The lower mantle covers the region of earth from 2891-670 km depth, bounded below by the core and the D"-layer (spoken as D-double-prime) and above by the transition zone. The pressure and temperature ranges cover 23.83 GPa, 1950 K to 135.75 GPa, 3750 K. read more
The lower mantle is the lower liquid portion of the mantle ranging from 400 miles below the surface to about 1,800 miles below the surface. The lower mantle is incredibly large and takes up most of the volume of the earth. Being so deep inside the earth, the temperature and pressure of the lower mantle are extremely high. read more