Chapter 1: The Beginnings

Author: Merticaru Dorin Nicolae

In this exploration of Earth’s history, I initially intended to delve straight into water and its crucial role as the foundation for life. However, I realized that a comprehensive understanding of these descriptions requires a foundational knowledge of the planet's early stages. Thus, I present a structured timeline of Earth’s evolutionary "steps." While you may view it through your own lens of time, my primary goal is to outline the significant "periods" and "steps" of our planet's journey.

When Earth was a molten lava ocean, researchers identified this as the "Red Earth" phase. Following its cooling—after the Moon’s formation—it transitioned into what is known as "Black Earth," characterized by the dominant black hue of the newly formed rocks.

As we recount this evolutionary process, it's essential to note that evidence of Earth's age began to emerge following this cooling phase. This evidence was confirmed through studies of asteroids and meteorites, which preserved their original ages due to the absence of melting caused by catastrophic collisions.

The groundwork for these discoveries was laid by James Hutton, often referred to as the father of geology. He challenged the established belief of a mere few thousand years of Earth's existence—an idea propagated by religious interpretations (notably from Christianity, which I identify with). Hutton proposed that millions of years were necessary for the geological processes he observed, particularly sedimentation.

As we continue our narrative, Lord Kelvin, an expert in thermodynamics, was the first to describe Earth's "last" liquid state through direct deductions from volcanic phenomena. Kelvin estimated that Earth was a liquid planet that had been steadily cooling, calculating its minimum age to be 20 million years. However, he was unaware of one of Earth’s primary thermal sources: radioactivity from elements like uranium and potassium, which has kept our planet warm to this day, leading to significant errors in his calculations.

Furthermore, the abundance of these radioactive elements in proto-Earth allowed precise dating of certain rocks using their characteristic "half-life." This concept, vital in various scientific fields like pharmacology, biology, and geology, refers to the time required for half of the radioactive nuclei in a sample to decay into stable compounds.

The initial application of this technique was conducted by Arthur Holmes, who determined that Earth is approximately 4.5 billion years old—a figure still widely accepted today based on data collected from diverse rock samples throughout Earth's history. This marks the beginning of discussions about Earth's "ancient times."

The first 100 million years following these events is referred to as the "Age of Water," during which at least 90% of Earth's surface was submerged. This era is aptly named "Blue Earth." Evidence supporting this claim comes from rocks found in southern Africa, dated to about 3.5 billion years ago, which exhibited characteristics indicating they formed under water.

During this period, Earth's atmosphere was far from conducive to life. From the appearance of water until at least 3.5 billion years ago, the atmosphere was a toxic mix of carbon dioxide and other harmful gases, creating a devastating greenhouse effect with exceedingly high temperatures, comparable to present-day Venus.

It is noteworthy that with the arrival of water, Earth experienced massive storms, leading to incessant rainfall for millions of years. The energy from these storms was fueled by high temperatures, the immense gravitational pull of a close Moon, and Earth's rapid rotation.

In this ocean, volcanoes gradually emerged, contributing to the expansion of land through volcanic islands. Over time, the oceans, rich in iron, imparted a green-olive hue to the planet's surface (hence why it could be referred to as "Green Earth").

As time progressed, the thick layer of carbon dioxide generated immense pressures and extremely high temperatures (exceeding 200 degrees Celsius), causing the planet to take on a red hue, thus becoming "Red Earth." This intense, toxic ocean environment fostered the early evolution of life, likely giving rise to extremophiles, which played a crucial role in the development of life over at least 500 million years during the so-called "chemical soup" period when the first single-celled organisms emerged.

Evidence of this early life includes stromatolites, structures formed by colonies of single-celled organisms, dated to about 3.5 billion years ago. These organisms utilized photosynthesis to convert carbon dioxide into glucose, releasing oxygen and water in the process.

However, dramatic changes were imminent. Volcanic activity led to the formation of granite, marking a new geological era around 3.4 billion years ago, referred to by geologists as "Gray Earth." The first continental forms of Earth’s existence, composed of granite, began to emerge in South Africa.

Thus, after one billion years, Earth began to function geologically in a manner similar to today. The crust started to show fissures resembling today’s tectonic plates, albeit on a much smaller scale. Water seeped into the magma beneath the crust, leading to the formation of granite.

This initiated the process of forming continents with a geological structure akin to what we recognize today, a process that continued for another billion years, culminating around 2.5 billion years ago. It is said that the era of oceanic dominance had ended, although two-thirds of Earth's surface remains water today.

The emergence of the first proto-continents from granite not only altered Earth's appearance but also marked significant biological developments. At this time, life was primarily represented by extremophiles, which thrived in the newly formed continental environments.

These early life forms began producing oxygen, which would later support the development of more complex organisms. The microbial life present in the oceans formed the basis of the planet’s microbiome, which would eventually be found in all subsequent life forms.

