Transcript Foundation 1 - Discovering Astronomy

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 (4.4-4.6 billion years ago):
hydrogen and helium
• Second atmosphere (4.4-4.0 billion years ago):
water vapor, ammonia, and methane
• Third atmosphere (3.3-4.0 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!
Cyanobacteria helped to
produce oxygen and remove carbon dioxide
Current atmosphere (present
day-3.3 billion years ago):
78% nitrogen and 21% oxygen
Thank you ozone layer!
• Oxygen was important for
producing ozone since ozone
is O3
• 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
Plate
Tectonics
Earth’s surface
is composed of
about twelve
major plates
which slowly
move relative
to one another
Collision
of two plates
separation
forms mountains
The San Andreas Fault
Plate tectonics is driven by convective
currents in Earth’s mantle
Continental
Drifting
Plate tectonics produced
major changes to the
Earth’s surface over the
past 200 million years
Earth in the Future