Most buildings stones are rock-forming minerals, such as quartz, feldspar, mice or calcite

Is a mixture of such minerals, rock fragments, volcanic glass, organic matter or other natural materials

3 types of rocks1. Igneous2. Metamorphic3. Sedimentary

Rocks change through processes slowly over time

Sedimentary rock changes by heat and pressure to form a metamorphic rock

Metamorphic rock melts and cools to form an igneous

Magma cools to form igneous rock Sediments are compacted into

sedimentary rock

Over time igneous rocks can be changed into sediments by weathering and erosion

Rock cycle processes neither create or destroy matter (principle of conservation of matter)

first recognized by James Hutton in the late 18th century

Igneous rock comes from hot magma that has been cooled

Magma comes from deep below Earth’s surface

Rocks melt deep below Earth’s surface from the pressure and temperature there

Temperature of magma ranges from 650˚ C to 1,200 ˚ C

Heat that melts rocks comes from the decay of radioactive elements

1. Intrusive Rocks Are rocks that form from magma below

Earth’s surface Form as magma cools and mineral

grains grow together Are only found on the surface after

layers of rock and soil that covered them have been removed by erosion

It takes a long time for them too cool, therefore mineral grains are large

2. Extrusive Rock Are formed as lava cools on the Earth’s

surface Exposed to air and water, causing the

lava to cool quickly Quick cooling forms small mineral grains

Igneous rocks are first classified as intrusive or extrusive

Further classified by the magma from which they form

3 forms:1.Basaltic Rocks Dense dark-colored rocks Form from magma that is rich in iron

and magnesium and poor in silica Magma flows freely from volcanoes in

Hawaii

2. Granitic Rocks Light colored rocks Lower density than basaltic rocks Magma is thick and stiff Contains lots of silica, lesser amounts of

iron and magnesium Magma builds up a great deal of gas

pressure and causes violent volcanic eruptions

3. Andesitic Rocks Mineral compositions are between

basaltic and granitic rocks Volcanoes that erupt andesitic magma

can be violent

Rocks that have changed because of changes in temperature and pressure and hot fluids

Can form from igneous, sedimentary or other metamorphic rocks

2 processes that form metamorphic rocks

1. Heat and Pressure Rocks under Earth’ surface are under

great pressure and temperature Depending on the amount of pressure

and temperature applied, one type of rock can change into several different metamorphic rocks

Metamorphic rocks can come from several kinds of parent rocks

Ex: slate can change into phyllite then schist, and finally gneiss

2. Hot Fluids Fluids, which are water mixed with

dissolved elements, react chemically with rocks

This changes the rock’s composition This heat from the fluid changes the

rocks during metamorphic processes

Classified according to its composition and texture

2 classifications1.Foliated Rocks mineral grains line up in parallel layers Ex: Slate

› Forms from sedimentary rock shale› Arranged into layers when exposed to

heat and pressure› Water can’t pass between the layers easily› Ideal for paving around pools and patios

› Useful for roofing and tiling Ex: Gneiss

› Forms when granite and other rocks are changed

› Foliation shows up as alternating light and dark bands

› Dark minerals-biotite mica› Light minerals-quartz and feldspar

2. Nonfoliated Rocks Mineral grains grow and rearrange Do not form layers Ex: quartzite

› Parent rock sandstone› Composed mostly of quartz grains that

changes from a lot of pressure and heat› Quartz grows in size and becomes

interlocking Ex: Marble

› parent rock limestone› Composed of calcite› Used by artists for sculptures because it is

not as hard

75% of exposed rocks are sedimentary Sediments are loose materials such as

rock fragments , mineral grains and bits of shell

Sediments come from already existing rocks that are weathered and eroded

Sedimentary rocks form when sediments are pressed and cemented together or when minerals form from solutions

Form as layers-older layers are on the bottom

Sometimes forces within Earth overturn layers of rocks and the oldest are no longer on the bottom

Are classified by their composition and by how they formed

3 classifications:1.Detrital Sedimentary Rocks Detritus-means wears away Made from the broken fragments of other

rocks Weathering breaks the rock into smaller

pieces Erosion moves sediments and causes them

to layer on top of one another

Pressure from the top layers causes small sediments to stick together and form a solid rock

large sediments are cemented together by minerals quartz and calcite

named according to the shapes and sizes of the sediments that form them

Sizes: Clay, silt, sand, gravel (see table 2 Pg 105)

Shapes:› Conglomerate-sediments are rounded› Breccia-sediments have sharp angles

2. Chemical Sedimentary Rocks Form when dissolved minerals come

out of a solution Not made from pieces of pre-existing

rocks Ex: Limestone

› Calcium carbonate comes out of a solution as calcite

› its crystals grow together to form limestone

› Usually found on the bottom of lakes or shallow seas

Ex: Rock Salt› Water, rich in dissolved salt evaporates

and deposits halite› Halite forms rock salt› It is mined to use in the manufacturing

of glass, paper, soap and dairy products› Processed and used as table salt

3. Organic Sedimentary Rock Made of the remains of once-living things Ex: Most common is fossil-rich limestone Mostly contains remains of once-living

ocean organisms, instead of only calcite Shells cement together to form limestone Coquina-made completely of shell

fragments Ex: chalk-made of microscopic shells Ex: coal-forms when pieces of dead

plants are buried under other sediments in swamps