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Geography HL

Units 1 & 2, Elective 5, Option 7 - from Edco Today's World Books 1&3

Laush WQ

on 31 May 2014

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Transcript of Geography HL

Elective 5 - The Human Environment
Option 7 - Geoecology
Unit 2 - Regional Geography
Biome Rainforest
Leaving Cert 2014
Physical Geography
Geography HL
by Shula WQ
outermost layer, made of solid rock
oceanic and continental
>75% Earth's volume
several layers of rock
semi-molten at surface, molten deeper
"soft" enough to flow
Outer Core
mainly iron
so hot that constantly fluid
Inner Core
iron and nickel
hottest layer of earth
solid due to pressure
Oceanic Crust
5-10 km thick
on top blanket of sediment, i.e. clay and shells
beneath, heavy rock: e.g. basalt
lica and
Continental Crust
30 km where continents stretched to >60 km @ mountain belts (continents stretched)
younger, lighter rock e.g. granite
lica and
The Lithosphere
crust + upper part mantle
stretches to 150km depth, strong + rigid
outer shell that doesn't flow easily
region just below lithosphere
partially melted so plates can slide
Earth's Structure
Plate Tectonics
Continental Drift
continuous process of moving plates
Continental Fit
- coasts of continents surrounding Atlantic ocean could fit together

Matching Rocks and Mountains
- Appalachian Mts USA and Caledonian Mts Britain, Ie, Scandinavia, N/W Africa

Matching Glacial Deposits

S America, Africa, India, Australia - when continents were joined in cold climate
Sea - Floor Spreading
The cracking of the lithosphere, molten magma rising up and filling the opening.
rock samples taken from the ocean floor get progressively younger tward ridge @ centre of ocean
@edge: up to 200 myo
@centre: <10 myo
sediments become much thicker with increasing distance from the mid-ocean ridge
How do the Plates move?
thermal convection currents
current of molten magma rises slowly
as it comes closer to the top of the asthenosphere
magma moves in
as it cools, it
, where reheated
betw. plates and convection currents -> this
plates along, i.e. continental drift
: when one plate begins to sink it pulls the rest of the plate down with it
*destructive plate boundaries
Oceanic - Oceanic plate convergence
: Plate collision
: Island Arc, Ocean Trench
older, heavier plate subducts beneath younger, lighter
fiction between plates and convection currents pulls plates along
also, slab-pull
long, deep narrow
ocean trench
develops@ point of subduction
melted plate rises to begin volcanic activity
erupted lava + volcanic
pile up as
island volcanoes
normally strung out in chains called

e.g. Japan
Eurasian plate + Pacific plate
Oceanic - Continental
Process: Plate Collision
Landforms: Fold Mountains, Ocean Trench, Volcanoes
continental crust subducts under oceanic due to being lighter
friction - slab-pull force pull plate along
as oceanic plate subducts, ocean trench is formed
stresses cause edge continental plate to buckle upwards: fold montain forms
as oceanic plate melts, trapped water is released & magma rises & forms volcanoes
sometimes subducting plate locks, then releases as strong earthquake
e.g. Andes fold mountains -> Nazca plate subducted under South American Plate
Continental - Continental
Landforms: fold mountains
since continental crust is very thick, neither is subducted
intense pressure fractures edges of bothplates & forces to buckle upward
formed in interior of new continent
stresses may result in earthquakes
Indian moved northwards + Eurasian plate
-> Himalayas & Tibetan platea to present height
Landforms: Mid-ocean ridges, Volcanic islands
two or more plates pull away from each other
new crust is created, oceans grow: constructive plate boundaries
magma rises from the mantle & moves through crack
forms new crust
crust gradually forms underwater mountain range or mid-ocean range
e.g. Mid-Atlantic Ridge
north-south direction
2,500 - 3,000 metres high
occasionally rises above ocean: Iceland
American and Eurasian plates move apart @ 2.5cm a year
Atlantic Ocean grows wider, Pacific shrinks
Transform plate boundaries
Landforms: fault lines, e.g. San Andreas Fault
plates may move in opposite directions or in same d.
nothing created or destroyed
movement not smooth - friction - earthquakes
Case Study: Africa, a continent Breaking Apart
early stages of continental plate breaking apart
crust here damaged when African & Eurasian plates collided
rising plumes of magma caused the crust to warp upwards
this weakened crust, causing it to fracture
rifts began to open, diff. sections of plate begin to separate
Arabian Peninsula has split from Africa, opening the Red Sea and Gulf of Aden
if rifting continues, Eastern Africa may break away from rest & form new sea floor and continent
Volcanic Activity
Folding & Faulting
Rock Cycle
Cycle Landscape Evolution
Weathering + Karst
Mass Movement
River Processes
Coastal Processes
Glacial Processes
Ordnance Survey Maps
aerial, satellite images + weather charts
Population Change over Time and Space
Population Movements
Settlement - site, situation & function
Ordnance Survey maps
Urban Land use and Planning
Urban Growth - Problems and issues
Population Distribution
Population Density
Population Growth + Change
Demographic Transition Model
Three Types Population Pyramid
Dependency Ratio
The spread of population over a region or country - evenly or unevenly
globally, the population is unevenly distributed. high altitudes, aridity, very dry, too wet or cold
almost 90% population live in northern Hemisphere
most betw. latitudes 20° and 60° because temperate climates
2/3 world's population lives in 1/10 of global land area, e.g. floodplains etc
FACTORS affecting population:
access to services
historically along rivers: trade, transport, fertile
altitude, terrain
The average nr. of people per km² in a country or region.
e.g. 4,588,252 : 70,283 = 65.28
people/ km² Ireland

