Understanding GCSE Geography for AQA A - Pearson Schools

24 Pages·2008·9.46 MB·English

Contents
1
The ResTless eaRTh 5
2
Rocks, ResouRces and sceneRy 25
3
challenGe of WeaTheR and climaTe 43
4
livinG WoRld 61
5
WaTeR on The land 79
6
ice on The land 99
7
The coasTal Zone 115
8
populaTion chanGe 133
9
chanGinG uRban enviRonmenTs 153
10
chanGinG RuRal enviRonmenTs 173
11
The developmenT Gap 193
12
GlobalisaTion 213
13
TouRism 233
exam café 253
GRade sTudio 256
GlossaRy 259
index 262
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Chapter 1
The Restless Earth
Plymouth, island of Montserrat in the Caribbean, was destroyed by the
massive eruption of the Soufrière Hills volcano in 1997. Ten years on and
the volcano still erupts from time to time. Why could this not happen in
Plymouth, UK?
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Questions
• Why are plate margins so important – for landforms and people?
• Why do high fold mountain ranges, active volcanoes and main
earthquake zones hug plate margins?
• How can the risks to life and property be reduced in countries located
on plate margins? Does it matter whether they are rich or poor?
• Why are people in countries away from plate margins not completely
safe? Remember the Asian tsunami of 2006? What could happen if a
super volcano were to blow its top?
The Earth’s crust is unstable
What happens at different plate margins?
We live on a thin skin of cool rock - the crust (Figure 1).
Crust
At the centre of the Earth is the core surrounded by a large
mass of molten rock called the mantle. There are two main Mantle
types of crust: oceanic crust which is denser and about five
Core
kilometres thick and continental crust which is lighter but
30 or more kilometres thick.
The Earth’s crust is not one continuous layer but is made
up of seven large tectonic plates and many smaller ones.
Figure 2 shows the distribution of the main tectonic plates.
The Earth’s crust is unstable because the plates are moving in
response to rising hot currents called convection currents
within the mantle. The movement of the plates has greatest
impact at the plate margins, where two tectonic plates meet.
The centres of the plates, away from the margins, tend to be
stable and away from major tectonic activity. How far away is
the UK from the nearest plate margin? Figure 1 The structure of the Earth.
Plates may move apart, or closer together, or slide past
each other. These movements lead to earthquakes and the
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oceanic crust sinks into the mantle where
formation of fold mountains and volcanoes.
it melts in the subduction zone, an
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h destructive plate margins oceanic trench. Energy builds up in the
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o Plates move together. Figure 3 shows what happens. The
e be released as an earthquake. The moltenJo b No: J6644
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se Nazca plate is made of oceanic crust which is denser than rock, called magma, may rise upwards, FAirgtw Noork: SB3y5 H1l7 S10tu_daiows_193
c the continental crust of the South American plate. The Nazca
G causing volcanic eruptions and leading
G plate is forced to sink below the South American plate. The
din to the creation of composite volcanoes.
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Eurasian Plate
North
American
Plate
N CaPrilbabteean APfrlaictaen Arabian Plate hilippin ePlate
P
Pacific
Plate
South
American Indo-Australian
0 1000 Miles Nazca Plate Plate
Plate
0 2000 Kilometres
Key
Plate margins
Antarctic Plate Direction of plate movement
Figure 2 Earth’s tectonic plates.
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The lighter continental crust stays at the surface but
sediment becomes crumpled into fold mountains.
The Andes are the fold mountains that have formed
along the west coast of South America.
Fold mountains (Andes)
W E
Pacific Ocean
Volcano
Approx.
Rising magma
depth
(km) Ocean trench
0
10 Nazca Plate South American Plate
20
Subduction zone Earthquake focus
Figure 3 A destructive plate margin.
Figure 5 The San Andreas fault, which passes through the
constructive plate margins
San Francisco Bay where 7 million people live.
Some plates, like the North American and Eurasian
plates, are moving in opposite directions, away from
Activities
each other. This type of movement mostly happens
under the oceans. As the plates move apart the gap is
Cl1ie n(t:a H) eWinehmaat nanre the differences between (i) plates made
filled by magma rising up from the mantle below. The Job No: J6644
of oceanic and continental crust (ii) destructive
rising magma creates shield volcanoes which, if they Fig No: S351710_aw_195
Artwork Bay nHdl Sctoundisotsructive margins? 1
become high enough, form volcanic islands, such as
(b) How is a conservative margin different?
