A vast prehistoric sea that covered what’s now northwestern Oklahoma colored the soil a deep red-brown, and left a few other surprises as well. Like the cedar-flecked canyons in Roman Nose State Park, carved by receding water, or the Alabaster Caverns, the world's largest gypsum-lined cave. Shifting sand dunes tower 40 feet high at Little Sahara State Park and the 4,973-foot-high, lava topped Black Mesa near Kenton was created by an ancient volcano.