Preheat the oven to 350°F (175°C). Grease and flour the cake pan.

In a mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add milk, vegetable oil, eggs, and vanilla extract. Mix until smooth.

Pour the batter into the prepared cake pan and bake for 30 minutes or until a toothpick comes out clean.

Allow the cake to cool completely before frosting.

In a mixing bowl, beat the softened butter until creamy.

Gradually add powdered sugar, milk, and vanilla extract. Mix until smooth.

Add green food coloring until desired color is achieved.

Spread the green frosting evenly over the cooled cake.

Place dinosaur cake toppers on top and sprinkle candy rocks around for decoration.