Terra

Terra, also called "Holy Terra" or, in the most ancient records, "Earth," is the throne world of the Imperium of Man and the original homeworld of Mankind and of the God-Emperor. It is the most sacred and revered place in all the million worlds that comprise the Imperium. Billions of human pilgrims from across the galaxy flock to Terra -- even the barren and contaminated soil that these pious folk tread upon when they reach humanity's homeworld is considered sacred by the faithful of the Imperial Creed.

Terra was plagued by a long age of civil war and anarchy known as the Age of Strife, which only came to an end when the Emperor personally waged the Unification Wars to reunite all the Terran factions under his own enlightened leadership.

The Age of Terra, also called the Age of Progress, is the name given by Imperial scholars to the time from the dawn of Mankind's civilisation before the Imperial Calendar was instituted in the 1st Millennium AD to the founding of the first truly united interstellar human civilisation at some point in the 15th Millennium. Cities such as Atlantys and Nova Yourk are cited as being the most legendary and ancient cities of Old Earth in this time.

For the next 10,000 standard years, during the era called the Dark Age of Technology in Imperial chronologies, Terra served as the capital of Mankind's first galactic civilisation. This period was a Golden Age of scientific advancement when many technological wonders such as the Standard Template Construct (STC) databases and the artificially intelligent Men of Iron were brought into being. Humanity developed the Warp-Drive and spread at an explosive pace across the galaxy, settling thousands of new colony worlds and making first contact with the other intelligent races of the galaxy, including the Eldar and the Orks. This period ended in violence and horror as the Men of Iron revolted against their human masters and the first widespread appearance of human psykers caused the deaths of hundreds of millions of people when these men and women, unprepared to wield their new powers, unleashed the horrors of the Warp upon their unsuspecting fellow citizens.

The final nail in the coffin for the advanced human civilisation of this period came when the gestation of the Chaos God Slaanesh in the Immaterium led to the onset of giant Warp Storms across the galaxy, completely disrupting interstellar travel and communications. Terra itself was consumed by terrible civil wars between nations of techno-barbarians that began in the 27th Millennium and resulted in the use of biological, chemical and thermonuclear weapons of mass destruction that killed billions and forever scarred the sacred landscape of Mankind's homeworld.

Only with the end of the Age of Strife in the 30th Millennium following the birth of Slaanesh and the Fall of the Eldar was sanity restored to the people of Terra when the Emperor of Mankind first rose from deliberate obscurity to launch the Unification Wars that would unite all the nations of Terra beneath his rule and formally establish the Imperium of Man.

The Great Ocean
By the time of the Unification Wars there was only one remaining ocean on Terra -- the so-called Great Ocean which was the ancient Pacific Ocean. The size of the Pacific was vastly smaller than it once was, due to the vaporisation of a massive stretch of the ocean during the nuclear wars that had consumed much of Old Earth in the lost years of the Age of Strife. This missing portion of the Pacific stretched from the Marianas Trench down past Australia and all the way to the frozen continent of Antarctica. The Atlantic Ocean had also been largely vaporised as the great body of water that had once been near Europe was now mostly gone, particularly to the south of what had been the Iberian Peninsula.