Chapter 4 Rocks


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  • Ripple Marks indicate water currents such as would be found in rock that formed at the bottom of a stream bed.
  • 1847 – date Shaler was named. Shale is made of pieces of mud and clay. Shale often forms in quiet lakes and swamps.
  • The salt works by lowering the melting or freezing point of water. When you add salt to water, you introduce dissolved foreign particles into the water. The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving. When you pour rock salt onto ice, the sodium and chloride ions interfere with the bonds between the water molecules that make up the ice. This makes it easier for the water molecules to break free of the bond and makes it harder for them to refreeze. This shifts the balance so more molecules are melting than freezing, and the ice begins to melt. CaCl2 works better (at lower temperatures) than NaCl because 3 ions will form, not just 2.
  • These chalk beds were formed around 70 to 100 million years ago, during the “Cretaceous period,” when the southern portion of England was submerged by a shallow tropical sea. Chalk slowly accumulated and the land was eventually uplifted by movements of the earth’s crust to where the cliffs tower over the Strait of Dover up to 350 feet (105 m) high. Although traditionally composed of natural chalk, modern blackboard chalk is generally made from the mineral gypsum ( calcium sulfate ), often supplied in sticks of compressed powder about 4 in (10 cm) long.
  • Metamorphic Rocks can sometimes look squished!
  • Contact with hot magma but not enough to melt it….just enough to change it!
  • Chapter 4 Rocks

    1. 1. Chapter 4 - RocksIdentifying rocks and their place in the rock cycle. Section 2: Igneous Rocks
    2. 2. Igneous Rocks  The Latin prefix “igni” means fire, so Igneous Rocks are born of “fire”.  When magma or lava cools, minerals begin to crystallize.  When different minerals form interlocking crystals, a rock is formed.  These crystals make up the mineral grains of a rock.
    3. 3. Magma Composition The type of rock formed often depends on what minerals are in the magma/lava. Some magma/lava has a lot of Silica (Silicon and Oxygen compound, Quartz) Magma/lava that has a lot of silica in it will produce light colored rocks like granite. Magma/lava that has little silica in it will produce dark colored rocks like basalt.
    4. 4. Intrusive Igneous Rocks Sometimes the mineral grains are large and sometimes they are small. If the grains are large, the minerals that make up the rock must have had a longer time to form-this is because the magma cooled slowly underground. These rocks are called Intrusive Igneous Rocks. They are said to be coarse grained. Example, Granite!
    5. 5. Intrusive Igneous Rocks  Due to its ability to hold up against weathering and erosion, Granite is used as a building material and for tombstones.
    6. 6. Intrusive Igneous Rock = Slowcooling of magma underground
    7. 7. Extrusive Igneous Rocks If the grains are really really small, the minerals that make up the rock must have formed from quickly cooling LAVA. Rocks exposed to the atmosphere cool very fast. These rocks are called Extrusive Igneous Rocks are said to be fine grained. “Fast is Fine”
    8. 8. Very Fast Cooling Extrusive Igneous Rocks This is called a “volcanic glass” or obsidian. It has no mineral grains because it cooled soooo fast! Also, sometimes extrusive rocks have holes in them. These are from trapped gas bubbles…A sign of very fast cooling. Ex. Pumice
    9. 9. Pumice Scoria
    10. 10. Extrusive Igneous Rocks = Fast cooling of lava above ground
    11. 11. Complete the activity on identifying the seven Igneous Rocks…
    12. 12. Section 3: Sedimentary Rocks
    13. 13. Sedimentary Rocks  95% of the crust is made of Igneous Rocks, but 75% of the visible rocks at the surface are Sedimentary Rocks.  Sediments can include rock fragments, mineral grains, bits of plant / animal remains and even minerals dissolved in water!  Sedimentary Rocks form mainly in layers.
    14. 14. Sedimentary Rocks
    15. 15. Steps to the formation of a Sedimentary Rock… 3. Deposition- Particles “Settle Out” of water or1. Weathering- sometimes wind. OftenWater and wind this means the particlesbreak up rocks at will fall to the bottom of aEarth’s surface 2. lake or ocean. 4. 5.
    16. 16. Sedimentary Rocks Form in Layers-Law of Superposition -oldest rock layers will be onthe bottom-Sedimentary rock layers often give clues to Earth’spast environments.-Exs. Fossils and ripple marks
    17. 17. Classifying Sedimentary Rocks  Sedimentary Rocks are classified by how they form ( & sometimes what they are made from).  1. Chemical-some rocks form from evaporation.  2. Organic- some from dead organisms.  3. Clastic- some from other rock or mineral pieces.We will look at the seven common Sedimentary Rocks!
