What is the lower part of the mantle that extends down to the core called.?

The lower part of the mantle that extends down to the core is known as the "lower mantle." This layer lies beneath the upper mantle and above the outer core, reaching depths of about 660 to 2,900 kilometers (410 to 1,800 miles) below the Earth's surface. It is characterized by high temperatures and pressures, and its composition primarily consists of silicate minerals rich in iron and magnesium.