Creationers believe in many nonsensical things; a flat, 6,000 year old earth, talking snakes, etc.A global flood would cause what happened with the Himalayas and Mt. Everest (with limestone on top).
With The Cliffs of Dover, the oceans rose over the cliffs and left the chalk fossils from the seafloor on the sides of the cliffs with a volcanic action.
With The Grand Canyon, I agree it was erosion, but it happened in a short amount of time, i.e. not millions of years.
I doubt we will agree on geology as your side believes in uniformitarianism while my side is strictly catastrophism.
There is no belief required in science. Science relies on hypothesis, testing and fact gathering.
BTW, the planet is spherical.