rockcycle

The Rock Cycle:

The Rock Cycle Thinking about relationships among the major rock groups

Major Rock Groups:

Major Rock Groups Igneous Formed from a melt (molten rock) Plutonic (intrusive):slow cooling and crystallization Volcanic (extrusion): quick cooling at the surface Sedimentary Formed at the Earth’s surface Clastic (Mineral Fragments or grains, clays) Chemical (crystalline chemical/biochemical precipitates) Metamorphic Changed by pressure, temperature and fluids. 2

Fig. 2.9:

Fig. 2.9 MAGMA

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4 MAGMA Crystallization IGNEOUS

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5 MAGMA IGNEOUS Plutonic Crystallization

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6 MAGMA Volcanic IGNEOUS Plutonic Crystallization

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7 MAGMA Volcanic IGNEOUS Plutonic Uplift Crystallization Weathering

Slide 8:

8 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT Uplift Crystallization Weathering SEDIMENT

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9 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY Uplift Crystallization Weathering Erosion Transport Deposition

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10 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY Uplift Crystallization Weathering Erosion Transport Deposition

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11 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Crystallization Weathering Erosion Transport Deposition

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12 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition Can you see any shortcuts?

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13 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition

Slide 14:

The rock cycle demonstrates the relationships among the three major rock groups It is powered by the interior heat of the Earth As well as earth’s momentum and… The energy from the sun It involves processes on the Earth’s surface as well as the Earth’s interior It connects the “hydrologic cycle” with the “tectonic cycle”. In Conclusion…

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16 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition

Formation:

Formation Igneous rocks form from cooling magma. If they cool inside the Earth, they are called __________ igneous rocks and have _______ crystals. If they cool on the surface, they are called __________ igneous rocks and have _______ crystals. intrusive large extrusive small

Crystal Size:

Crystal Size This piece of obsidian cooled so _____ on the surface that it did not have time to form any crystals. fast

Crystal Size:

Crystal Size This piece of rhyolite also cooled on the surface very fast and has ______ crystals. small

Crystal Size:

Crystal Size This piece of granite cooled _______ inside the Earth and has ______ crystals. slowly large

Classification is based on crystal size and composition.:

Classification is based on crystal size and composition.

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magma igneous rock lava intrusive extrusive

Slide 23:

small extrusive; small grain size gabbro has a large grain size intrusive; its large grain size

MAGMA CRYSTALLIZES TO FORM IGNEOUS ROCKS:

THE SOLIDS ARE MINERAL CRYSTALS;WHILE THE LIQUID ARE THE IONS MOVING FREELY USUALLY MOLTEN CRYSTALLIZATION DOES NOT HAPPEN AT THE SAME TIME 24 MAGMA CRYSTALLIZES TO FORM IGNEOUS ROCKS

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IONS ARE ADDED AT THEIR CENTERS, WHEN THE CRYSTAL GROWS LARGE ENOUGH FOR THEIR EDGES TO MEET THEY GROWTH CEASES FOR LACK OF SPACE AND THEY GROW ON ELSEWHERE. EVENTUALLY ALL OF IONS ARE CONVERTED INTO SOLID INTERLOCKING CRSYTALS. 25

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THE RATE OF COOLING HIGHLY AFFECTS CRYSTAL SIZE. SLOW COOLING RESULTS IN LARGE CRYSTAL SIZE QUICK COLLING RESULTS IN SMALL CRYSTALS 26

CLASSIFYING IGNEOUS ROCKS:

-THE COMPOSITION OF MAGMA AND THE AMOUNT OF DISSOLVED GASES INFLUENCE CRYSTALLIZATION. 27 CLASSIFYING IGNEOUS ROCKS

IGNEOUS TEXTURES:

BASED ON THE SIZE OF ITS INTERLOCKING CRYSTALS -FINE GRAINED VOIDS LEFT BY GASES THAT ESCAPE AS MAGMA SOLIDIFIES THESE ARE CALLED VESICLES 28 IGNEOUS TEXTURES

COARSE GRAINED IGNEOUS ROCKS:

MASS OF INTERGROWN CRYSTALS 29 COARSE GRAINED IGNEOUS ROCKS

PORPHYRITIC:

IT HAS LARGE CRYSTALS EMBEDDED IN A MATRIX OF SMALL CRYSTALS 30 PORPHYRITIC

GLASSY:

EJECTED IN THE ATMOSPHERE WHERE MAGMA COOLS QUICKLY.; MOLTEN ROCKS ARE QUENCHED VERY QUICKLY. OBSIDIAN PUMICE- IS FORMED WHEN LARGE AMOUNTS OF GAS ESCAPE THROUGH LAVA 31 GLASSY

MINERAL COMPOSITION:

32 MINERAL COMPOSITION

Compositional terms for igneous rocks:

Compositional terms for igneous rocks Felsic: fel dspar + si lica ~55-70% silica, K-feldspar > 1/3 of feldspars present light-colored silicate minerals — Continental crust Intermediate: between felsic and mafic ~55-65% silica, plag > 2/3 of feldspars present Na-rich plag predominates over Ca-rich plag Mafic: ma gnesium + fe rric iron ~45-50% silica; Ca-rich plag dominant feldspar dark silicate minerals — Oceanic crust Ultramafic: >90% mafic minerals, silica < 45%, few or no feldspars Mantle-derived

Classification of common igneous rocks:

Classification of common igneous rocks Composition Phaneritic Aphanitic Color index (% dark minerals) Felsic Granite Syenite Monzonite Rhyolite Trachyte Latite 10 15 20 Intermediate Granodiorite Diorite Dacite Andesite 20 25 Mafic Gabbro Basalt 50 Ultramafic Peridotite 95

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Composition of Igneous Rocks

NAMING IGNEOUS ROCKS:

36 NAMING IGNEOUS ROCKS

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Igneous Rock samples as above: (1) OBSIDIAN: Volcanic grass formed from quick-cooling lavas. (2) PUMICE: Light frothy lava containing so many air cells that is floats readily on water. (3) SCORIA: Volcanic slag formed like Pumice but having fewer and larger cavities. (4) BASALT: Very fine-grained and dark colored rock. (5) RHYOLITE (FELSITE): Very fine-grained and light colored rock. (6) RHYOLITE PORPHYRY: Small crystals of Quartz and Feldspar. (7) BIOTITE GRANITE: Feldspar, Quartz and black Biotite Mica. (8) PEGMATITE: Coarse-grained granite, contains Quartz and Feldspar. (9) SYENITE: Looks like granite, but no Quartz. (10) DIORITE (TRAP ROCK): Medium and dark colored rock. (11) GABBRO: Coarser grained dark colored rock (than Diorite). (12) PERIDOTITE: Usually occurs in dikes or in pipe-like intrusions. 37

GRANITE:

38 GRANITE

ANDESITE:

ANDESITE 39