Prepared byPrepared byPat Davis, Science Teacher,Pat Davis, Science Teacher,Durham Middle School, Durham Middle School, Lewisville ISDLewisville ISD

The Science of GeologyThe Science of Geology The Science of GeologyThe Science of Geology

GeologyGeology is the study of planet Earth, is the study of planet Earth, including Earth’s surface and interior.including Earth’s surface and interior. GeologistsGeologists study the physical and study the physical and

chemical characteristics of minerals and chemical characteristics of minerals and rocks, plus the processes that have rocks, plus the processes that have shaped Earth. shaped Earth.

Geologists study physical conditions, such as temperature and pressure, inside Earth. Geologists also study the forces inside Earth that affect the surface.

Inside EarthInside Earth Inside EarthInside Earth

RockRock is the material that makes up is the material that makes up Earth’s hard outer surface. Earth’s hard outer surface. A layer of solid rock called the A layer of solid rock called the crustcrust

surrounds Earth’s surface like the tough surrounds Earth’s surface like the tough shell of a walnut. shell of a walnut.

Rocks and the Rock CycleRocks and the Rock Cycle Rocks and the Rock CycleRocks and the Rock Cycle

Rock forms Earth’s crust.Rock forms Earth’s crust. RockRock is a solid material made up of one or is a solid material made up of one or

more minerals or other substances, more minerals or other substances, including the remains of once-living things. including the remains of once-living things.

»Most of Earth’s rocks are made up of about 20 common minerals

»Called rock-forming minerals.

Classifying RocksClassifying Rocks Classifying RocksClassifying Rocks How they are formed:How they are formed:

Three ways:Three ways:

IgneousIgneousSedimentarySedimentaryMetamorphic Metamorphic

Igneous RockIgneous Rock Igneous RockIgneous Rock forms when forms when magmamagma

or or lavalava cools cools and hardens and hardens

Magma rises through cracks Magma rises through cracks in rock deep beneath the in rock deep beneath the surface. surface.

Cools very slowly Cools very slowly Geologists classify igneous Geologists classify igneous

rocks according to whether rocks according to whether the rocks formedthe rocks formed above above or or beneathbeneath Earth’s surface Earth’s surface intrusive rockintrusive rock – formed beneath – formed beneath

the surfacethe surface granite granite

extrusive rockextrusive rock – formed above – formed above the surfacethe surface

basalt basalt

Two common igneous rocks are basalt and granite. Basalt is a dark, extrusive rock that makes up much of the oceanic crust. Granite is a light-colored intrusive rock that is common in continental crust.

GraniteGraniteGraniteGraniteBasaltBasaltBasaltBasalt

Igneous Rocks: GraniteIgneous Rocks: GraniteIgneous Rocks: GraniteIgneous Rocks: Granite

Sedimentary RockSedimentary Rock Sedimentary RockSedimentary Rock forms when particles of rock and other forms when particles of rock and other

materials are pressed and stuck together. materials are pressed and stuck together. sedimentsediment --- particles of rock or --- particles of rock or

material from living things. material from living things. sand and gravel on a beach and the sand and gravel on a beach and the mud on a riverbank are sediments. mud on a riverbank are sediments.

All of these can make sedimentary All of these can make sedimentary rock.rock. erosionerosion moves sediment from place moves sediment from place to placeto place

sediment is laid down in a process sediment is laid down in a process called called depositiondeposition. .

Horizontal Beds of Sedimentary RockHorizontal Beds of Sedimentary RockHorizontal Beds of Sedimentary RockHorizontal Beds of Sedimentary Rock

Source: William E. Ferguson

How How SedimentarySedimentary Rock is Rock is FormedFormed

How How SedimentarySedimentary Rock is Rock is FormedFormed LayersLayers of of

sediment build up sediment build up Weight of the Weight of the

layers above layers above pressespresses down down

CompactionCompaction, , squeezes the squeezes the layers layers

CementationCementation, , glues the glues the sediment together sediment together Occurs when water Occurs when water

dissolves some of dissolves some of the sediment the sediment

Compaction Compaction and and cementation may cementation may continue for continue for millions of years. millions of years.

The sediment The sediment changes to changes to sedimentary rock sedimentary rock

Sedimentary rocks form through the erosion, deposition, compaction, and cementation of sediments. (A) Water or wind deposits sediment. (B) The heavy sediments press down on the layers beneath. (C) Dissolved minerals flow between the particles and cement them together.

