(This is a bit faster on TurboWarp) Set your resolution right after you click the green flag. This will take a little while, the larger your resolution the lower quality your generation, and the shorter amount of time that it will take. It works by generating many creekbeds, canyons and craters and forming the terrain around it using distance algorithms.
Note: Do not change the resolution after the Martian Noise generating screen (Orange) disappears. This may cause the renderer to break. This is a new form of 3d/2d terrain generation that I made. Press see inside and export the list called terrain to add this terrain to your Scratch projects. (Note: It is arranged in a grid. Each row/colomn is arranged by tthe width/length of the screen divided by the resolution rounded to the floor.