I just has a interresting thought, in regards to Gaea's navel's appearing. It maybe possible that the navel is similar to Giant's Claw. For unknown reasons, a big enough geological shift pushed up the opening to where prehistory creatures survived and only slightly evolved. What if Gaea's navel had another colloection of prehistories that survived underground. When FATE made the surrounding walls to El Nido, it unearth that area. And to insure any very little inaction with the people, reform it to it circlar shape.
Whether Leah is related to THE Ayla of keystone timeline is unknown and, I think, unlikely. But most sighs point to her being transported but a gate from 65000000 B.C. and/or from the Reptite dimension(that's if it's anything like the CT ending where human still exist).