Study Guide Are you taking your notes???
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Rocks help us discover Earth's past. They are constantly being reworked. A rock is an aggregate of minerals.
There are three types of rocks. They are classified by how they form. Igneous Sedimentary Metamorphic
Igneous Igneous means, "formed by fire “ Form by the cooling and crystallization of magma and lava Basalt and granite are common ones. Igneous makes up 95% of the earth's crust Ocean floor—basalt Continents—granite and andesite
Sedimentary Formed from weathered materials (sediments) that are carried by wind, water or ice. Most common type on the uppermost part of the Earth's crust.
Common typesCommon types of sedimentary rx limestone sandstone shale
Metamorphic Formed from preexisting rock (sedimentary, metamorphic, or igneous) Changed by heat, pressure or both Metamorphic means "changed in form"
Two Types Of Metamorphism Regional Contact Of Metamorphic Rocks Foliated Non-foliated
Mineral Identification Minerals are identified using their physical properties. physical properties. These include crystal form, hardness, cleavage, luster, color, streak, and specific gravity Also fizz, taste, smell
Mineral Characteristics A mineral is a naturally occuring, inorganic, solid with a definite chemical composition, an orderly internal structure (crystalline structure), and characteristic set of physical properties
Crystal Form Crystal form is caused by the orderly internal arrangement of atoms Quartz is the most commonly identified by its crystal form Not often found because minerals often grow in cramped places
Two or more minerals that have the same chemical composition but different crystal structures are called polymorphs.
Fizz If a mineral contains CO 3 it will effervesce (fizz) when you drop dilute HCl (hydrochloric acid) on it. Ex. Calcite CaCO 3 The acid frees CO 2 (think of pop)
Origin of igneous rocks Igneous rocks are formed by molten material from a volcano or molten material within Earth Temps are 1600 at km beneath the surface
Classification of Magmas Mafic —high in iron and magnesium Felsic —high in feldspar and silica (quartz) Mafic—50% silica Colors-- black, green, red Intermediate—60% silica Felsic—70% silica Colors-- pink, white, light gray
Common Ig Rx The continents are mainly granite The oceans are basalt
Volcanoes Volcanoes Volcanoes occur two places: plate boundaries hot spots
Hawaii is an example of a hotspot Plate movement oldest youngest Yellowstone is also located over a hotspot.
The Cascades are an example of a plate boundary.
Three types of volcanoes: Shield Composite Cinder cone
Composites are the typical volcano shape. Mt. Saint Helens is a composite Most violent because of high silica content
Paracutin, Mexico: cinder cone Steep sides, not held together well made of scoria
Shield volcanoes are low with gentle slopes They are the kind in Hawaii Mauna Loa in Hawaii
The lava there is mafic The two forms of lava are pahoehoe and aa. Pahoehoe is ropey and aa is like a moving rubble field.
Sedimentary rocks Most common rock at Earth's surface Thin blanket over 2/3 of the surface covering igneous and metamorphic rocks
Sedimentation Volcanism builds new rocks Weathering breaks them down
Two types of weathering: Mechanical and Chemical 1. Mechanical breaks rock into smaller pieces Frost wedging Root wedging Gravity
2. Chemical Reactions with water dissolve rock H 2 O + CO 2 H 2 CO 3 Weak Carbonic acid This is what dissolves limestone and makes caves
Erosion Erosion--movement of seds Deposition--seds are deposited The larger the sediment the harder it is to move.
What can move sediments? Wind Water Ice
When deposited sediment accumulates, it begins to transform into sedimentary rock
Transformation occurs in two ways: Compaction Cementation Calcite, silica, and iron oxide are the most common cements.
Clastic sediments bits and pieces of old rock/plants/animals Clastic sedimentary rocks are classified by their sediment size and shape Most common is shale--very fine particles Sandstone—sand sized particles Siltstone—silt size
Conglomerate- rounded seds
Breccia—angular seds
Chemical Sediments Chemical sediments precipitate from water Two types Carbonates Evaporites
Carbonates Made of mostly calcite CaCO 3 or CaMgCO 3 Limestone CaCO 3 Dolomite CaMgCO 3
Evaporites Evaporites evaporate from water when a basin dries up Gypsum Ca SO 4. H 2 O Halite (Rock Salt) NaCl We find halite in Hutch
Metamorphism Change occurs by Recrystallization Often lose H 2 O or CO 2 Mechanical deformation No minerals are melted
Two Types Foliated Non foliated
Foliated rocks Increasing grades of metamorphism with increasing heat and pressure Slate-Phyllite-Schist-Gneiss
Slate-Phyllite-Schist-Gneiss ???????????????????????????? What would rock would come before slate? shale What kind of rock is it? sedimentary What happens after gneiss? (more heat and pressure) melting What kind of rock is it? After cooling it is igneous
Slate Very flat--fissile Used for pool tables Roofing they can break along planes of weakness (cleavage) where soft, platy minerals like mica and chlorite grow during metamorphism
Schist Flakes of mica visible on surface Often has larger mineral, like garnet schist
Gneiss— alternating layers of dark and light minerals Minerals align perpendicular to direction of force
Non-foliated— not layered looking formed around igneous intrusions where the temperatures are high but the pressures are relatively low and equal in all directions (confining pressure).
Marble Marble forms from metamorphosed limestone CaCO 3 so it fizzes
Sediment Metamorphic rock Heat and pressure Sedimentary rock Cementation & compaction Heat and pressure Weathering, erosion and deposition Melting Weathering, erosion and deposition WED igneous magma Cooling and crystallization
Study bold words in Sedimentary and Metamorphic Sections
Honors Content Bowen’s Reaction Series Ternary Diagrams Igneous Rock Composition Non-silicate Minerals
LocationFelsicIntermediateMaficTexture IntrusiveGraniteDioriteGabbroPhaneritic ExtrusiveRhyoliteAndesiteBasaltAphanitic