The Science of Climate Change: Mass Extinctions and What They Tell Us About The Climate Crisis
Over the course of the last few years, climate change has come to the forefront of social justice issues. Some say it’s a hoax, but science has proven time and time again that we are very quickly running out of time to turn back the clock on climate change. While many know about climate change on a surface level, not too many know about climate change on a scientific level. Many would be surprised to know that we are in our sixth mass extinction since Earth’s formation, and scientists have slowly discovered patterns and reasons as to why that might be. Armed with the information that can be discovered from previous mass extinctions, we can more easily identify what needs to be done in order to spearhead a fight against climate change.
To begin our journey, we’re going to take a look at how Earth’s continents were formed. Continents make up 42% of the Earth’s surface. They are typically made of two types of igneous rocks that come from volcanoes: granite, while ocean crust is made of basalt. As a result of plate tectonics, continents have been able to expand over time. Diverging plates form a new crust, and convergent plates go underneath each other. In a way the crust gets recycled again and again (the crust subducts again and again), which is evidenced by the fact that most of the oceanic crust on Earth is less than 200 million years old. Plate tectonics also contributes to the creation of mountains. If a continent is on convergent plates, the continent folds in on itself, which results in mountain ranges like the Himalayas, which formed when Asia and India collided. This process has an important impact on climate and temperature, and might be vital for life on Earth to exist. As subduction increases, the temperature of Earth increases because more energy is being expended, which results in the release of CO2 when volcanoes undergo subduction and erupt. In this sense, plate tectonics are a temperature regulator subduction is a cycle that has continued over a very long period of time.
Next, we have to look at how the carbon cycle affects the climate on a biological and geological level. The release of carbon into the air and any biogeological cycles that form from that are derived fundamentally from the carbon cycle. The carbon cycle is actually two separate cycles, one that is biological and one that is inorganic. The biological process deals with carbon exchanges in living organisms, but the inorganic process deals with carbon exchanges through a geological process. Over time, the Earth has transitioned from a warmer climate during the Cretaceous period to a more icy climate during the Pleistocene period. Overall, changes in the carbon cycle lead to oscillations between warm and cold climates. Once the Ice Age ended, the amount of carbon dioxide increased (and has continued to increase over time), resulting in a warmer climate. An incredibly large amount of Earth’s carbon is stored in rocks. The geological cycle is a longer process than the biological one. When organisms die, they eventually decompose and become part of the sedimentary rock in oceans. The sediment becomes limestone. Carbon can also be found on land through decomposition of animals, or in the form of inorganic carbon, which is a byproduct of weathering of rock. Fossil fuels found underground also contain carbon, so when they are burned, the trapped carbon is released into the atmosphere. The biological cycle involves the capture of carbon through photosynthesis by plants. Humans and other animals eat plants, and carbon is released through cellular respiration and waste.
Historically, the geologic carbon cycle affected the climate when the Himalayan Mountains formed about 50 million years ago. Chemical weathering caused an uptick of carbon being used in the “slow” carbon cycle, resulting in a drop in temperature. Ice sheets formed. During the Pleistocene Epoch (about 2.6 million years ago) the Ice Age occurred.
Finally, it’s important to note some of the other primary factors of mass extinctions like flood basalt volcanism (which contributed to the extinction of the dinosaurs). Flood basalts are areas of Earth that have basaltic rock, and they are created when plume heads have enough magma to erupt. Plumes are in the mantle, and they give rise to hotspot volcanism. An example of a flood basalt is the Siberian Traps. Each time a flood basalt occurs, they cause climate change because greenhouse gases erupt and the temperature of the Earth increases. When that happens, mass extinctions of life like the PT boundary occur. The PT boundary is a mass extinction caused by the Siberian Traps that obliterated 90% of species of Earth. The most important factor in mass extinctions is the greenhouse effect. CO2, water vapor, and methane (CH3), are the most important gases in regards to the greenhouse effect. Carbon dioxide has a long-term impact because it is hard to remove it from the atmosphere. The more greenhouse gasses there are, the higher the planetary temperature, which leads to accelerated climate change, which can further lead to a mass extinction.
There is more than one way to cause a mass extinction. The flood basalts and other forms of geological volcanism are one way, but snowball earths are another. There are two major snowball Earth episodes that scientists tend to focus on. The snowball Earth is when the Earth glaciated and was covered in ice. During the first set of snowballs, oxygen replaced a greenhouse gas and caused the snowball. The Great Oxidation event (cyanobacteria altered the composition of the atmosphere) that occurred soon after gave rise to enough oxygen to change the composition of the atmosphere, reducing the amount of greenhouse gases in the atmosphere rapidly giving rise to glaciation. The second set of snowballs happened before the Cambrian period. Foreign rocks are glacial deposits, and a sign that the Earth was covered in ice. Banded iron formations are thick layers of rusty iron in rock. They are composed of sulfates, oxides, and carbonates. They were produced in Australia between 3.5 and 1.8 billion years ago and they are the consequences of oxidation of oceans due to photosynthesis. Scientific evidence suggests that ice sheets had to have covered the oceans because if that were the case, the ocean would become anoxic, which means they are depleted of oxygen. When waters are anoxic, the amount of iron in them increases. For anoxic water to occur, there must be a limited exchange with the oxygenated atmosphere, and that can occur if the oceans are covered in ice. When the ice melts, the oceans would come into contact with the oxygenated atmosphere producing the aforementioned banded iron formations.
In conclusion, there is a lot of science backing the idea of mass extinctions as the product of climate change. Climate change is a real phenomenon, and the presumption that another mass extinction can’t occur is terrible because the idea that we can lose everything we care about on this planet if we don’t take massive steps now.
Whitney Kuma (she/her) is a high school senior at Westerville North High School and aspiring astrophysicist. Whitney is a member of OHYCJ’s Communications team and enjoys playing tennis in her spare time.