figures vary throughout:
Galway: 42 ppl/km²
Dublin: 1,382 ppl/km²
: Population explosion
: birth rates, death rates, immigration
natural increase
: birth rates exceed death rates.
natural decrease
: birth rates are lower than death rates
Fertility rates globally: the nr of children per mother in a country
in poor countries parents have
more children because:
some may die young
provision for old age
women have low status
poor education
economic asset
wealthy countries, parents have less children because
low child mortality
pensions: less dependence on children
well educated women
family planning
economic liability
Death Rates
Death rates have been reduced by:
Clean drinking water
prevents spread of illnesses such as typhoid and cholera. Urban sewage systems
Better nutrition
improves health. better resistance to infection
Health services & mass vaccination
: smallpox eliminated 1976
1. High Fluctuating Phase
birth + death rates high, cancel out
no population growth
mediaeval times:
e.g. Black Death but lack of contraceptives
Rwanda in 1990s civil war
2. Early Expanding
Death rates decline quickly: vaccination, ower infant mortality. clean drinking water.
birth rates remain high, illiteracy, no family planning
Children seen as economic assets
Europe 19th century
Sub-Saharan Africa, e.g. Mozambique, Kenya, Nigeria
3. Late Expanding
rapidly improving
standard of living
death rates decline: good
care, widespread
, good
Mothers are better
, practise

large families not necessary
most people in
urban centres
where accommodation tight -> children are an economic
4. Low Fluctuating
has passed through
population transition
2nd half 20th century
rates very
children =
economic liability
- costly education, urban centres. many mothers work outside home
high life expectancy ca. 80 yrs
very advanced
5. old age or senile
e.g. Germany, Japan
death rates higher than birth rates
v. low birth rate - population ages
fewer that 2 babies per mother: below replacement levels
countries need young inward migrants to fill vacant jobs and prevent population from serious decline
prop of people different age groups in population
prop. males to females
percentage dependants in population
Stage 2
larger families
lower life expectancy
dependants mostly under 15
narrower base: fewer children per mother
mothers well educated
most practise family planning
percentage 65+ is < or = to 14-
mothers continue to have fewer than 2 children
many choose to have none
population becomes older, ~40% 65+
life expectancy
Young dependants: 14-
Elderly depentants: 65+
What is overpopulation?
The number of people in a region exceeds what can be sustained by the resources of that region.
What is optimum population?
The number of people who can live in a region at a high standard of living using the natural resources and technology available to them at any time.
When does underpopulation occur?
Too few people in a region to exploit the resources of that region.
e.g. western Australia + interior Canada: large mineral resources
resources of a region
income levels of population
social & cultural influences
impact of technology
Population density & overpopulation
not to be confused
e.g. Germany: pop ~ 82 mio pop. density 234 ppl/km²
one most advanced economies globally
excellent resources
strong work ethos
high income levels
modern technologies
strong export
pop. has high living standards and
Case Study: overpopulation Horn of Africa
cause: semi-arid region south of the Sahara
Burkina Faso, Niger, parts of Ethiopia, N Kenya + Somalia
severe food shortages + overpopulation 2010-12
The Sahel
The Depletion of Resources
two consecutive failed rainy seasons 2010-11
worst drought in region for 60 yrs
water resources + food resources severely depleted
long-term climate change
previously, drought occurred every 6-8 yrs, now every 1-2 yrs
livestock die
trees+bushes die
soil resources dry and blow away as dust
crop failures 2010+2011 -> 300% food price increase (scarce food resources)
price maize, millet, sorghum beyond reach of poor (great majority population)
animals (goats+cattle) began to die - shortage fodder
region had one highest rates malnutrition before crisis 2011, >1/3 population malnourished
drought tipped Sahel into famine
Because food and water resources in the region were depleted, famine and hunger occurred.
The Income Levels of the Population


