Place the cake on your cake board in the center of a turntable cake stand. Using your hands, press the crumbs into the side of the cake in a strip around the center of the cake. Create a horizontal strip of crumbs around the center of the side of the cake.
Place your chocolate icing in a piping bag and cut a small tip. Ice the top and bottom of the cake leaving the crumbed area exposed. Smooth out the icing using your offset spatula and a bench scraper to make the sides smooth. Cover the top of your cake in crumbs to resemble dirt. Chill for 30 minutes.
If you would like to add an extra dimension you can use copper or gold petal dust to paint the edges of the fault line. Place a small amount of dust in a small bowl and dilute with a few drops of vodka or other alcohol. Using a paint brush, paint along the edges where the icing meets the crumbs (this will be easier to execute if the cake has been chilled).
To make the decorations, warm the modeling chocolates by kneading them in your hands. Marble some gray, brown and black modeling chocolate together to create a stone color and press into a tombstone mold. (If you do not have a mold you can sculpt the shape using a picture for reference.) Roll long tubes of white modeling chocolate and wrap them around toothpicks. Manipulate the end of the tube to resemble a skeleton hand. Place all your decorations on the top of the cake to create a scary graveyard scene.