Table of Contents

1. Table of Contents Classifying Rocks Igneous Rocks Sedimentary Rocks Rocks from Reefs Metamorphic Rocks The Rock Cycle

2. When studying a rock sample, geologists observe the rock’s mineral composition, color, and texture. - Classifying Rocks Studying Rocks

3. - Classifying Rocks Mineral Composition and Color • Rock – a solid mixture of minerals and other materials. • Rock-forming minerals – the common minerals that make up most of the rocks of Earth’s crust. • Granite – tends to be a light-colored rock that has highsilica content • Basalt – tends to be a dark-colored rock that is low in silica

4. - Classifying Rocks Texture • Grains – particles of minerals or other rocks that give a rock its texture. • Texture – the look and feel of a rock’s surface, determined by the size, shape, and pattern of a rock’s grains.

5. - Classifying Rocks Texture • Grain size • Coarse-grained – large easy to see grains • Fine-grained – so small they can only be seen under a microscope

6. - Classifying Rocks Texture • Grain Shape – varies greatly from sand grains to large triangular grains • Grain Pattern – can vary also from layers to swirls to bands

7. - Classifying Rocks How Rocks Form • Geologists classify rocks into three major groups: • igneous rock, sedimentary rock, and metamorphic rock.

8. - Classifying Rocks How Rocks Form • Igneous rock – type of rock that forms from the melting then cooling of molten rock at or below the surface. • Sedimentary rock – type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together. • Metamorphic rock – type of rock that forms from an existing rock that is changed by heat and pressure

9. - Igneous Rocks Classifying Igneous Rocks • Igneous rocks are classified according to their origin, texture, and mineral composition.

10. Classifying Igneous Rocks • Extrusive igneous rock – forms from lava on Earth’s surface. • Intrusive igneous rock – forms when magma hardens beneath Earth’s surface. • The faster igneous rock cools, the finer the grains • Extrusive igneous rock tends to be a finer-grained rock than intrusive igneous rock

11. - Igneous Rocks Mineral Mixture • Granite is a mixture of light-colored minerals, such as feldspar and quartz, and dark-colored minerals, including hornblende and different types of mica. But granite can vary in mineral composition. This affects its color and texture.

12. Feldspar Reading Graphs: What mineral is most abundant in granite? - Igneous Rocks Mineral Mixture

13. 10% Reading Graphs: About what percentage of granite is made up of dark minerals? - Igneous Rocks Mineral Mixture

14. 100% - (35% + 10%) = 55% Calculating: If the amount of quartz increases to 35 percent and the amount of dark-colored minerals stays the same, what percentage of the granite will be made up of feldspar? - Igneous Rocks Mineral Mixture

15. The overall color would be darker. Predicting: How would the color of the granite change if it contained less feldspar and more mica and hornblende? - Igneous Rocks Mineral Mixture

16. - Igneous Rocks Links on Igneous Rocks • Click the SciLinks button for links on igneous rocks.

17. - Sedimentary Rocks From Sediment to Rock • Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

18. - Sedimentary Rocks From Sediment to Rock • Sediment – small, solid pieces of material that come from rocks or organisms. • Usually forms due to erosion • Erosion – a destructive process in which water or wind loosens and carries away fragments of rock. • Deposition – process by which sediment settles out of the water or wind that is carrying it.

19. - Sedimentary Rocks From Sediment to Rock • Compaction – process by which sediments are pressed together under their own weight. • Occurs over millions of years as layers build • Cementation – process by which dissolved minerals crystallize and glue particles of sediment together into one mass. • Takes place when sediment is in the presence of water

20. - Sedimentary Rocks Types of Sedimentary Rock • There are three major groups of sedimentary rocks: • clastic rocks, organic rocks, and chemical rocks. • Clastic rock – sedimentary rock that forms when rock fragments are squeezed together under high pressure. • Can range in size from microscopic clay particles to large boulders • Ex: shale, sandstone, conglomerate, and breccia

21. - Sedimentary Rocks Types of Sedimentary Rock Peat • Organic rock – sedimentary rock that forms from remains of organisms deposited in thick layers. • Ex: Coal and Limestone • Coal forms from the remains of swampplants buried in water. • Limestone forms in the ocean, where many living things, such as coral, clams, and oysters, have hard shells made of calcite that collect on the ocean floor. Lignite Bituminous Anthracite

22. - Sedimentary Rocks Types of Sedimentary Rock • Chemical rock – sedimentary rock that forms when minerals crystallize from a solution. (Reacts to HCl) • Ex: Limestone forms from calcite deposits dissolved in lakes, rivers, streams.

23. - Sedimentary Rocks Uses of Sedimentary Rock • Sedimentary rock has been used for thousands of years in building structures, tools, and statues. • Ex: The White House in Washington D.C. is constructed of sandstone.

24. - Sedimentary Rocks Links on Sedimentary Rocks • Click the SciLinks button for links on sedimentary rocks.

25. - Rocks From Reefs Coral Reefs • Coral reef – a structure of calcite skeletons built up by coral animals in warm, shallow ocean water. • When coral animals die, their skeletons remain. More corals build on top of them, gradually forming a coral reef. • Only form in ocean water between 30°N and 30°S latitude

26. Coral Reefs(not in notes) • Coral reef is really organic(from living things) limestone. • Deposits of organic limestone help geologists figure out what the environment was like long ago. • If they find a fossil of coral reef, they would know that location used to contain warm, shallow ocean water.

27. - Rocks From Reefs More on Coral Landforms • Click the PHSchool.com button for an activityabout coral landforms.

28. - Metamorphic Rocks Metamorphic Rock • Metamorphic rock – forms when heat and pressure beneath Earth’s surface changes the appearance, texture, crystalstructure, and mineral content of either igneous, sedimentary, or other metamorphic rock.

29. - Metamorphic Rocks Types of Metamorphic Rocks • Geologists classify metamorphic rocks according to the arrangement of the grains that make up the rocks. • Foliated rocks– metamorphic rocks that have grains arranged in parallel layers or bands. • Ex: Slate – metamorphic shale (denser and more compact than shale) Shale Slate Gneiss

30. - Metamorphic Rocks Types of Metamorphic Rocks • Nonfoliated rocks – metamorphic rocks that have randomly arranged metamorphic grains that do notsplit into layers • Ex: Quartzite – metamorphic sandstone Marble – metamorphic limestone

31. - Metamorphic Rocks Links on Metamorphic Rocks • Click the SciLinks button for links on metamorphic rocks.

32. - The Rock Cycle A Cycle of Many Pathways • Forces deep inside Earth and at the surface produce a slow cycle that builds, destroys, and changes the rocks in the crust.

33. - The Rock Cycle • Rock cycle – processes on the surface and inside Earth that slowly change rocks from one kind to another.

34. - The Rock Cycle The Rock Cycle and Plate Tectonics • Plate movements start the rock cycle by helping to form magma, the source of igneous rocks. • Plate movements also cause faulting, folding, and other motions of the crust that help to form sedimentary and metamorphic rocks.

35. - The Rock Cycle Rock Cycle Activity • Click the Active Art button to open a browser window and access Active Art about the rock cycle.

36. - The Rock Cycle Metamorphic Igneous Sedimentary

37. Graphic Organizer Metamorphic Igneous Organic Foliated Extrusive Chemical