Science: Rocks

Igneous Rocks

Igneous Rocks

Rocks that form when magma cools and crystalises either above or below the earths surface

How to Igneous rocks form?

form either, Intrusive or Extrusive

Intrusive rocks

are cooled below the earths surface slowly in the crust with large crystals. Has a rough texture

Extrusive Rocks

are cooled on the earth’s surface in a matter of minutes with little to no crystals

Eg of Igneous rocks

Diorite

Granite

Sedimentary Rocks

are rocks that are composed of sediments that have been cemented together

Examples of sediments

mud

clay

sand

sily

gravel

Bones

shell

dead organisms

Form of Sedimentary rocks

Weathering

Erosion

Deposition

Compacting

Cementation

Weathering

the process of breaking down rocks either physically or chemically. Example of Physical is Frost Wedging and an example of Chemical is Acid Rain

Erosion

the process of water, wind or any forces of matter pick up sediments and is moved to another place

Deposition

the process of water and wind depositing the sediment to a new spot like water bodies

Compaction

the process of lots of pressure build up over time on water filled pore spaces between particles compacting the sediment

Cementation

the process of filling up pore spaces between sediment to fully cement the sediment together to make a sedimentary rock

Strata

is the layers of sedmentary rocks

Why does sedimentary rocks have fossils and igneous and metamorphic dont

because sedimentary rocks are more gentler than the cycle of other rocks

Eg of sedimentary rocks

Sandstone

Limestone

Shale

Metamorphic Rocks

are pre-existing rocks that are changes by the process of extreme heat and pressure

2 ways metamorphic rocks can change

Mineral Changes: grow new crystals

Textural Changes: Recrystallisation

Metamorphic rocks are also put into 2 catagories

Foliated and Non Foliated

Foliated Metamorphic rocks

has a layered banded appearance due to forming under high temperature and pressure

Non-Foliated Metamorphic rocks

has a lack of banded appearance due to be formed under high temperture but low pressure

Eg of metamorphic rocks

Gneiss: parent is granite

Marble: parent is sandstone

Slate: parent is shale

Minerals

are inorganic soil that has a crystalline structure and chemical deposition

What are the Characteristics of a mineral

Must Naturally formed

Must be inorganic

Must be a solid

Must have particles that line up in a repeating pattern

Must have a definite chemical composition

Identifying a Mineral

Colour

Streak

Luster

Density

Hardness

Crystal System

Cleavage

Colour

is the colour of a mineral

Streak

is the colour of a minerals powder which can be done by scraping the mineral across a unglazed porcelain plate

Luster

is the reflection of light off a mineral

Density

is the ratio of mass to its volume

Hardness

is a test if a mineral will scratch or be scratched, using the Mohs scale

crystal system

is the assigned one of seven crystal systems depending on it shape

Cleavage

Is the way a mineral breaks along specific lines of planes within its structure