Sedimentary and Sedimentary and Metamorphic RocksMetamorphic Rocks

Chapter 6Chapter 6

Formation of Sedimentary RocksFormation of Sedimentary Rocks

• Sediments- pieces of solid material that have been deposited on the earth’s surface by water, wind, ice, gravity, or chemical precipitation.

• Weathering- a set of physical and chemical properties that break rock into smaller pieces.

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Formation of sedimentary RocksFormation of sedimentary Rocks• Clastic sediments- rock and mineral

fragments formed by weathering

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Formation of Sedimentary RockFormation of Sedimentary Rock

• Erosion- the removal and movement of surface materials from one location to another.– Wind– Water (moving)– Gravity– Glaciers

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Formation of sedimentary rocksFormation of sedimentary rocks

• Deposition- sediments are dropped by the erosional force in a new location causing them to “pile” up on each other.– Largest sedments typically settle out first

(bottom)– Small sediments typically settle out last (top)– Not all sediments are sorted-- glaciers

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Formation of sedimentary rocksFormation of sedimentary rocks

• Burial- sediments are typically deposited on low areas of the earth called sedimentary basins. The sediments layer or “pile” on top of each other causing lithification

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Formation of Sedimentary RockFormation of Sedimentary Rock

• Litification- physical and chemical process of changing sediment into sedimentary rock– Begins with pressure (weight) of the overlying

sediments forcing grains of sediments below close together.

– Sediments buried 3-4km below the earth’s surface will experience relatively high temperatures causing cementation.

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Formation of sedimentary rockFormation of sedimentary rock

• Cementation- occurs when mineral growth cements sediment grains together into solid rock.– New mineral forms from ground water

precipitation.– Existing mineral grows larger

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Features of sedimentary rockFeatures of sedimentary rock

• Bedding- horizontal layering

• Graded bedding- particle size becomes progressively heavier and larger toward the bottom.

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Features of sedimentary rockFeatures of sedimentary rock

• Cross bedding- formed when inclined layers of sediment move forward across a horizontal surface

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Features of sedimentary rockFeatures of sedimentary rock

• Fossils- preserved remains, impressions, or any other evidence of once-living organisms

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Types of sedimentary rocksTypes of sedimentary rocks

• Clastic sedimentary rocks- form from deposited loose sediment– Course grained- gravel-sized rock and

mineral fragments (conglomerate)

Types of sedimentary RocksTypes of sedimentary Rocks

• Clastic– Medium grianed- sand-sized sediments

(sandstone)

Types of sedimentary rocksTypes of sedimentary rocks

• Clastic– sandstone

Red Rock Canyon, Nevada

Types of sedimentary rocksTypes of sedimentary rocks

• Clastic– sandstone

Balanced sandstone formation at Red Rock Canyon

Types of sedimentary rocksTypes of sedimentary rocks

• Clastic– sandstone

Types of sedimentary RockTypes of sedimentary Rock

• Clastic– Fine grained- silt and clay size particles

(shale)

Types of sedimentary rocksTypes of sedimentary rocks

• Chemical- minerals dissolved in water are left behind when the water evaporates– Evaporites- most common calcite, halite,

gypsum

Types of sedimentary rockTypes of sedimentary rock

• Chemical– Organic- formed from the remains of

organisms (limestone)

Metamorphic rockMetamorphic rock• Metamorphism- change in the

combination of minerals in a rock because of added heat and pressure.

• Regional metamorphism- metamorphism in a large region of the earth’s crust.

Metamorphic RockMetamorphic Rock

• Contact metamorphism- occurs when molten rocks come in contact with other rocks.

• Hydrothermal metamorphism- very hot water reacts with rock.

Sedim

entary

Met

amor

phic

Metamorphic rockMetamorphic rock• Metamorphic textures-

– Foliated- wavy layers or bands– Nonfoliated- rocks that lack

mineral grains in bands. – Porphyroblasts- some minerals

will grow large and be surrounded by other smaller minerals.

Nonfoliated

GneissChlorite and Biotite

Marble

porphyroblastfoliated

Metamorphic rockMetamorphic rock

• Solid state alterations- a mineral changes to a new mineral without melting.

Granite Gneiss

Rock CycleRock Cycle