IGCSE Physical Geography Topic Revision Part 2

Ecosystems 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 (leaf fall) (living matter) Decomposition

Ecosystem Interactions Diagram Relief Climate Soils Vegetation

Biomes (Global Ecosystems) 4 main biome climates: Equatorial (High constant temperatures, High convectional rainfall) Tropical Continental (Seasonal: hot & wet – cooler & dry) Hot Desert (High annual temp & temp range, high daily temp range, very low rainfall) Mediterranean (moderate annual temp, temp range & rainfall. Seasonal: hot dry summers, warm wet winters)

Biomes - Vegetation: Equatorial (Luxuriant rainforests with continuous growing seasons. thin fertile soil layer) Tropical Continental (diverse vegetation from rainforest to savannah ‘xerophytic’ to desert) Hot Desert (sparse vegetation – drought resistant) Mediterranean (Originally woodland & scrub – now deforested for agricultural development)

Plate Tectonics The theory that the earths crust is made up of plates that move (continental drift) due to convection currents in the earths mantle. Where plates meet is called a plate margin. These margins can be: 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 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 Volcanoes can be classified several ways: 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 Hazards from Volcanoes: Lava flows, Lahars, Dust & Ash clouds, Nuee ardentes. Benefits from Volcanoes: Fertile soil, geothermal energy, rocks for building, tourism

Earthquakes 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 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: 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)