1. Rocks & The Rock Cycle ADVANCED EARTH SCIENCE VA SOL ES. 5

2. Rocks are different minerals combined REMEMBER... Minerals are the alphabet and rocks are the words made from the alphabet 3 main types of rocks: ◦Igneous ◦Metamorphic ◦Sedimentary Rocks can be identified by their mineral content and texture

3. The Rock Cycle Rocks are connected to each other through the rock cycle We will look at this more in depth as we go

4. Igneous Rocks Comes from MAGMA (molten rock) that cools and solidifies Form in the mantle and lower continental crust Magma vs. Lava???

5. Factors that affect magma formation ◦Temperature ◦Pressure ◦Mineral Composition ◦Water content

6. 2 Basic Classifications of Igneous Rocks: Intrusive vs. Extrusive Granite = most common INTRUSIVE igneous rock Cools quick = fine or no grains/crystals Cools slow = coarse/large grains

7. Intrusive Igneous Rocks – AKA: Plutonic

8. Extrusive Rocks – AKA: Volcanic

9. Textures FINE-GRAINED Extrusive Called Aphanitic Small crystals that cannot be seen by the eye. Entire rock is made up of small crystals generally less than ½ mm in size. Results from rapid cooling environments COARSE-GRAINED Intrusive Called Phaneritic Large crystals that are clearly visible to the eye. Results from slow cooling of magma deep underground Rhyolite Gabbro

10. Textures VERY COARSE-GRAINED Intrusive Exceptionally large crystals PORPHYRITIC Texture which is aphanitic AND phaneritic Large and small crystals mixed in the rock Implies 2-stage cooling – an early stage of slow cooling followed by a later stage of rapid cooling Pegmatite Andesite

11. Textures GLASSY Non-crystalline (glassy) structure of the rock, in which no minerals are present Glass results from cooling that is so fast that minerals do not have a chance to crystallize VESICULAR Refers to vesicles (holes, pores, or cavities) within the igneous rock. Vesicles are the result of gas expansion (bubbles), which often occurs during volcanic eruptions if lava has a thick consistency Can be considered a glassy texture due to a lack of crystals Obsidian Pumice Scoria

12. Igneous Rock Color (mineral composition) Felsic – contain high amounts of light colored minerals such as feldspars (K, Na, Ca) and silica – also called rhyolitic Intermediate (between felsic and mafic) – contain a mixture of light and dark colored minerals – also called andesitic Mafic – contain dark colored minerals. Rich in magnesium and iron. Less silica – also called basaltic Ultramafic – contain very dark colored or green minerals. More magnesium and iron. Even less silica. Increase in Silicon and Oxygen Increase in Iron and Magnesium

13. Classification of Igneous Rocks

14. Extrusive FelsicIntermediateMaficUltramaficTexture Obsidian (usually appears black) Basaltic Glass Glassy (non- crystalline) PumiceScoriaVesicular RhyoliteAndesiteBasaltFine-grained Intrusive GraniteDioriteGabbroPeridotite/DuniteCoarse-grained Pegmatite Very coarse- grained Word Bank: the eight words highlighted are the eight rock samples up front

15. Igneous Rock Resources ◦Resistant to weather – strong because of interlocking grains ◦Granite is the most durable igneous rock – used to make the Vietnam memorial in DC ◦Pumice – used as a polishing material

16. Sedimentary Rocks ◦Starts with weathering and erosion – ◦Weathering – physical and chemical breakdown of rocks into smaller pieces (sediments) ◦Chemical – minerals in a rock are dissolved or chemically changed ◦Physical – rock fragments simply break off ◦Creates “clastic” sediments ◦Erosion – removal and movement of surface materials from one location to another ◦Wind ◦Water ◦Gravity ◦Glaciers

17. Sedimentary Rocks ◦Deposition – sediments are laid down on the ground or sink to the bottoms of bodies of water ◦Sediments are deposited when transport (erosion) stops ◦Largest particles settle out first and smaller particles settle later Classification of Clastic Sediments Particle SizeSedimentRock > 256 mm 256-64 mm 62-2 mm Boulder Gravel Cobble Pebble Conglomerate 2-0.062 mmSandSandstone 0.062-0.0039 mmSiltSiltstone < 0.0039 mmClayMudstone or Shale

