Any geographical inconsistent with past editions can be chalked up to the spellplague.

From a the fan made wiki: https://forgottenrealms.fandom.com/wiki/Spellplague

The Spellplague affected the landscape, making the ground rumble and heave up and down like the surface of the sea.[4] Curtains of blue flame swept the landscape, reshaping the land by cutting crevasses or lifting and sculpting the plain into hills and ridges.[33] Shards of earth wrenched themselves free and became earthmotes.[34] Such areas changed by the Spellplague came to be known as "changelands".[12][13]