Minerals and Rocks powerpoint presentation
- 4. Answer: Left picture: blocky/cubic or equant (it has equal growth rate in three dimensions). Middle picture: bladed habit (it resembles a blade, with varied growth rates in 3 dimensions). Right picture: needle-like habit (rapid growth of crystals in one dimension while slow in other dimensions).
- 9. MINERALS AND ROCKS At the end of the lesson, the learners will be able to 1. Classify and describe the three basic rock types; 2. Establish relationships between rock types and the origin and environment of deposition/formation; 3. Understand the different geologic processes involved in rock formation
- 10. Rock Classifications Rocks are classified on the basis of the mode of formation. The three rock types are igneous, sedimentary and metamorphic rocks. IGNEOUS ROCKS rocks that are formed from the solidification of molten rock material (magma or lava). Molten rock material can solidify below the surface of the earth (plutonic igneous rocks) or at the surface of the Earth (volcanic igneous rocks). Minerals are formed during the crystallization of the magma. Note that the rate of cooling is one of the most important factors that control crystal size and the texture of the rock in general.
- 11. Differentiate magma and lava Magma is a molten rock material beneath the surface of the earth. Lava is molten rock material extruded to the surface of the earth through volcanic or fissure eruptions.
- 12. Describe plutonic or intrusive rocks and define the process of formation, the texture and give examples. • from solidified magma underneath the earth • gradual lowering of the temperature gradient at depth towards the surface would cause slow cooling/crystallization • Phaneritic texture • Examples: granite, diorite, gabbro
- 13. Describe volcanic or extrusive rocks and define the process of formation, the texture and give examples. • from solidified lava at or near the surface of the earth • fast rate of cooling/crystallization due to huge variance in the temperature between Earth’s surface and underneath • common textures: aphanitic, porphyritic and vesicular • examples: rhyolite, andesite, basalt • pyroclastic rocks: fragmental rocks usually associated with violent or explosive type of eruption. Examples tuff and pyroclastic flow deposits (ignimbrite)
- 14. 1. Granite on the top left with phaneritic texture and rhyolite on the top right with aphanitic and vesicular texture. 2. Diorite on middle left with phaneritic texture vs andesite on middle right with aphanitic texture. Same composition but different textures 3. Gabbro on bottom left with phaneritic texture vs basalt on bottom right with aphanitic texture. Although the crystals in the gabbro may not be large, they are still visible.
- 15. Igneous rocks are also classified according to silica content: felsic, intermediate, mafic and ultramafic. • felsic: also called granitic; >65% silica, generally light- colored • intermediate: also called andesitic; 55-65% silica; generally medium colored (medium gray) • mafic: also called basaltic; 45-55% silica; generally dark colored • ultramafic: <45% silica; generally very dark colored; composed mainly of olivine and pyroxene which are the major constituents of the upper mantle
- 16. Sedimentary rocks These are rocks that formed through the accumulation, compaction, and cementation of sediments. They generally form at surface or near surface conditions. • Sedimentary processes at or near the surface of the Earth include: weathering of rocks, sediment transport and deposition, compaction and cementation • Factors in sedimentary processes: weathering and transport agents (water, wind ice) • Common sedimentary features: strata and fossils • Strata: >1cm is called bedding and anything less is called lamination; layering is the result of a change in grain size and composition; each layer represents a distinct period of deposition. • Fossils: remains and traces of plants and animals that are preserved in rocks
- 17. Non-clastic / Chemical/Biochemical – derived from sediments that precipitated from concentrated solutions (e.g. seawater) or from the accumulation of biologic or organic material (e.g. shells, plant material). They are further classified on the basis of chemical composition. Clastic/terrigenous - form from the accumulation and lithification of sediments derived from the breakdown of pre-existing rocks. They are further classified according to dominant grain size.
- 18. 1. Conglomerate on top left relatively large and rounded clasts as compared to the angular clasts of the breccia on top right. 2. Sandstone middle left with visible grains and prominent layering and claystone on middle right with several embedded fossils. 3. Non-clastic sedimentary rocks limestone on bottom left and coquina on bottom right.
