Snow Ball Earth

Snow Ball Earth
2012
Really an Ice Age
Pere Frontera Pericàs
Snow Ball Earth
2012
Really an Ice Age
Pere Frontera Pericàs

SECTION A
What’s Snowball Earth?
Definition
Snow Ball Earth is a term to describe the period when it happen the coldest global climate in the Earth. During this period, at the end of the Proterozoic, our planet was completely covered with ice (from pole to pole,included the equator).
Impacts of superficial Snow
During the Snow Ball Earth, the Earth was covered by snow and ice. It was an important factor during the Snow Ball Earth. Also, the ice helped us to know about this glacial period. But how?
There’s a process, called Albedo, which was very important for the persistence of Snow Ball Earth. The Albedo is the term we use to define how much solarradiation is reflected (returned back to space) in the Earth. No all the materials reflect the same amount of solar radiation. Generally, the white objects reflect more solar radiation than other colors objects.
For example, the typical Albedo values for natural surfaces are between the 30 and 40% of solar radiation reflected. But for white surfaces, as snow, the Albedo values are between the 75and 95% of solar radiation reflected.
So, if the Earth was covered by ice and snow (white materials), the most part of the solar radiation was returned back to space. And if the radiation was back to space, the Earth would be colder. And when something is very cold, it normally freezes.
So, the Earth was frozen. It was covered by ice. And this ice allows us to know about the Snow Ball Earth.But how, if the ice is melted?
Well, the big concentrations of ice form glaciers. During the glaciation, the glaciers were in constant movement (the glacial flowage). This process produced sedimentary deposits, as moraines (accumulation of boulders, stones, or other debris carried and deposited by a glacier), for example. Those sedimentary deposits have endured in time and we can find them today.And they’re evidences of the Snow Ball Earth glaciation.
We can say, without dude, that the ice helped the persistence of Snow Ball Earth. But it also helped us for know more about the coldest global climate ever. Maybe, without the ice, we won’t know the Snow Ball Earth.

SECTION B
When did Snow Ball Earth occur?
Enumerating about important aspects
-There were 3 Snow Ball Earth periods:Makganyene, Sturtian and Marinoan (in chronological order).
-The Marinoan is the youngest Snow Ball Earth. It ended 635 million years ago, near the end of the Proterozoic.
-We haven’t found any suitable material from the beginning of the Marinoan, so we don’t know well when this period started.
-We think the Marinoan Snow Ball Earth lasted for 6-12 million years, but it isn’t very reliable.-We can find sedimentary deposits of this period in all the continents.
-Also, there’re sedimentary deposits of the Sturtian period in all the continents.
-The Sturtian period started later than 746 million years ago, and it finished around 710 million years ago (but it’s not directly dated).
-In South Australia there’re glacial sedimentary deposits from the Sturtian period, and there we canfind large sedimentary iron deposits.
-The Makganyene glaciation occurred 2200 million years ago (approximately).
- The distribution of glacial deposits from this period isn’t regular in the present. We can find them principally in South Africa.
-There’re paleomagnetic evidences (Earth magnetic field “fossilized” in rock) about this period.
-The Makganyene is related to the rise of molecularoxygen in the Earth’s atmosphere. They occurred near in time.
-There’re glacial sedimentary deposits older than Makganyene in central North America, northern Europe and South Africa. They represent the most ancient Snow Ball Earth.
-The evidences of this glaciation are inconclusive, so we can’t be sure about if it’s a Snow Ball Earth.
-Also, they’re more inconclusive evidences about the most...