Heat oven to 350°F. Coat a 10-cup Bundt pan and a 4-cup glass measuring cup with cooking spray. Prepare cake mix according to package directions.
Pour 2 cups of batter into measuring cup and remaining batter into Bundt pan. Bake Bundt cake 30 minutes and cake in measuring cup 40 to 45 minutes, or until a toothpick inserted in centers comes out clean. Cool cakes 15 minutes before inverting onto a wire rack to cool completely.
Separate 1/4 cup frosting and tint dark orange-red. Tint remaining frosting bright orange. Set aside.
Place Bundt cake on a large platter, leaving a 3- to 4-inch border. Loosely fill middle cavity with a piece of foil crushed into a ball (for support). Place small cake, rounded-side-up, over Bundt cake. With a small serrated knife, cut away rounded sides of Bundt cake to make it look like a mountain. Press cut pieces around base of small cake to fill in the space between the two cakes.
Cut out a 1-1/2-inch-wide hole in the center of smaller cake (save the crumbs to make dirt); then cut a narrow V-shaped wedge from the hole down the length of the cake. This will be where the lava will flow. Discard wedge pieces.
In food processor, process cookies until they form crumbs. Combine 3 tablespoons water and 12 drops green food coloring. Add to cookies and process until crumbs clump together and are tinted green (add more water, if necessary). Sprinkle crumbs around cake base to resemble greenery.
Microwave bright-orange frosting about 10 seconds, until thin enough to flow. Spoon frosting around rim of volcano, letting it flow down sides and along lava path. Pat some cake crumbs onto frosting.
Microwave dark orange-red frosting. Spoon it into crater; let it flow down lava path, overlapping orange frosting. Sprinkle rim of crater with sugar crystals. Sprinkle lava flow with more crystals and edible glitter.