- 19. Metamorphic rocks rocks that form from the transformation of pre- existing rocks (igneous, sedimentary, or metamorphic rocks) through the process of metamorphism. Metamorphism can involve changes in the physical and chemical properties of rocks in response to heat, pressure, and chemically active fluids. They are commonly formed underneath the earth through metamorphism
- 20. Contact metamorphism • Heat as the main factor: occurs when a pre- existing rocks get in contact with a heat source (magma) • Occurs on a relatively small scale: around the vicinity of intruding magma •Creates non-foliated metamorphic rocks (e.g. hornfels)
- 21. Regional metamorphism • Pressure as main factor: occurs in areas that have undergone deformation during orogenic event resulting in mountain belts • Occurs in a regional/large scale • Creates foliated metamorphic rocks such as schist and gneiss • Non-foliated rocks like marble also form thru regional metamorphism, where pressure is not intense, far from the main geologic event
- 23. Exogenic Processes At the end of the lesson, the learners will be able to 1. Define weathering and distinguish between the two main types of weathering 2. Identify the factors that affect the rate of weathering
- 24. CAN YOU DEFINE EACH TERMS: a. Weathering b. Mechanical weathering c. Abrasion d. Chemical weathering e. Hydrolysis f. Carbonation g. Oxidation h. Frost wedging
- 25. QUESTIONS "Can you name any natural cause or process that could possibly break the rock into smaller pieces?" “If the early Earth’s crust was mainly composed of rocks, why do we have layers of soil on the surface now? Where did these soils came from?”
- 26. Processes that lead to the mechanical disintegration of rocks: a. Frost wedging- when water gets inside the joints, alternate freezing and thawing episodes pry the rock apart. b. Salt crystal growth- force exerted by salt crystal that formed as water evaporates from pore spaces or cracks in rocks can cause the rock to fall apart c. Abrasion – wearing away of rocks by constant collision of loose particles d. Biological activity – plants and animals as agents of mechanical weathering
- 27. Processes of chemical weathering : a. Dissolution – dissociation of molecules into ions; common example includes dissolution of calcite and salt b. Oxidation- reaction between minerals and oxygen dissolved in water c. Hydrolysis- change in the composition of minerals when they react with water
- 28. Factors that affect the type, extent, and rate at which weathering takes place: a. Climate – areas that are cold and dry tend to have slow rates of chemical weathering and weathering is mostly physical; chemical weathering is most active in areas with high temperature and rainfall b. Rock type – the minerals that constitute rocks have different susceptibilities to weathering. Those that are most stable to surface conditions will be the most resistant to weathering. Thus, olivine for example which crystallizes at high temperature conditions will weather first than quartz which crystallizes at lower temperature conditions. c. Rock structure- rate of weathering is affected by the presence of joints, folds, faults, bedding planes through which agents of weathering enter a rock mass. Highly-jointed/fractured rocks disintegrate faster than a solid mass of rock of the same dimension d. Topography- weathering occurs more quickly on a steep slope than on a gentle one e. Time- length of exposure to agents of weather determines the degree of weathering of a rock
- 29. ENRICHMENT: Break Me Down 1. Divide the class into small groups of 3-5 students. Each group will need the following set of materials: antacid tablets, 2 clear cups, and stopwatch. 2. Put equal volume of equal temperature water into 2 cups. 3. Drop one whole antacid tablet into one of the cups. Record your observation and the time from when the tablet is added until it is completely dissolved and no traces of the tablet is visible. 4. Break one tablet into smaller pieces by putting pressure on it and drop into the other cup. Record your observation and dissolution time of the tablet. 5. Wash the cups making sure there are no pieces of antacid tablet left. 6. Repeat steps 3 to 5 but this time use hot water. 7. Fill the table with dissolution times (in seconds) they have recorded.