As oxygen levels rose, it initially dissolved in the oceans, oxidizing existing iron deposits. This transformation led to a shift from green to blue waters, thus giving rise to the designation "Blue Planet." The atmosphere gradually cleared of carbon dioxide and became saturated with oxygen, setting the stage for the life forms we recognize today.

The time came, approximately 1.5 billion years ago, when Earth's atmosphere was rich in oxygen, days were longer (16 hours), and the Moon had moved away to about one-third of its current distance. This led to tectonic realignments of the continents, resulting in a supercontinent known as "Rodinia."

Rodinia's formation caused significant changes in ocean currents and a surge in volcanic activity, which ultimately triggered what is known as the "Great Freeze." Changes in ocean currents led to increased precipitation, and the high CO2 levels in the atmosphere, coupled with volcanic gases, resulted in massive acid rains.

This combination led to a significant reduction in CO2 levels, which decreased the greenhouse effect and initiated a cooling period. This epoch is referred to as "Snowball Earth," characterized by a global ice cover.

During this time, life continued to evolve, primarily through extremophiles and unicellular organisms. Photosynthesizing organisms adapted and diversified, thriving even in melting regions due to massive volcanic activity.

As the immense weight of the ice caused uneven pressure on the crust, supervolcanoes emerged, further accelerating tectonic movements, leading to the fragmentation of Rodinia into distinct tectonic plates. The released CO2 from super-eruptions contributed to a warming atmosphere, resulting in gradual melting.

Around 550 million years ago, Rodinia split into the continents we recognize today, and life began to flourish once more, leading to what is known as the "Cambrian Explosion." Oceans transformed into true "cradles of life," with algae rapidly proliferating and multicellular organisms—especially worms, sponges, and corals—becoming increasingly prominent.

During this time, life exhibited an astonishing diversity, although predominantly aquatic, with land remaining largely uninhabited. The evolutionary experiments of life laid the groundwork for all future forms of life.

The elevated oxygen levels in the oceans spurred this explosion of life, which in turn altered atmospheric conditions. Over the next 100 million years, oxygen levels reached those of today, allowing for the formation of the ozone layer, providing a protective barrier against solar radiation.

The reduced intensity of radiation allowed life to transition onto land around 400 million years ago. This shift was primarily facilitated by plant forms, fungi, and algae, which evolved to adapt to terrestrial environments.

Significantly, around 460 million years ago, the land saw the emergence of a new continent named Gondwana. At this time, temperatures were comparatively mild, but the ozone layer was still insufficient to shield terrestrial life from harmful solar radiation.

By around 370 million years ago, the ozone layer reached optimal thickness, enabling a surge of life on land. Algae began to populate coastal areas, gradually evolving into the plants of the Carboniferous period, which would dominate for the next 60 million years.

This era left behind abundant evidence in the form of coal deposits and marked the delineation of major oil and gas reserves found on Earth today. During this period, the first ancestors of reptiles appeared, moving away from aquatic egg-laying to nesting on land.

Following a massive volcanic eruption in present-day Siberia, which lasted for a million years, the Permian extinction occurred about 250 million years ago. Toxic gas clouds spread across the globe, blocking sunlight and raising CO2 and methane levels, leading to extreme atmospheric heating and the extinction of over 95% of existing life forms.

The rise of "Pink Earth" was temporary and localized, impacting primarily the oceans. Eventually, a new supercontinent named "Pangaea" emerged, and conditions gradually became favorable for life once again.

As temperatures stabilized and vegetation reclaimed the land, the age of reptiles began, heralding the dominance of dinosaurs. Around 180 to 190 million years ago, volcanic activity disrupted this supercontinent, forming the Tethys Sea and initiating the separation of landmasses into the continents we recognize today.

With volcanic activity persisting, global warming led to CO2 levels exceeding 40% of the atmosphere's composition, supporting the growth of tropical forests. Approximately 100 million years ago, massive volcanic activities left deposits of diamonds, evidence of the dynamic geological processes occurring at that time.

However, about 65 million years ago, a catastrophic asteroid impact triggered a mass extinction event that wiped out the dinosaurs and 75% of all other life forms. Geological layers from this period, rich in iridium—a rare element on Earth but common in asteroids—attest to this event.

This impact, coupled with volcanic activity, unleashed an extinction force of unprecedented scale. Yet, life slowly began to recover over the next 50 million years, giving rise to mammals and eventually humans.

As the continents shifted into their current configurations, the emergence of early human ancestors occurred between 2 to 4 million years ago, coinciding with the onset of glaciation caused by the joining of North and South America.

This union disrupted ocean currents, leading to climatic phenomena associated with ice ages. The last 70 to 80,000 years have been marked by human development, leading to significant cultural and technological advancements.

What conclusions can we draw?

Earth, as we know it today, remains susceptible to new disasters and extinctions. It is a planet like any other, subject to external calamities. Yet, through it all, life persists, adapting and evolving despite the monumental changes. This resilience illustrates the ongoing cycle of life and evolution.

In a sense, this is the essence of our universe—time and evolution through life.

With love and understanding,

Merticaru Dorin Nicolae