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Exploring Earth's Rocks: Textures, Formations, and Uses

Discover the classification, formation, and uses of rocks including igneous, sedimentary, and metamorphic types. Learn about texture, grains, and mineral composition. Explore how rocks from reefs are formed and utilized in construction.

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Exploring Earth's Rocks: Textures, Formations, and Uses

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  1. http://www.indiana.edu/~g103/G103/wk3/wk3.htmlsite on rocks with crystallization demo (need 3-D glasses for one section)http://www.youtube.com/watch?v=fCGrXtdSv2c Inside Earth Chapter 5 Notes: Rocks

  2. Section 1: How Do Geologists Classify Rocks? • When studying a rock sample, geologists observe the rock’s color and texture and determine its mineral composition

  3. What Is Texture? • Texture – the look and feel of the rock’s surface • Most rocks are made up of grains – particles of minerals or other rocks • A rock’s grain gives it its texture

  4. How Do Geologists Describe a Rock’s Texture? • Terms: • Grain size • Grain shape • Grain pattern

  5. How Does Grain Size Help Identify a Rock? • If the grains in a rock are large and easy to see they are said to be coarse-grained • If the grains are small they are said to be fine-grained

  6. How Does Grain Shape Help Identify a Rock? • Different rocks have different grain shapes – some are smooth while others are jagged

  7. How Does Grain Pattern Help Identify a Rock? • The grains in a rock form patterns; Some are flat others are wavy

  8. What Does It Mean to Have No Visible Grain? • Some rocks cool so quickly they have no crystal grains - glassy • Ex. Flint

  9. What Do Geologists Do When Texture Does Not Give Them Enough Information About a Rock? • They look at the mineral’s composition under a microscope • A small sliver of rock allows them to see the shape and size of the crystals • They use mineral tests too -Scratch test, acid test, or a magnet

  10. What Are the Major Groups of Rocks? • Igneous • Sedimentary • Metamorphic

  11. How Are Igneous Rocks Formed? • Igneous – forms from the cooling of molten rock – either magma below the surface or lava at the surface

  12. How Are Sedimentary Rocks Formed? • Sedimentary – forms when particles of other rocks or the remains of plants and animals are pressed and cemented together

  13. How Are Metamorphic Rocks Formed? • Metamorphic – formed when an existing rock is changed by heat, pressure, or chemical reactions • Most of these rocks are formed underground

  14. Section 2: Igneous RocksWhat Characteristics Are Used to Classify Igneous Rock? • Origin • Texture • Mineralcomposition

  15. Where Do Igneous Rocks Come From? • Origin – where they are formed • Extrusive – rock that has erupted on to earth’s surface ex. Basalt • Intrusive – rock that formed when magma hardened beneath earth’s surface ex. Granite

  16. What Is the Texture of Igneous Rock Like? • Texture depends on the size and shape of the mineral crystals – can have large or small crystals • Porphyritic Texture – a rock with large crystals scattered on a background of much smallercrystals

  17. What is the Mineral Composition of an Igneous Rock? • Igneous Rocks differ in mineral composition depending on how much silica and other minerals are present in magma and lava • Higher silica forms light-colored rocks like granite • Lower silica forms dark-colored rocks like basalt

  18. How are Igneous Rocks Used? • Tools – obsidian was used to make ancient tools • Building – Granite structures • Basalt is used to make gravel in construction • Pumice is used for cleaning and polishing

  19. Section 3:Sedimentary RocksWhat Makes up Sedimentary Rock? • Sediment – small, solid pieces of material that come from rocks or living things

  20. What Turns These Sediments Into Solid Rock? • Erosion • Deposition • Compaction • Cementation

  21. What Is Erosion? • Destructive forces break up and wear away the rock on the earth’s surface • Occurs when running water or wind loosen and carry away fragments of rock

  22. What Is Deposition? • The process by which sediment settles out of the water or wind carrying it • Sediment can include shells, bones, and leaves. Over time the remains of living things may harden and change into fossils

  23. What Is Compaction and Cementation? • Compaction – the process that presses sediments together • Cementation – the process by which dissolved materials crystallize and glue particles of sediment together

  24. What Are the Types of Sedimentary Rocks? • Clastic rocks • Organic rocks • Chemical rocks

  25. What Is a Clastic Rock? • A sedimentary rock that forms when rock fragments are squeezed together • Ex. Shale, sandstone, and conglomerate

  26. What Are Organic Rocks? • Rocks that are formed where the remains of plants and animals are deposited in thick layers • Ex. Coal, and limestone (chalk)

  27. What Are Chemical Rocks? • Rocks that form when minerals that are dissolved in a solution crystallize • Ex. Rock salt is a chemical rock made up of the mineral halite

  28. Chapel of Saint Kinga the largest among underground chapels in the Wieliczka (Krakow, Poland) Salt mine, is actually a sizable subterranean church carved in rock salt and embellished with salty sculptures and bas-reliefs. 

  29. How Is Sedimentary Rock Used? • Building materials – sandstone (WhiteHouse) and limestone

  30. Section 4: Rocks from ReefsWhat is a Coral Reef? • A structure of calcite skeletons built up by coral animals in warm, shallow ocean water

  31. How Does a Coral Reef Form? • Coral animals absorbcalcium from the ocean water. The calcium is then changed into calcite and forms their shells. • When an animal dies, their skeleton remains and more corals build on top of them

  32. What Are the Types of Coral Reefs? • Fringing reefs– close to shore • Barrier reefs– farther out from land • Atolls– ring- shaped coral island

  33. How Can Limestone Be Found Above the Ocean Floor? • Limestone that begun as coral can be found on continents in places where uplift has raised ancient sea floors above sea level Ex. El Capitan, Texas

  34. Section 5: Metamorphic Rocks How Do Metamorphic Rocks Form? • Heat and pressure deep beneath earth’s surface can change any rock into metamorphic rock • Granite to Gneiss

  35. 1 How Do You Classify Metamorphic Rocks? 2 3 • The arrangement of the grains that make up the rocks – metamorphic rocks can be foliatedor nonfoliated • Foliated – metamorphic rocks whose grains are arranged in parallel layers or bands ex. Slate 4 Shale (sedimentary) 5 6 7 8 9 Slate (metamorphic) 10 Next

  36. How Is Metamorphic Rock Used? • Most useful metamorphic rocks: marble and slate • Uses: buildings and statues

  37. Section 6: The Rock CycleWhat Is the Rock Cycle? • A series of processes on Earth’s surface and inside the planet slowly change rocks from one kind to another

  38. What Drives the Rock Cycle? • Convectioncurrents within the mantle cause the plates to move pushing rock back into the mantle

  39. What is the role of plate tectonics in the rock cycle? • Plate movements start the rock cycle by help to form magma (the source of igneous rocks) and cause faulting, folding, and other motions of the crust that help to form sedimentary and metamorphic rocks.

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