- 31. DISCUSSION a. In which setup did the reaction occur most rapidly? In which setup did it occur most slowly? b. What is the relationship between particle size and speed it takes for the tablet to dissolve? How does this relationship apply to weathering in nature? c. In the activity you have just finished, how does mechanical weathering contribute to chemical weathering? How can you demonstrate the fact that chemical weathering can hasten mechanical weathering? d. Compare dissolution times in room temperature water and hot water. What is the relationship between temperature and weathering rate
- 32. List some everyday examples of weathering. Identify and explain whether these everyday occurrences show physical or chemical weathering. During your recent visit to the cemetery, you noticed the inscriptions on some headstones have become barely legible whereas inscriptions on others are sharp and clear. Cite three possible factors that contributed to the present state of the headstone inscriptions.
- 33. Exogenic Processes (Erosion and Deposition) At the end of this lesson, the learners will be able to: 1. Identify the different agents of erosion and deposition 2. Describe characteristic surface features and landforms created and the processes that contributed to their formation
- 34. KEY TERMS: A. Erosion B. Deposition C. Abrasion D. Alluvial fans E. Oxbow lake F. Glacier G. Arete H. Drumlin I. Dune J. Deflation J. Ventifacts K. Barrier island L. Spit
- 35. WEATHERING VS. EROSION 1. Weathering — the disintegration and decomposition of rock at or near the Earth surface 2. Erosion — the incorporation and transportation of material by a mobile agent such as water, wind, or ice 3. Weathering occurs in situ, that is, particles stay put and no movement is involved. As soon as the weathering product starts moving (due to fluid flow) we call the process erosion. 4. Weathering, erosion/transportation, and deposition are exogenic processes that act in concert, but in differing relative degrees, to bring about changes in the configuration of the Earth’s surface.
- 36. AGENTS OF EROSION 1. Running Water “running water” encompasses both overland flow and stream flow.
- 38. Factors that affect stream erosion and deposition i. Velocity – dictates the ability of stream to erode and transport; controlled by gradient, channel size and shape, channel roughness, and the amount of water flowing in the channel ii. Discharge – volume of water passing through a cross- section of a stream during a given time; as the discharge increases, the width of the channel, the depth of flow, or flow velocity increase individually or simultaneously
- 39. How various properties of stream channel change from its headwaters to its mouth. From headwaters to mouth: Channel slope ↓, Channel roughness ↓, Discharge ↑, Channel size↑, Flow velocity↓
- 40. How streams erode their channels, transport, and deposit sediments? i. Styles of erosion: Vertical erosion (downcutting), lateral erosion, headward erosion ii. Stream flow erosion occurs through: Hydraulic action, abrasion, solution iii. Streams transport their sediment load in three ways: in solution (dissolved load), in suspension (suspended load), sliding and rolling along the bottom (bed load) iv. A stream’s ability to transport solid particles is described by: competence (size of the largest particle that can be transported by the stream) and capacity (maximum load a stream can transport under given conditions) v. Deposition occurs when a river loses its capacity to transport sediments. With decrease in velocity and competence, sediments start to settle out. River deposits are sorted by particle size.
- 42. Erosional and depositional landforms created by a stream: i. Erosional landforms: River valleys, waterfalls, potholes, terraces, gulley/ rills, meanders (exhibit both erosional and depositional features), oxbow lake, peneplane ii. Depositional landforms: Alluvial fans/cones, natural levees, deltas
- 44. 2. Ocean or sea waves
- 51. How waves erode and move sediment along the shore? i. Shoreline erosion processes: Hydraulic action, abrasion, corrosion ii. Transport by waves and currents: Longshore current, beach drift
- 52. Features created by wave erosion and deposition. i. Erosional features: wave-cut cliff, wave-cut platform, marine terrace, headland, stacks and sea arches ii. Depositional features: beach, spit, baymouth bar, tombolo, barrier island
- 53. 3. Glaciers a. Glacier — a moving body of ice on land that moves downslope or outward from an area of accumulation (Monroe et. al., 2007)
- 54. Types of glaciers: i. Valley (alpine) glaciers — bounded by valleys and tend to be long and narrow ii. Ice sheets (continental glaciers) — cover large areas of the land surface; unconfined by topography. Modern ice sheets cover Antarctica and Greenland iii. Ice shelves — sheets of ice floating on water and attached to the land. They usually occupy coastal embayments.