    18. 18. Clastic Sedimentary Rocks  Clastic rocks form from bits and pieces of other older rocks that are smashed together!  Conglomerate is an example of a clastic rock.
    19. 19. Clastic Sedimentary Rocks  Sandstone is made of sand grains.  Shale is mainly made of small pieces of clay.  Shale is very common here and can be in many different shades!Look at thelayers in theshale…
    20. 20. Where did Shaler get it’s name? Contrary to popular belief, Shaler is not named for its many shale deposits. Shaler was named in honor of a Pittsburgh judge, Charles Shaler in 1847.
    21. 21. Clastic Sedimentary Rocks  The white house is made of painted sandstone!
    22. 22. Chemical Sedimentary Rocks  Chemical rocks form when minerals dissolved in a solution evaporate.  Limestone and Rock Salt are examples of chemical sedimentary rocks.
    23. 23. Chemical Sedimentary Rocks Water in the ocean contains dissolved calcite (a mineral and compound of calcium, carbon and oxygen – CaCO3). When water evaporates, calcite forms crystals. This is the main mineral in limestone. Limestone is used in cement and is also part of the smelting process in steelmaking.
    24. 24. Chemical Sedimentary Rocks  Much of the bedrock in the United States is made of limestone which indicates that large portions of the country were once under water in shallow oceans.Generalized geographic map of the United States 300 mya.
    25. 25. Chemical Sedimentary Rocks  Rock Salt is used to melt snow and ice.  Rock Salt contains the mineral halite, plus traces of other materials.  Recall that halite forms when seawater evaporates.
    26. 26. Organic Sedimentary Rocks  Organic rocks form from the remains of once living things.  Coquina (Fossil Limestone) is formed from shells pressed and cemented together.  Sea organisms make shells mainly from calcite (CaCO3 they extract the ingredients from the ocean).  Although Fossil Limestone and chemical limestone are both made mainly of calcite, they formed differently.
    27. 27. Organic Sedimentary Rocks  Larger mussels, coral and snail shells cement together to produce Coquina, but tiny shells combine to produce Chalk, another form of organic fossil limestone.  The White Cliffs of Dover in England are entirely made of tiny dead animals!
    28. 28. Living Coral
    29. 29. Organic Sedimentary Rocks  Coral Reefs are created as small animals create skeletons around themselves from dissolved calcite, die, and leave behind their skeletons which more Coral build upon. A coral reef is another form of organic fossil limestone!  They are found on the warm, shallow edges of oceans and are important habitats for many sea animals. Ancient Coral Reef!
    30. 30. Organic Sedimentary Rocks  Coal formed from plant remains buried in low oxygen swampy areas for millions of years.  It is the primary fossil fuel source for producing electricity in the United States.  It is also the primary cause for air pollution and possibly Global Warming!
    31. 31. Complete the activity on identifying the seven Sedimentary Rocks…
    32. 32. Section 4Metamorphic Rocks
    33. 33. Metamorphic Rocks  The word metamorphic means change.  Intense heat and pressure can change any rock into a metamorphic rock.  The intense heat and pressure for Metamorphism is caused by things like…
    34. 34. Metamorphism1. Mountain Building (Pieces of Earth’s crust colliding and uplifting)2. Contact with hot Magma3. Pressure from overlying rocks
    35. 35. Classifying Metamorphic Rocks  Metamorphic Rocks are classified by the pattern in their mineral grains.  High temperatures change the size and shape of the crystals or grains in the rock.  Tremendous pressure may cause the mineral Flat, Parallel Layers grains to line up in flat, parallel layers.
    36. 36. Foliated Metamorphic Rocks  This results in the rock either cleaving into flat sheets, or a banding of the minerals in the rock.  Geologists call this banding texture and/or flat sheets foliated. Flat, Parallel Layers Flat Sheets
    37. 37. Foliated Metamorphic Rocks  Slate is a foliated rock used for building materials and roofing.
    38. 38. Non-Foliated Metamorphic Rocks  Metamorphic rocks which have minerals grains that are not banded or layered are considered to be non-foliated.  Ex. Marble.
    39. 39. Non-Foliated Metamorphic Rocks  Marble is a non- foliated rock used for building materials and due to it being fairly soft, for carving statues and monuments.
    40. 40. Complete the activity on identifying the five Metamorphic Rocks and their Igneous or Sedimentary counterparts…