I was reading around the UESP out of boredom and I came across the article about http://www.uesp.net/wiki/Morrowind:Red_Mountain. Apparently, after the Oblivion Crisis the Ministry of Truth crashes into Vvardenfell, causing Red Mountain to erupt and destroy most of either Vvardenfell or Morrowind proper.
.....What the hell? And what other insane things happened to Tamriel after Oblivion?
There is a thread about the novel:
http://www.gamesas.com/bgsforums/index.php?showtopic=1058959
A lot of the new stuff is discussed there.
Off the top of my head,
Argonia invades Morrowind
A lot of the Dunmer leave Morrowind, lots go to Soulstheim
The Mage's Guild is replaced by a Whisper College (can't remember exact name)
And a lot of other stuff I can't think of right now