Transcript C1b 6.3 the earth`s atmosphere in the past

Earth’s Atmosphere
C1b 6.3
What was the Earth's
atmosphere like in the past?
 John Simmons NatGeos
Do as the
start of
Holiday 2205
Holiday
Welcome to the Holiday 2205 Show! In
2005report
or
tonight’s program we have a special
similar
on time travel through the various
stages of
holidaycools
the Earth’s atmosphere, as the planet
and the atmosphere thickens. program.
No atmosphere detected
4.2 billion
years ago
The Earth – all rock
and volcanoes, no
real atmosphere at
all. The planet is
cooling and
solidifies as heat
radiates into space.
We won’t be
stopping here!
Ox conc 0.000%
4 billion years ago
Volcanic activity is the main attraction on
this stop. Volcanoes release nitrogen,
carbon dioxide, hydrogen and water vapour
to make a fairly dangerous atmosphere. You
won’t be able to leave the capsule without a
suit here, I’m afraid.
Ox conc 0.001%
3.2 billion years ago
Not much to look at but these tiny
photosynthetic bacteria are
everywhere. They give out oxygen as
a waste product and its concentration
in the atmosphere is slowly rising. Still
not safe to walk around – oxygen
levels are dangerously low!
Ox conc 0.21%
600 million years ago
Oxygen is now at about 1% of modern
day values. The photosynthetic bacteria
can now safely get nearer the light and
produce even more oxygen.
 John Simmons
NatGeos
Ox conc 2.1%
400 million years ago
Oxygen concentration now at 10%
of modern day levels. Land plants
start to appear and they produce
even more oxygen. Things are
starting to speed up now on the
oxygen-production front. Some of
the older bacteria are starting to
die out. They evolved in a time with
no oxygen and they are damaged
by the rise in oxygen levels. Next
step London!
Ox conc 21.0%
AD 2006
The city of London and oxygen levels are
stabilised at about 21% of the atmosphere.
The oxygen level hasn’t changed for 200
million years.