My take on how Korra survived around 220 odd years

Okay, so we know roughly that Korra was likely mid to late 40s by the start of the cataclysm, if the flashbacks from the trailer are anything to go by. She was in Republic City with the Spirit Portal behind her.

My theory is that the third Spirit Portal, owing to its unnatural formation, started causing massive disturbance in the world's natural order. So much so that natural disasters became more common. Republic City is situated right on a coastline, so it'd be a prime target for natural disasters, as it'd have earthquakes, tsunamis, tornadoes. So Korra, not really have any other options, tried to do what Wan did and close the portals again. Or at least, tried to close the newest one.

This then backfired, causing a massive surge in spiritual energy, which basically started to cause the events occurring in Republic City to become global crises. The planet got hotter, sea levels dropped creating more deserts, tornadoes mixed with spirit energy tore the land apart. So, Korra being as Korra is, she tried to close the others, which only made matters worse. The Krew coming to the conclusion that the only way to sort the natural disasters was to close the third portal, Korra tried to brute force it, attempting to destroy the spirit portal with energy bending. Which *sort of* worked. It basically caused a reverse effect of the explosion that created it, not destroying the portal, but at the very least closing it, and Korra, being right in the middle of all that energy, gained some kind of limited temporal immortality, akin to what Earth Benders can achieve. So, instead of dying in the explosion, she simply walked out of it. With the third portal finally dormant, the natural disasters started to ease, and all seemed well. But as time went on, the portal began to reopen itself, but by this time, Korra was effectively alone. Mako, Bolin and Asami would have likely died of natural causes, by now, and the world had already begun to view her as the cause of the chaos. At most, she would likely have had allies in the Air Nation, with Jinora, Iki, Meelo and the now grown Rowan all trying to pitch in to help limit the damage.

But it eventually got way too big for any one to handle. And by the time Korra died, likely only recently, she had no real answer on how to close the third portal as it was nearing a breaking point. Knowing Korra, she likely died fighting, working with what remained of the White Lotus and Tenzin's descendants to keep people safe, but ultimately failing, giving way to allow Pavi to be born.