Earth Science Notes
ROCK TYPES:Igneous
MetamorphicSedimentary
Igneous Rocks
Igneous Rocks Rocks that form from magma or lava
Igneous RockMagma: molten rock below the earth’s surfaceTemperature: 1202oF to 2192oFLocated about 90 miles below the surface of the
earth.Magma is less dense than the surrounding solid
rock, so it is forced to the surface.
Igneous Rock
Lava: molten rock on the surface of the earthDensity of lava effects how fluid it is.Dense lava flows very slow and has a
different chemical composition than fast moving, less dense lava.
Types of Igneous Rocks
Intrusive rocks: rocks made from magma When magma cools the molecules and
atoms in the magma begin to crystallize. These rocks cannot be seen until the rock
that is around it is worn away.Sometimes earthquakes will expose intrusive
rocks.
Intrusive Rocks
Types of Igneous Rocks
Extrusive Rocks – rocks formed from lava. Created when lava cools and hardens on
the surface Because of exposure to the air and other
elements (i.e. water) lava will cool quickly keeping crystals small.
Volcanic glass forms this way.
Extrusive Rocks
Tuff: formed from volcanic ash, pumice and scoria
Classifications of Igneous Rock
Basaltic Rocks High Density, Dark Colored,
Very Fluid Chemical Composition: Iron,
Magnesium, low silica (SiO2)
Basalt Rock Formations
Classifications of Igneous Rock Granitic Rocks
Light Colored, Low Density, Very rigid
Chemical Composition: low magnesium and Iron, high silica (SiO2)
Granitic Rock Formations
Classifications of Igneous Rock
Andesitic Rocks Intermediate between Basaltic and Granitic
IGNEOUS ROCKS
Summary Where do Igneous Rocks come from?
Magma and Lava Types of Igneous Rocks
Intrusive / Extrusive Classification of Igneous Rocks
Basaltic / Granitic / Andesitic
Metamorphic Rocks
Metamorphic Rocks Rocks that are created because of a
change in pressure and temperature.
Metamorphic Rock Formation Metamorphic rocks can form igneous,
sedimentary, or other metamorphic rocks. Pressure on these rocks can be due to the
immense amount of force applied from the rock above it.
Temperature can come from a rock being in close proximately of magma.
Classification of Metamorphic Rock
Rocks are classified according to composition and texture. Foliated rocks – formed when mineral
grains line up in parallel layers.Ex: Slate – used for blackboards, roofs,
sidewalks
Foliated rocks
Classification of Metamorphic Rock
Rocks are classified according to composition and texture. Nonfoliated rocks – metamorphic rocks where
mineral grains (crystals) grow and rearrange, but they do not form layers. Ex: Quartzite – formed from sandstone that was
changed by immense heat and pressure. Quartz crystals grow in size and become interlocking.
Ex: Marble – marble forms when limestone is put under extreme pressure and temperature.
Nonfoliated rocks
Metamorphic Rocks
Summary Metamorphic Rock Formation
Heat and pressureAny rock type can become metamorphic
ClassificationFoliated / Nonfoliated
Sedimentary Rocks
Sedimentary Rocks Rocks formed from sediments Sedimentary rocks often form as layers on
the bottom of a body of water.
Sedimentary Rock Formation Sediments are loose materials like small rocks,
minerals, and organic debris. Weathering and erosion produce sediments
Weathering – the breaking down of rocks into bits via chemical and mechanical means.
Erosion – the moving of these small bits of rock to a new location where they are deposited.
Sedimentary Rock Formation Weathering and Erosion
Sedimentary Rock Formation Sedimentary rocks form from other rocks These rocks are compacted and cemented
together. Compaction – sediments stick together due to
pressure
Cementation – minerals are deposited between pieces of sediment – holding it together.
Sedimentary Rock Formation Compaction and Cementation
Classification of Sedimentary Rocks
Detrital Sedimentary Rocks: sedimentary rocks made from broken bits of other rocks
Ex: Conglomerate – large sediments, rounded rocks These types of rocks have rounded sediments because they
were near wind and water EX: Breccia – large sediments, sediments have sharp
angles These types of rocks have jagged sediments because they
were not near wind and water
Detrital Sedimentary RocksConglomerate Breccia
Classification of Sedimentary Rocks
Chemical Sedimentary Rocks: sedimentary rocks that form when dissolved minerals come out of solution.
Often founds along seas or lakeshores. This type of rock is the only form of sedimentary
rock that did not form from preexisting rocks. Ex: Limestone (CaCO3) – forms when calcium carbonate comes out of
a solution. Limestone is deposited on bottom of lakes and seas.
Ex: Rock salt – forms when the evaporation of water occurs, leaving behind the salt
Chemical Sedimentary Rocks
Classification of Sedimentary RocksOrganic Sedimentary Rocks: sedimentary rocks made of once living things
This type of rock will form when clams, corals, snails, and mussels die and let their shells accumulate on the ocean floor. Ex: Chalk – made from the shells of organisms. Ex: Coal – formed from the decay and compaction of
plant materials.
Organic Sedimentary Rocks
Sedimentary Rocks
Summary What makes a rock
Sedimentary? Formation of Sedimentary
Rocks Classification of
Sedimentary Rocks Detrital / Chemical / Organics