Iceland. So much magma is poured out that ridges are
built up from the sea bed, like the Mid-Atlantic ridge 2 Copy and complete a table like the one below: h
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shown in Figure 4, upon which Iceland is located. a
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Type of Examples Features Example s
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plate margin of plates produced country/area e
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W Mid-Atlantic Volcanic island E h
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Ridge (e.g. Iceland)
Approx. 3 Study Figure 2.
depth
(km) (a) What does it show about the likelihood of
0 North tectonic activity in the UK?
American Eurasian (b) Tectonic activity in Europe is concentrated in
Plate Plate
10 Iceland and southern Italy. State one tectonic
similarity and one difference between Iceland and
Rising magma
20 Italy.
4 Scientists warn that San Francisco is more than 60
Figure 4 A constructive plate margin.
per cent likely to experience a damaging earthquake
by 2038. Why?
conservative plate margins
At the San Andreas fault in California, the North
exAm prepArAtion
American plate and the Pacific plate are sliding past
each other. They are moving in the same direction
TracCe litehnet: mHeainine mpalantne margins in Figure 2. Keep it at hand
but the North American plate is moving slightly
for uJsoeb wNoh:e Jn6 6s4t4udying:
faster. Pressure builds up along the fault until one Fig No: S351710_aw_196
• Fold mountains
plate jerks past the other, causing an earthquake. Artwork By Hl Studios
• Volcanoes
The movement has also caused the land to become
• Earthquakes.
ridged and crumpled, as shown in Figure 5.
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Landforms at plate margins –
Fold mountains and ocean trenches
Highest mountain 8848m. Deepest ocean 11 022m. How can tectonic activity explain both?
Roc
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Alps
Pyrenees Caucasus Himala
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N Atlas
0 1000 Miles An
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0 2000 Kilometres s
Key
Young fold mountains
Ocean trenches
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Mount Everest
Mariana trench
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h Figure 1 The world distribution of young fold mountains and ocean trenches.
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G fold mountains
se A Geosyncline Rivers carry
Gc Young fold mountains are found in many parts of the world Rivers sediment
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din (Figure 1) and a glance back at Figure 2 on page 6 shows Plates Plates
an that they form along the plate margins where great Earth Sea Sediment
sT movements have taken place. Client:a Hcceuinmeumlaatnens
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were long periods of quiet between Earth movements
during which sedimentary rocks, thousands of metres thick, B Geosyncline filled with
sediments compressed
formed in huge depressions called geosynclines. Rivers
into rock
carried sediments and deposited them into the depressions.
Over millions of years the sediments were compressed into Plate Plate
sedimentary rocks such as sandstone and limestone. These movement movement
Compression
sedimentary rocks were then forced upwards into a series
of folds by the movement of the tectonic plates. Sometimes
the folds were simple upfolds (anticlines) and downfolds Sediments folded
(synclines), as shown in Figure 3. In some places the folds C into fold
mountains
were pushed over on one side, giving overfolds.
Fold mountains have been formed at times in the Earth’s
geological history called mountain-building periods. Recent
Continued compression
mountain-building movements have created the Alps, the
from plate movement
Himalayas, the Rockies and the Andes, some of which are
still rising. For this reason many of these ranges are called
Figure 2 The formation of fold mountains.
young fold mountains.
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Fig No: S351710_aw_198
Artwork By Hl Studios
Simple folds
Anticline
Syncline
possibilities for human use
Simple folds Overfolds
Anticline Ocean trenches are inaccessible to humans. The
Syncline
ocean area of greatest importance is the continental
shelf, the shallow zone less than 200 metres deep
off the coast. The main opportunities here are for
fishing and drilling for oil and gas.
Figure 3 Types of folds.
On land, most high fold mountains are places with
Overfolds low densities of population. Physical problems can
be formidable:
• Relief – mainly high and steep. Rock outcrops are
frequent and many mountain valleys are narrow
and gorge-like. There is little flat land for farming
and building settlements.
• Climate – with increasing heigChliet nitt: bHeecinoemmaensn
colder, windier and wetter, anJdo bm Noor:e J 6o6f4 t4he
Fig No: S351710_aw_199
precipitation falls as snow. The growing season is
Artwork By Hl Studios
short and it is often impossible to grow crops at
high levels.
• Soils – mountain soils are typically stony, thin and
Figure 4 Evidence of folding can be seen where layers of rock are
infertile.
exposed.
• AcceCsliseinbt:i lHiteyin –e mroanands and railways are expensive
and Jdoibf fiNcou: Jlt6 6to44 build; travel on them is frequently
ocean trenches
Fig No: S351710_aw_199
disrupted by rock falls, avalanches and bad
Notice from Figure 1 that the majority of ocean Artwork By Hl Studios 1
weather. High mountains in inland locations, such
trenches are located around the sides of the Pacific
as the Himalayas, are the least accessible of all.
