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