rock lecture 1.pdf
- 1. Lecturer Department of Civil Engineering Lecture on rock S M Sazzad Ahmed Shovon Dhaka International University
- 2. What is a rock? A rock is a naturally occurring aggregate minerals and/or her rock fragments
- 3. How do Rocks form? • How much time does it take to form a rock? • If you squeeze and heat a rock for a few million years, it can turn into a new kind of rock.
- 4. Continued… • Where does the heat come from? • When rocks are close enough to the magma to be heated but not close enough to be melted, the rocks can be changed.
- 5. Continued… • Where does the pressure come from? • Rocks below the surface are squeezed by the layers of rock above them. The thicker the layers, the more pressure there is.
- 6. If you were to ask a geologist what the earth is … What do you think the response would be?
- 7. Diagram of the Interior of the Earth Crust 0 to 40 km 0°C Upper Mantle 40 to 670 km 1,000°C Lower Mantle 670 to 2,890 km 2,000°C Outer Core 2,890 to 5,150 km 3,700°C Inner Core 5,150 to 6,370 km 4,300°C
- 8. What makes up the earth? Crust 1% Mantle 69% Core 30% Crust Mantle Core
- 9. lets move to some of the smallest components of Geology … Now that we better understand the largest components of Geology …
- 10. . Minerals make up rocks. Natural compounds and elements combine to form minerals. Elements combine to form the natural compounds. Rocks make up the Earth. There is a hierarchy to the elements of Geology Atoms make up elements.
- 11. Elements can be arranged, based on their identifiable properties, into the Periodic Table Atomic Theory proposes that all matter is composed of the atoms of about 100 different chemical elements. It further proposes that chemical compounds are formed by the combination of the atoms of different chemical elements.
- 12. Only eight elements make up over 98% of the earth’s crust! Mg Na K O Si Al Fe Ca
- 13. What is the difference between rocks and minerals? • A mineral is a nonliving solid found in nature. • But, aren’t rocks nonliving and found in nature too?? • Then what is the difference between a rock and a mineral?
- 14. Rocks and Minerals • Rocks are made up of one or more minerals!!! • The reason why some rocks have more than one color, is because they contain more than one mineral. • Also, some rocks are made of other things, such as sand and pebbles, in addition to minerals.
- 15. Igneous rock is formed from molten rock that has cooled and hardened. Sedimentary rock is formed from material that has settled into layers and hardened. Metamorphic rock is a rock that has changed by heat and pressure. What are the 3 types of Rocks?
- 16. 3 types of Rocks
- 17. Rocks Have Been Used For Many Years and For Many Things
- 26. is a sequence of events involving the formation, alteration, destruction, and reformation of rocks as a result of natural processes ... Glossary of Geology, Bates & Jackson, AGI RockCycle
- 27. The Rock Cycle Igneous Sedimentary Metamorphic
- 31. Definitions Definitions • Metamorphic Rock - "Meta"= Change (Grk) - "Morph"= form (Grk) • Metamorphic Rock - "Meta"= Change (Grk) - "Morph"= form (Grk) - a rock that has been changed from its original form ( parent ) by heat , pressure , and fluid activity into a new rock ( daughter ). - a rock that has been changed from its original form ( parent ) by heat , pressure , and fluid activity into a new rock ( daughter ). Metamorphic Rocks Metamorphic Rocks
- 32. Heat Heat • Magma - temperature of magma - composition of magma • Magma - temperature of magma - composition of magma • Geothermal gradient - temperature increases with depth of burial - core of Earth is warmer than outer crust • Geothermal gradient - temperature increases with depth of burial - core of Earth is warmer than outer crust Sources Include..... Sources Include.....
- 33. Uniform Pressure Uniform Pressure vs Directed Pressure • Lithostatic - "Lithos"= rock, static= unchanged (pressure) - uniform (aka non-directed) - equal intensity from all directions by rocks • Lithostatic - "Lithos"= rock, static= unchanged (pressure) - uniform (aka non-directed) - equal intensity from all directions by rocks
- 34. Directed Pressure one direction of squeezing is much stronger than the others Minerals align themselves to reduce stress.
