Weaver The Kervanian Chronicles Book 1

Weaver is a novel by Katherine Arandez, about a girl named Kate Merin. She and her two brothers stumble across a portal, and are transported back somewhere around the late Cretaceous period, where they find the Earth inhabited by a race known as Kervanians, originally from a moon on the other side of the universe from Earth. They have a few adventures, and eventually make their way home, only to find that there were greater powers working to send them back to that time than a faulty old portal, and Kate is now caught in the middle of a feud spanning thousands of millenia and several universes.