Earth Science

A study in Change: RocksWatch for

&

It will tell you when/where information will be used in this unit!

RocksAny sold mass of minerals, or

mineral like material.Inorganic solid, crystalline structure,

definite chemical composition.Isn’t a rock, just a rock? So what?They aren’t static objects. They

change with the earth and can tell us about it. Their timeline is just different than ours!

Most Common Minerals (pg 35)

OxygenSiliconAluminumIronCalciumSodiumPotassiumMagnesiumOther

Know these!

Main Types of RockIgneousSedimentaryMetamorphicProcesses that change rock

Melting & coolingWeathering & erosionCompaction & cementationHeat & Pressure

Igneous RocksForm from the cooling of magma or

lava.Magma = molten rock below the

surface of the earth (625oC or 1032oF, low end)Intrusive igneous rockComposed of silicon, oxygen, & gases like

water vaporLava = molten rock above the surface

of the earth Extrusive igneous rockSimilar in composition to intrusive igneous,

without the gases (low pressure = escape)

Igneous Characteristics

TextureCourse grained - large crystals caused by

slow cooling of magma, usually intrusiveFine grained - small interlocking crystals

due to relatively fast coolingGlassy - cools too quickly to form crystals,

may appear glassy, may not (obsidian vs. pumice)

Porphyritic - both large and small crystals due to varying rates of cooling

Igneous Characteristics

CompositionGranitic - made up of mostly quartz

or feldsparTend to be light colored

Basaltic- made up of mostly dark silicates, rich in magnesium and ironTend to be dark colored

Other - either a combination of the above or ultramafic (really old rocks)

Igneous Rock Examples

ObsidianLava flow= basalt Granite

AphaniticPorphyritic

Sedimentary RocksForm when existing rocks are

broken down into sediments and the sediments are cemented together to form a “new” (recycled) rock.

Weathering - process by which existing rock is broken down.Physical weathering - breaking of a

large rock into smaller pieces(physical changes)

Chemical weathering - changing of rock composition due to chemical changes

Processes Forming Sedimentary Rocks

WeatheringIce wedging, root action, acid rainFaster when there is lots of water in

environmentErosion - process by which weathered

sediment is transported away from original parent rock.Wind, Water, Ice, Gravity

Deposition - fancy term for when the eroded particles are dropped!

Processes Forming Sedimentary Rocks

Compaction - process of squeezing or smashing of deposited sediments into a smaller volumeUsually due to the weight of new sediments

being deposited above.Cementation - process of gluing

sediments togetherDissolved minerals precipitate out of solution

and are deposited in the space between sediments.

Classification of Sedimentary Rocks

Clastic Sedimentary- composed of weathered sediments and mineralsConglomerate, sandstone, shaleBits and pieces stuck together.Looks or feels chunky

Chemical Sedimentary - composed from precipitates of dissolved mineralsLimestone, rock salt, gypsum(drywall)

Sedimentary Rock Examples

Sandstone-

ClasticLimestone-Chemical

Conglomerate - Clastic

Metamorphic RockFormed when existing rocks are changed by

heat and pressure(causes chemical reactions).

Heat - provides energy for chemical reactionsEarth structure provides heat sourceAmount required to change a rock depends

upon its mineral compositionChemical Reactions - hot water containing

other substances that allow recrystallizationPressure - from all directions, affected by

depth

Types of metamorphic rock

Foliated - layered or banded appearance of metamorphic rocksDue to parallel orientation of mineral

crystalsForms when sedimentary rock is

smashedNonfoliated - does not have banded

texture, usually made up of only one mineral.

Metamorphic Rock examples

Sandstone, before/after, nonfoliated

Slate (parent = shale)

foliated

Metamorphic Examples

Marble

nonfoliated

Quartzite

nonfoliated

Rock Cycle (final exam)