- 55. Mechanisms that account for glacial movement. i. Glaciers form in regions where more snow falls than melts. Snow accumulates then goes through compaction and recrystallization, eventually transforming into glacial ice ii. Glaciers move to lower elevations by plastic flow due to great stress on the ice at depth, and basal slip facilitated by meltwater which acts as lubricant between the glacier and the surface over which it moves.
- 56. features created by erosion due to glaciers. i. Ice cannot erode the bedrock on its own. Glaciers pick up rock fragments and use them to abrade the surfaces over which they pass. ii. Processes responsible for glacial erosion: Plucking (lifting pieces of bedrock beneath the glacier) and abrasion (grinding and scraping by sediments already in the ice). Plucking is responsible for creating roche moutonnee (Landforms created by continental glaciers). Abrasion yields glacial polish and glacial striations. iii. Landforms created by valley glacier erosion: cirque, tarn, arête, horn, hanging valley, ushaped valley, pater noster lakes, fjord
- 59. All glacial deposits are called glacial drift, and glacial drift are comprised of two types: (1) till, deposited directly by ice, unsorted, and composed of many different particle sizes; and (2) stratified drift, deposited by the glacial meltwater and thus has experienced the sorting action of water. As its name suggests, deposits are layered and exhibit some degree of sorting.
- 61. 2. Moraines are ridges of till, classified according to their position relative to the glacier: lateral (edge of valley glaciers) moraine; end (front or head of glacier) moraine; ground (base of glacier) moraine; and medial (middle) moraine. Medial moraines form when lateral moraines join as tributary glaciers come together. Other till features: erratics and drumlins.
- 62. 4. Wind a. Processes associated with erosion and transportation by wind. i. Wind erodes by: deflation (removal of loose, fine particles from the surface), and abrasion (grinding action and sandblasting) ii. Deflation results in features such as blowout and desert pavement. Abrasion yields ventifacts and yardangs. iii. Wind, just like flowing water, can carry sediments such as: (1) bed load (consists of sand hopping and bouncing through the process of saltation), and (2) suspended load (clay and silt-sized particles held aloft).
- 63. B. Features associated with aeolian erosion and deposition. i. Features created by wind erosion: blowout and desert pavement created by deflation, ventifacts and yardangs resulting from abrasion ii. Two types of wind deposits: (1) dunes which are hills or ridges of wind-blown sand, and (2) loess which are extensive blankets of silt that were once carried in suspension iii. The size, shape, and arrangement of dunes are controlled by factors such as sand supply, direction and velocity of prevailing wind, and amount of vegetation. There are six major kinds of dunes: barchan dunes, transverse dunes, barchanoid dunes, longitudinal dunes, parabolic dunes, star dunes. iv. The primary sources of sediments contributing to loess deposits are deserts and glacial deposits.
- 64. 5. Groundwater How groundwater erodes rock material? i. The main erosional process associated with groundwater is solution. Slow-moving groundwater cannot erode rocks by mechanical processes, as a stream does, but it can dissolve rocks and carry these off in solution. This process is particularly effective in areas underlain by soluble rocks, such as limestone, which readily undergoes solution in the presence of acidic water. ii. Rainwater reacts with carbon dioxide from atmosphere and soil to form a solution of dilute carbonic acid. This acidic water then percolates through fractures and bedding planes, and slowly dissolves the limestone by forming soluble calcium bicarbonate which is carried away in solution.
