Here is the full list of all 12 The Ramp achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Do a 10m boardslide.
Spin 1080 degrees while airborne.
Spin 720 degrees while airborne.
Spin 540 degrees while airborne.
Spin 360 degrees while airborne.
Spin 900 degrees while airborne.
Spin 1260 degrees while airborne.
Crash a 100 times.
Do a 18m boardslide.
Do a 25m boardslide.
Spin 900 degrees while airborne. In any level, except for the Megaramp.
Spin 1080 degrees while airborne. In any level, except for the Megaramp.