#cryogenian

2025: Great exposure of a stromatolite bioherm in the Trezona Formation (upper Cryogenian, approx 640 Ma) in the Flinders Ranges, South Australia . Sunnies for scale!

scale of 1-10 for geologically significant paleoclimitalogial events?

How do you think algae survived them?

I think slushball is a little more likely than snowball

One of the most significant, since it seems we got "modern-type" (ediacaran to phanerozoic) life out of it; probably would rank it in the top five, but I'd have to think about it more

A frozen world heaves through the void, its bright surface reflecting the light and heat of the Sun back into space. What little surface water there is at the equator barely evaporates, leaving the atmosphere almost free of clouds. Is this one of the moons of the gas giants? No, it's our own Earth during the Cryogenian period, 640 million years ago. Twice during the Cryogenian, these Snowball Earth events caused the entire planet to freeze over for millions of years. Life held on by the skin of its teeth, whether under the ice or in equatorial lakes.

Type: Rock/Fairy

Evolves from Porowink

During a shock ice age, many Porowink were torn from the ground they lived near and incorporated into large icebergs. As these icebergs moved across the globe, the sediment the Porowinks inhabited merged with the Pokémon to form Dropsponges. They’d eventually return to the ocean floor as the ice age ended and the icebergs they lived on melted.

Feel the Rhythm

These centimeter scale sedimentary layers in Virginia are really quite neat. They’re considered “Rhythmites” – sedimentary layers deposted in a repeating pattern. A number of processes can create rhythmites, including tides, annual floods, rainy and dry seasons, and even orbital changes that trigger changes in climate over thousands of years.

Some of the most common rhythmites on earth are found near the ends of glaciers where the conditions create extreme differences between winter and summer. During the winter, any lakes or ponds will commonly freeze over, cutting them off from access to the weather and creating a setting where photosynthetic organisms can still live. In the summer, these lakes will melt and be open to sedimentary input, and they will often get that sediment supplied by the nearby glacier that also melts a little.

Rhythmites like these, where there is likely annual banding produced once a year, receive the special name “Varves”.

These rocks are extra neat because of where they’re found. These sediments in Virginia are found in the Appalachian Mountains today. The sediments in this mountain range were originally deposited hundreds of millions of years ago, all the way back in the Precambrian. During the latter part of the Precambrian, the Proterozoic eon, there are several large glacial advances recorded in sedimentary rocks around the world. One part of the Proterozoic is nicknamed the “Cryogenian” due to the abundance of glacial deposits in that time span. This time period is the likely time when the Earth may have frozen over completely, forming an icy planet nicknamed “Snowball Earth”.

-JBB

Image credit: James St. John https://flic.kr/p/NntMeS

The Cryogenian Ice Age - More than once in history, our planet was covered in ice. It is yet to be known if the Earth was entirely frozen solid, or covered in slush instead.

Read more at Earth Archives. 

As a Winterist id greatly appreciate it