- 35. Metamorphic Rocks What are They? • Rocks that have changed • They were once igneous or sedimentary • Pressure and heat changed the rocks
- 36. Examples of Metamorphic Rocks Schist Gneiss
- 37. Types of Metamorphism Types of Metamorphism • Contact - caused by igneous activity • Dynamic - aka cataclastic - associated with faults & earthquake zones • Regional - caused by tremendous pressures associated with tectonic plate activity • Contact - caused by igneous activity • Dynamic - aka cataclastic - associated with faults & earthquake zones • Regional - caused by tremendous pressures associated with tectonic plate activity
- 38. Contact Metamorphism Contact Metamorphism • Igneous Intrusions - size and type of magma important > mafic magma hotter than felsic - heat decreases away from magma > forms a zone of altered country rocks called Aureoles • Igneous Intrusions - size and type of magma important > mafic magma hotter than felsic - heat decreases away from magma > forms a zone of altered country rocks called Aureoles
- 39. Dynamic Metamorphism Dynamic Metamorphism • aka Cataclastic Metamorphism • associated with Fault Zones - Places where the Earth's crust ruptured - Rock pulverized > heat and pressure come from movement along the Fault • resultant rock is known as a Mylonite • aka Cataclastic Metamorphism • associated with Fault Zones - Places where the Earth's crust ruptured - Rock pulverized > heat and pressure come from movement along the Fault • resultant rock is known as a Mylonite
- 40. Regional Metamorphism Regional Metamorphism • Most common form of metamorphism • caused by large scale forces - lithospheric plate collision • covers very large areas - metamorphic belts or zones - Zones are characterized by Index Minerals > form under specific temperatures and pressures > metamorphic facies • commonly associated with - shields: stable areas of crystalline rocks • Most common form of metamorphism • caused by large scale forces - lithospheric plate collision • covers very large areas - metamorphic belts or zones - Zones are characterized by Index Minerals > form under specific temperatures and pressures > metamorphic facies • commonly associated with - Shields and Mountains: areas of crystalline rocks
- 42. Metamorphic Textures Metamorphic Textures • Foliated - Folios = page or leaf-like - rock has distinct banding or layering > often not smooth like in sedimentary rocks - formed under directed pressure • Non-foliated - no distinct layering character - often a massive crystalline texture - formed under uniform pressures • Foliated - Folios = page or leaf-like - rock has distinct banding or layering > often not smooth like in sedimentary rocks - formed under directed pressure • Non-foliated - no distinct layering character - often a massive crystalline texture - formed under uniform pressures
- 45. Foliated Textures Foliated Textures • Slatey - looks like blackboard > dull surface - smooth, thin layering - breaks into flat slabs > referred to as slatey cleavage - no mineral grains visible • Phyllitic - looks like waxed surface > has a "sheen" to it - may have little "waves" on surface > referred to as crenulations - some small grains visible • Slatey - looks like blackboard > dull surface - smooth, thin layering - breaks into flat slabs > referred to as slatey cleavage - no mineral grains visible • Phyllitic - looks like waxed surface > has a "sheen" to it - may have little "waves" on surface > referred to as crenulations - some small grains visible • Schistose - - visible grains > garnets, staurolites - may have shiny > due to mica minerals • Gneissic - larger grains - may look like igneous rock - may have crude banding > intensely distorted - different minerals than schistose • Schistose - distinct bands of minerals - visible mineral grains > garnets, staurolites - may have shiny appearance > due to mica minerals • Gneissic - larger grains - may look like igneous rock - may have crude banding > intensely distorted - different minerals than schistose
