Rocks Flashcards
Rock
a natural solid mixture of minerals or grains
Geologists
classify rocks
collect and study samples
observe rocks
Texture
the size, shape, and pattern of the grains
Grains
particles of minerals or other rocks
>the rock’s grains give the rock it’s texture
>some are smooth or rough
Coarse- grained
when the grains in a rock are large and easy to see
Fine- grained
when the grains are so small you can only see them under a miscrope
Grain shape
very widely in shape
some may be small and round, while others may be large and jagged.
Grain- pattern
some grains lay in flat layers
some grains form wavy swirling patterns
some have grains randomly throughout
No visible grain
some rocks have no grain pattern because they cooled very quickly when formed
some other rocks with no visible grain are maid up of extremely small particles
Mineral composition
Geologist can look under a microscope and identify the mineral a rock contains
>Geologist can run other tests to determine the mineral composition of the rock
Three main types of rocks
- Igneous rocks
- Sedimentary rocks
- Metamorphic rocks
Igneous rocks
forms from the cooling of molten rock
(from magma below the surface)
(from lave on the surface)
Sedimentary rocks
forms when particles of other rocks or the remains of plants and other animals are pressed and cemented together
Metamorphic rocks
formed when an existing rock changed by heat, pressure, or chemical reaction
(most metamorphic rocks form deep underground)
Characteristics of Igneous rocks
> Origin
Texture
Mineral Composition
Origin
classified according to where they are found
Extrusive rocks
igneous rock formed from lava that erupted onto Earth’s surface
Volcanic glass
rock that forms when lava cools too quickly to form crystals
>obsidian looks like this, but isn’t
Pumice
forms when gases escape from the cooling lava and leave holes in the rock
Intrusive rock
igneous rock that formed when magma hardened underneath Earth’s surface
Granite
most abundant intrusive, igneous rock; part of the crust that makes up mast of the continents; forms the core of many mountain ranges
What is the texture of extrusive rocks?
> crystals are small or impossible to see
formed from rapid cooling lava
can also be fine- grained
What is the texture of Intrusive rocks?
> crystals are large and easy to see
formed from slow- cooling magma
can be coarse-grained
May be porphyritic
Fast then slow cooling forms a mix of large particles with a background of small particles
Sediment
small, solid pieces of material that come from rocks or living things
Destructive forces
are constantly breaking up and wearing away all of the rock on Earth
Erosion
occurs when running water or wind loosen and carry away fragmented rock
Deposition
the process by which sediment settles out of the water or wind carrying it
What happens after sediment has been deposited?
the process of compaction and cementation change the sediment into sedimentary rock
What can sediment include?
shells,. leaves. bones, or other remains of living things
Compaction
the process that presses sediment together
> layers of sediment build up over millions of years
> the weight of layer upon layer over time squeezes them tightly together
Cementation
the process in which dissolved minerals crystallize and glue particles of sediment together
Clastic rock
a sedimentary rock that forms when rock fragments are squeezed together
Slate
common clastic rock that forms when tiny particles of clay are compacted together
> forms in thin, flat layers
>feels smooth and splits in flat pieces
Sandstone
formed from the compaction and cementation of small particles of sand
Conglorinmate
a classic rock formed from fragments that have rounded edges
Breccia
a clastic rock that is formed from large fragments with sharp edges
Chemical rock
forms when minerals that are dissolved in a solution crystalline
>Chemical rock can also form from mineral deposits left when lakes and seas evaporate
Sedimentary rock is used for…
Sandstone and limestone are used for building material
> they are easy to cut
> Used in making cement
> Used for decorating the outside of buildings
(the white house is made out of sandstone
Biochemical rock
forms when the remains of plants and animals are deposited in thick layers
Coal
forms from the remains of swamp plants that have built up layers over millions of years
limestone
hard shells of living things such as coral, clams, oysters, and snail shells made from calcite produce some kinds of limestone
> when calcite from these shells cement they layer over time forming limestone
> clalk is a form of limestone
What makes up metamorphic rocks?
Heat and pressure deep beneath Earth’s surface can change any rock into metamorphic rock
> can form from igneous, sedimentary, or other metamorphic rocks
>Changes in appearance, texture, crystal structure and mineral context will change
How do geologists classify metamorphic rocks
by the arrangement of the grains that make up the rock
Foliated
metamorphic rocks that have their grains arranged in parrallel layers or bands. May split layers
(examples: Slate, Schist, Gneiss)
Nonfoliated
the mineral grians are arranged randomely
They do not split in layers
(examples: Marble, Quartzite
Uses of metamorphic rock:
Marble and slate are 2 of the most useful metamorphic rocks >Easy to cut into slates >Easily polished >Used for many buildings and statues > Taj Mahal is built from white marble
What forms Slate?
Shale
>foliated and splits easily into flat pieces
used for roofing, flooring, walkways, and chalkboards
The Rock Cycle
Forces inside Earth at the surface produce a rock that builds, destroys, and changes the rock in the crust
