Earth’s outer solid shell is broken into large and small sections called tectonic plates. These plates move slowly relative to one another over geological time. Their interactions help explain earthquakes, volcanoes, mountain ranges and ocean basins.

Continental drift is the idea that continents have changed position over geological time. Alfred Wegener strongly promoted this idea in the early 20th century and proposed that today’s continents were once joined in a large landmass commonly called Pangaea.

An earthquake is the shaking of the ground caused by the sudden release of energy within Earth’s crust or upper mantle. Many earthquakes occur along faults and near tectonic plate boundaries.

A volcano is an opening or volcanic landform through which molten rock, gases and other materials may reach Earth’s surface. Molten rock below the surface is called magma; once it reaches the surface it is called lava.

Mountain building, or orogeny, commonly occurs where tectonic plates interact. Compression, folding, faulting, uplift and volcanic activity can all contribute to the development of mountain landscapes.

Rivers continuously reshape landscapes. Flowing water can erode rock and soil, transport sediment and later deposit that material when the river loses energy.

Glaciers are slowly moving masses of ice. As they move, they can erode, transport and deposit rock material, producing distinctive landscapes.

The term aeolian refers to geological processes involving wind. Wind can remove, transport and deposit fine particles, especially in dry regions where vegetation cover is limited.

Karst landscapes develop mainly where soluble rocks such as limestone are gradually dissolved by slightly acidic water. They often contain unusual surface and underground drainage features.

A drainage system consists of a main river and its tributaries. The land area from which water drains toward the same river system is called a drainage basin. A watershed or drainage divide separates neighbouring drainage basins.

Tropical rainforests occur mainly near the equatorial zone where temperatures remain warm and rainfall is generally abundant. They contain exceptionally rich biological diversity.

Savannas are tropical and subtropical grass-dominated ecosystems with scattered trees and strong seasonal rainfall patterns. Many savannas have distinct wet and dry seasons.

Temperate forests occur mainly in middle latitudes. Many experience distinct seasonal changes and moderate precipitation.

Mediterranean-type ecosystems are associated with climates that generally have hot or warm dry summers and mild wetter winters. Vegetation is often adapted to summer drought and periodic fire.

Large coniferous forests occur across northern North America, Europe and Asia. The extensive northern forest zone is often called the taiga or boreal forest.

Tundra ecosystems occur in extremely cold environments where low temperatures and short growing seasons limit tree growth. Arctic tundra is widespread at high northern latitudes.

A biodiversity hotspot is a region with exceptionally high biological importance that has also experienced extensive habitat loss. Hotspots are important priorities for conservation because many species found within them occur nowhere else.

Forests provide materials and ecological services that support both people and natural systems. Their importance extends far beyond timber production.

Water resources include surface water, groundwater, glaciers and other freshwater stores that can support human societies and ecosystems. Freshwater is essential but unevenly distributed across the world.

Mineral resources are naturally occurring geological materials that can be used economically. They provide raw materials for construction, manufacturing, transport, technology and many other activities.

Energy resources provide power for homes, transport, industries and services. They can be broadly divided into renewable and non-renewable sources according to how quickly they are naturally replenished.

Renewable resources are naturally replenished on timescales that can allow continued human use when they are managed appropriately. Some renewable energy flows, such as sunlight and wind, are continuously available.

Non-renewable resources form so slowly that they cannot be replaced on a human timescale once consumed. Fossil fuels and many mineral resources belong to this category.

Resource conservation means using natural resources carefully so that environmental damage is reduced and resources remain available for future generations.

Desertification is land degradation in dryland regions caused by interacting climatic variations and human activities. It can reduce soil productivity, vegetation cover and the ability of land to support livelihoods.

Soil erosion is the removal and transportation of soil by agents such as water and wind. Erosion is natural, but human activities can greatly accelerate it. Land degradation is a broader decline in the quality and productive capacity of land.

Deforestation is the long-term conversion or removal of forests for other land uses. Causes vary by region and may include agricultural expansion, infrastructure development, logging, mining and settlement.

Wetlands are areas where water strongly influences soil and ecological conditions for all or part of the year. They include marshes, swamps, peatlands and many other water-dominated environments.

Marine ecosystems occur in oceans and seas and include environments ranging from sunlit coastal waters to the dark deep ocean. They support enormous biological diversity and play a major role in Earth’s climate system.

Environmental conservation is the protection, responsible management and restoration of natural environments and resources. Its goal is to maintain healthy ecosystems while supporting human well-being.