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http://www.indiana.edu/~g103/G103/wk3/wk3.html site 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. Section 1: How Do Geologists Classify Rocks?.
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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
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
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
How Do Geologists Describe a Rock’s Texture? • Terms: • Grain size • Grain shape • Grain pattern
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
How Does Grain Shape Help Identify a Rock? • Different rocks have different grain shapes – some are smooth while others are jagged
How Does Grain Pattern Help Identify a Rock? • The grains in a rock form patterns; Some are flat others are wavy
What Does It Mean to Have No Visible Grain? • Some rocks cool so quickly they have no crystal grains - glassy • Ex. Flint
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
What Are the Major Groups of Rocks? • Igneous • Sedimentary • Metamorphic
How Are Igneous Rocks Formed? • Igneous – forms from the cooling of molten rock – either magma below the surface or lava at the surface
How Are Sedimentary Rocks Formed? • Sedimentary – forms when particles of other rocks or the remains of plants and animals are pressed and cemented together
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
Section 2: Igneous RocksWhat Characteristics Are Used to Classify Igneous Rock? • Origin • Texture • Mineralcomposition
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
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
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
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
Section 3:Sedimentary RocksWhat Makes up Sedimentary Rock? • Sediment – small, solid pieces of material that come from rocks or living things
What Turns These Sediments Into Solid Rock? • Erosion • Deposition • Compaction • Cementation
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
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
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
What Are the Types of Sedimentary Rocks? • Clastic rocks • Organic rocks • Chemical rocks
What Is a Clastic Rock? • A sedimentary rock that forms when rock fragments are squeezed together • Ex. Shale, sandstone, and conglomerate
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)
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
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.
How Is Sedimentary Rock Used? • Building materials – sandstone (WhiteHouse) and limestone
Section 4: Rocks from ReefsWhat is a Coral Reef? • A structure of calcite skeletons built up by coral animals in warm, shallow ocean water
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
What Are the Types of Coral Reefs? • Fringing reefs– close to shore • Barrier reefs– farther out from land • Atolls– ring- shaped coral island
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
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
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
How Is Metamorphic Rock Used? • Most useful metamorphic rocks: marble and slate • Uses: buildings and statues
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
What Drives the Rock Cycle? • Convectioncurrents within the mantle cause the plates to move pushing rock back into the mantle
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.