Transcript IGCSE Physical Geography

IGCSE Physical Geography
Topic Revision
Part 2
Ecosystems
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An ecosystem is a natural system in which life
cycles of plants and animals are closely linked
to each other and to the non-living
environment (water, air, rocks & soils).
Ecosystems can vary in size from Global to
Micro.
Ecosystems are sustained by the energy flow
through it – starting with plants converting the
suns energy (photosynthesis) then through
the food chain’s trophic levels.
Ecosystem Nutrient Cycle
Dying organisms
LITTER
BIOMASS
(leaf fall)
(living matter)
Soil
Ecosystem Interactions Diagram
Relief
Climate
Soils
Vegetation
Biomes (Global Ecosystems)
4 main biome climates:
Equatorial
(High constant temperatures, High convectional rainfall)
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Tropical Continental
(Seasonal: hot & wet – cooler & dry)
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Hot Desert
(High annual temp & temp range, high daily temp range,
very low rainfall)
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Mediterranean
(moderate annual temp, temp range & rainfall.
Seasonal: hot dry summers, warm wet winters)
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Biomes - Vegetation:
Equatorial
(Luxuriant rainforests with continuous growing seasons.
thin fertile soil layer)
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Tropical Continental
(diverse vegetation from rainforest to savannah
‘xerophytic’ to desert)
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Hot Desert
(sparse vegetation – drought resistant)
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Mediterranean
(Originally woodland & scrub – now deforested for
agricultural development)
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Plate Tectonics
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The theory that the earths crust is made up
of plates that move (continental drift) due to
convection currents in the earths mantle.
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Where plates meet is called a plate margin.
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These margins can be:
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Destructive (plates converging – subduction or
folding/faulting) Violent EQ’s & Volcanoes
Constructive (plates move apart – oceanic ridges)
Gentle Volcanoes & weak EQ’s
Conservative (plates move past each other)
Frequent, sometimes violent EQ’s
Effects of Plate Tectonics
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Plate Tectonics is the cause of most Earthquakes
and Volcanoes.
There is a clear pattern between the distribution
of EQ’s / volcanoes and plate margins.
The formation of many of the world’s landforms
are associated with tectonics e.g. the Himalayas,
the Andes, The Pacific Ring of Fire ….. etc.
Volcanoes
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Volcanoes can be classified several ways:
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By activity (active, dormant, extinct)
Shape/Composition (cone shaped ‘ash & composite’,
shield)
Cone shaped – thick slow moving lava >> steep sided
Shield – runny fast moving lava (basaltic)>> gentle slope
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Hazards from Volcanoes:
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Lava flows, Lahars, Dust & Ash clouds, Nuee ardentes.
Benefits from Volcanoes:
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Fertile soil, geothermal energy, rocks for building,
tourism
Earthquakes
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An earthquake is the vibration of the Earth’s crust caused
by shock waves travelling outwards from sudden movement
deep within the crust.
The source is the focus which is directly below the epicentre
on the surface.
Shockwaves are measured on a seismograph which
measures the magnitude on the Richter scale.
Impacts include Primary (deaths/injury, building collapse,
damage to infrastructure) & Secondary (fire/flood, lack of
services, disease, homeless, unemployment, psychological)
Factors affecting impacts: strength & depth, distance
from epicentre, geology, population density (urbanisation),
time of day or season, remoteness, country wealth/location.
Earthquake – Prediction & Preparation
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It is not possible to predict EQ’s with any
accuracy but there are some signs
(increased tremors, unusual animal
behaviour, gas emissions from ground).
However cities in high risk areas can
prepare by:
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Land use planning & building codes
Improved building design (EQ resistant buildings)
Emergency plans (Civil Defense) and evacuation
procedures.
Public education of how to prepare and what to
do during and after an earthquake.
Case Studies
Volcanoes
 Mt St Helens (1980)
Earthquakes
 Kobe, Japan (1995)