Here is the full list of all 20 Alto's Adventure (Windows) achievements worth 1,000 gamerscore.
You played as Izel.
You snowboarded for 30 in-game days (cumulative).
You recovered 1,000 llamas (cumulative).
You played as Paz.
You rode for 100,000m (cumulative).
You snowboarded for seven in-game days (cumulative).
You played as Maya.
You rode for 10,000m (cumulative).
Your board stuck straight up after a crash. Oops!
You played one run with Alto.
You completed the tutorial.
Snowboard for five in-game years (cumulative).
Snowboard for 365 in-game days (cumulative).
Complete all 180 goals.
Recover 10,000 llamas (cumulative).
Recover 100,000 llamas (cumulative).
Ride for 1,000,000m (cumulative).
Ride for 10,000,000m (cumulative).
Play as Felipe.
Play as Tupa.