Zestiria vs Berseria map comparison
It is the same part of the world. 


  Following the awakening of the four Empyreans, the next 1,000 years saw a great change in the landscape of the former Holy Midgand Empire. The islands of Northgand, Westgand, Midgand, Eastgand, and Islegand shifted with the movement of tectonic plates, and by the time of Tales of Zestiria, they formed the continent known as Glenwood.  


see Aselia Wiki.
There is also a skit in the game regarding the cause of the changes:


  Eizen: With the four Empyreans revived, the land has awakened.
Eizen: Changes in the earth that once took eons will now happen in a few hundred years.  


Source: Skit "No Eruption...So Far" in Tales of Berseria