ROCKS
Rocks If a mineral is a naturally occurring homogeneous solid, inorganically formed, with a definite chemical composi:on and a crystalline structure then what is a rock?
Rocks Rocks are composed of 1 or more minerals. Rocks are classified based on how they formed (origin). 3 classes of rocks: Igneous Sedimentary Metamorphic
Igneous Rocks Form from the cooling and solidifica:on (crystalliza:on) of molten lava and magma
Intrusive (Plutonic): slow cooling of magma deep within the Earth Characteris:cs: Large crystals Coarse, rough texture Inter-grown crystals
Obsidian Rhyolite Extrusive (Volcanic): fast cooling lava at Earth s surface Characteris:cs: Small crystals No crystals/glassy Fine/smooth texture Vesicular: contains air/gas pockets
Intrusive: slow cooling of magma deep within the Earth Characteris:cs: Large crystals Coarse, rough texture Inter-grown crystals Extrusive: fast cooling lava at Earth s surface Characteris:cs: Small crystals No crystals/glassy Fine/smooth texture Vesicular: contains air/ gas pockets
Comparison Granite Rhyolite
Igneous Rocks Textures to look for: Crystals Gas pockets Glass Surface
Igneous Rocks Rocks to know: Pumice: look for gas pockets Obsidian: black and glassy Basalt: black and FINE (small) grained Gabbro: dark and large crystals Granite: dark or light, large crystals
Pumice: look for empty gas pockets
Obsidian: black and glassy
Basalt : black and fine (small) grained
Gabbro
Granite
Scheme for Igneous Rock Identification CRYSTAL SIZE TEXTURE IGNEOUS ROCKS ENVIRONMENT OF FORMATION EXTRUSIVE (Volcanic) INTRUSIVE (Plutonic) Obsidian (usually appears black) Pumice Vesicular rhyolite Rhyolite Granite Pegmatite Vesicular andesite Andesite Diorite Basaltic glass Scoria Vesicular basalt Basalt Diabase Gabbro Dunite less than 1 mm 1 mm to 10 mm 10 mm or larger Glassy Fine Coarse Very coarse Vesicular (gas pockets) noncrystalline Peridotite Nonvesicular Nonvesicular CHARACTERISTICS LIGHTER LOWER FELSIC (rich in Si, Al) 100% Potassium feldspar (pink to white) COLOR DENSITY COMPOSITION DARKER HIGHER MAFIC (rich in Fe, Mg) 100% MINERAL COMPOSITION (relative by volume) 75% 50% 25% Quartz (clear to white) Plagioclase feldspar (white to gray) Biotite (black) Amphibole (black) Pyroxene (green) Olivine (green) 75% 50% 25% 0% 0%
Do Now Copy the ques:on below and write down an answer What is the mineral composition of the igneous rock: Rhyolite Andesite Gabbro
Sedimentary Rocks Form from pieces of other rocks, animals or plants. The pieces get compacted and glued together Cementa:on, lithifica:on
Sedimentary Rocks Clas=c: made from other pieces of rocks Characteris:cs Visible fragments/pieces (pebbles, sand, mud/clay)
Sedimentary Rocks Crystalline: Form from the evapora:on and precipita:on of dissolved minerals. Crystals Fine to coarse
Sedimentary Rocks Bioclas=c: Made from once living plants or animals Fossils Black coal
Sedimentary Rocks Look for SEDIMENT! (pebbles, sand) Look for FOSSILS! (shells, plant imprints, animals)
Sedimentary Rocks Rocks to know: Conglomerate: look for pebbles Sandstone: look for sand particles Shale: compact silt or clay, can have fossils Limestone: look for sea shells Coal: black
Conglomerate
Sandstone
Shale
Limestone
Coal
INORGANIC LAND-DERIVED SEDIMENTARY ROCKS TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Clastic (fragmental) Pebbles, cobbles, and/or boulders embedded in sand, silt, and/or clay Sand (0.006 to 0.2 cm) Silt (0.0004 to 0.006 cm) Clay (less than 0.0004 cm) Scheme for Sedimentary Rock Identification Mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks and minerals Rounded fragments Angular fragments Fine to coarse Very fine grain Compact; may split easily Conglomerate Breccia Sandstone Siltstone CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS.................. TEXTURE GRAIN SIZE COMPOSITION COMMENTS ROCK NAME MAP SYMBOL Shale Crystalline Fine to coarse crystals Halite Gypsum Dolomite Crystals from chemical precipitates and evaporites Rock salt Rock gypsum Dolostone Crystalline or bioclastic Bioclastic Microscopic to very coarse Calcite Carbon Precipitates of biologic origin or cemented shell fragments Compacted plant remains Limestone Bituminous coal Scheme for Metamorphic Rock Identification
Do Now Copy the ques:on below and write down an answer What mineral is limestone and rock salt made from. List the hardness of both minerals.