- 65. karst topography and its associated landforms. i. Karst topography —a distinctive type of landscape which develops as a consequence of subsurface solution. It consists of an assemblage of landforms that is most common in carbonate rocks, but also associated with soluble evaporate deposits. (1) Cave/Cavern – forms when circulating groundwater at or below the water table dissolves carbonate rock along interconnected fractures and bedding planes. A common feature found in caverns is dripstone, which is deposited by the dripping of water containing calcium carbonate. Dripstone features are collectively called speleothems, and include stalactites, stalagmites, and columns (2) Sinkholes (Dolines) – circular depressions which form through dissolution of underlying soluble rocks or the collapse of a cave’s roof. (3) Tower karst – tall, steep-sided hills created in highly eroded karst regions.
- 66. 6. Gravity a. Mass wasting — the downslope movement of soil, rock, and regolith under the direct influence of gravity b. Factors that control mass wasting processes include: i. As the slope angle increases, the tendency to slide down the slope becomes greater. ii. Role of water: adds weight to the slope, has the ability to change angle of repose, reduces friction on a sliding surface , and water pore pressure reduces shear strength of materials c. State that there are various types of mass movements, which will be discussed in upcoming lessons.
- 67. ENRICHMENT (15 MINS) Activity: Annotated sketch of areas of erosion and deposition Have learners use a map to locate a river or coastline nearest their community. Direct them to identify locations of erosion and deposition by making an annotated sketch of the river or coast. Explain how the different erosional and depositional features may have formed. Predict how the river/coast may change shape in the future, and identify areas susceptible to fluvial/coastal erosion. (A satellite image from Google Earth of the lower and middle course of Agno River, provided in an appendix to this teaching guide, may be used for this activity).
- 69. Exogenic Processes (Mass Wasting) At the end of this lesson, the learners will be able to: 1. Identify the controls and triggers of mass wasting 2. Distinguish between different mass wasting processes
- 70. KEY TERMS a. Mass wasting b. Landslide c. Regolith d. Angle of repose e. Debris flow f. Creep g. Slump h. Rock slide i. Submarine slump
- 71. Controlling factors in mass wasting SLOPE ANGLE i. Component of gravity perpendicular to the slope which helps hold the object in place ii. Component of gravity parallel to the slope which causes shear stress and helps move objects downslope iii. On a steep slope, the slope-parallel component increases while the slope- perpendicular component decreases.
- 72. ROLE OF WATER i. Water has the ability to change the angle of repose (the steepest slope at which a pile of unconsolidated grains remain stable). ii. Addition of water from rainfall or snowmelt adds weight to the slope. iii. Water can reduce the friction along a sliding surface
- 73. PRESENCE OF TROUBLESOME EARTH MATERIALS i. Expansive and hydrocompacting soils – contain a high proportion of smectite or montmorillonite which expand when wet and shrink when they dry out, ii. Sensitive soils – clays in some soils rearrange themselves after dissolution of salts in the pore spaces. Clay minerals line up with one another and the pore space is reduced. iii. Quick clays – water-saturated clays that spontaneously liquefies when disturbed
- 74. WEAK MATERIALS AND STRUCTURES i. Become slippage surfaces if weight is added or support is removed (bedding planes, weak layers, joints and fractures, foliation planes
- 75. Classify mass wasting processes A. SLOPE FAILURES - sudden failure of the slope resulting in transport of debris downhill by rolling, sliding, and slumping. i. Slump – type of slide wherein downward rotation of rock or regolith occurs along a curved surface ii. Rock fall and debris fall– free falling of dislodged bodies of rocks or a mixture of rock, regolith, and soil in the case of debris fall iii. Rock slide and debris slide- involves the rapid displacement of masses of rock or debris along an inclined surface
- 76. B. SEDIMENT FLOW - materials flow downhill mixed with water or air; Slurry and granular flows are further subdivided based on velocity at which flow occurs i. Slurry flow – water-saturated flow which contains 20-40% water; above 40% water content, slurry flows grade into streams (1) Solifluction – common wherever water cannot escape from the saturated surface layer by infiltrating to deeper levels; creates distinctive features: lobes and sheets of debris (2) Debris flow – results from heavy rains causing soil and regolith to be saturated with water; commonly have a tongue-like front; Debris flows composed mostly of volcanic materials on the flanks of volcanoes are called lahars. (3) Mud flow – highly fluid, high velocity mixture of sediment and water; can start as a muddy stream that becomes a moving dam of mud and rubble; differs with debris flow in that fine-grained material is predominant
- 77. II. GRANULAR FLOW – contains low amounts of water, 0- 20% water; fluid-like behaviour is possible by mixing with air (1) Creep – slowest type of mass wasting requiring several years of gradual movement to have a pronounced effect on the slope ; evidence often seen in bent trees, offset in roads and fences, inclined utility poles. the pore spaces such as sand flowing down the dune face (3) Debris avalanche – very high velocity flows involving huge masses of falling rocks and debris that break up and pulverize on impact; often occurs in very steep mountain ranges.
