Lithosphere for silicate rocks, and formula_4 is the age of the given part of the lithosphere. The age is often equal to L/V, where L is the distance from the spreading centre of mid-oceanic ridge, and V is velocity of the lithospheric plate. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years but after this becomes increasingly denser than asthenosphere. This is because the chemically differentiated oceanic crust is lighter than asthenosphere, but thermal contraction of the mantle lithosphere makes it more dense than the asthenosphere. The gravitational instability of mature oceanic lithosphere has the
Rikki and the Last Days of Earth "When the history of the new wave finally started to get written, Rikki and the Last Days of Earth were conspicuous by their absence. No one remembered; nobody cared. Yet without them, a lot of what is now taken for granted about the early '80s might never have occurred". Rikki and the Last Days of Earth Rikki and the Last Days of Earth (formerly Rikki and the Last Days on Earth) were an early British punk group. They were chronicled in 's book "". "Billboard" credited them with paving the way for 1980s new romantic acts. The band was formed