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GCSE Geology Revision Check that you know the following words and understand all of the main ideas:
Book 1 - Earth Materials (RED)
Minerals: Do you know how to test the properties of minerals?
Cleavage Form Hardness (Moh’s scale) Streak
Lustre Density (how do you test it?)
Acid test (does it fizz with dilute hydrochloric acid)
Main minerals see below:
How do minerals form? * Hydrothermal – heat from magma dissolves
elements in water and as water cools (moving up through cracks) it leaves
crystals of metallic minerals behind in veins, Evaporites etc.
Rocks: Can you recognise rocks of the three main rock groups?
1) Igneous – crystalline rocks formed by the cooling of magma, they can
be intrusive forming plutons, sills and dykes or extrusive as lava, ash,
pyroclastic flows etc.
* Key point * Rapid cooling = small crystals (lava)
* Slow cooling = large crystals (pluton).
2) Metamorphic – formed by the altering of rocks due to heat and/or
pressure under the ground. They can be formed by contact
metamorphism (heat) or regional metamorphism (heat and pressure).
Key terms – metamorphic aureole, burial, foliation.
* Key point – Heat causes recrystallisation, pressure causes foliation *
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3) Sedimentary – formed by sediments being deposited by rivers, ice,
sea or the wind. These sediments have been eroded or weathered
and transported before formation. The rocks are deposited in layers
or beds. How are they formed and by what processes?
Key terms:
freeze thaw weathering – shattered, loose boulders,
chemical weathering – limestone to form limestone pavements
erosion – abrasion and attrition of particles to become rounded
sorting of particles to same size and shape with transport
* Key point – size of particles tells you energy of environment *
Only rock that breaks the rule are turbidites – all sizes together
Main rock types – Basalt, Granite, Peridotite, Andesite, Slate, Schist,
Metaquartzite, Marble, Breccia, Conglomerate, Sandstone, Shale, Coal and
Limestone.
* Do you know how these rocks are linked through the rock cycle*
Acidic rainfall dissolves limestone
along weaknesses (joints and bedding
planes). This slowly forms this
distinctive paving stone like feature
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Book 2 – Plate Tectonics and Hazards (YELLOW)
Structure:
Crust (oceanic and continental)
Structure of the Earth Lithosphere
Mantle (partial melt, convection)
Outer Core (Liquid, magnetism)
Inner Core (Solid, gravity, NiFe)
Tectonic Hazards: How are people affected by: (Earthquakes, volcanoes, tsunamis and landslides?)
How can the effects be managed?
The Three P’s – Prediction Protection Preparation
Learn the case studies
Mount Pinatubo 1991 Kobe Earthquake 1995
Haiti Earthquake 2010 Japan Tsunami 2011
Vargas Landslides 1999
Why do they happen? Where do they happen?
Plate Tectonics: Continental Drift – what is it and why is it happening?
Types of plate boundary:
a) Constructive (divergent) – sea floor spreading, basalt, pillow lavas,
partial melting, high heat flow, ocean ridge,
rift valley, shield (basaltic) volcanoes
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b) Destructive (convergent) - subduction, Benioff zone, epicentre, focus,
collision zone, island arc, andesitic magma
forming cone volcanoes, fold mountains.
Earthquakes range from shallow to deep.
c) Conservative – transform faults, earthquakes, San Andreas fault. Only
shallow earthquakes and no volcanoes.
*Can you draw diagrams of each of these types of plate boundary*
Can you recognise the plate boundaries on a map?
High heat flow from rising convection currents brings basaltic
magma to the surface. Shield volcanoes form and pillow lavas are
erupted under the sea creating new oceanic plates that spread
away from mid-ocean ridge.
The subducting plate drags with it
water that makes the magma andesitic
(gassy) as the plate melts. Explosive
(cone) volcanoes on the surface.
The subducting oceanic plate descends into
mantle and rubs against continental plate.
As it does, it creates a pattern of deeper
focus earthquakes (Benioff Zone).
B = _________________
Reasons why? _________
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C = _________________
Reasons why? _________
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D = _________________
Reasons why? _________
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Book 3 – Planetary Geology (PINK) What are the main bodies in the solar system?
Objects from space: Asteroids
Meteoroids
Comets
Effects of impacts from space are positive and negative?
Better preserved on Mars/Moon than Earth – why?
Lunar rocks and features – impact evidence, volcanic/igneous
evidence (rocks are all igneous)
Martian rocks and features – impacts, igneous and volcanic rocks and
features, sedimentary features (evidence of water), wind-blown
(desert) features, evidence of ice
Book 4 - Geological Structures (GREEN) Do you know the main types of geological structures seen on maps, in the
field or on photos?
1) Horizontal / dipping rocks
2) Folding – Anticlines (up-folds), Synclines (down-folds)
3) Faults – Normal Reverse/Thrust Strike slip (horizontal movement)
4) Sedimentary structures – can be used to determine the way up of
rocks or where they were formed. * Mud cracks
* Cross bedding * Graded bedding * Ripple marks
5) Other features: Baked margins, cross cutting, included fragments
6) Unconformity (rocks don’t match either side of a boundary)
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7) Interpreting Block Diagrams:
Can you work out the geological
history from the clues? Cross cutting (dykes, plutons, faults),
Superposition (younger on top of older),
Unconformities, Folding and Faulting
8) Features on maps
Which of these represents the cross-section from F-G on the map above?
