1. The Rock Cycle Classifying Rocks

2. What is a rock?
A group of minerals bound together in some way.

3. The Rock Cycle
A series of processes above/below the Earth that change rocks from one kind to another over time!
Can follow various paths
The food web of geology!

4. 3 main types of rocks 1) Igneous -formed by…
2) Sedimentary- formed by erosion, pressure of layers of sediments
3) Metamorphic- formed by heat/pressure over time.
Molten rock- formed by melting

5. How do we classify rocks?
Color
Texture
Mineral composition (remember minerals make up rocks)

6. Texture
Size, shape and pattern of the rock grains (particles of minerals)
Smooth/glassy
Rough/chalky

7. Grain size
Large- easy to see ? (course grains)
Small- fine grained

8. Grain shape
Round?
Jagged?
Stars?
Stripes?

9. Grain pattern
Flat (like a pancake)
Wavy/swirling
Bands

10. No visible grain? In this case it means the rock cooled quickly!
It probably has a smooth/shiny texture like glass…

11. Mineral composition
Look at the size/shape of crystals
Coloration

12. Origin
Can you identify which of the three major types of rocks it is?

14. Igneous Rocks Rocks that formed from magma/lava “fire”
Most have mineral crystals
Hard, dense, durable rocks

15. Igneous rocks are used for

16. 2 origins of igneous rocks
1) Extrusive/Volcanic – from lava
Forms outside of the volcano on the surface.
Example- basalt
2) Intrusive/Plutonic- forms from magma cooling below surface
Continents and mountain ranges can be intrusive
Example- granite

17. Texture of igneous rocks
Texture can vary
Rapid cooling (small crystal structures, fine grains)
Slow cooling (large crystals, course grains)

18. Mineral composition of igneous rocks
Silica
Amount of silica present can determine color of igneous rocks

19. Let’s look at igneous rocks!

20. Sedimentary Rocks
Form from particles (sediment) deposited from water and wind.

21. Process of sediment to rock…
1) Erosion- water/wind or other forces carry away rock fragments.
2) Deposition- sediment is eventually separated or “deposited.”
3) Compaction- sediment is crushed or pressed together
4) Cementation- dissolved minerals crystalize and glue together (forming a rock)

22. 3 major types of sedimentary rocks
1) Clastic- formed from rock fragments being squeezed together.
Organized by size of grain/size of fragments.
Examples:
Shale- forms from clay, often soft, splits into flat pieces
Sandstone- feels gritty, forms from sand, contains quartz
Conglomerate and Breccia- rocks within rocks, vary in size. Look for shape of rocks within (round- conglomerate, jagged- breccia

23. Organic rocks- formed from plant/animal remains. Were once “living.”
Examples:
Coal- remains of swamp plants buried in mud/water.
Limestone- shells of animal remains (calcite) pile up and cement together. (Not all limestone has visible shells and skeletons). Compact and shell limestone. Chalk- is another form of limestone.
Chert/Flint- sharp edges, used for tools

24. Chemical rocks- form from minerals being dissolved in solutions and crystallizing. Can form from evaporation of liquid.
Examples:
Halite (rock salt) -
Gypsum-

25. Uses of sedimentary rocks

26. Metamorphic rocks Meta “change” Morphosis “form”
Formed from heat and pressure
Can form from igneous, sedimentary or from other metamorphic rocks.

27. Classifying metamorphic rocks
Heat can change the crystal size and shape of mineral grains
Pressure can rearrange the organization of minerals
Rocks that have parallel grains are “foliated”

28. Uses of metamorphic rock
Marble
Slate

29. Weathering/Erosion of Rocks

30. Weathering
Process that breaks down rocks and other substances over time.
Water, wind, heat, cold, salt, and ice can weather materials.

31. Erosion
Movement of rock particles (sediment) by wind, water, ice or gravity.
Works with weathering
Slow process

32. Mechanical Weathering
Physical breakdown of rocks (cracking, peeling)
Freezing/Thawing
Pressure
Animals breaking apart
Sediment has similar chemical composition as original rock.

33. Chemical Weathering
Breaks down rock through chemical changes/reactions
Acid rain, water, oxygen, carbon dioxide
Sediment has a different chemical composition than original rock

34. Factors that influence weathering
1) Climate
Wet climates weather faster
High temperature increases weathering
2) Type of rock
Minerals in rock determine how fast it weathers
Are they water soluble?
Permeable?