Final answer:
The largest sphere on Earth is the geosphere, consisting of the inner core, outer core, and mantle. The geosphere interacts with the hydrosphere through erosion, sedimentation, and volcanic activity.
Step-by-step explanation:
The largest sphere on Earth is the geosphere, which is the Earth's solid rock mass, consisting of its inner core, outer core, and mantle. The inner core is a dense, solid sphere made primarily of iron and nickel at very high temperatures and pressures. Surrounding the inner core, the outer core is composed of molten iron and nickel, giving rise to Earth's magnetic field.
The mantle above the outer core is made of semi-solid rock that flows very slowly, contributing to plate tectonics. As for the interactions with the hydrosphere, the geosphere interacts with the hydrosphere in various ways, such as the erosion of rocks by water, the formation of sedimentary layers through deposition, as well as volcanic activity that can also influence the temperature and composition of oceans.