The balance that Walker had needed when fusing the light and darkness elemental manas was not a huge requirement for the earth and fire. If there was more fire elemental mana he found that the earth would become more liquid. If there was more of the earth elemental mana he found that the earth would slow and have more heat before beginning to become lava.
This was an interesting occurrence that guided him to the realization that he could manipulate the two at the same time in the same way he did water if he had the right balance of elemental manas.
Walker decided to use the space in front of him to continue his experimenting. He isolated a portion of the stones and dirt to gather more and more of the earth elemental mana. This caused it to solidify more and more in to a very condensed circle of stone.
