This is quite an interesting question, and this issue was previously analyzed by Robert M. Hazen in his book “The Story of Earth.”
This book introduces the idea that, over 4.6 billion years, Earth has undergone many changes in its appearance. From a newly formed black planet to a blue one, experiencing ice ages that turned it white, and over time evolving into the image we see today. With the continuous changes of Earth, life gradually began to emerge. The most remarkable aspect of this book is how the author traces the interaction between living and non-living entities through the evolutionary process of the planet. In other words, without life, there would be no Earth as we know it today.
Stage 1: The Black Earth Covered in Basalt
About 4.6 billion years ago, after the formation of the Solar System, various fragments and cosmic dust began to collide continuously and slowly merged together through gravitational forces, forming the initial Earth. However, our planet at that time had a rather terrible environment, with red cracks everywhere, and magma could erupt from the ground at any moment. Along with continuous collisions with asteroids and comets from the outer world, the temperature of the entire Earth at this time exceeded 1,200 degrees Celsius. Essentially, Earth resembled a block of high-temperature, high-pressure mud continuously impacted by external cosmic objects. Geologists metaphorically refer to this initial 500 million years of Earth as a hellish landscape.
Essentially, Earth resembled a block of high-temperature, high-pressure mud…
During this time, the temperature of outer space was much lower than that of Earth, so after each collision, the surface of Earth quickly cooled down and turned black, much like red-hot iron bars dipped in water. Over time, a layer of rock formed on the Earth’s surface, becoming the initial crust of the entire planet. Since the crust was primarily composed of basalt and was black in color, the author described the first 500 million years of Earth’s formation as the Black Earth.
Stage 2: The Blue Earth Covered in Water
Approximately 4.4 to 4.3 billion years ago, the overall temperature of Earth gradually decreased, and steam released from the ground slowly cooled down, with part of it remaining in the atmosphere, forming a water vapor-rich atmosphere. Another part fell to the surface, creating oceans, and Earth began to slowly turn blue with the emergence of liquid water. This marked the second transformation of Earth’s appearance – the Blue Earth.
We often say that water is the source of life, and there are very important reasons for this: water has two outstanding advantages.
This marked the second transformation of Earth’s appearance – the Blue Earth.
First: Water is a super solvent, so the inorganic substances initially present in water had a greater chance of combining to form organic substances, eventually leading to the origin of life.
Second: The density of water in its liquid state is greater than in its solid state; in other words, ice floats on top of liquid water, creating a vital protective layer for life. Just imagine what would happen if ice sank in water? When it gets cold, the surface of the water would freeze, and then the ice would continue to sink, with the water above freezing upon direct contact with the cold air, causing all the water on our planet to freeze, making it incredibly difficult for life to arise and evolve.
Water on Earth has facilitated the emergence of life, and that life in turn continued to transform Earth, with the planet’s appearance closely linked to the organisms that emerged on it.
Stage 3: The Red Earth Oxidized
With the appearance of the first life forms, some more intelligent cells, such as algae, developed the ability to harness solar energy. This was the initial process of photosynthesis. It didn’t take long for these organisms to grow strong enough to influence the planet’s climate.
Oxygen will cause the oxidation of substances.
They absorbed solar energy and fixed carbon from carbon dioxide in the air, releasing oxygen. Oxygen would trigger the oxidation of substances. As a result, these tiny organisms produced a significant amount of oxygen for our planet, leading to dramatic changes across Earth’s surface.
The most abundant element on Earth is iron, and when exposed to high concentrations of oxygen in the atmosphere, it rusts. In a short time, rust covered the entire planet. The Great Oxidation Event lasted from about 3.5 to 1.8 billion years ago. This process transformed Earth into a red globe.
Stage 4: The Snowball Earth
With the abundant development of plants, oxygen continued to be released into the atmosphere from carbon dioxide, while carbon gradually accumulated underground. As the amount of carbon in the atmosphere decreased, the greenhouse effect weakened, leading to a gradual cooling of Earth. As the planet’s temperature dropped, ice began to spread from the poles to the equator.
For millions of years, the entire Earth, except for a few areas around the equator, was covered in ice, a stage referred to by the author as the Snowball Earth. During the Snowball Earth period, nearly all ecosystems were frozen, and a significant amount of life on our planet was wiped out.
For 150 million years, Earth oscillated between these two extreme states at least three times.
However, over time, the molten core of Earth, combined with tectonic plate movements and volcanic eruptions… led to a significant accumulation of carbon dioxide in the atmosphere, and the greenhouse effect began again due to the mass extinction of algae. As Earth warmed, algae began to flourish again, causing carbon dioxide levels to decline, and Earth started to freeze once more. Over the course of 150 million years, Earth oscillated between these two extreme states at least three times.
Stage 5: The Green Earth
After the aforementioned freezing stage, due to the continuous movement of tectonic plates and the recovery process of the ecosystem, Earth’s climate seemed to maintain a rare balance for the next 1.4 billion years. The environment on our planet was neither too hot nor too cold, creating extremely favorable conditions for life to thrive. This led to an explosion of biodiversity, as seen in the Cambrian period around 560 million years ago, where life became increasingly rich. After many cycles, the emergence and evolution of countless organisms formed an ecosystem with plant and animal species as we see today. This period represents the current stage of Earth – the Green Earth.
Therefore, it can be said that without life on our planet, there certainly would not have been the stages of the Red Earth, Snowball Earth, or the Green Earth as we know them today.
