Fossil fuel resources, crucial for our energy needs, were predominantly formed during the Mesozoic Era, specifically the Jurassic and Cretaceous periods, which spanned approximately 201 to 66 million years ago. These valuable resources originated from source rocks, including shales, siltstones, and fine-grained sandstones, deposited in marine environments such as shallow seas and lagoons.

Over millions of years, the organic matter trapped within these rocks underwent a transformation process. Buried deep underground, shielded from decomposition, it experienced immense heat and pressure, eventually breaking down and converting into petroleum and natural gas.

Coal, on the other hand, formed during the Cretaceous Period and peaked around 66 million to 2.6 million years ago, during the Paleogene and Neogene periods of the Cenozoic Era.

During the Jurassic period, which lasted from approximately 201 to 145 million years ago, the Earth’s atmosphere possessed a different chemical composition compared to today. Carbon dioxide (CO2) levels were significantly higher, fostering a warmer climate and promoting abundant plant life. Notably, vast quantities of phytoplankton thrived in the shallow proto-oceans, utilizing sunlight to flourish and sequestering substantial amounts of atmospheric CO2. Upon their demise, phytoplankton settled on the ocean floor, becoming covered by sediment and salt, thus preventing decomposition. This remarkable sequence of events created unique conditions that facilitated the geological storage of CO2, resulting in a vital period of atmospheric cleansing.

Various natural processes contributed to the evolution of our present-day atmosphere. Photosynthesis and the weathering of rocks played essential roles in removing CO2 from the atmosphere, with the latter reacting with the gas to form bicarbonate ions. These gradual mechanisms gradually decreased CO2 levels, regulated methane, and accumulated oxygen, ultimately supporting the emergence of complex life forms, including our own.

Geological evidence and modeling studies suggest that the Jurassic atmosphere contained CO2 levels significantly higher than today, likely two or three times greater. Additionally, atmospheric oxygen (O2) levels were probably somewhat higher, ranging from 15-25 percent, in contrast to the present-day 21 percent. Other gases, such as nitrogen (N2), argon (Ar), and trace gases, likely existed in proportions similar to those observed today.

Regrettably, human activities have been releasing the long-contained CO2 stored in geological formations, leading to an atmosphere that increasingly resembles conditions from millions of years ago. In essence, we are conducting a real-scale and highly consequential experiment, effectively transforming our atmosphere to resemble that of the Mesozoic Era within a few short decades.