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?

• 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 Rocks

What Characteristics Are Used to Classify Igneous Rock?

• Origin

• Texture

• Mineral composition

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 smaller crystals

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 Kingathe 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 (White House) 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 absorb calcium

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

How Do You Classify Metamorphic Rocks?

• The arrangement of the grains that make up the rocks – metamorphic rocks can be foliated or nonfoliated

• Foliated – metamorphic rocks whose grains are arranged in parallel layers or bands ex. Slate

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Shale (sedimentary)

Slate (metamorphic)

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?

• Convection currents 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.