rocks!!! ch. 3. any solid mass of mineral or mineral-like matter that occurs naturally as part of...
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ROCKS!!!
CH
. 3
• Any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet
• 3 types Igneous Sedimentary Metamorphic
WHAT IS A ROCK?
• Interactions among Earth’s water, air, land, and living things can cause rocks to change from one type to another
• A continuous process
THE ROCK CYCLE
• Forms when lava or magma hardens.
• Lava:• Molten rock on the
surface of the Earth
• Magma:• Molten rock beneath
Earth’s surface.
IGNEOUS ROCKS
• Igneous rocks are formed by the cooling of molten rocks and the crystallization of minerals.
IGNEOUS ROCK FORMATION
• Intrusive Igneous rock: forms when magma hardens beneath Earth’s surface
• Extrusive Igneous Rock: forms when lava hardens on the surface of the Earth
TYPES OF IGNEOUS ROCKS
Igneous Rocks are classified based on their texture and composition.
CLASSIFYING IGNEOUS ROCKS
• Texture: size, shape, and arrangement of interlocking crystals.
• Course Grained: slow cooling, large crystals.
• Fine Grained: rapid cooling, small interconnected mineral grains.
• Glassy: looks like glass, extrusive igneous rocks. Ex. Obsidian
• Porphyrite: large crystals embedded in a matrix of much smaller crystals.
TEXTURE CLASSIFICATION
Composition: based on proportions of light to dark minerals
Basaltic Composition Contains many dark silicates minerals and plageoclase
feldspar Rich in magnesium and iron Ex: basalt and gabbro
Granitic Composition Made almost entirely of light-colored silicate minerals like
quartz and feldspar 0 to 25% dark minerals Biotite and amphibole
COMPOSITION CLASSIFICATION
Andesitic Composition
Between basltic and granitic composition
At least 25% dark minerals
Ultramafic Composition
Composed mainly of iron and magnesium rich mineral
Almost entirely dark minerals
COMPOSITION CLASSIFICATION
Composition and Texture
Granite Andesitic Basaltic Ultramafic
Coarse Granite Diorite Gabbro Peridotite
Fine Phyolite Andesite Basalt Kematite
Porphyritic Inside any given rock Uncommon
Glassy Obsidian, Pumice
IGNEOUS CHART
Forms when existing rocks are broken down into sediment then compacted and cemented together
ProcessesCementing Compaction
WHAT IS A SEDIMENTARY ROCK?
Weathering: Any process that break rocks into sediments
Erosion : The removal of weathered rocks
Deposition: when an agent of erosion (water, wind, ice, or gravity) loses energy, it drops the sediment
Compaction: is a process that squeezes or compacts sediments together
Cementation: takes place when dissolved minerals are deposited in the tiny spaces among the sediments
HOW DO THEY FORM?
• Classified by the way they form
• Clastic or chemical
CLASSIFICATION OF SEDIMENTARY ROCKS
• Made of weathered bits of rocks and minerals
• Grouped according to the size of the sediment.
CLASTIC SEDIMENTARY ROCKS
Texture Sediments Name of Rock
Coarse(over 2 mm in size)
Gravel - rounded Conglomerate
Gravel- angular Breccia
Medium (2mm to 1/6 mm)
Sand Sandstone
Fine (1/16 to 1/256 mm)
Silt Siltstone
Very Fine (< 1/256 mm)
Mud Shale/mudstone
CLASTIC SEDIMENTARY ROCKS
Form when dissolved minerals precipitate from water solution
Biochemical Sedimentary Rock: made from once living organisms (like shells and skeleton remains)
Ex: limestone, chalk, conquina, rock salt, and bituminous coal
CHEMICAL SEDIMENTARY ROCKS
Form when existing rocks are changed by heat and pressure
Metamorphism: means “change form”
WHAT IS A METAMORPHIC ROCK?
Heat: provides the energy needed to drive chemical reactions which causes existing minerals to recrystallize
Pressure: applied in all directions on a rock which causes spaces between mineral grains to close
Hydrothermal Solutions: hot, water based solutions that promote recrystallization by dissolving original minerals and then depositing new ones
WHAT CAUSES METAMORPHISM?
Classified by texture and composition
Foliated Rock with layered or banded
appearance Ex: Gneiss
Nonfoliated No layered or banded appearance Contains only one mineral Ex: Marble
CLASSIFICATION OF METAMORPHIC ROCKS
CLASSIFICATION OF FOLIATED METAMORPHIC ROCKSName Texture/Grain
SizeParent Rock
Slate Very fine Shale, mudstone
Phyllite Fine Slate
Schist Medium to course Phyllite
Gneiss Coarse Schist, granite
CLASSIFICATION OF NON-FOLIATED METAMORPHIC ROCKSName Texture/grain size Parent rock
Marble Medium to coarse Limestone
Quartzite Medium to coarse Quartz, sandstone
Anthracite Fine Coal