The temperature of the Earth's mantle varies significantly with depth. The outermost layer of the mantle, known as the lithosphere, is relatively cool and rigid. The temperature at the base of the lithosphere, which is about 100 kilometers (62 miles) below the Earth's surface, is around 1,000 degrees Celsius (1,832 degrees Fahrenheit).

From the base of the lithosphere to a depth of about 670 kilometers (416 miles), the mantle temperature increases gradually with depth. In this region, known as the asthenosphere, the temperature ranges from about 1,000 degrees Celsius to about 1,300 degrees Celsius (1,832 degrees Fahrenheit to 2,372 degrees Fahrenheit).

Below the asthenosphere, the mantle temperature continues to increase more rapidly with depth. At the core-mantle boundary, which is about 2,900 kilometers (1,802 miles) below the Earth's surface, the temperature is estimated to be around 3,700 degrees Celsius (6,692 degrees Fahrenheit).

It is important to note that these temperature values are approximate and can vary depending on the specific region of the mantle and the geological conditions.