How Volcanoes Froze the Earth (Twice)

Summary

The video explores 'Snowball Earth,' a period of intense glaciation between 716 and 635 million years ago when the planet was covered in ice from the poles to the equator. It explains how volcanic activity, the breakup of the supercontinent Rodinia, and a dimmer sun caused Earth's temperatures to plummet. Geological evidence like dropstones and carbonate rock disappearance supports this theory. Despite the extreme cold, life managed to survive, and eventually, CO2 from volcanoes warmed the Earth again, leading to the emergence of diverse life in the post-glaciation Ediacaran period.

Takeaways

• ❄️ Earth experienced two intense global glaciation events between 716 million and 635 million years ago, known as Snowball Earth.
• 🌍 The world was covered in ice, including the tropics, with temperatures at the poles reaching as low as -130°C.
• 🪨 Evidence of these freezes comes from dropstones and carbonate rocks, which show ice extended from poles to the equator.
• 🔄 The glaciations were likely caused by disruptions to Earth's carbon cycle due to the breakup of the supercontinent Rodinia and the dimmer sun.
• 🌋 Volcanic activity, particularly from the Franklin Large Igneous Province, released sulfur dioxide, further cooling the planet.
• 🌡️ A runaway icehouse effect occurred, where the growing ice reflected more light, causing further cooling and ice expansion.
• 🧊 Life, including early photosynthetic organisms, managed to survive during the ice ages, possibly in areas of thin ice or open water.
• 💨 The glaciation ended when volcanic activity continued to emit CO2, eventually building up enough greenhouse gases to melt the ice.
• 🧬 Animal life, including sponges, survived through the Snowball Earth, leading to a burst of biodiversity in the following Ediacaran period.
• 📅 These glaciations were pivotal events in Earth's history, reshaping its climate, geology, and the evolution of early life.

Q & A

What is Snowball Earth?

Snowball Earth refers to two periods during the Cryogenian, between 716 and 635 million years ago, when the planet was almost completely covered in ice, including the equator.

How did scientists first discover evidence of Snowball Earth?

Scientists found evidence in the form of dropstones, which are rocks carried by glaciers and dropped into ancient ocean sediments. These dropstones have been found on every continent.

Why was it surprising to find evidence of ice at the equator?

It was surprising because the equator is typically warm. Scientists initially thought Earth may have tilted on its side rather than accept that the equatorial oceans froze.

What geological evidence supports the Snowball Earth hypothesis?

In addition to dropstones, scientists found evidence in the form of carbonate rocks. During the periods of glaciation, carbonate rock formation ceased due to the lack of weathering under ice-covered continents.

How did early life survive during Snowball Earth?

Scientists propose several models, including 'Slushball Earth,' where some equatorial areas remained ice-free, or that the ice was thin enough to allow sunlight to penetrate, enabling photosynthetic life to survive.

What role did volcanoes play in the formation of Snowball Earth?

Volcanoes emitted CO2 into the atmosphere, but when the supercontinent Rodinia broke up, it exposed large amounts of basalt rock, which absorbed CO2 rapidly, disrupting Earth's carbon cycle and leading to global cooling.

How did sulfur dioxide contribute to cooling the Earth during this period?

A massive volcanic eruption in the Franklin Large Igneous Province released sulfur dioxide into the atmosphere, which reflected sunlight and cooled the Earth further, contributing to the glaciation.

What is the runaway icehouse effect?

The runaway icehouse effect is a feedback loop where growing ice reflects more sunlight, causing more cooling and ice formation, making the process of freezing the planet unstoppable once ice extended below 30 degrees latitude.

How did Earth eventually thaw after the glaciations?

Volcanoes continued to release CO2 into the atmosphere, but with most rocks covered in ice, CO2 built up over millions of years, eventually warming the planet and melting the ice.

What happened to life on Earth after the ice melted?

After the ice melted, the oceans warmed, and life flourished, particularly during the Ediacaran period, which followed the Cryogenian and saw the emergence of new forms of animal life.