% ppl in relative poverty


Yearly income p/person


Ethiopia, Somalia + Kenya among poorest countries in world, ppl have v. little income
many people cannot afford food available
children starve
highly dependant on subsistence agriculture
exports mainly: coffee, livestock, animal skins for leather industry, bananas
when drought kills livestock, income is lost
subsistence farmers have no money set aside
prolonged drought -> famine
food insecurity: no reserves of food in granaries
many communities dependant on food aid for years
region plagued by (cause)civil war + corrupt & inefficient government
food security & children's health forgotten (effect)
Social and cultural influences
why are populations growing so quickly?
Ethiopia, Kenya, Somalia @ Stage 2 demographic transition.
Poor Status + Educational Level Women
culturally tied to the traditional role of motherhood
Very few couples practise family planning
Absence of pensions for the elderly
children are a provision for old age, an economic asset
High Infant Mortality Rate
parents have additional children as they know that some will die
Islam is the religion of a minority in Ethiopia, Kenya, but majority in Somalia
Islamic communities traditionally value large families
this changes as women become urbanised + educated

The level of available technology
among poorest countries in world
v. low levels technology
great majority rural areas no electricity
no refrigerators or deep freezers to store food
can't afford electric or diesel pumps to pump water from deep wells
hardly computers or internet access

Agricultural Technology
generally primitive
tractors far beyond means of almost all farmers
-> oxen
-> hand hoe to break soil
cannot afford chemical inputs to boost crops
very low farm output
Seed Technology
very poor
Farmers save seed every year from part of their crop
modern high-output crops used in Asia generally not available
food output low even @ best of times
Irrigation Technology
e.g. dams, canals, plastic piping - very limited
would help to overcome challenges of drought + to survive prolonged drought

The Effects of Overpopulation
1. Food Shortages & Famine
Hunger becomes famine when:
20% of households in a district face extreme food shortage
acute malnutrition rates affect >30% population
death rates per day exceed 2 for every 10,000 people
months before famine was declared, cattle & goats were dying, grains & vegetables became very scarce and children lost weight
immunity to infections declined
2. The Flight to Refugee Camps
civil war + famine in Somalia -> tens of thousands became famine refugees
fled to refugee camps in Kenya and Ethiopia
Dadaab Kenya became world's larges refugee camp 2011 w/ 500,000 refugees
yet built for 90,000
stretched for almost 50km
arid and barren landscape
blinding dust storms
"These proud, independent people want a hand up, not a hand out"
emergency food and medical aid
TV news coverage was vital, as currency problems in eurozone and Greek debt crisis took precedence
3. Migration
overpopulation leads to outmigration
push: civil war Somalia, famine
collapse central government Somalia 1991
-> years bloodshed between rival clans
weak Somalian government now controls very little of the country and is hopelessly
Al-Shabaab (Islamic militant organisation) prevented many aid organisations from operating in area under its control
Al-Shabaab claimed in 2011 that despite some food shortages there was no famine in Somalia
-> international media exaggerating
many k people crossed from Horn of Africa over Red Sea to Yemen
one of most dangerous sea passages, as busy shipping lane
Yemen very poor and has difficulty coping with influx refugees
such as poverty, cultural differences & prejudice
The Situation 2012
seasonal rains returned
13 mio ppl still @ risk of hunger
World Food Programme continues to provide food aid to 7.9 mio people
political disorder continues
region remains highly vulnerable and overpopulated