Can you recognise these on a map? Folds (anticline and syncline), Faults, Unconformities, Plutons, dykes, sills or lava flows
* Key rules
1) Rocks dip towards younger rocks
2) Younger features cut across older ones
3) Older rocks in middle of anticline, younger in middle of syncline
4) Rocks don’t match at an unconformity
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Book 5 - Earth History (ORANGE) – two books!
Earth History: ‘The present is the key to the past’
Relative dating: Comparing the ages of rocks and geological events.
a) Superposition – younger on top of older
b) Cross cutting – younger features cross cut older ones
c) Folding – older folded rocks below horizontal rocks
d) Unconformities – boundaries between young and old
e) Metamorphism – rocks heated are older
f) Fossils – Same fossils in rocks = same age
g) Sedimentary Structures (way-up structures) that allow us to
put layers of rock in order. Examples are mud cracks, graded
bedding, cross bedding, ripple marks.
Absolute dating - Using radioactive
decay of elements to give accurate
dates to igneous rocks. The Half-life
of an element is fixed and is the key.
Example uranium which decays to lead
over millions of years.
Fossils – Recognise them by number of hard parts or by their symmetry
1) Trilobites (three parts)
2) Dinosaurs
3) Corals – Septa (tropical seas)
4) Plants (coal swamps)
5) Trace Fossils – evidence of their life
Septa
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Suture lines became more complex over time from:
Goniatites – simplest
Ceratites – rounded
Ammonites - complex
* What are zone fossils and how are they used by geologists?
* Graptolites and Cephalopods as zone fossils.
6) Graptolites – Stipes, Theca
7) Cephalopods – Suture lines
* Five key features of zone fossils lived all over the world, large numbers,
easily recognised, lived in the sea, evolved quickly
Geological Evolution of Britain: What do the
rocks tell us about Britain’s past geological
history and movement?
* Desert sandstones – North of Equator
* Limestone, Chalk and Corals – Tropical
* Breccia – Glaciers, mountains
* Overall northward movement
Exceptional Fossils: How do finds such as Archaeopteryx (reptile/bird)
and ‘Lucy’ (early human) help us unravel the past?
Extinctions: How and why do these happen? (Dinosaurs 65mya – meteorite
impact leaving a large crater and iridium deposits)
Climate change: Icehouse vs Greenhouse, causes of climate change (ice
melt, thermal expansion of oceans, albedo effect and carbon cycle. Human
climate change - evidence? What can we do? (CCS) – see blue book.
Simpler body plan over time
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Book 6 – Economic Geology (BLUE) 1) Main resources – How do we use Limestone, Haematite and Uraninite?
2) Prospecting for minerals – How are resources found?
Geophysical surveys – magnetic, gravity
Geochemical surveys – testing soil and river water
3) Oil and Natural Gas – How are they
formed, migrate and are trapped?
Formed in shale (source rock) from slow
heating and breakdown of plankton. Migrate
through permeable rocks until they are
trapped by an impermeable cap rock (shale,
halite) inside a porous and permeable rock
(sandstone)
The four types of trap
* Oil prospecting using:
Mapping
Seismic surveys
Drilling
* Production – oil rigs
* Environmental problems
Pollution, spills, CO2
* New technology
Shale gas, fracking
* Carbon capture and
storage (CCS)
Reserves vs Resources
4) Hydrogeology – Groundwater and aquifers (properties of rocks such as
sandstone – porosity and permeability), water table, the siting of dams
and reservoirs.
5) Landfill Sites – Burial of waste, solving environmental problems of
leachate, noise and visual pollution. Where to site a landfill and what to
use them for after closure? What to do with Radioactive Waste?
The proven amounts of oil or minerals that
can be extracted at a profit. The unproven amounts of oil or minerals or
ones which cannot be extracted at a profit – yet!
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Practical Skills – Paper 2 Rock Texture: This is described from hand specimens or
micrographs using the three S’s. Always refer to Size, Shape
and Sorting of the particles making up the rock. Are they
crystals/grains, are they random or not?
Sedimentary Logs: These show a sequence of rocks from
oldest (bottom) to youngest (top). They are used to interpret the
change in environments over time. Remember that the further to
the right a rock goes the larger the particles inside it are. You
may be asked to complete one of these.
Dip and Strike: This is a way of recording how layers (beds)
of rock have been folded/tilted by compression. Dip is the angle
at which the bed is tilted and strike is the horizontal line across
the surface (bedding plane) of the rocks layer.
Maps and Cross-Sections: These are two ways of
showing geological information about layers of rock
underground. One is from above (map) and the other is
from a sideways/slice view into the ground (cross-section).
Measuring Directional Information: Rose diagrams
can be used to display and interpret any directional
information such as:
Wind (desert sediments)
Lava/magma flowing (crystals)
Alignment of fossils
Strike of beds
Testing Minerals: Minerals can be tested using a variety of
methods such as density, reaction to acid (dilute HCl), hardness, streak and cleavage.
*Remember you always have the date sheet with the ten main minerals to help you.
Sketching and Scale: You will be asked to
draw a scaled sketch of a feature and to label the
main geological features. Always include scale and
look to draw the key feature shown.