autumn equinox
An instant of time in September when the Sun shines directly at the equator. 

biodiversity hotspot
A place (such as the island of Madagascar) where the biodiversity is exceptionally high.

biodiversity
The amount of different species of living organisms living on Earth.

broadleaf forest
A vegetation type of the temperate zone. Characterized by broadleaf trees.

catchment area
The area from which water travels down to a river, lake, or sea.

climate change
The accelerated greenhouse effect caused by human activity. As a result of climate change, the planet's temperature is increasing drastically.

climate diagram
A diagram that displays the average monthly temperature and total monthly precipitation of a certain area.

coniferous forest
A vegetation zone that is dominated by coniferous trees (such as spruce and pine) adapted to cold and snowy winters.

continent
A large, unified mass of land. Earth's continents are North America, South America, Eurasia, Africa, Australia, and Antarctica.

continental climate
A climate type of the temperate zone characterized by large temperature variation between the seasons.

convection rain
A rain type caused by a rising and cooling air mass. 

coordinate grid
A grid that consists of lines of latitude and longitude.

current
An ocean current is a stable flow of water in one of the Earth's oceans.

day
The time it takes for planet Earth to complete one rotation around its axis. 24 hours.

desert
A vegetation zone that receives only very little rain. This results in a barren environment free of vegetation.

endogenous process
A process that occurs inside Earth's crust. E.g. earthquakes.

erosion
The wearing down of rock or soil, caused for example by the wind or flowing water. 

European Union
A political union of European states.

frontal rain
A rain type that is created when fronts of cold and warm air collide with each other.

galaxy
A star system that consists of millions of stars and other celestial bodies.

geographic zone
A horizontal segment of planet Earth where the climatic conditions are similar. The tropical, subtropical, temperate, and frigid zones.

greenhouse effect
A phenomenon where greenhouse gases in the Earth's atmosphere prevent heat radiation from escaping into space. The greenhouse effect keeps the planet's atmosphere warm. 

greenhouse gases
Gases that prevent heat radiation from escaping the atmosphere. E.g. carbon dioxide and methane. 

Greenwich meridian
The longitude of 0 that divides the planet into a Western and Eastern hemisphere. The Greenwich meridian runs through London.

gross domestic product
The dollar value of the total yearly economic production of a certain nation.

hurricane
A tropical storm that occurs in America.

intermediate climate
A climatic region found in areas located between maritime and continental climates.

lava
Molten volcanic rock erupted on to Earth's surface.

light year
The distance that a ray of light travels during a year. Approximately 9,5 billion kilometers. 

lithospheric plate
A unified sheet of Earth's crust.

magma
Molten rock material contained in volcanoes and inside Earth's crust.

map projection
A method where the planet or a part of the planet is projected as a two-dimensional map.

maritime climate
A climate type of the temperate zone characterized by high precipitation and smaller temperature variations between the seasons.

meandering
The twists and turns of a river caused by erosion.

Mediterranean vegetation
A vegetation type found in the subtropical zone. Also known as chaparral.

month
The time it takes for the Moon to complete its orbit around the Earth. Approximately 27 days and 7 hours.

mountain vegetation
A sparse vegetation type found in high elevations.

orographic mountain range
A mountain range that has formed as a result of a collision between two lithospheric plates.

orographic rain
A rain type that is created when temperate, humid air flowing inland from an ocean rises as it collides with a mountain range.

rainforest 
A lush, diverse vegetation type common to the tropical zone characterized by high precipitation and warm temperatures.

savanna
A vegetation type that is also known as tropical grassland. 

solar system
A system that consists of a central star, planets, and other satellites. 

spring equinox
An instant of time in March when the Sun shines directly at the equator. 

stalactite cavern
A cave formed as a result of chemical erosion.

summer solstice
An instant of time in June when the Sun shines directly at the Tropic of Cancer.

temperate grassland
A vegetation type where the soil is rich in nutrients, but the conditions are not suitable for tree growth. E.g. the prairies of the United States.

tide
The rise and fall of sea levels as a result of the gravities of the Moon and the Sun. 

time zone
A vertical segment of planet Earth where the time on the clock is the same. For example, Finland, Greece, and Kenya all belong to the time zone GMT+2.

tornado
A strong, cone-shaped storm that can form alongside thunder clouds.

trade winds
Planetary winds that flow towards the equator.

tsunami
A strong wave caused by activity (such as an earthquake) in the ocean floor.

tundra
A vegetation zone in the frigid geographic zone. Tundra is characterized by the lack of trees.

typhoon
A tropical storm that occurs in East Asia.

U valley
A valley created by glacial erosion. U valleys have gentle slopes and flat valleys.

universe
Space and all the substances and energy that are contained inside it.

V valley
A valley formed as a result of water erosion. V valleys have steep slopes.

weathering
The breaking down of soil or rock as a result of exogenous processes.

winter solstice
An instant of time in December when the Sun shines directly at the Tropic of Capricorn.