Annual Population Growth


Population 0-14 as % of total


Birth & Death Rates per 1,000
38 VS 12

38 VS 11

44 VS 16
SRPs Volcanic Activity + Plate Tectonics (2008)
@ site of mid-ocean ridges where plates diverge

asthenosphere rises to fill voids left in extended lithosphere

rise of hot mantle provides thermal buoyancy to ridge area

-> why they stand as high ridges in centre ocean basins
as hot asthenosphere rises to shallow levels -> decompresses & melts -> basalt magmas

pond in crustal magma chambers where periodically tapped by vertical fractures

-> conduits for rapid rise of magma to the surface

typically produces fise eruptions

erupting basalt can generate vast submarine lava fields

typically, lava quenches quickly agains bottom waters -> characteristic bulbuous pillow basalt
high heat content mid-oceanic ridges evident -> hydrothermal vents
surface water seeps down & is heated by hot rocks lying above magma chambers
rise back through overlying crust
leach silica and minerals from basaltic lava
emerge on surface
called black smokers because of billowing dark clouds of metal-rich fluids
most volcanically active belt known as
Ring of Fire
subduction zone volcanism surrounding Pacific Ocean
[explain subduction in this case]
as descending plate bends downward @ surface
creates large linear depression =
oceanic trench
trenches = deepest topographic features

Mariana trench: 11 km below sea level, on western margin Ring of Fire

Aleutian trench: northern rim
crustal portion subducting slab contains lots of surface water
+ water in hydrated minerals within seafloor basalt
greater temperatures & pressures cause slab to release water into overlying mantle wedge
water lowers melting temperature of mantle -> melts
magma thus produced varies from basalt to andesite

rises upward to produce linear belt of volcanoes parallel to ocean trench

island arc
when oceanic plate subducts under adjacent continental lithosphere
similar belt volcanoes generated on oceanic crust
volcanic arc
e.g. Andes volcanic arc South America
e.g. Cascade volcanic arc U.S. Pacific northwest
Hawaii geologically unique -> "hot spot"
most islands found @ tectonic plate boundaries
- spreading centres: (e.g. Iceland)
- subduction zones: (e.g. Aleutian Islands)
few "hot spots" & one under Hawaii is central to one of largest crustal plates on Earth - Pacific Pl
geologic 'hot spot' = area middle of crustal plate
-> volcanism occurs
molten magma breaks through crustal plate
-> either weak/thin mantle or v. hot mantle
hot spot under American Plate -> Yellowstone National Park has geysers + other thermal features
where hot spot under seafloor -> undersea volcanoes
some build up on seafloor -> islands
over millions of years plate may move over 'spot' creating chain of progressively extinct volcanoes
N/W moving Pacific Plate has moved over 'hot spot' for millions of yrs
-> Hawaii
as islands move N/W begin to erode + become inactive
over time may erode so much -> underwater seamount
Kauai oldest, eroding
Oahu next, volcanism inactive
Maui could still come to life one more time
youngest, Hawaii: 'Big Island'
surface lavas <1 mio years old
active volcanism
sea floor 20 miles to S/E active volcanic area w/ periodic eruptions
called Loihi, will be site of next Hawaiian Island if geological processes continue for next 10,000 yrs as they have the last millions

active volcanism today:
Hawaii largest of islands & made of 5 volcanoes
Kohala, Mauna Kea, Hualalai, Mauna Loa & Kilauea
Kohala: last erupted 60,000 yrs ago
Mauna Kea: 3,500 yrs ago
---> considered dormant
Hualalai's last eruption: 1801
Kilauea considered one of most active volcanoes today
has erupted 30 times in last 40 yrs
Hawaii one of few places on Earth where one can safely watch volcanic processes shaping Earth today
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