More Related Content
Chapter 4 - Rocks
- 1. Chapter 4 -Rocks Identifying rocks and their place in the rock cycle. Section 2: Igneous Rocks
- 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. 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. 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. 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. Intrusive Igneous Rock= Slow cooling of magma underground
- 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. Very Fast CoolingExtrusive 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. Pumice Scoria
- 10. Extrusive Igneous Rocks= Fast cooling of lava above ground
- 11. Complete the activityon identifying the seven Igneous Rocks…
- 12. Section 3: Sedimentary Rocks
- 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. Steps to theformation of a Sedimentary Rock… 3. Deposition- Particles “Settle Out” of water or 1. Weathering- sometimes wind. Often Water and wind this means the particles break up rocks at will fall to the bottom of a Earth’s surface 2. lake or ocean. 4. 5.
- 15. Sedimentary Rocks Formin Layers -Law of Superposition -oldest rock layers will be on the bottom -Sedimentary rock layers often give clues to Earth’s past environments. -Exs. Fossils and ripple marks
- 16. 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!
- 17. 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.
- 18. 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 the layers in the shale…
- 19. Where did Shalerget 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.
- 20. Clastic Sedimentary Rocks The white house is made of painted sandstone!
- 21. Chemical Sedimentary Rocks Chemical rocks form when minerals dissolved in a solution evaporate. Limestone and Rock Salt are examples of chemical sedimentary rocks.
- 22. 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.
- 23. 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.
- 24. 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.
- 25. 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.
- 26. 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!
- 27.
- 28. 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!
- 29. 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. Complete the activityon identifying the seven Sedimentary Rocks…
- 32.
- 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. Metamorphism 1. Mountain Building (Pieces of Earth’s crust colliding and uplifting) 2. Contact with Hot Magma 3. Pressure from overlying rocks
- 36. 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.
- 37. 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
- 38. Foliated Metamorphic Rocks Slate is a foliated rock used for building materials and roofing.
- 39. Non-Foliated Metamorphic Rocks Metamorphic rocks which have minerals grains that are not banded or layered are considered to be non-foliated. Ex. Marble.
- 40. 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.
- 42. Complete the activityon identifying the five Metamorphic Rocks and their Igneous or Sedimentary counterparts…