Preheat oven to 350°F
In a small bowl, mix together the chili powder, garlic powder, onion powder, cumin, salt, and pepper.
Heat the oil in a large skillet over medium-high heat. Add the ground turkey to the skillet and sprinkle with the seasoning mix. Stir, to mix well. Cook the ground turkey until browned, approximately 4-5 minutes. Stir the turkey frequently, breaking up the pieces with a wooden spoon or spatula.
Add the tomato sauce and the water to the skillet, stir well to combine. Lower the heat to medium-low, cover and cook about 20 minutes, stirring occasionally.
Build the nachos
Add a layer of tortilla chips to a 9x13 sheet pan or shallow baking dish. Do not overlap the chips.
Sprinkle about ½ the ground turkey over the tortilla chips.
Sprinkle about half of the corn, black beans, black olives and green onions.
Top with about half the cheddar cheese.
Add another layer of tortilla chips, and top with the remaining ground turkey, corn, black beans, black olives, and green onions. Add the remaining cheese.
Reserve the chopped tomatoes and a few green onions to garnish when the nachos come out of the oven.
Bake the nachos for 10 minutes or so, until the cheese is melted. Top with the chopped tomatoes and some extra chopped green onions, if desired.
Serve the loaded sheet pan nachos with sour cream hot sauce on the side.