The Icy Epoch: Understanding Snowball Earth and Its Impact
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Chapter 1: The Frozen Planet
Around 700 million years ago, the Earth was enveloped in ice, a phenomenon that plays a crucial role in our existence today. Welcome to Part 40 of the History of Earth.
A History of Ice
The icy conditions we refer to were not unprecedented. In fact, about 1.5 billion years earlier, the Huronian Glaciation had encased the Earth in ice for an astonishing 300 million years. While we previously highlighted its relationship with oxygen in Part 24, the real focal point should have been carbon dioxide. When discussing climate, the answer almost always revolves around carbon dioxide.
The Disruption of Balance
In most scenarios, the levels of carbon dioxide in our atmosphere remain stable, a topic we explored in our discussion on the carbon cycle. However, there are moments when this equilibrium is disrupted.
Before the Huronian Glaciation, two significant events occurred: an increase in atmospheric oxygen due to cyanobacteria and the fracturing of Kenorland, one of the earliest supercontinents. The latter event, which we'll delve into further, also relates to the glaciation of around 800 million years ago. So, how does the breakup of a supercontinent trigger glaciation? The answer lies in chemistry.
As these landmasses split apart, volcanic activity intensified along tectonic plate edges, leading to the formation of new basaltic rock. This basalt contains calcium, which reacts with carbon dioxide, forming calcium carbonate, commonly known as limescale. Consequently, carbon is sequestered in the rock, reducing atmospheric carbon dioxide levels and, in turn, lowering global temperatures.
Interestingly, this chemical reaction might offer a solution in our current fight against climate change. By applying crushed basalt rock dust to agricultural land—a process known as enhanced rock weathering—we could potentially sequester up to two billion tonnes of carbon dioxide annually while simultaneously enhancing soil fertility without relying on costly phosphorus fertilizers.
The Breakup of Rodinia
Moving forward to 800 million years ago, the disintegration of the supercontinent Rodinia led to the creation of new basalt, which began absorbing carbon dioxide from the atmosphere. Gradually, the climate cooled enough for ice caps to form at the poles.
As long as Rodinia continued to absorb carbon dioxide, the ice caps expanded across the oceans. However, Rodinia was positioned near the equator, far from the poles. If the ice had formed directly over Rodinia, it could have insulated the newly formed basalt from the atmospheric carbon dioxide, halting the decline in temperatures. Instead, as ice caps spread, Rodinia kept absorbing carbon dioxide.
This process accelerated the cooling as sunlight was reflected back into space—a phenomenon known as the albedo effect—further intensifying the growth of ice caps.
The ice expanded relentlessly. By the time it began to cover Rodinia’s landmass, the situation had spiraled beyond control, resulting in the entire planet becoming encased in ice. The Sturtian glaciation commenced around 720 million years ago and persisted for 60 million years. This event is often referred to as Snowball Earth.
While it may have seemed like an ending, it actually marked the beginning of a transformative era in Earth’s biological evolution.
This article is Part 40 in a series of 50 exploring Earth's history, each covering a 100-million-year timeframe.
Chapter 2: The Snowball Earth Phenomenon
To further understand this fascinating period, watch the following videos:
The first video titled "Snowball Earth or Slushball Earth? 3 Times Earth Was Covered in Ice" offers insightful perspectives on the various phases of ice coverage on our planet.
The second video, "Snowball Earth? | National Geographic," delves deeper into this intriguing period in Earth's history.
If you’re curious to explore further, check out Part 39: SUPERPLUME and Part 41: THAW. Follow me for more articles on the captivating story of our planet.