6th Grade Unit 2 Lesson 4 Three Classes of Rock

Petrologist

a scientist who studies rocks

Rock cycle

Series of processes in which rock changes from one type to another.

Composition

the chemical makeup of something; describes the minerals or other materials in the rock

Texture

The look and feel of a rock's surface, determined by the size, shape, and pattern of a rock's grains.

Coarse

Texture of large crystal grain, like what forms when molten rock cools slowly

fine

Texture of small crystal grain, like what forms when molten rock cools quickly

Fire

The Latin word 'ignis' in English

Igneous rock

Main rock type formed when lava or magma cools and solidifies

Magma

Molten (melted) rock below the surface

Intrusive Igneous rock

Igneous rocks that form as magma slowly cools below Earth's surface

Granite

A coarse-grained intrusive igneous rock that is often used for buildings and monuments

Gabbro

Dark, coarse-grained intrusive igneous rock similar to basalt in mineral make up

Basalt

A dark, dense, igneous rock with a fine texture, often found in oceanic crust

Lava

Molten (melted) rock on Earth's surface

Extrusive Igneous rock

Igneous rocks that form as lava rapidly cools and hardens on Earth's surface

Obsidian

A glassy extrusive igneous rock that forms when lava cools very quickly

Pumice

A light, frothy extrusive rock formed when lava cools so fast that it traps pockets or air inside

Ryholite

An extrusive rock with a composition similar to granite but with smaller crystals

Sediments

Fragments that result from the breaking of rocks, minerals, and organic matter

Sedimentary rock

Main rock type formed when sediments are compacted and cemented together

Compaction

Process in which air and water are squeezed out of sediments; helps form sedimentary rock

Pressure (sedimentary process)

This builds up as a layer of sediments pile on top of each other. It is necessary for the process of compaction.

Cementation

The process where sediments are glued together as minerals crystallize

Lithification

The process that converts sediments into solid rock by compaction and/or cementation

Stratification

the process in which sedimentary rocks are arranged in layers

Clastic Sedimentary rock

Type of rock made up of fragments from pre-existing rocks (also called Detrital Sedimentary Rock)

Conglomerate

Coarse-grained Sedimentary rock made from large sediments like rocks and pebbles.

Sandstone

Medium-grained Sedimentary rock composed of small grains of sand (Quartz and Feldspar)

Shale

Fine-grained Sedimentary rock made of compacted and cemented clay

Chemical Sedimentary rock

Type of rock that forms from minerals that crystallize when water evaporates from a solution containing dissolved minerals - like the salt in the petri dish

Chert

Very hard sedimentary rock that often forms inside limestone

Limestone

Sedimentary rock composed of the mineral calcite, may form from evaporated seabed and/or compacted shell sediments

Organic sedimentary rock

Type of rock formed from the remains of organisms; (also called biochemical sedimentary rock)

Coal

A fossil fuel formed from ancient plant deposits that have compacted and cemented (an organic sedimentary rock)

Fossil

Trace or remains of a plant or an animal in sedimentary rock

Morph

Another word for change

Metamorphic rock

Main rock type made underground when an existing rock is exposed to extreme heat, pressure, and/or chemical processes

Metamorphism

The changing of rock that affects rocks over large areas during periods of tectonic activity

Contact metamorphism

This occurs when rocks come into contact with a heat source such as magma and the rocks surrounding the heat source get "cooked" but not melted

Pressure (metamorphic)

A kind of force that gets exerted as tectonic plates push against each other

Foliated Metamorphic rock

The kind of metamorphic rock that forms when minerals align in layers or bands

Slate

A foliated metamorphic rock formed from shale

Gneiss

A foliated metamorphic rock formed from granite

Schist

A foliated metamorphic rock often use as decorative stone

Nonfoliated Metamorphic rock

Describes a metamorphic rock without parallel bands/layers

Marble

A nonfoliated metamorphic rock formed from limestone

Quartzite

A nonfoliated metamorphic rock formed from sandstone

Soapstone

A soft metamorphic rock composed of the mineral talc

Anthracite

Very hard form of coal that burns with a high heat and a little smoke