- 46. Foliated MM Rocks Foliated MM Rocks slate slate schist schist gneiss gneiss phyllite phyllite MM Rocks that could form as a shale (sedimentary) parent rock is MM Rocks that could form as a shale (sedimentary) parent rock is exposed to increasing directed pressure and temperature
- 47. • Marble: - metamorphosed limestone • Quartzite: - metamorphosed quartz sandstone • Quartzite: - metamorphosed quartz sandstone Non-foliated Rocks Non-foliated Rocks
- 49. IGNEOUS ROCKS EXTRUSIVE Volcanic- Fine-grained INTRUSIVE Plutonic- Coarse-grained
- 50. Igneous Rocks What are They? • Fire Rocks • Formed underground by trapped, cooled magma • Formed above ground when volcanoes erupt and magma cools
- 51. Examples of Igneous Rocks Granite Scoria Pumice Obsidian
- 52. MAGMA • Molten Rock • Usually with dissolved gasses • Generated at depth • Eruptions if magma (lava) reaches surface • If doesn’t reach surface, Solidifies underground • Intrudes country or host rock • Intrusive contact • Xenolith- ‘foreign body’
- 54. Igneous Rocks • Names based on mineral composition reflects chemical composition of the magma and... Grain size • Very coarse-grained Pegmatitic • Coarse-grained: Phaneritic > 1 mm. • Fine-grained: Aphanitic < 1 mm. • Porphyritic- 2 crystal sizes
- 59. Igneous Rocks- Classification • Coarse-grained- • Plutonic (Intrusive) • Granite (Sialic) (SIlica and ALuminum rich) • Diorite • Gabbro (Mafic) (MAgnesium and iron (FE) rich) • Dunite & Peridotite (Ultramafic) • Fine-Grained • Volcanic (Extrusive) • Rhyolite (Sialic) • Andesite • Basalt (Mafic)
- 61. Igneous Rock Identification • Granite (& Rhyolite) • High in Si + O • Low in Fe + Mg • Mostly feldspar & quartz • Light-colored • Basalt (& Gabbro) • “Low” in Si + O • High in Fe + Mg • no quartz, abundant ferromagnesian minerals • Dark colored • Andesite (& Diorite- intermediate)
- 67. Sedimentary Rocks How They are Made • Wind and water break down the earth • Bits of earth settle in lakes and rivers • Layers are formed and build up • Pressure and time turn the layers to rock 1. Weathering and erosion 2. Transportation 3. Deposition 4. Consolidation and cementation
- 68. Examples of Sedimentary Rocks Gypsum Sandstone Shale Limestone Conglomerate
- 69. WEATHERING, EROSION, TRANSPORTATION • Weathering- Physical disintegration and chemical decomposition of rocks • Erosion- Physical removal • Transportation- Movement of eroded particles • Chemical vs. Physical Weathering • Effects of weathering • Surface alteration of outcrops • Spheroidal weathering • Differential weathering
- 77. Frost Action
- 78. SEDIMENT • Particle size • Pebbles, cobbles, boulders • Gravel- > 2mm • Sand- 2mm - 0.063mm • Silt - 0.063mm - 0.004mm • Clay- < 0.004 • Deposition Clay-sized particle vs. clay mineral
- 83. Quartz Sandstone
- 84. CHEMICAL SEDIMENTARY ROCKS • Carbonate Rocks • Limestone- made of calcite • Inorganic varieties • micrite, oolites, travertine • Dolomite • Recrystallization • Chert- silica • Evaporites • Rock gypsum • Rock salt
- 86. BIOCHEMICAL SEDIMENTARY ROCKS • Coal • Develops from peat • plant fragments • Lignite • Bituminous Coal • Carbonate Rocks • Limestone- made of calcite • organic varieties • Coquina • Fossiliferous Limestone • Chalk
- 91. Mudcracks
- 94. Sedimentary Rocks as Resources • Non-Metallic • Sand and gravel • Limestone • Clay • Gypsum • Energy Resources • Oil and Gas • Coal
- 95. Thank you For your kind attention