- 78. Subaqueous mass wasting Subaqueous mass movement occurs on slopes in the ocean basins. This may occur as a result of an earthquake or due to an over-accumulation of sediment on slope or submarine canyon. 3 types: a. Submarine slumps - similar to slumps on land b. Submarine debris flow – similar to debris flows on land c. Turbidity current – sediment moves as a turbulent cloud
- 79. Events that trigger mass wasting processes a. Shocks and vibrations – earthquakes and minor shocks such as those produced by heavy trucks on the road, man-made explosions b. Slope modification – creating artificially steep slope so it is no longer at the angle of repose c. Undercutting – due to streams eroding banks or surf action undercutting a slope d. Changes in hydrologic characteristics – heavy rains lead to water- saturated regolith increasing its weight, reducing grain to grain contact and angle of repose; e. Changes in slope strength – weathering weakens the rock and leads to slope failure; vegetation holds soil in place and slows the influx of water; tree roots strengthen slope by holding the ground together f. Volcanic eruptions - produce shocks; may produce large volumes of water from melting of glaciers during eruption, resulting to mudflows and debris flows
- 80. Enumerate and discuss some landslide warning signs a. Springs, seeps, or saturated ground in areas that have not typically been wet before. b. New cracks or unusual bulges in the ground, street pavements or sidewalks. c. Soil moving away from foundations. d. Ancillary structures such as decks and patios tilting and/or moving relative to the main house. e. Tilting or cracking of concrete floors and foundations. f. Broken water lines and other underground utilities. g. Leaning telephone poles, trees, retaining walls or fences. H. Offset fence lines. i. Sunken or down-dropped road beds. j. Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil content). k. Sudden decrease in creek water levels though rain is still falling or just recently stopped. l. Sticking doors and windows, and visible open spaces indicating jambs and frames out of plumb. m. A faint rumbling sound that increases in volume is noticeable as the landslide nears. n. Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.
- 81. ENRICHMENT Three friends (Sara, Amira, and Gozen) live in the small city of Shahrabad, which is located in a beautiful mountain valley. The bottom of the valley has a small river running through it. The walls of the valley have land that includes forests and farms. The friends have lived there since they were young and they know that earthquakes sometimes happen there. They have only felt one small earthquake, but their parents and grandparents have told stories about some strong earthquakes that have happened in the area. Sometimes, during extreme weather like heavy snow or rain, the road that comes into Shahrabad from a nearby city is closed because rocks have fallen on the road or the road has washed away. Sara and Amira live next to each other on farms located on slopes in the valley. Sara's farm used to have a natural spring at a crack between two rocks that produced drinking water for both Sara's and Amira's families, but the spring stopped producing water about a year ago. Recently, a neighbour has started complaining that some parts of his land have become very soggy and soaked with water, especially near the bottom
- 82. DISCUSSION Question 1: What are natural springs, and what are a couple of reasons why the spring on Sara's farm stopped giving water? Question 2: What are some possible reasons for why the fence is slowly tipping over? Question 3: What are some possible reasons for the cracks in the walls? What are some ways to find out what is really happening? Question 4: What would cause trees to grow like this? Question 5: Where should the friends go first? Question 6: What are some possible causes for the low river water level, and what should the girls do about it