Mantle (geology) Mantle (geology) The mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets (including Earth), a number of asteroids, and some planetary moons have mantles. The Earth's mantle is a layer of silicate rock between the crust and the outer core. Its mass of 4.01 × 10 kg is 67% the mass of the Earth. It has
What Shall We Do Now? What Shall We Do Now? "What Shall We Do Now?" (working title "Backs to the Wall") is a song by Pink Floyd, written by Roger Waters. It was originally intended to be on their 1979 album "The Wall", and appeared in demo versions of "The Wall", but was omitted due to the time restraints of the vinyl format. In its place is a much shorter song, titled "Empty Spaces", which segues directly into "Young Lust". This was a last-minute decision; the album's sleeve notes still feature the song in its track listing, and include its lyrics. The beginning of the