Multiple problems with terrain including-
Floating blocks/islands
High walls and corners on chunk borders
Entire chunks missing snow or ice
Floating grass
Odd mineshaft generation in mesa biomes
Snow and desert biome generation next to each other
Everything seem too course and needs to be smoothed out a little.
All screenshots taken by myself was done in a single freshly generated world using Minecraft 1.13-pre1 with seed: 1453522920
Environment
Java (64bit) version 8 update 161, Windows 10 PC x86_64
Linked issues
duplicates 3
MC-610
Grass / Flowers / Snow are placed incorrectly in newly created chunks
Resolved
MC-125007
World fails to generate decorations on seemingly random quarter chunks
Reopened
MC-125343
Mineshaft halls generating on top of each other fail to properly generate plank floor, causing rails to float
Open
Most of this looks normal, the rest are duplicates.