1. Rocks
Introduction to the three types of rocks and the cycle that forms them.

2. Igneous, Sedimentary, and Metamorphic Rocks
The three types of rocks—igneous, sedimentary, and metamorphic—are all subject to processes that change one rock type into another. The the rock cycle diagram clearly shows how this happens.

3. What is the relationship between the three types of rock?
Rock is recycled, constantly changing from one form to another.

4. The Rock Cycle (top of p.6 in your reference table)

5. Let’s see how this happens
Igneous Rock Formation
Lava flowing from a volcano in Hawaii forms igneous rocks

6. Metamorphic Rock
Metamorphic rocks in Arizona show formerly flat sedimentary layers squeezed into new shapes

7. Sedimentary Rock
Rocks in Hawaii have been broken into sediments and have accumulated on this beach, where they might form a sedimentary rock.

8. The Grand Canyon (a perfect example of erosion)
Sedimentary and and metamorphic rocks in Arizona were broken into sediments and carried away, leaving the Grand Canyon behind.

9. Animation of the Rock Cycle
This cutaway view of Earth shows where some common rock-forming processes occur. Embedded animations will illustrate the path of a rock moving through the rock cycle

10. Let’s Summarize the Rock Cycle

11. How Does Igneous Rock Form?
Igneous rocks are called fire rocks and are formed either underground or above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks.

12. Igneous Rock (Continued)
Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground.

13. Some Examples Of Igneous Rock
Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface. Granite is used for long lasting monuments and for trim and decoration on buildings
Scoria rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. Scoria is actually a kind of glass and not a mixture of minerals.

14. Examples of Igneous Rock (continued)
Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. This rock is so light, that many pumice rocks will actually float in water. Pumice is actually a kind of glass and not a mixture of minerals. Because this rock is so light, it is used quite often as a decorative landscape stone. Ground to a powder, it is used as an abrasive in polish compounds and in Lava© soap
Obsidian rocks are igneous rocks that form when lava cools quickly above ground. Obsidian is actually glass and not a mixture of minerals. The edges of this rock are very sharp.

15. What do I look for when identifying Igneous Rock?
Extrusive (Volcanic Rock)-Cools Fast
Minerals are very small, not visible to the naked eye (fine texture)
Gas pockets may be visible (vesicles)
The minerals that make up the rock look like one big picture.
Intrusive (Plutonic Rock)-Cools slowly
Minerals are very large (visible to the naked eye)
Gas pockets are not found
The minerals that make up the rock look like one big picture.

16. Igneous Rock Identification Chart, bottom of p.6 in reference table

17. How Do Sedimentary Rocks Form?
For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.

18. Examples of Sedimentary Rock
Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers as seen in this picture. They are often used as building stones.
Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions

19. More Examples of Sedimentary Rock
Shale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks and other material that is fired in a kiln
Conglomerate rocks are sedimentary rocks. They are made up of large sediments like sand and pebbles. The sediment is so large that pressure alone cannot hold the rock together; it is also cemented together with dissolved minerals.

20. Last Example of Sedimentary Rock
Gypsum rocks are sedimentary rocks made up of sulfate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, molds, and wallboards

21. What do I look for when identifying sedimentary rock?
Since most clastic sedimentary rocks form by the weathering and erosion of different parent rocks, look for different minerals of different sizes.
The chemically formed, (crystalline) sedimentary rocks formed due to evaporation of water. These rocks are usually uniform in appearance (rock salt and rock gypsum)
Bioclastic: Only rock that is formed by organic (plant) matter is coal. It is a dull, black rock.
Limestone is another bioclastic rock, look for remnants of shells.

22. Sedimentary Rock Identification Chart, top of p.7 in reference table

23. How Does Metamorphic Rock Form?
Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change.
If you examine metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.

24. What does Metamorphic mean?
The term "metamorphic" means "to change form." Changes in the temperature and pressure conditions cause the minerals in the rock to become unstable so they either reorient themselves into layers (foliation) or recrystallize into larger crystals, all without undergoing melting.

25. How does Metamorphic Rock Form? (continued)
When rock is subducted, it is exposed to extreme levels of heat and pressure. This changes the arrangement of minerals.

26. Recall the Properties of Earth’s Interior (p.10 in reference table)
Recall as depth increases, both Temperature and Pressure increase.

27. Examples of Metamorphic Rock
Schist rocks are metamorphic. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock.
Gneiss rocks are metamorphic. These rocks may have been granite, which is an igneous rock, but heat and pressure changed it. You can see how the mineral grains in the rock were flattened through tremendous heat and pressure and are arranged in alternating patterns.

28. What do I look for when identifying a metamorphic rock?
Non-Foliation
Nonfoliated metamorphic rocks are formed around igneous intrusions where the temperatures are high but the pressures are relatively low and equal in all directions (confining pressure). The original minerals within the rock recrystallize into larger sizes and the atoms become more tightly packed together, increasing the density of the rock.
Foliation
Foliated metamorphic rocks are formed within the Earth's interior under extremely high pressures that are unequal, occurring when the pressure is greater in one direction than in the others (directed pressure). This causes the minerals in the original rock reorient themselves with the long and flat minerals aligning perpendicular to the greatest pressure direction. This reduces the overall pressure on the rock and gives it a stripped look.

29. What Does Foliation Look Like?
Minerals in the original rock reorient themselves due to high heat and/or pressure, with the long and flat minerals aligning perpendicular to the greatest pressure direction. This reduces the overall pressure on the rock and gives it a stripped look.

30. Examples of Foliated Metamorphic Rocks
Slate= formed at very low temperatures and pressures, rock breaks along nearly perfect parallel planes; used in pool tables and as roofing material
Phyllite=low to intermediate temperatures and pressures; slightly more crystallized which gives the rock a shiny appearance; layers may also be wavy or crinkled

31. More examples of foliation
Schist
Gneiss (this rock also shows banding)

32. Non Foliated Rock
Nonfoliated metamorphic rocks are identified on the basis of their composition

33. Examples of Non Foliated Metamorphic Rock
Quartzite= composed of the mineral quartz, metamorphosed sandstone
Marble=composed of the mineral calcite; metamorphosed limestone

34. Metamorphic Rock Identification Chart, bottom of p
Metamorphic Rock Identification Chart, bottom of p.7 in reference table