11 The rock cycle

James Hutton and the cycle

• The Scottish scientist James Hutton (1785) was the first to link the three types of rock with the action of the atmosphere and hydrosphere, which change rocks from one type to another in one cycle: the rock cycle.

Stages

• Weathering: breaking up of the crust rocks by chemical and mechanical factors.
• Transportation: the fragments are carried by natural agents and by gravity, exposing a new surface to weathering.
• Deposition: when the transporting agent loses its energy, it drops its load as sediments.
• Lithification: the sediments are compressed and cemented by a binding material, forming sedimentary rocks.
• Metamorphism: heat, or heat and pressure, change rocks into new metamorphic rocks that suit the new conditions.
• Melting: when the temperature reaches the melting point, the rocks melt and form magma.
• Cooling and crystallization: magma moves out, loses heat and crystallizes into igneous rocks.
• Uplift then brings rocks back to the surface, and the cycle starts again.