THE ROCK CYCLE

 Doc Brown's Chemistry - Earth Science & Geology Revision Notes

for KS4 Science, GCSE, IGCSE & O Level Courses

INDEX OF EARTH SCIENCE PAGES

All my GCSE/IGCSE level chemistry revision notes

2. The ROCK CYCLE explained - the relationship between igneous, metamorphic and sedimentary rocks

This pages summarises the connection between the different types of rock and how they are formed. Parts 3. to 9. expand on this theme with detailed notes on all the geological processes occurring.

2. The Rock Cycle - A 1st "Big Picture" View

Many of the features of the rock cycle are illustrated below in Fig 1. The Rock cycle. (see also Fig 2. below)

Fig 1. Summary of the features of THE ROCK CYCLE

The 'Rock Cycle' summarises the formation and relationship between the three types of rock, namely, igneous, metamorphic and sedimentary

Fig 2. The complexity of igneous and metamorphic rock formation

Sections 3. to 9. take you through all the details.

Rocks are classified into groups of IGNEOUS, METAMORPHIC and SEDIMENTARY ROCKS depending on their origin.

• All rocks have crystalline structure based on giant ionic or covalent structures (Chemical Bonding Notes)
• Physically they are relatively insoluble in water, poor heat and electrical conductors and have high melting points. They are generally hard materials but with quite some variation between rock types e.g. softer limestone (easily weathered) and much harder basalt rocks used for street cobbles.
• Generally speaking, igneous rocks like granite and basalt are much harder and 'weather resistant' than sedimentary rocks like limestone, shale and sandstone which erode much more easily. Rock type details are given in 4. to 6. below.
• The three generalised type of rock are discussed in detail in sections 4. to 6.
  • Section 4. Igneous rocks are formed from cooled molten magma or lava from the Earth's mantle below the crust.
  • Section 5. Sedimentary rocks are formed deep in the Earth's crust from highly compressed deposits of weathered rock material or mineral deposits from plants and animals.
  • Section 6. Metamorphic rocks are formed from re-existing sedimentary or igneous rocks by the action of heat and pressure deep underground in the Earth's crust.

Below is a simpler approach to the "THE ROCK CYCLE" to show the relationship between the three types of rocks

Fig 3. A simplified version of the ROCK CYCLE

Fig 4. An alternative detailed version of the ROCK CYCLE

[x] try to match up with the notes below