Determine whether each sentence describes oceanic crust, continental crust, or both. It is the topmost crust
during subduction.
It is formed when
magma solidifies.
It is made of
denser rock.

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?