Which of these writers invented the fictional place on Earth called Pellucidar?

A fictional 'Hollow Earth' known as Pellucidar was invented by American writer Edgar Rice Burroughs for a series of action adventure stories. In a crossover event (one where stories combining characters from different series takes place), Tarzan, who was also created by Burroughs, visits Pellucidar. In Burroughs' concept, the Earth is a hollow shell with Pellucidar as the internal surface of its shell.

The stories concerning Pellucidar are ones that initially involve the adventures of mining heir David Innes and his inventor friend Abner Perry, after they use an "iron mole" to burrow 500 miles into the Earth's crust. Later protagonists include indigenous caveman Tanar and additional visitors from the surface world, notably Tarzan, Jason Gridley, and Frederich Wilhelm Eric von Mendeldorf und von Horst. The Pellucidar location is featured in " At the Earth's Core" (1914), "Pellucidar" (1915), "Tanar of Pellucidar" (1929), "Tarzan at the Earth's Core" (1929), "Back to the Stone Age" (1937), "Land of Terror" (1944), and "Savage Pellucidar" (1963).

Edgar Rice Burroughs (September 1875, Chicago, Illinois – March 1950, Encino, California) is best known for his prolific output in the adventure, science fiction, and fantasy genres. Best known for creating the characters Tarzan and John Carter, Burroughs also wrote the "Pellucidar" series, the "Amtor" series, and the "Caspak" trilogy. As a very popular novelist, Burroughs created a folk hero (Tarzan) known around all the world.