I have two questions concerning the Red Year.

1) Who or what caused the Red Year and could it have been preventable?

2) If the Nerevarine was still in Morrowind, could they have stopped it?

I ask these, cause I want to rp as my Nerevarine character in Skyrim.

1. The short answer? The Nerevarine.

2. Nope, since he caused it.

Now I leave it to others to explain the details, since I am really tired.

Red Year was ultimately caused by the Ministry of Truth resuming its original course and landing smack dab on Vivec City, which inadvertently triggered Red Mountains eruption. The Nerevarine was partially responsible, since Lie Rock was only being held up by Vivec, who lost his powers when the Heart of Lorkhan was finally unbound during the course of Morrowinds main quest. The events that lead to its fall is a part of the plot in the novels.

As to the Nerevarine being able to stop it...it was sort of out of his/her scope, though you could make it so he/she helped Dunmeri people to safety on their exodus to Solstheim/Skyrim. Mine was killed during the whole sordid affair, along with the CoC.

This is the path I took. I can't think of any other way the Nerevarine could stop a volcano eruption, once the series of events leading up to it began... that being the fulfillment of the Nerevarine prophecy in the first place.

Thank you for your in depth answer.