1. The Rock Cycle
Sixth Grade Science
Unit 2
Lesson 7

2. The Earth began as a mass of molten material that cooled to form igneous rock

3. That igneous rock weathered to form Earth’s landscape.

4. Then the plate movements we’ve been learning about began to take their turn in shaping Earth’s surface.

5. In Time, the ROCK CYCLE IS “BORN.”

6. Igneous rock is made…
Igneous rock is exposed to mechanical and chemical weathering
Igneous rock becomes gravel, pebbles, sand, silt, clay
Over time, layers of these materials are made and cover Earth’s crust
Until they become…

7. …SEDIMENTARY ROCK.
Sedimentary rock can contain fossil remains of plants and animals
Sediment created by weathering, and the fossil record it holds, have made it possible for scientists to piece together what we know about the history of Earth.

8. Sedimentary Rock, over time, is subjected to heat and pressure…
It then becomes
some type of METAMORPHIC ROCK

9. Metamorphic Rock, over time, can then be subjected to heat and pressure as in a subduction zone.
It will then melt to become magma
Magma will eventually either cool or go to the surface in some sort of eruption
Then the rock material is back to IGNEOUS ROCK

10. Rock Cycle

11. Formation of Igneous Rock
Scoria & Pumice
Basalt
Obsidian

12. Igneous Rock
Pumice
Basalt
Scoria

13. IGNEOUS ROCK
Scoria and pumice are violently shot out of a volcano by force and pressure below ground. They are very light weight because they cool with lots of air bubbles. Pumice is the lightest and will float in water.

14. Basalt is formed by lava that cools slowly outside the volcanic eruption.

15. Obsidian forms from lava that cools very fast outside the volcanic eruption.

16. When magma cools underground, it cools more slowly than magma cooling above ground.

17. Igneous rock cools at different rates; slow cooling forms large crystals & fast cooling forms small or no crystals

19. This is most often the combination of rocks we find around us.

20. All of these processes are going on at the same time on all of the materials on Earth’s crust..

21. Igneous rock weathers to sediments and the sediments form sedimentary rocks. Heat and pressure transform sedimentary rock into metamorphic rock. Sedimentary & metamorphic rock is melted to form igneous rock. Weathering occurs continuously throughout the cycle.

23. The Rock Cycle is caused by :
Heat
Pressure
Weathering

26. It’s A Cycle That Continues to Repeat Itself Over & Over

27. Weathering

28. Weathering’s Connection
1. Precipitation falls on part of Earth’s crust
2. Water weathers crust materials
3. Weathered materials result in erosion
3. Eroded crust materials transported to body of water
4. Transported materials fall out of suspension
5. Materials form a layer on the bottom of water
6. Materials may be affected by vulcanism
7. Tectonic forces move material to subduction zone
8. Melted material forced again to surface by eruption
CYCLE REPEATS

29. Granite Weathering: sometimes erosion creates interesting shapes.

30. Granite Tombstones Weather: Although it’s very hard, names carved into granite will disappear due to weathering.

31. Weathering & Erosion Leave Harder Materials Behind

32. Soil Particles Eroded To Expose Root Systems

33. Silt and Eroded Materials Transported by Water

34. Sediments Suspended In Water

35. These Were Igneous Intrusions underground until weathering exposed them.

36. Sedimentary Layers

37. Sediments Will Fill In Low Areas

38. Weathering Is Also Done By Wind.

40. Fossils Are Preserved In Sedimentary Layers

41. Sedimentary Layers of Rock
Scientists have gotten the information that we have explaining the geologic history of the Earth from sedimentary layers deposited over thousands/millions of years.
Sedimentary is the only type of rock that preserves fossilized evidence of previous life on Earth.

42. Gneiss
(metamorphic)
Granite (igneous)

43. Metamorphic Rock
Granite is an igneous rock that is changed to gneiss, a metamorphic rock, when subjected to enough heat and pressure.

44. Shale (sedimentary) turns to Slate (metamorphic) with heat & pressure

45. HOMEWORK:
Make a detailed, labeled diagram of the rock cycle that explains how each type of rock is created.