Here is the full list of all 20 Alto's Adventure (Windows) achievements worth 1,000 gamerscore.
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 30 in-game days (cumulative).
Snowboard for seven in-game days (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 10,000m (cumulative).
Ride for 100,000m (cumulative).
Ride for 1,000,000m (cumulative).
Ride for 10,000,000m (cumulative).
Play as Maya.
Play as Paz.
Play as Felipe.
Play as Tupa.
Play as Izel.