A Rock is a solid, cohesive, natural aggregate of one or more minerals.  Rocks are composed of 90% or more, by volume, of oxygen atoms.  Most rock-forming minerals are composed of oxygen and silicon.

There are three kinds of rock.

1.    Igneous Rocks formed by solidification of Magma, which is molten rock material, including any dissolved gases and crystals, that originate far below Earth's surface, and is called Lava, when it reaches the surface.

2.    Sedimentary Rocks formed at Earth's surface in one of three ways.

    a.    conversion of any preexisting sediment into rock,

    b.    precipitation of a mineral from a solution, or

    c.    consolidation of plant or animal remains.

3.    Metamorphic Rocks formed by the alteration of any preexisting rock due to the effects of pressure, temperature, or the gain or loss of chemical components.

In a Rock Cycle, Magma by cooling, solidification and crystallization becomes Igneous rock.   Now three things can happen.

1.    By weathering and erosion, it turns to Sedimentary rock.

2.    By heat and pressure, it becomes Metamorphic rock, or

3.    By heat and Melting, back to Magma.

The Sedimentary rock can become Metamorphic rock also by heat and pressure.

Two things can happen to Metamorphic rocks.

1.    By weathering and erosion turned back to Sedimentary rock

2.    By heat and melting back to Magma.

For more details -click appropriate box
 
 

IGNEOUS ROCKS

SEDIMENTARY ROCKS

METAMORPHIC ROCKS

ON TO STRUCTURAL GEOLOGY

BACK TO MINERALS

BACK TO GEOLOGY

BACK TO EARTH AND SPACE SCIENCE