Earth "too soft", Yisou Network, Blog Translation

The middle of our planet may be wetter and squishier than previously thought. New research shows that extreme heat and pressure deep inside Earth slows the speed of sound waves traveling through the lower mantle, indicating that part of Earth's interior is softer than expected. The lower mantle lies beneath the hard outer shell (the layer we stand on) and above the stiffer upper mantle and liquid outer core. It extends from about 400 to 1,800 miles (660 to 2,900 kilometers) below Earth's surface.