How Volcanoes Affect the Earth and Influence Evolution


Part 1 of Volcanoes and Our Word

Volcanoes might be known as bringers of death and destruction, but they also demonstrate that our planet is alive. They’re the most obvious indicators of tectonic activity, a phenomenon that has been instrumental in the formation of the Earth’s surface and even life itself. Without volcanoes, we wouldn’t be here today, and our planet would become a lifeless desert world like our neighbour Mars. Understanding how volcanoes affect the Earth is a crucial step towards understanding one of the driving forces behind the course of evolution and perhaps even the origin of life itself.

The oceans and landmasses alike span 17 major tectonic plates sitting atop a rocky shell some 1,793 miles (2,886 km) deep. The mantle, as this layer of the planet is known, is not entirely solid. Instead, it is quite viscous, particularly at deeper levels, effectively acting as a magmatic sea that the crust of the Earth floats upon. An erupting volcano or earthquake is simply the result of the viscosity of the mantle temporarily increasing in areas where the plates meet.

Over millions of years, the gradual collision between plates also creates an orogeny, the process by which mountain ranges, volcanoes and valleys are formed. Over the aeons, this tectonic activity has transformed the face of the Earth countless times over, profoundly influencing the path of evolution and even the appearance of life in the first place.

The Ancient Earth Is Forged by Fire

The Earth during the Late Heavy Bombardment was a truly formidable place. This image show the combination of rampant volcanism and ongoing impact events.

It’s a universal rule in the world of physics that chaos begets order, and at no time in the history of our world was this more evident than during its own formation. Forged by fire, the young Earth was a hot and hellish place with a surface covered by an ocean of magma. Eventually, this ocean cooled and solidified, forming the crust, while the mantle remained relatively viscous. Geological activity continued, however, shaping the continents and mountains; the entire face of the Earth. To this day and far beyond, this geological activity continues to redefine the surface of the world over the aeons.

While the continents were being forged in the fiery hell of the early Earth, rampant volcanism, many orders of magnitude greater than what it is today, was also changing the atmosphere. In a process known as volcanic outgassing, volcanoes were, combined with constant bombardment by asteroids, responsible for replacing the primarily hydrogen-based atmosphere left over from the Earth’s formation. Heavier gasses, such as CO2, produced in great abundance by these ancient volcanoes, created the second atmosphere, pushing lighter gasses like hydrogen further up into the atmosphere so that they were swept away by the solar wind.

Volcanoes continued to play a vital role in the stabilisation of the earth atmosphere for some 2 billion years. They were, and continue to be, an essential part of the carbon cycle too, one of many sequences of events that make our world habitable. Without this smooth cycle, by which carbon is exchanged between the various layers of the Earth’s crust and atmosphere, our world would simply never have been stable enough for life to evolve, let alone survive and thrive for billions of years. The migration of volcanism from primarily submarine environments to terrestrial ones also had the effect of allowing free oxygen to exist in the atmosphere some 2.5 billion years ago, something that we all know is critical to advanced life.

The Warming World and the Richness of Life

Concept art from the movie SnowpiercerConcept art from the movie Snowpiercer

This is what our modern world would look like if we didn’t have any global warming, as illustrated for the Korean science fiction thriller Snowpiercer.

Throughout the Earth’s history, volcanism has been the main producer of CO2, a powerful greenhouse gas that plays a critical role in our climate. Although CO2 is mostly spoken of today as public enemy number one, our world would be a frigid place without it. Average surface temperatures would be around -18 °C (0 °F) compared to today’s 15 °C (59 °F).

Volcanoes basically serve as the fuel needed for the enrichment of biological diversity. They form new lands for life to colonise but, even more importantly, their effect on global warming is yet another way in which they make the Earth habitable. In fact, it was rampant volcanism that caused the Cambrian Explosion, a biological revolution that began some 541 million years ago and saw the formation of most of the animal phyla that survive to this day. We can thank a period of volcanic chaos for the fact that our beautiful world is home to such a variety of plants and animals. In those far-off times, it warmed the Earth and was instrumental in forming the first continents and tidal flats where life evolved, thrived and eventually made it to land.