Ocean. Take another look at Figure 2 on page 6 h
There are exceptions. Parts of the Andes are well T
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– with which type of plate margin are the ocean a
settled. Countries such as Chile, Bolivia and Peru e
trenches associated? s
are rich in mineral resources including copper, tin, es
l
The subduction zone is an ocean trench (Figure silver and gold. Volcanic soils can be very fertile sT
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3 on page 7). One wall is formed by subducted (pages 14–15). R
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ocean plate (the Nazca plate in this Figure), the T
other by the overriding continental plate (the South
Activities
American plate). These ocean trenches are very
deep, typically 5000-10 000 metres. 1 Study Figure 1.
(a) Describe the two main directions in which ranges
Figure 5 The Earth’s surface from of young fold mountains are aligned.
highest to lowest.
(b) For one range of fold mountains, name the two
tectonic plates responsible for its formation.
Mount Everest
8848m (c) Explain why fold mountains are formed along
destructive plate margins.
2 Draw a simple labelled sketch to show the evidence
that the mountains in Figure 4 are fold mountains.
Island arc
Sea Continental shelf (e.g. Philippines) 3 Describe how tectonic activity explains the big
0
Level difference between highest and lowest.
Further reseArch
Mariana Calculate the height difference between the highest
trench mountain and lowest ocean on Earth. Check on the
11 022m
companion website.
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Fig No: 045353308_aw_1.8
Artwork By Hl Studios
CasE sTudy The alps
Case study of a range of fold mountains
– The alps
The Alps were formed about 35 million years ago 1. farming and forestry
by the African plate pushing north against the
Most farms are located on the sunnier and warmer
Eurasian plate. As it moved, sediments which had
south-facing slopes. The traditional pattern of farming
accumulated in the sea of Tethys (the geosyncline
is dairy farming using a system called transhumance,
between the plate) were squeezed upwards to form a
the seasonal movement of animals. In summer the
fold mountain range. Today the Alps form the border
cattle are taken up to the high Alp to graze, which
between Italy and the neighbouring countries of
allows hay and other fodder crops to be grown on the
France, Switzerland, Austria and Slovenia. The
small fields on the flat land in the valley floor. Here
highest peak is Mont Blanc near the Franco-Italian
summers are warmest and soils are deepest and most
border at 4810 metres, but there are many other
fertile. In winter the animals return to the farm on
peaks above 3800 metres (Figure 1 on page 102).
the valley floor, where they are kept in cattle sheds
From above, the Alps look like a wasteland of rock,
and stall-fed on the fodder crops grown in summer.
ice and snow: only the valleys give a hint that
human settlement may be possible (Figure 1). Over the years there have been many changes to
this traditional system of farming.
human activities in the alps
• Cable cars (built for skiers and tourists) are now
These vary according to height, which creates used to bring milk to the co-operative dairies
vertical zones of land use. Figure 2 summarizes down on the valley floor. In the past the farmers
typical land uses in an Alpine valley. Many Alpine stayed with the cattle all summer and turned
valleys are aligned west to east so that better the milk into butter and cheese (which keep for
opportunities for settlement, farming and other longer) on the high Alp.
economic activities are created on sunny south-
• Farmers buy in additional feedstuffs, so that they
facing slopes. Land uses are less varied on more
and their cattle can stay on the valley floor farm
shaded north-facing slopes.
all year.
S
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Rocky peaks
Snowfields
high alp
Village/small
Winter ski town Glaciers
resorts
Winter ski Summer pastures
slopes
Summer Snow line
Coniferous forest
grazing
<insert figure 2 from previous book
Railway
Cultivated fields
– same size but with changes as indi-
for crops in summer
cateTdun>nel
Farming and
Figure 1 Aerial view over the Alpine
settlement
fold mountain range.
Figure 2 Land use and human activities in an Alpine valley.
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Fig No: 045353308_aw_1.9
Artwork By Hl Studioss
3. hydro-electric power (hep) and
industry
The steep slopes, high precipitation and
summer melting of the glaciers produce fast-
flowing rivers that are ideal for generating
HEP. The narrow valleys are easy to dam
and there are lakes in which to store water.
Some of the cheap HEP is used by industries
which require a high input of electricity,
such as sawmills, electrochemicals, fertilizer
manufacture and aluminium smelting. Some
of the electricity is also exported to other
regions to supply towns and cities.
how do human activities in the alps
compare with other fold mountains?