Metamorphic Rocks Form from intense heat and pressure. There is no mel:ng!
Metamorphosis The process of transforma:on A change into something completely different
Metamorphic FOLIATED Regional metamorphism where applied pressure produces layers. Shinny Flakes Mineral Alignment Layering
Regional Metamorphism
Metamorphic NON-FOLIATED Contact metamorphism where applied heat recrystallizes the minerals. Shiny Flakes Crystals Mashed Together Granular
Contact Metamorphism
Metamorphic Rocks New minerals due to recrystalliza:on The growth of new mineral crystals without mel:ng Increased density Rock is squeezed under pressure Mineral Alginment Layered arrangement of inter-grown crystals due to pressure
Metamorphic Rock What to look for: Shiny flakes (mica) Crystals all mashed together Layering of crystals!
Metamorphic Rock Rocks to know: Schist: flakey, shiny crystals (Shale) Gneiss: mineral alignment, flat, folded crystals (Granite) Marble: crystals mashed together (Limestone)
Schist: flakey, shiny crystals
Gneiss: layering and folding of crystals
Marble: crystals mashed together
Sandstone Sedimentary Quartzite Metamorphic
TEXTURE Scheme for Metamorphic Rock Identification GRAIN TYPE OF SIZE COMPOSITION METAMORPHISM COMMENTS ROCK NAME MAP SYMBOL FOLIATED MINERAL ALIGNMENT BAND- ING Fine Fine to medium Medium to coarse MICA QUARTZ FELDSPAR AMPHIBOLE GARNET PYROXENE Regional (Heat and pressure increases) Low-grade metamorphism of shale Foliation surfaces shiny from microscopic mica crystals Platy mica crystals visible from metamorphism of clay or feldspars High-grade metamorphism; mineral types segregated into bands Slate Phyllite Schist Gneiss Fine Carbon Regional Metamorphism of bituminous coal Anthracite coal NONFOLIATED Fine Fine to coarse Various minerals Quartz Calcite and/or dolomite Contact (heat) Regional or contact Various rocks changed by heat from nearby magma/lava Metamorphism of quartz sandstone Metamorphism of limestone or dolostone Hornfels Quartzite Marble Coarse Various minerals Pebbles may be distorted or stretched Metaconglomerate
Coal Vs. Obsidian
Gneiss Vs. Sandstone
Granite Vs. Gneiss
Do Now Copy the ques:on below and write down an answer Describe the main difference between each rock class: Igneous, sedimentary and metamorphic
Do Now Copy the ques:on below and write down an answer What is the difference between regional and contact metamorphism? What characteristic does the rock show for each?
The Rock Cycle Any class of rock can change and form into another class of rock.
Igneous Rock Mel:ng Igneous Rock Weathering and Erosion Sedimentary Heat and Pressure Metamorphic Rock
Sedimentary Rock Mel:ng Igneous Rock Weathering and Erosion Sedimentary Rock Heat and Pressure Metamorphic Rock
Weathering The breakdown of rocks when exposed to condi:ons at Earth s surface.
Erosion The movement of broken down rock by water, air, glacier, or by gravity.
Metamorphic Rock Mel:ng Igneous Rock Weathering and Erosion Sedimentary Heat and Pressure Metamorphic Rock
Rock Cycle in Earth s Crust Cementation Compaction and/or Deposition and Burial SEDIMENTS SEDIMENTARY ROCK Metamorphism Heat and/or Pressure METAMORPHIC ROCK Melting Melting (Uplift) Weathering & Erosion Heat and/or Pressure Metamorphism (Uplift) Weathering & Erosion Melting MAGMA Erosion Solidification Weathering & Erosion (Uplift) IGNEOUS ROCK