Section 2.1

Earth Facts Average Distance from the Sun: 149,597,890 km Travels through space at 107,229 km/h The earth isn't perfectly round, it is slightly fattened at the north and south poles. Scientists have the dated the Earth as being between 4 and 5 billion years old! Earth is mostly iron, oxygen and silicon 70% of the Earth's surface is covered in water The Earth's atmosphere extends out to 10,000 km

The Atmosphere Layers of gases that surround Earth Made up of 78% nitrogen, 21% oxygen and <1% argon, water vapour, carbon dioxide and other gases Acts like a blanket and moderates surface temperatures. Blocks solar radiation (UV light) Made up of the troposphere, stratosphere and mesosphere.

The Lithosphere Earth’s outer layer, the rocky shell of Earth The mountains, ocean floors and rest of Earth’s solid landscape. Ranges from 50 to 150 km in thickness

The Hydrosphere Made up of all the water on Earth: Solid - glaciers Liquid – lakes, oceans, etc and groundwater Gas – clouds, water vapour 97% of Earth’s water is contained in the oceans.

The Biosphere The zone around Earth where life can exist Most can be found on land and in water Some micro-organisms can live several kms below the earth’s surface Can have artificial biospheres