Although the Cambrian Explosion was really a continuation of the already biologically diverse Ediacaran Period, the world before that was a very different place. 600 million years ago, during the aptly named Cryogenian, glaciers may have even reached equatorial latitudes! Volcanic activity during this time was evidently low but, as the world awoke from its slumber, life took heed and the age of plants and animals began.

The Bringer of Death Changes the Course of Evolution

Volcano in IcelandPixabay

Volcanoes, such as this one in Iceland, might look magnificent, but they can also bring death and destruction on an extinction-level scale.

Mother nature works in mysterious ways. On one hand, she’s incredibly creative; on the other, her wrath is so destructive that it can stop the course of evolution dead in its tracks. Just as volcanoes are and continue to be essential to the very existence of life, they can also be credited with the demise of countless species over the billions of years that life has existed on Earth.

While global warming undoubtedly enriches the diversity of life (the dinosaurs, for example, lived in a much hotter and more CO2-rich world than we do today), it can also be deadly. Evolution is truly unforgiving – it’s a biological arms race that only the strongest can survive. Volcanoes have been instrumental in shifting the course of evolution many times before. Sometimes, volcanic activity has been so rampant, that it warmed the world too much for many forms of life to handle, as was the case with the Palaeocene-Eocene Thermal Maximum extinction event about 55.5 million years ago. Global warming, ultimately caused by volcanism, may have also played a major role in turning much of the world into an arid desert in the Permian-Triassic extinction.

Although life is usually more likely to thrive rather than suffer during periods of global warming, a lack of volcanic activity is usually even deadlier, since it can lead to drastic cooling. Global cooling was likely a major factor in many of the worst mass extinction events the world has ever known, such as the End-Ordovician and Late Devonian.

Exotic Ecosystems and the Origin of Life

Despite the incredibly hostile environment with enormous pressures and temperatures, life appears to thrive around hydrothermal fissures.

We’ve already seen how a world that is geologically dead cannot support life as we know it. The dynamism of planets like Earth is exactly what gives evolution a guiding hand, even if it does, on occasion, go completely berserk. However, volcanoes may be even more than just something life relies on to keep its home world comfortably warm. Volcanoes may be the origin of life itself. The earliest life started as a chemical reaction, and all chemical reactions need a catalyst, and volcanic activity might just have been the catalyst that created the first biogenic compounds.

Although there are several popular theories for the origin of life, the reality remains shrouded in mystery. What is for certain, however, is that volcanism forms an exclusive ecosystem right here on Earth in the form of hydrothermal vents. These volcanic fissures in the deepest ocean trenches are home to incredibly exotic ecosystems that live completely independently of the sun. Unlike many other deep-sea animals, these ecosystems don’t even rely indirectly on the sun. In other words, they are not dependent on any organisms that rely on photosynthesis to exist.

EnceladusNASA

Beneath this granite-hard icy crust on Saturn’s moon Enceladus, there’s expected to be a global ocean. Could it be home to extraterrestrial life like that at the bottom of Earth’s oceans?

The discovery and greater understanding of how hydrothermal vent ecosystems work has greatly enhanced the prospects of finding extraterrestrial life in our own solar system. Vast global oceans, deep beneath their rocky crusts, are expected to exist on several moons, namely Europa, Enceladus and Titan. Could these subterranean oceans, kept liquid by the tidal heating of their host planets, be home to exotic ecosystems like those found at the bottom of the Earth’s oceans? One day, and I suspect quite soon, we’ll know.

Be sure to keep in touch since, next week, I’ll be publishing the second instalment of this two-part series, in which we’ll explore the impact of volcanism on our own human history. I’ll also be publishing a listicle exploring some of the most impressive sites of volcanic activity in the world, places that you can (and really should) actually visit.

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