Final answer:
The B horizon or subsoil of the soil profile is also known as the 'zone of accumulation' because it's where materials leached from the topsoil accumulate.
Step-by-step explanation:
The layer of the soil profile that is also known as the zone of accumulation is called the B Horizon, also known as the subsoil. During the process of soil formation, certain materials like clay, iron, or calcium carbonate are leached (washed away) from the A horizon or topsoil, and then accumulate in the B horizon. Hence, it's often referred to as the 'zone of accumulation.' The B horizon typically lies beneath the topsoil and above the C horizon or parent material. It may vary in color, but often it is browner and denser than the topsoil.
Learn more about Soil Profile