Apocalyptic Story Ideas

I'm currently about 2/3rd of the way into the Silo Series by Hugh Howey and it's got me in a little bit of an apocalyptic mood. But I definitely have my own ideas about the end of the world. So here are just a few of my apocalyptic ideas:

A Virtual Reality Future

The year is 2230 and man has all but left the Earth - at least mentally. With most of the resources on dry land becoming scarce, and life becoming more miserable, an inventive technologist develops a series of ships (or a better defining term might be arks). These arks are capable of harvesting protein from the oceans and distilling the salt water into fresh. But the ship's inhabitants don't live life like they're on a perpetual cruise. Rather, they live in small pods with their brains tuned into a virtual reality world where life is much rosier.

Unexplained Natural Disaster

For reasons beyond our ability to understand the Earth is spinning faster. Oceans are rising at the equator causing a "water world" type environment, while the oceans slowly recede further north and south.

Nano-Tech Apocalyptic Story

A dormant nano-tech virus has spread throughout the Earth and most humans are completely unaware. After being activated by a mad scientist nine tenths of the worlds population drops dead. Those remaining have been left for a purpose they've yet to learn. Is this man a savior of humanity or the most evil to ever walk the earth. A genius or a monster?

Memory Loss Apocalyptic Story

A virus has rapidly spread across the earth rendering it's victims speechless and with little memory of their past. Many have to learn basic skills over, and many are simply incapable of taking care of themselves, causing mass confusion and hysteria.

Alien Virus Story

The year is 2120. Due to an aggressive alien planted super-virus, Earth's population has dwindled to around 100,000 humans who are immune. Now the aliens have arrived to clear the remaining survivors and inhabit the planet they've just cleared. But a leader has emerged from the 100,000 who believes he just might have a plan for defeating the aliens and securing our planet.