Snowball Earth – Our Planet’s Icy History
Once upon a time, Earth went through a dramatic freeze, known as “Snowball Earth”. This happened over 600 million years ago. Picture Earth, not as a blue and green globe, but as a white, icy snowball.
The story starts with Earth’s climate gradually cooling. But what caused “Snowball Earth”?
Why Did Earth Freeze?
Things were very different during the Cryogenian period, 600 million years ago. What actually started the deep freeze of Earth? We don’t know 100%. But we do have a couple of ideas.
Some of the triggers might have been the eruption of a supervolcano, less incoming solar radiation, or a decrease in greenhouse gases. Either way, less CO2 meant less warmth. As a result, Earth began to cool.
First, ice sheets formed at the poles. Because ice reflected sunlight, it made the planet even cooler – a climate feedback loop. This caused more ice to form, spreading towards the equator. In every passing second, Earth was getting icier.
The oceans, normally warm and fluid, started to freeze. This disrupted the water cycle and caused a chain reaction again. Less evaporation meant fewer clouds and less trapped heat. Earth was stuck in a deep freeze.
Almost the entire planet was covered in ice. Tropical regions, usually warm, were now icy. Life struggled to survive in these harsh conditions. Over millions of years, the planet remained as “Snowball Earth”.
How Did Earth Turn Back Into the Blue Marble?
All great stories have a twist. This one’s no different. Earth fought back. Likely, volcanoes reawakened, spewing out CO2. Over time, this greenhouse gas built up, trapping heat again.
Gradually, the ice began to melt. The oceans opened up, restarting the water cycle. Life began to thrive again during the Cambrian explosion. The Earth was coming out of its icy prison.
“Snowball Earth” wasn’t just a freeze. It reshaped Earth and possibly even kick-started the evolution of complex life. It’s a story of our planet’s resilience and geologic change.
How Do We Know This Theory is Correct?
What’s the actual evidence that “Snowball Earth” happened? Here are some reasons that support this theory:
- Glacial Deposits: These types of deposits are from ancient glaciers. They suggest areas in low latitudes were once covered in ice.
- Iron-rich Rocks: Known as “Banded Iron Formations,” they formed in oceans under ice. Their presence aligns with the Snowball Earth periods.
- Climate Models: These models show Earth could freeze over under certain conditions. They match what we know about Earth’s past atmosphere and geography.
Together, these pieces form a strong case for the Snowball Earth theory. Each one paints a picture of a planet that once became a giant snowball.
Was It Actually a Slushball?
Maybe, it wasn’t a snowball at all? NASA also acknowledges the “Snowball Earth” hypothesis. They agree that Earth was once almost entirely frozen.
But they looked even deeper into whether tropical oceans were completely ice-covered. So instead of a “Snowball”, NASA suggests it might have been more of a “Slushball” scenario. This is important for early multi-cellular life’s survival during extreme ice ages.
NASA also details climate simulations conducted to study this. For example, it considers factors like solar luminosity, geographic changes, and CO2 levels. Results suggest that complete ocean freezing at lower latitudes was less likely in the coldest periods. In turn, this supports the “Slushball” idea rather than a full “Snowball”.
The Story of Snowball Earth
The “Snowball Earth” theory presents a time when our planet was largely covered in ice. It’s an incredible story, which changed our planet and life on it.
We hope you enjoyed our take on “Snowball Earth”. Do you have any questions? Please let us know in the comments section below and we’ll be happy to get back to you.
