I discovered what an awesome thing reference is. Can't draw cliffs, mountains and trees? Get reference! Google image search is your friend.

This is a scene from Shax's fic Project Mobitropolis. It is as follows:

Sonic had his own difficulties, though. With one dangling hand, he held onto Tails. With the other, he held onto the backpack, which had left the fox's grip at the time of his falling, and which Sonic had managed to grab simultaniously with the rescue of his companion. He stared through the space between bag and fox, down a half-kilometre of sheer drop. At the base of it, he saw the railroad that he had spotted from the Tornado. It looked just as distant from this altitude.
"Help me, Sonic!" Tails pleaded.
Sonic tried to hoist them up, but their combined weight was too heavy to manage. His own centre of gravity shifted precariously and threatened to hurl both of them (and baggie makes three) into the rocky abyss.
"Can't you fly?" Sonic demanded.
"I can't!" Tails replied urgently, "I have to get a boost! It doesn't work unless I jump!"
There was a mechanical noise far below them. A black train was running along the track, now, its carriages distantly thudding and screeching as its smoke filled the canyon. Sonic looked from bag to fox, sweat pouring down his forehead, along his snout, and dripping like rain into infinity.
Three times he almost dropped the bag, but hesitated each time. Losing the emeralds meant losing his quest. The prince and his robots would surely locate the bag before Sonic had a hope of finding his way to the bottom of this canyon. Again, he tried to hoist up the bag, but the effort only shifted his body, creating a rain of little stones that fell from the cliff beneath him and into space. The knowledge of what was happening instilled terror in the young fox, who began to wail helplessly, and he began grappling and clawing at Sonic's arm.
Sonic was wailing too, now, the sheer helplessness of the situation hitting home. Death to Tails or death to Mobitropolis, and if he waited too long to decide, death to all of them at once.

Read the fic here: [link]