Metamorphic RockMetamorphic Rock Metamorphic RockMetamorphic Rock Created by Created by hheat and and

great great pressurepressure deep beneath Earth’s deep beneath Earth’s surface.surface. Sometimes, heat from Sometimes, heat from

a volcano. a volcano. AnyAny kind of rock can kind of rock can

become a become a metamorphic rock metamorphic rock

Heat and pressure can change any rock into metamorphic rock. For example, granite becomes gneiss, and sandstone changes to quartzite.

NAMENAME(Examples)(Examples) CAUSECAUSE LOCATIONLOCATION CHARACTERISTICSCHARACTERISTICS

SedimentarySedimentarylimestone; limestone;

sandstone; chalk; sandstone; chalk; coal; rock salt; coal; rock salt;

shale; dolomite; shale; dolomite; conglomerateconglomerate

created when layers of created when layers of sediment (mud, sand, gravel sediment (mud, sand, gravel and minerals) settle to the and minerals) settle to the

bottom of the ocean and then bottom of the ocean and then compacted (pressed compacted (pressed

together) over thousands of together) over thousands of yearsyears

where oceans or where oceans or bodies of water once bodies of water once existed or still existexisted or still exist

soft, layered, may soft, layered, may contain fossilscontain fossils

IgneousIgneousquartz; pumice; quartz; pumice; granite; basalt; granite; basalt;

obsidianobsidian

created when molten rock created when molten rock (lava) inside the Earth pushes (lava) inside the Earth pushes

through the crust (like in a through the crust (like in a volcanic eruption) and then volcanic eruption) and then

coolscools

where volcanoes have where volcanoes have or do existor do exist

crystalline, glossy, crystalline, glossy, coarse-grainedcoarse-grained

MetamorphicMetamorphicmarble; slate; marble; slate; gneiss; schist; gneiss; schist;

quartzite; eclogitequartzite; eclogite

created when sedimentary or created when sedimentary or igneous rocks undergo igneous rocks undergo

metamorphosis (change) metamorphosis (change) caused by pressure, heat, and caused by pressure, heat, and

water acting on the rockswater acting on the rocks

deep within the earth deep within the earth (where pressure and (where pressure and

heat have a very large heat have a very large affect)affect)

hard, may contain hard, may contain bands or layers, may bands or layers, may

contain crystalscontain crystals

The Rock The Rock CycleCycle

The Rock The Rock CycleCycle

Forces inside Forces inside Earth and at the Earth and at the surface produce surface produce a a rock cyclerock cycle that that builds, destroys, builds, destroys, and changes the and changes the rocks in the rocks in the crust. crust. rock cyclerock cycle is a is a

series of series of processes on processes on and beneath and beneath Earth’s surface Earth’s surface that slowly that slowly change rocks change rocks from one kind to from one kind to another. another.

Igneous, sedimentary,

and metamorphic rocks change continuously through the rock cycle.

Igneous, sedimentary,

and metamorphic rocks change continuously through the rock cycle.

The Rock Cycle The Rock Cycle The Rock Cycle The Rock Cycle

Key Ideas Key Ideas Key Ideas Key Ideas

Geologists study Earth and the Geologists study Earth and the processes that have shaped processes that have shaped Earth over time. They study the Earth over time. They study the minerals and rocks that make up minerals and rocks that make up Earth, physical conditions inside Earth, physical conditions inside Earth, and the forces inside Earth, and the forces inside Earth that affect the surface. Earth that affect the surface.

Key Ideas Key Ideas Key Ideas Key Ideas

The three major groups of rocks The three major groups of rocks are are igneous, sedimentaryigneous, sedimentary, , and and metamorphicmetamorphic. .

The series of processes on and beneath The series of processes on and beneath Earth’s surface that change rocks from Earth’s surface that change rocks from one type to another is called the rock one type to another is called the rock cycle.cycle.

Rocks can be formed when magma or Rocks can be formed when magma or lava hardens, when sediments are lava hardens, when sediments are cemented and compacted together, or cemented and compacted together, or when heat and pressure change rock when heat and pressure change rock deep beneath Earth’s surface. deep beneath Earth’s surface.