Final answer:
The thickness of typical layers of soil for rammed earth walls can vary, but based on the given information, they are often several inches thick.
Step-by-step explanation:
The thickness of typical layers of soil when initially poured into forms for rammed earth walls can vary depending on various factors. However, based on the provided information, it can be inferred that the thickness of these layers is often significant and can be several inches thick. The mentioned process involves using wooden frames to outline the building and filling the gaps with small rocks and dirt, which are tamped down to create a thick, sturdy wall. While no specific measurement is mentioned, it can be assumed that options C) 12 inches or D) 24 inches are more likely to be accurate.