Great Cataclysm

The Great Cataclysm could refer to any number of fictional events that signifies a natural disaster of epic proportions. These are usually world shattering, sometimes even reality-altering events that completely changes the landscape of a known environment. In fictionalized Earth history, such events signify "End of the World" circumstances that can sometimes give way to a post-apocalyptic reality.

DC Universe
The Great Deluge, sometimes referred to as the Great Flood, was a geological catastrophe that occurred some 9,600 years ago. A giant skull-shaped meteor from outer space crashed into the Earth somewhere near the North Sea. The impact was so tremendous that it caused worldwide geological upheaval. Tectonic plates shifted, yielding massive flooding so intense that it caused the entire continent of Atlantis to sink beneath the waves. Though nearly all of Atlantean culture had been wiped away forever, those of the capital city of Poseidonis managed to survive due to the erection of a giant dome that shielded the entire city. It was believed by some, that the destruction of Atlantis was the result of Suula - Goddess of the Sky -- who took offense to the creation of the dome that cut Poseidonis off from the skies above. These Atlanteans managed to eke out a life for themselves, though they could never again leave the safety of their city.

Some Atlanteans however, found an alternative in the priest-mage known as Shalako. Shalako used his magic to protect his followers from the crushing pressure of the ocean depths, and they migrated from Poseidonis and re-established a colony in the ruins of the sister-city Tritonis.

A few short years after the calamity, Atlantis' monarch, King Orin, had his scientists develop a means so that his people could survive underwater, without having to stay within the city. The experiment was a success and the serum transformed the Atlanteans from normal human beings into aquatic amphibians who could survive the ocean depths and draw oxygen from water to breathe.

Earth-AD
The Great Disaster was a cataclysmic event of global proportions which eradicated civilized society on Earth-AD. In fact, the planetary designation, Earth-AD actually stands for "After Disaster". This is not to be confused with the Great Cataclysm—the event that caused the continent of Atlantis to sink beneath the waves.

The story of Earth-AD begins in the future of a parallel dimension. A group of peaceful, humanoid aliens arrived on Earth with the foreknowledge of a coming Great Disaster. Hoping to prevent the Disaster from ever taking place, they established a united defense force known as the Global Peace Agency. One of the GPA's scientists, a human named Professor Myron Forest created a powerful satellite computer system called Brother Eye to help oversee over Earth's affairs. He also became provincial in transforming an army stockroom clerk named Buddy Blank into a one-man army corps. Using the name O.M.A.C., Buddy worked in the interests of the Global Peace Agency in fighting Earth's enemies.

For all of OMAC's efforts, the Great Disaster could not be averted. Very little is known as to the true causes of the Disaster, but what scant evidence exists points towards a mysterious energy wall known only as the Vortex. Earthquakes and tidal waves erupted all across the globe and the nations of Earth found themselves at the mercy of nuclear Armageddon. Shortly before the final bastions of humanity were to fall, a scientist named Doctor Michael Grant invented a mutagenic chemical known as Cortexin. Although he would not survive long enough to witness the fruits of his labor, the Cortexin drug would succeed in carving out its own legacy in the wake of global annihilation.

Earth-51
The Monitors of the Multiverse and Raymond Palmer of New Earth had foreseen a Great Disaster that would befell an Earth. Ray Palmer discovered this after venturing into Earth-51 and learned from notes written by this universe's Ray Palmer of the Morticoccus virus, which potentially precipitated the viral outbreak of catastrophic proportions. In a turn of events, Karate Kid of the Legion of Super-Heroes was infected with Morticoccus virus and became patient zero for the Great Disaster.

After Earth-51 was destroyed and recreated, Monitor Solomon deliberately let the Great Disaster happen in this universe by sending the infected Karate Kid and his friends there. Ray Palmer and Cadmus' scientists failed to prevent the outbreak, as humans de-evolved to develop animal features, and animals developed human features. As a result, civilization fell as humanity panicked and nations accused one another for causing the outbreak, causing a nuclear holocaust across the Earth. Furthermore, the universe fell into the same circumstances as Earth when Earth-51's Green Lantern Hal Jordan attempted to seek help from alien worlds, inadvertently spreading the Morticoccus virus.

Marvel Universe
Some eighteen thousand years before the common era, most of the land masses on Earth connected as a super-continent. This included the lands of Altantis, Lemuria, Mu, Thuria, and Pangea. While Atlantis was ruled by humans, Lemuria and Mu were dominated by the monstrous Deviants - failed genetic experiments cultivated by a race of space gods known as the Celestials. Conflict between the various growing empires was inevitable, and it was only a matter of time before the Deviants of Lemuria waged full-scale war against Atlantis. Although the Atlantean city-state was protected by a great dome, it would not take much for the full company of Lemurian siege weapons to shatter their protective shield. Atlantean king Kamuu, in a last ditch effort to stem the tide of warriors, opened up the city's magma pits to drive them back. While this tactic proved successful, it also had adverse side-effects on the land's continental crust, and the seismic upheavel resulted in Atlantis beginning to sink beneath the waves.

Coinciding with this incident was the arrival of the Second Host of Celestials. The Deviants rebelled against their creators, opening fire upon the great Celestial ship. The Celestial known as Arishem the Judge deemed the denizens of Earth to be unworthy of life, and so he unleashed a cosmic super-weapon that caused a worldwide conflagration. This resulted in a Great Flood that split apart the various continents, causing them to drift, and ultimately sink beneath the waves.

Notes & Trivia

 * The Great Cataclysm has also been referred to as the Great Deluge.


 * In the Marvel Cinematic Universe, there is a cataclysmic event referred to as the "Decimation". This event was precipitated by Thanos using the full power of the Infinity Gauntlet to wipe out half of all life in the galaxy. Even bunnies!

Appearances

 * Atlantis Chronicles 1
 * Atlantis Chronicles 2
 * Eternals 2
 * Sub-Mariner 62
 * Sub-Mariner 63