Rocks

1. Rocks Chapter 4

2. Classifying Rocks • Mineral Composition - Look with a magnifying glass to determine the mineral that makes up the rock • Color - Light or dark color, glassy? • Texture – look and feel of the rocks surface • Grain size – Fine, coarse or no visible grain • Grain Shape – Rounded or jagged • Grain Pattern – non-banded, banded

3. Rocks • What is a rock? • mixture of minerals, mineraloids, glass or organic matter • 3 Types of Rocks: • 1. Igneus Rock – molten material inside earth or from a volcano cools slowly due to the insulation of rock allowing the atoms to arrange themselves into large crystals called mineral grains

4. Remember: magma forms from great temperatures (1400oC) and pressure in the earth this melts the minerals and forms magma • When magma flows to the surface it is called lava

5. Intrusive Rocks Intrusive Rocks– formed when magma insulated and trapped below the earth surface, holds heat and cools slowly – large mineral grains • Granitic – light colored rocks, lower density contains a lot of silicon and oxygen, mountains

6. Extrusive Rocks • Extrusive Rocks – Formed when magma cools on the earths surface and cools rapidly – fine grained texture Basaltic – dense, heavy, dark colored (magma) examples iron, magnesium, covers ocean floorCombination:Andresitic – in between basaltic and granitic in mineral composition

7. Igneous Rocks - Texture • Intrusive—Large crystals • Extrusive—Small Crystals (maybe not visible: obsidian & Pumice) • Mafic—Dark • Felsic—Light

8. Obsidian

9. Pumice

10. Andesite

11. Rhyolite

12. Diorite-Dark color w/ large black crystals

13. Basalt

14. Gabbro

15. Granite

16. Sedimentary Rock • Sedimentary rock -comprises 75 % rocks on earth -formed when sediments pressed or cemented together – may form layers • Sediments – loose materials such as rock fragments, grains and bits of plant and animals • Compactation – pressure causes sediments to form rock • Cementation – water dissolves minerals (quartz, calcite, hematite, limonite) natural cements

17. Classification of sedimentary rock: • Clastic – broken, named for size & shape of sediments example – conglomerate, breccia, sandstone, shale • Chemical – minerals precipitated from a solution or evaporates example – limestone, rock salt • Organic – from once living things examples – coal, chalk

18. Sedimentary Rocks • Compacted or Cemented (layering is key) • Sandstone • Shale • Coal (rock or not? Some debate) • Clastic • Breccia—sharp angles • Conglomerate—rounded edges (concrete) • Coquina—Shells

19. Coal

20. Sandstone

21. Mudstone-gray & silky soft

22. Shale

23. Conglomerate

24. Breccia

25. Coquina

26. Coral Reefs • Formed from skeletons of tiny coral animals that grow together to form the coral reef structure • Almost all coral reef growth occurs within the top 40 meters of the surface where sunlight penetrates • Coral organisms need warm water, found only in tropical oceans • Limestone deposits formed from coral reefs

27. Metamorphic Rock • Metamorphic rock – rocks changed due to temperature and pressure increases or change in composition • Classification of Metamorphic Rock • Foliated – mineral grains flatten and line up in parallel bands Example slate and gneiss • Slate forms from shale which is arranged in layers when exposed to heat and pressure • Nonfoliated – no banding occurs, the mineral grains change, grow and rearrange but no bands Example is marble which forms from sedimentary rock calcite – shiny. Hornblende and serpentine – green. Hermatite - red

28. Metamorphic Rocks • Gneiss—Zebra strips • Schist—Metallic shine • Marble—Contains Calcite (bubbles w/HCl) • Or Morphed sedimentary rock • Slate (shale that has hardened)

29. Gneiss

30. Slate

31. Schist

32. Marble

33. Phyllite

34. Rock Cycle