[MUSIC]
Hello again.
In this second part, we will look at the mechanism and
the conditions that are important for the Snowball Earth.
There is a mechanism in favor of Snowball Earth, and
some required conditions includes the Fainter sun idea.
And we have a global oxygen event, I've mentioned that in the former part.
And then we have a global ice cover, of course is important.
And then we have talking about weathering and erosion shut down.
I mentioned that a little bit before, but we take it again.
And then the breakup of equatorial supercontinent,
which is about 770 million years before now.
Now if you look at the Faint sun, the presence of glacial deposits in the early
part of earth history is possible, because of a less radiant young sun.
It's only about 80% of the power as it is today.
So in the Fainter sun would have emitted like six percent less radiation in
the Neoproterozoic, and is considered as an important factor for
the cooling conditions.
Another thing is that you probably already know that,
when you go out in the snow, you can get sun in the eyes, so
we call that Albedo, that fresh snow can reflect lots of light, and
especially sunlight hitting a snow covered surface on earth.
You would get the sun rays would go back into space without heating anything.
And this is also a good condition for starting a Snowball Earth,
because there will be starting a little cooling mechanism that will
result in an increase of the earth covers of snow and ice.
Now, in the increase of the earth's covers of snow and ice, would in turn increase
the earth's Albedo, which would result in the positive feedback for cooling.
If you have enough snow and ice accumulate,
then runaway cooling would result.
This positive feedback is facilitated by the equatorial continental distribution.
Which would allow ice to accumulate in regions closer to
the equator where solar radiation is most direct.
Another idea in support for this Snowball Earth creation or event,
is that the person called Williams in 1975 he proposed actually,
that the angle between the Earth's spin axis and
the light like this, it would be much greater in the past.
So it means that it was deeply tilted up to about 54 degrees,
and that has to do at when you go into a cool period.
That means the equatorial regions would have been preferably glaciate and
subject to season temperature fluctuations.
The proposed high obliquity state in Earths early history,
may have been a result from the huge impact that produced the Moon,
in the very early days of the history.
If you look at the oxygen change through time,
the free oxygen formed by the activities bacteria, the oxygen came from
photosynthesis by this bacteria, and they provide the free oxygen to the atmosphere.