Dorothy and the Wizard in Oz (Oz Series, Book 4)

Dorothy and the Wizard in Oz is the fourth book set in the Land of Oz written by L. Frank Baum. It was published on June 18, 1908 and reunites Dorothy Gale with the humbug Wizard from The Wonderful Wizard of Oz.
Dorothy Gale is gladly joining her Uncle Henry in California to visit relatives who live at Hugson's Ranch, after their vacation from Australia in Ozma of Oz. Dorothy meets Hugson's nephew who is her second cousin, Zeb of Hugson's Ranch. Dorothy, Eureka (her cat) and Zeb are riding a buggy being pulled by a cab-horse named Jim when a violent earthquake strikes. A crevice opens in the ground beneath them and they fall deep into the Earth.