to end) and (and so nest).

• Heat and (perusers) can lead to (a chem import) rocks such as (stale) and (ambler).

• Some of these will melt and eventually cool as they approach the surface to form (I ruin vets) (go in use) rocks such as (get rain).

Weathering

sedimentary

mudstone sandstone

pressure metamorphic

slate marble

intrusive

igneous granite

Activity

What gases would have formed the original atmosphere around planet Earth?

1. Hydrogen and helium

2. Oxygen and nitrogen

3. Methane and ammonia

4. Carbon dioxide and water

What gases form the majority of the present atmosphere around planet Earth?

1. Hydrogen and helium

2. Oxygen and nitrogen

3. Methane and ammonia

4. Carbon dioxide and water

What gas protects us against dangerous UV radiation?

1. Sulphur dioxide

2. Nitrogen oxide

3. Methane

4. Ozone

What gas is a major cause of the greenhouse effect?

1. Sulphur dioxide

2. Nitrogen oxide

3. Carbon dioxide

4. Chlorine dioxide

What process increases atmospheric carbon dioxide levels?

1. Photosynthesis

2. Respiration

3. Formation of Fossil fules

4. Formation of carbonate rocks

What layer of the Earth is around 50Km thick and high in silicon and oxygen?

1. Inner core

2. Outer core

3. Mantle

4. Crust

What layer of the Earth is mostly molten iron and nickel?

1. Inner core

2. Outer core

3. Mantle

4. Crust

What layer of the Earth is made of viscous semi-molten magma?

1.Inner core

2.Outer core

3.Mantle

4.Crust

What type of rock is formed by solidification of molten magma?

1. Igneous

2. Metamorphic

3. Sedimentary

4. Fossilised

What type of rock is formed by cementation of small particles of weathered rock?

1. Igneous

2. Metamorphic

3. Sedimentary

4. Fossilised

What type of rock is formed by the effect of heat and pressure upon other rocks?

1. Igneous

2. Metamorphic

3. Sedimentary

4. Fossilised

What type of rock is least likely to contain fossils?

1. Igneous

2. Metamorphic

3. Sedimentary

4. Fossilised

What is the process where tectonic plates separate and magma creates new solid crust?

1. Weathering

2. Ageing

3. Sea floor spreading

4. Sedimentation

What is the process where tectonic plates move gradually apart?

1. Continental breakfast

2. Continental drift

3. The rock cycle

4. Subduction

Which of these is notnot evidence for continental drift theories?

1. Similarities of fossils

2. Similarities of rock layers

3. Jig-saw fit of coastal shapes

4. Similarities of climate