A Rock is a solid aggregate of minerals.

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2 Quartz A Rock is a solid aggregate of minerals. Orthoclase Feldspar Plagioclase Feldspar Biotite Four different minerals are obvious in this piece of Granite.

3 The average automobile contains: Minerals are solid compounds that we use every day! > a ton of iron and steel, 240 lbs of aluminum, 50 lbs of carbon, 42 lbs of copper, 41 lbs of silicon, 22 lbs of zinc, and > thirty other minerals including titanium, gold and platinum.

4 Three families of rock: Igneous Metamorphic Sedimentary Formed through interaction, mixing, and recycling through the rock cycle.

5 Igneous Three ways to form: Sedimentary Metamorphic

6 Igneous Rocks Igneous composition and texture

7 Sedimentary composition and texture

8 Metamorphic composition and texture

9 Plate Movement Powers the Rock Cycle

10 Minerals are solid crystalline compounds with a definite (but variable) chemical composition. Copper C Feldspar Na/Ca (Al, Si) 4 O 8 Hematite Fe 2 O 3 Fluorite CaF 2 Gypsum CaSO 4-2H 2 O Pyrite FeS 2

11 Hawaii s second most common mineral marine Calcite CaCO 3 Hawaii s most common mineral volcanic Olivine (Mg, Fe) 2 SiO 4

12 A mineral is a naturally occurring, inorganic, crystalline solid with a definite, but sometimes variable, chemical composition.

13 Atoms are the smallest components of nature with the properties of a given substance. Electrons (negative charge) Protons (positive charge) Neutrons (no charge)

14 For any given element: Atomic Number is the number of protons in the nucleus. Mass Number is the number of neutrons and protons in nucleus.

15 Variations in mass number create Isotopes

16 Atoms bond to achieve a stable electron configuration. Most atoms bond to achieve 8 electrons in the outer shell - the so-called Octet Rule

17 Variations in electrical charge form Ions negative charge = Anion positive charge = Cation

18 Minerals are compounds of atoms bonded together to achieve a stable electron configuration IONIC BONDING

19 COVALENT BONDING to achieve a stable electron configuration METALLIC BONDING Bonding between atoms within metals. All free electrons shared in an electron sea.

20 Ions in a dissolved state (magma, groundwater, seawater, etc.) that bond and produce a solid compound have made a mineral the net charge must be neutral. Igneous Minerals crystallize from cooling magma. Sedimentary Minerals crystallize from dissolved elements in water, or as a product of biological metabolism. Metamorphic Minerals recrystallize from existing minerals where conditions in the crust cause high heat and pressure.

21 Silicates Earths most abundant mineral group

22 Oxygen and Silicon are the two most abundant elements in the crust.

23 Silica - 4 oxygen atoms surround a single silicon atom, forming (Si 4+ O 2-4) 4- Each oxygen atom covalently shares 1 electron with the silicon atom, jointly filling its outermost shell. O 2-8P 2e 6e 1e covalent Si 4+ 2e 14P 8e 4e

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25 Types of Silicate Structures Si 4+ O 2- Na + Ca 2+ Al 3+ Fe 2+ (3+) Mg 2+ K + Metallic Cations

26 9C40Svt5g

27 Metallic Cations Join Silicate Structures to Form Neutral Compounds. Cations of like size and charge substitute within silicate structures. This forms a wide variety of minerals. Most substituted Cation pairs are Na + /Ca 2+, Al 3+ /Si 4+, and Fe 2+ /Mg 2+. Olivine forms by Single Cation Substitution. Plagioclase Feldspar forms by Double Cation Substitution. (Mg 2+ or Fe 2+ ) 2 Si 4+ O 2-4

28 Forsterite Mg 2 2+ (Si 4+ O 4 2- ) 4- Mg 2+ Fe 2+ Fayalite Fe 2 2+ (Si 4+ O 4 2- ) 4- Olivine Single Substitution Al 3+ Plagioclase Feldspar Ca 2+ Double Substitution Al 3+ Na + Si 4+ Albite plagioclase Na 1+ Al 3+ Si 3 4+ O 8 2- Anorthite plagioclase Ca 2+ Al 2 3+ Si 2 4+ O 8 2-

29 Olivine: single tetrahedron (SiO 4 ) 4- [Fe 2 2+ (Si 4+ O 4 2- ) 4- ] or [Mg 2 2+ (Si 4+ O 4 2- ) 4- ] = 0 or =0 Fayalite (Fe 2 SiO 4 ) Forsterite (Mg 2 SiO 4 ) Feldspar: 3-D framework (Si 3 O 8 ) 4- [Na 1+ Al 3+ Si 3 4+ O 8 2- ]or [Ca 2+ Al 2 3+ Si 2 4+ O 8 2- ] =0 or =0 Albite NaAlSi 3 O 8 Anorthite CaAl 2 Si 2 O 8

30 As the Si and O build crystalline structures and the metallic cations play single and double substitution, the entire magma chamber grows into a solid mass of minerals.

31 A mineral is a naturally occurring, inorganic, crystalline solid with a definite, but sometimes variable, chemical composition.

32 There are seven common rockforming minerals. Amphibole Olivine Pyroxene Quartz The Feldspar Group Orthoclase and Plagioclase Biotite Calcite

33 Earth s crust is 4/5 igneous rock. Every igneous rock begins life as magma. As magma migrates toward the surface, some of it chills and hardens underground into various types of igneous rocks. Magma that makes it to the surface erupts in either flowing or explosive volcanoes, generating lava or pyroclastic debris.