18. Lithification and Cementation ◦Sediments become “glued together” ◦Lithification – the physical and chemical processes that transform sediments into sedimentary rock ◦Begins with compaction ◦Cementation – mineral growth cements sediment grains together into solid rock

19. Features of Sedimentary Rocks ◦Bedding – horizontal layering ◦Graded bedding – particle sizes become heavier and coarser toward the bottom layers ◦Marine sedimentary rocks ◦Cross bedding – inclined layers of sediment move forward across a horizontal surface ◦Fossils – preserved remains, impressions, or any other evidence of once-living organisms

20. Types of Sedimentary Rock ◦Based on how they were formed ◦Clastic ◦Chemical ◦Organic

21. Clastic Sedimentary Rock ◦Formed from the abundant deposits of loose sediments on Earth ◦Classified by size of their particles ◦Coarse-grained – gravel sized rock and mineral fragments ◦Example: Conglomerate or Breccia ◦Medium-grained – Sand sized sediments ◦Example: Sandstone ◦Fine-grained – Silt and clay sized particles ◦Example: Shale

22. Chemical Sedimentary Rock ◦Formed from the precipitation of dissolved minerals from water ◦When the concentration of dissolved minerals equals saturation (no more minerals can be dissolved into the water) crystal grains precipitate out of solution and settle to the bottom ◦Layers of chemical sedimentary rocks are called evaporites ◦Form in arid regions ◦Three most common evaporite minerals: ◦Calcite (CaCO 3 ) ◦Halite (NaCl) ◦Gypsum (CaSO 4 )

23. Organic Sedimentary Rock ◦Formed from the remains of once living things ◦Most abundant organic sedimentary rock = limestone (composed primarily of calcite) – comes from skeleton and shell materials ◦Coquina – composed mainly of shell fragments ◦Coal – forms from the remains of plant material

24. Classification of Sedimentary Rocks Rock TypeRock NameMethod of Formation Clastic Coarse-grained Medium-grained Fine-grained Conglomerate or Breccia Sandstone Shale Lithification of clastic sediments Chemical Calcite Halite Gypsum Limestone Rock Salt Rock Gypsum Precipitation of dissolved minerals from water Organic Calcium carbonate – shells Plant matter Limestone Coal Accumulation and lithification of remains of living things

25. Importance of Sedimentary Rocks ◦Provide geologic “snapshots” of surface conditions in Earth’s past ◦Uranium – mined from sandstone – used for nuclear power ◦Phosphate – found in sedimentary rocks – used for fertilizer ◦Iron – found in sedimentary rocks – used for steel ◦Limestone – processed to make cement for construction

26. Metamorphic Rocks ◦High temperatures and pressure combine to alter the texture, mineralogy, or chemical composition of a rock ◦**This happens WITHOUT melting the rock – if temperature and pressure are TOO high the rock will just melt and form magma ◦The rock changes form while remaining solid

27. Types of Metamorphism ◦Regional metamorphism – high temperatures and pressure affect large regions of Earth’s crust ◦Contact metamorphism – molten rock come in contact with solid rock ◦Hydrothermal metamorphism – very hot water reacts with rock and alters its chemistry and mineralogy

28. Metamorphic Textures - Foliated vs. Non-foliated ◦Foliated – wavy layers and bands of minerals ◦High pressure during metamorphism causes minerals with flat crystals to create a parallel alignment ◦Two most common foliated rocks: ◦Schist – derived from shale ◦Gneiss – derived from granite ◦Non-foliated – lack mineral grains with bands in one direction ◦Two most common non-foliated rocks: ◦Quartzite – formed from quartz-rich sandstone ◦Marble - formed from limestone

29. Uses of Metamorphic Rocks ◦Slate – made from shale or mudstone – used in roofing because of its ability to be split into thin layers ◦Marble – made from limestone – used in sculpture and architecture

32. Answer the following questions on a separate sheet of paper – complete sentences or question and answer How would a metamorphic rock turn into an igneous rock? What would happen to a sedimentary rock like breccia for it to change into another sedimentary rock of any type? What process occur to form the rock granite? What would have to happen to granite for it to change into gneiss? How would granite turn into obsidian without becoming any other rock? How would schist turn into shale? What type of rock is schist? What type of rock is shale?