What is the difference between oceanic crust and oceanic lithosphere?

Answer 1

Geologists and geophysicists split the Earth up into different layers. They do this based on various properties.

One system is dependent on the composition of the material (i.e. it's chemistry). If you use this system, then the Earth is split broadly into the crust, upper and lower mantle and the outer and inner core.

Another system is based on the mechanical properties of the Earth (e.g. how it responds to stress). In this system, the Earth is split into the lithosphere, asthenosphere, mesosphere and outer and inner core.

The oceanic crust is composed of mafic (magnesium and iron rich rocks) such as basalt and gabbro that have formed from the partial melting of the material that forms the upper mantle. As such they have differing chemical properties and so are classed as differing layers.

The lithosphere is that portion of the Earth which responds to stress in a brittle manner. It is formed of the crust AND the upper mantle as they both meet the criteria for failing in a brittle manner (and so have the same mechanical properties) even though they have differing compositions. As such they are described as a single mechanical layer, even though they are part of different compositional layers.

Answer 2

There is only a slight difference between crust and lithosphere. The difference is that the lithosphere is part of the Earth that encompasses both the crust and the mantle below it. The crust is the outermost layer of a planet, usually made up of rocky materials.