34 Igneous rock is formed when molten, or partially molten, rock solidifies.

35 Igneous rock-forming environments

36 Igneous Rocks (two categories) Intrusive Magma crystallized slowly within the crust. No exposure to the cool atmosphere. Plutonic intrusive igneous rock at great depth within crust or mantle. Extrusive Lava and Pyroclastic Debris Extruded at surface or at very shallow levels. Granite is Intrusive Basalt is Extrusive

37 Igneous Rocks Igneous Rocks are named on the basis of their texture and composition. Texture of a rock is the size and arrangement of the minerals it contains. Composition of a rock is the assemblage of minerals it contains.

38 As magma crystallizes a network of interlocking minerals develops. The composition and texture of the resulting rock is determined by these minerals.

39 Texture Phaneritic texture - with large minerals (Granite) Large crystals had a long time to crystallize. Therefore, this is an intrusive rock

40 Texture Aphanitic texture - mineral grains too small to see with the unaided eye (Basalt) Small crystals had a short time to crystallize. Therefore, this is an extrusive rock

41 Texture Vesicular texture many pits from gas escape (Basalt) Extrusive rock.

42 Texture Porphyritic texture - with 2 distinct grain sizes, large and small (Andesite Porphyry) What is the cooling history?

43 Texture Glassy texturewithout obvious minerals (Obsidian) No crystals. This is an extrusive rock.

44 Texture is estimated using visual grain size (depends on crystallization history)

45 Composition Igneous color (gray scale) is used to estimate chemical composition Felsic Intermediate Mafic Low Fe/Mg content High Fe/Mg content High Si/O content Low Si/O content

46 Composition Felsic oxygen, silicon, sodium enriched iron, magnesium, calcium depleted Source partial melting, continental crust Intermediate Diorite Granite - (pink is considered felsic) Mafic - iron, magnesium, calcium enriched oxygen, silicon, sodium depleted Source mantle, oceanic crust Ultramafic Peridotite Basalt

47 Remember partial melting? Composition How do igneous rocks form in a cooling magma chamber? Silica (felsic) compounds melt first therefore in a cooling magma chamber they must crystallize last Iron-rich (mafic) compounds melt last therefore in a cooling magma chamber they must crystallize first last Mafic Fe/Mg/Ca first Mafic Fe/Mg/Ca Melting Crystallizing first Felsic Si/O/Na last Felsic Si/O/Na Therefore cooling magma will become enriched in Si/O as crystallization proceeds

48 Olivine Plagioclase Feldspar (Ca/Na) Pyroxene Igneous Rock-Forming Minerals Orthoclase Feldspar Amphibole Mafic Minerals Biotite Mica Felsic Minerals Muscovite Mica Quartz

49 How do igneous rocks form? Bowen s Reaction Series Types of Rocks formed Hot Olivine Pyroxene Amphibole Ultramafic Mafic Intermediate Ca - plagioclase Plagioclase feldspar Basalt Gabbro Andesite Diorite Biotite Na - plagioclase Felsic Cool Orthoclase feldspar Muscovite Quartz Rhyolite Granite

50 Texture The Igneous Minerals Intrusive Granite Diorite Gabbro The Igneous Rocks Rhyolite Andesite Basalt Peridotite Extrusive Felsic Intermediate Mafic Ultramafic Composition

51 Igneous rock is a ubiquitous component of Earth s crust because it evolves as a product of tectonic processes.

52 Can you predict the location of volcanoes?

53 What is causing this eruption? What factors influence its character? A volcano is any landform from which lava, gas, or ashes, escape from underground or have done so in the past.

54 We learned from Chapter 5 that magma (and lava) can be felsic, intermediate, or mafic. How does magma chemistry influence the nature of volcanic eruptions?

55 There are three common types of magma: BASALTIC Basaltic lava flows easily because of its low viscosity (low gas content). The low viscosity is due to low silica content. ANDESITIC Aa - rough, fragmented lava blocks called clinker RHYOLITIC Pahoehoe - smooth, shiny, and ropy surface

56 There are three common types of magma: BASALTIC ANDESITIC Andesitic magma erupts explosively because it tends to have high gas content. It is viscous and therefore traps gas, builds pressure and explosively erupts. High Viscosity is related to high silica content RHYOLITIC Mount St. Helens, 1980

57 There are three common types of magma: BASALTIC ANDESITIC RHYOLITIC Rhyolitic magma erupts catastrophically because it has high gas content. It is viscous and therefore traps gas, builds pressure and explosively erupts. High viscosity is related to high silica content an abundance of silica polymers (chains etc.) leads to the high viscosity. Rhyolitic lava flow

58 Comparison of common magma types

59 Pillow Basalt

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61 EXPLOSIVE ERUPTIONS are fueled by violent releases of volcanic gas

62 A cataclysmic Plinian-style eruption (schematic drawing)

63 Pyroclastic debris is produced by explosive eruption Tephra = airborne Pyroclastic Flow = gravity-driven down the slopes

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65 Reunion Island EFFUSIVE ERUPTIONS RELATIVELY FLUID LAVA FLOW DETERMINED BY: viscosity (low) temperature (high) gas content of magma (low)