Chapter 6 The Earth

Our Earth is a very special place.

Seeds Of Life

Thank you liquid water!

Not too hot, not too cold!

Composition of the Earth’s primitive atmosphere First atmosphere ( billion years ago): hydrogen and helium Second atmosphere ( billion years ago): water vapor, ammonia, and methane Third atmosphere ( billion years ago): 98% carbon dioxide, 2% water vapor and nitrogen

Volcanic eruptions and impacts from asteroids and comets may have created our primitive atmosphere

Thank you bacteria! Current atmosphere (present day-3.3 billion years ago): 78% nitrogen and 21% oxygen Cyanobacteria helped to produce oxygen and remove carbon dioxide

Thank you ozone layer! Oxygen was important for producing ozone since ozone is O 3 The ozone formed before early life could move from the oceans onto dry land The ozone protects the surface from hazardous UV radiation from the Sun

Chlorofluorocarbons (CFC’) Our Ozone is destroyed by CFCs which are chemicals produced by refrigeration, air conditioners, foam and aerosols They are very efficient at removing ozone Ozone slowly replenishes itself as it is created from sunlight and lightning

Thank you magnetic field! The Earth’s magnetic field shields us from the stream of charged particles from the Sun and cosmic ray particles from space

Aurora

Earth is the only terrestrial planet to have a significant magnetic field! To have a significant magnetic field, the planet must: 1.Be a fast rotator- Earth takes 24 hours to rotate 2.Liquid metallic interior- Earth has outer molten iron core

Earth’s interior consists of a rocky mantle and an iron rich core

Differentiation

Earth’s surface is composed of about twelve major plates which slowly move relative to one another separation Collision of two plates forms mountains Plate Tectonics

The San Andreas Fault

Plate tectonics is driven by convective currents in Earth’s mantle

Plate tectonics produced major changes to the Earth’s surface over the past 200 million years Continental Drifting

Earth in the Future