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
Costing the Earth Costing the Earth Costing the Earth is a programme on BBC Radio 4 about the environment. According to the programme´s website, it looks at man's effect on the environment and how the environment reacts, questioning accepted truths, challenging those in charge and reporting on progress towards improving the world. The programme reports on all matters relating to the environment. The most recent series has covered topics as diverse as the impact of having a baby on the environment and Germany's energy revolution. Notably the series worked with BBC2's Newsnight programme and the BBC World Channel's Our World to produce a