Earth

Continents

The Earth - Our living jewel

The internal structure of the Earth

Crust: 5 to 70 km Solid rock (granite, basalt)

Solid The outermost layer, where we live.

Mantle: ~2,900 km Solid but ductile rock (peridotite) Solid but slowly flowing (plastic)

Responsible for tectonic movements

Outer core: ~2,200 km Molten iron and nickel Liquid Generates the Earth’s magnetic field.

Inner core: ~1,200 km Solid Iron and nickel Solid Very hot, very dense

Biosphere and biomes

Tectonics and geological phenomena

Key figures

Earth is the only known planet with liquid water.
Rotation: 24 hours → day/night
Revolution: 365.25 days → year
71% of the surface is covered with water, 29% with land

The surface of the Earth

Atmosphere and climate

Layers: troposphere, stratosphere, mesosphere, thermosphere
Phenomena: winds, rain, storms, atmospheric currents
Greenhouse effect and the role of climate in life

Hydrosphere

Freshwater: rivers, lakes, glaciers, groundwater
Saltwater: oceans, seas, coastal areas
Water cycle: evaporation, condensation, precipitation, infiltration

Human interactions with the Earth

Urbanisation, agriculture, exploitation of natural resources
Pollution, climate change, deforestation
Conservation and protection of the environment

The terrestrial biomes

Climate: Subarctic and polar. Very cold, permafrost (soil characteristic of the tundra) -> soils that only thaw on the surface. Long winters. Temperatures between 0 and 10°C.

Dominant vegetation: Mosses, lichens, herbaceous plants (grasses, mosses), liverworts.

Typical fauna: Polar bears, Arctic foxes and Arctic hares.

Climate: Equatorial climate characterised by two seasons: wet and dry. Constant temperature between 25°C and 30°C.

Dominant vegetation: Very dense and tall (30 to 60 m), evergreen and semi-deciduous trees. Dense forests with closed canopy. Epiphytes (orchids, ferns, etc.)

Typical fauna: Great apes, big cats, sloths, amphibians (tropical frogs), reptiles (snakes, lizards, etc.), birds (toucans, parrots, etc.)

Climate: Dry season and rainy season. High temperatures throughout the year, grasses, trees, shrubs.

Dominant vegetation: Acacias, baobabs, eucalyptus. Tall grasses (up to 2 metres), adaptations to drought (deep roots, thick fire-resistant bark, etc.).

Typical fauna: Large herbivores (zebras, antelopes, giraffes, elephants, etc.), carnivores (lions, cheetahs, hyenas, etc.), birds (ostriches, vultures, etc.)

Climate: Very arid, hot during the day, cold at night, very low rainfall. Dry air, strong winds.

Dominant vegetation: Succulents such as cacti, deep-rooted plants (acacias). Poor, dry soil, little organic matter, severe wind erosion.

Typical fauna: mammals (camels, fennec foxes, etc.), reptiles (snakes, lizards), birds (vultures, eagles), insects.

Climate: Long, cold, snowy winters and short summers. Average annual temperatures below 0°C.

Dominant vegetation: Conifers (fir, spruce, pine, larch); deciduous trees (birch, willow, poplar)

Typical fauna: Bears, moose, lynx, wolves, beavers, caribou.

Climate: Hot summers, long cold winters, light to moderate rainfall. Temperatures range from -40°C in winter to +38°C in summer

Dominant vegetation: Annual herbaceous plants -> poaceae (= grasses), flowering plants (angiosperms)

Fertile soils used for agriculture

Typical fauna: Bison, wolves, rodents, antelopes, deer, grasshoppers, butterflies, etc.

Climate: Moderate rainfall, mild and wet winters, fairly warm summers. Temperatures between 10°C and 20°C.

Two distinct climate-related biomes:

Temperate evergreen forests -> coniferous forests

Temperate deciduous forests

Dominant vegetation: Deciduous trees (oak, beech, poplar, maple), sometimes conifers

Typical fauna: Deer, squirrels, foxes, chamois, roe deer, etc.

Freshwater biomes

Saltwater biomes

Continents and their major ecosystems

Savannahs (Serengeti, Kruger)

Tropical forests (Congo Basin)

Deserts (Sahara, Namib)

Wetlands (Okavango Delta, Nile)

Tropical and equatorial forests (Indonesia, Malaysia)

Himalayan mountains

Coral reefs (Coral Triangle)

Steppes (Mongolia, Kazakhstan)

Siberian taiga and tundra

Great Barrier Reef

Rainforests (Papua, northern Australia)

Australian deserts

Island ecosystems

Amazon rainforest

Andes

Pantanal

Cerrado and Caatinga

Peaceful coastal zones

Temperate forests (Canada, USA)

Great Plains

Rocky Mountains

Wetlands (Everglades, bayous)

Deserts (Sonora, Mojave)

Boreal and temperate forests

Alps and Carpathians

Wetlands (Camargue, Baltic lagoons)

Semi-natural agricultural areas

The problems faced by the Earth

Climate change

Main cause:

increase in greenhouse gases (CO₂, methane) due to human activities (industry, transport, deforestation).

Consequences:

❌ Global warming (+1.1°C since the pre-industrial era).
❌ Accelerated melting of glaciers and polar ice caps.
❌ Rising sea levels.
❌ Extreme weather events (hurricanes, droughts, floods).
❌ Disruption of ecosystems and loss of biodiversity.

Deforestation

Main cause:

Massive destruction of tropical and boreal forests and other wooded biomes.

‼️ Causes: intensive agriculture, logging, urbanisation.

‼️ Effects: reduction in the Earth’s capacity to store carbon, soil erosion, loss of habitats for many species.

Pollution

❌ Air, water and soil pollution.
❌ Contamination by plastics, pesticides, heavy metals.
❌ Impact on human health and wildlife.

Loss of biodiversity

❌ Rapid extinction of animal and plant species.
❌ Imbalances in food chains.
❌ Risk of ecosystem collapse.

Geological hazards

❌ Earthquakes: can cause destruction and loss of life, especially in densely populated areas.
❌ Volcanic eruptions: can cause major local damage and temporary climatic disruption.
❌ Landslides and tsunamis: often dramatic consequences in coastal and mountainous areas.