Tectonic Plates' Effect on Evolution

Tectonic Plates' Effect on Evolution

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Physical Changes That Affect Evolution

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The Earth is estimated to be about 4.6 billion years old. There is no doubt that in that very large amount of time, the Earth has undergone some drastic changes. This means that life on Earth has had to accumulate adaptations as well in order to survive. These physical changes to Earth can drive evolution as the species that are on the planet change as the planet itself changes. The changes on Earth can come from internal or external sources and are continuing to this day.

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Continental Drift

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It may feel like the ground that we stand on every day is stationary and solid, but that is not the case. The continents on Earth are divided up into large "plates" that move and float on the liquid-like rock that makes up the mantle of the Earth. These plates are like rafts that move as the convection currents in the mantle move below them. The idea that these plates move is called plate tectonics and the actual movement of the plates can be measured. Some plates move faster than others, but all are moving, albeit at a very slow rate of only a few centimeters, on average, per year.

This movement leads to what scientists call "continental drift". The actual continents move apart and come back together depending on which way the plates on which they are attached are moving. The continents have been all one big landmass at least twice in the history of the Earth. These supercontinents were called Rodinia and Pangaea. Eventually, the continents will come back together again at some point in the future to create a new supercontinent (which is currently dubbed "Pangaea Ultima").

How does continental drift affect evolution? As continents broke apart from Pangaea, species got separated by seas and oceans and speciation occurred. Individuals that were once able to interbreed were reproductively isolated from one another and eventually acquired adaptations that made them incompatible. This drove evolution by creating new species.

Also, as the continents drift, they move into new climates. What was once at the equator may now be near the poles. If species did not adapt to these changes in the weather and temperature, then they would not survive and go extinct. New species would take their place and learn to survive in the new areas.

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Global Climate Change

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While individual continents and their species had to adapt to new climates as they drifted, they also faced a different type of climate change. The Earth has periodically shifted between very cold ice ages across the planet, to extremely hot conditions. These changes are due to various things such as slight changes to our orbit around the sun, changes in ocean currents, and the build-up of greenhouse gases such as carbon dioxide, among other internal sources. No matter the cause, these sudden, or gradual, climate changes force species to adapt and evolve.

Periods of an extreme cold usually result in glaciation, which reduces the sea levels. Anything that lives in an aquatic biome would be affected by this type of climate change. Likewise, rapidly increasing temperatures melt ice caps and raise the sea levels. In fact, periods of extreme cold or extreme heat have often caused very quick mass extinctions of species that could not adapt in time throughout the Geologic Time Scale.

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Volcanic Eruptions

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Although volcanic eruptions that are on the scale that can cause widespread destruction and drive evolution have been few and far between, it is true that they have happened. In fact, one such eruption happened within recorded history in the 1880s. The volcano Krakatau in Indonesia erupted and the amount of ash and debris managed to reduce the global temperature significantly that year by blocking out the Sun. While this had a somewhat little-known effect on evolution, it is hypothesized that if several volcanoes were to erupt in this manner at around the same time, it could cause some serious changes in climate and therefore changes in species.​

It is known that in the early part of the Geologic Time Scale that Earth had a large number of very active volcanoes. While life on Earth was just getting started, these volcanoes could have contributed to the very early speciation and adaptations of species to help create the diversity of life that continued on as time passed.

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Space Debris

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Meteors, asteroids, and other space debris hitting the Earth are actually a pretty common occurrence. However, thanks to our nice and think atmosphere, extremely large pieces of these extraterrestrial chunks of rock usually do not make it to the Earth's surface to cause damage. However, Earth did not always have an atmosphere for the rock to burn up in before making it to the land.

Much like volcanoes, meteorite impacts can severely alter the climate and cause big changes in Earth's species - including mass extinctions. In fact, a very large meteor impact near the Yucatan Peninsula in Mexico is thought to be the cause of the mass extinction that wiped out the dinosaurs at the end of the Mesozoic Era. These impacts can also release ash and dust into the atmosphere and cause large changes in the ​amount of sunlight that reaches the Earth. Not only does that affect global temperatures, but a prolonged period of no sunlight can affect the energy getting to the plants that can undergo photosynthesis. Without energy production by the plants, animals would run out of energy to eat and keep themselves alive.

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Atmospheric Changes

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Earth is the only planet in our Solar System with known life. There are many reasons for this such as we are the only planet with liquid water and the only one with large amounts of oxygen in the atmosphere. Our atmosphere has undergone many changes since the Earth was formed. The most significant change came during what is known as the oxygen revolution. As life began to form on Earth, there was little to no oxygen in the atmosphere. As photosynthesizing organisms became the norm, their waste oxygen lingered in the atmosphere. Eventually, organisms that used oxygen evolved and thrived.

Changes in the atmosphere now, with the addition of many greenhouse gases due to the burning of fossil fuels, are also starting to show some effects on the evolution of species on Earth. The rate at which the global temperature is increasing on a yearly basis does not seem alarming, but it is causing the ice caps to melt and sea levels to rise just as they did during periods of mass extinction in the past.