The local temperature and gravity fields associated with a subducting plate are investigated using a finite-difference numerical approach. A model that simulates the downgoing slab is used to study various dip angles, different rates of subduction, heat sources and the effect of rising material from the upper surface of the slab. The model assumes a simple descent mechanism that is discussed in terms of the associated earthquake field. The amount of shear-strain heating along the upper surface of the slab is a crucial factor in determining the thermal regime. When melting occurs, rising material from the top of the slab produces high heat flow values at the surface of the Earth on the continental side of the oceanic trench. Also, the results indicate that rising melt will mask the gravity effect of the cold sinking slab at low subduction velocities, and it is the presence of rising melt that is the dominant factor that influences the surface heat flux and gravity field.