The Alps are not mineral-rich like the
Andes. However, compared with most
Figure 3 Alpine view – the Jungfrau region of the
other fold mountain ranges, Alpine areas
Lauterbrunnen valley in Switzerland.
are well populated. Because the countries
are rich, they have the money and
Coniferous trees cover many of the slopes, especially north-
technology to overcome high mountain
facing ones. Wood, as a plentiful local resource, has always
transport problems. Modern road tunnels,
been the main building material and winter fuel in Alpine
such as the St Bernard and Mont Blanc
lands. Most sawmills are located on the valley floors near to 1
have replaced old routes over the high
rivers; timber that cannot be used for construction is made into
passes. Many electrified railways link the
pulp and paper. s
Alpine valleys to the cities; rail tunnels p
l
a
2. Tourism under the Alps include the Brenner and St he
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Bernard. Mountain cog railways, cable cars –
The Alps have physical advantages for tourism all year round, y
and chair lifts link the valley floors to high d
attracting skiers, climbers and walkers as well as those who level benches and ski slopes above them. sTu
simply want to admire the spectacular scenery. These activities e
s
a
are a major industry. Activities c
A For winter tourism (examples of resorts are St Moritz,
1 Study Figures 1, 2 and 3.
Chamonix):
(a) List the problems for (i) settlement
• snow for skiing and other winter sports; in between the
(ii) farming (iii) transport in the Alps.
days with heavy snowfall are many sunny, crisp and
(b) Describe the attractions of the Alps for
clear days
tourism.
• flatter land on the high-level benches for easy building of
(c) Explain why most human activities in the
hotels, restaurants, ski-lifts and other facilities
Alps are concentrated on valley floors.
• steep slopes above the resorts for ski runs amid great
2 How have people tried to reduce the
mountain views.
problems
B For summer tourism (examples of resorts are Interlaken and
(a) in farming (b) for transport?
Garda):
3 Using Figure 2 on page 8 and information
• large glacial lakes on valley floors
about the Alps, draw labelled diagrams to
• beautiful mountain scenery with snow-capped peaks.
show how the Alps were formed.
The main worry is that Alpine winters are warming up and
becoming less snowy than they used to be. More people
Further reseArch
are skiing on worn slopes, damaging the vegetation and the
surface below and thereby increasing the number of bare
Find out about the Andes on the companion
surfaces and the risk of soil erosion on steep slopes.
website.
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Landforms at plate margins –
Volcanoes and supervolcanoes
Where are active volcanoes found? Why are not all volcanoes the same?
What is different about supervolcanoes?
Iceland
Rock
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Mount Yellowstone
St Helens
Mount
Etna
Hawaii
N Montserrat
El Chichon
Lake Toba
0 1000 Miles Krakatoa
0 2000 Kilometres
1
Key
Main active volcanoes
y
ph Supervolcanoes
a
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o Figure 1 World distribution of active volcanoes.
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s A volcano is a cone-shaped mountain formed by eruption and the form (height and shape) of the
c
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ndi the Earth. The magma that reaches the surface in shown in Figure 3. Basically Jtohbe N doi: vJ7is3i3o6n is between
a an eruption is called lava, and is one of the many volcanoes formed along constFriug cNtoi:v 0e4 5p3l5a3t3e0 8m_aawr_g1i.n10s
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n ash, cinders, pumice, dust, gases and steam. The different types of lava emitted. Along constructive
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world distribution of active volcanoes (Figure 1) margins the basic lava that has come from within
shows an almost perfect fit with the locations of the the mantle has a low silica content: it pours out
tectonic plate margins (see Figure 2 on page 6). easily, is runny and flows long distances, building up
shield volcanoes. However, along destructive margins
how are volcanoes formed? the acid lava has a high silica content, which makes
it more viscous so that it travels shorter distances
Volcanoes form where magma escapes through a
before cooling; these are more explosive volcanoes.
vent, which is a fracture or crack in the Earth’s crust.
After an eruption the vent becomes blocked, which
This happens most often at plate margins. Lava and
results in great pressure building up before the next
other products are thrown out from the circular hole
eruption. During explosive eruptions lava is shattered
at the top called the crater. Each time an eruption
into pieces so that bombs, ash and dust are showered
takes place, a new layer of lava is added to the
over a wide area.
surface of the volcano; since more accumulates closer
to the crater during every eruption, a mountain that
is cone-shaped is formed (Figure 2).
Figure 2 The Osorno volcano
different types of volcanoes
in Chile, an almost
perfect cone shape.
Volcanoes are divided into two main types,
Last eruption 1869.
depending upon the material thrown out in an
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