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