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Chapter 9: Weathering and Erosion - Griffith Public Schools

258258sections1 Weathering and SoilFormationLabClassifying Soils2 Erosion of Earth s SurfaceLabMeasuring Soil ErosionVirtual LabHow are Earth smaterials broken down?What happened to his face?Well, how would you feel if wind, sand, andrain blew in your face for over 5,000 years?Don t forget the blistering sun and nightlychill! Would you feel weathered and torn?Two processes help shape Earth s surface Weathering and a place a home, a park,river, or mountain. What would happen in a year, a hundredyears, even 5,000 years?Science JournalWeathering and ErosionAcademic Standard 3: Students collect and organize data to identify relationships betweenphysical objects, events, and processes.

STEP 3 STEP 3 STEP 2 STEP 1 Preview this chapter’s content and activities at in6.msscience.com a ing Both Erosion Carmen Redondo/CORBIS 530-S1-MSS05_G6_IN 8/17/04 3:33 PM Page 259. ... the atmosphere. Air and water con-tribute to the weathering and erosion of Earth’s surface.

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Transcription of Chapter 9: Weathering and Erosion - Griffith Public Schools

1 258258sections1 Weathering and SoilFormationLabClassifying Soils2 Erosion of Earth s SurfaceLabMeasuring Soil ErosionVirtual LabHow are Earth smaterials broken down?What happened to his face?Well, how would you feel if wind, sand, andrain blew in your face for over 5,000 years?Don t forget the blistering sun and nightlychill! Would you feel weathered and torn?Two processes help shape Earth s surface Weathering and a place a home, a park,river, or mountain. What would happen in a year, a hundredyears, even 5,000 years?Science JournalWeathering and ErosionAcademic Standard 3: Students collect and organize data to identify relationships betweenphysical objects, events, and processes.

2 They use logical reasoning to question their own ideasas new information challenges their conceptions of the natural covers: Academic Standard 2 (Detailed standards begin on page IN8.)Carmen Redondo/CORBISC armen Redondo/CORBIS530-S1-MSS05_G6_IN 8/17/04 3:33 PM Page 258259259 Start-Up ActivitiesWater s ForceThe Grand Canyon is 446 km long, up to 29km wide, and up to 1,829 m deep. The waterof the Colorado River carved the canyon outof rock by wearing away particles and carry-ing them away for millions of years. Overtime, Erosion has shaped and reshapedEarth s surface many times. In this lab, youwill explore how running water formed theGrand a bread pan with packed sand and form a smooth, even Place the bread pan in a plastic wash tub.

3 Position one end of the washtub in a sink under the a brick or wood block under the end of the bread pan beneath the on the water to form a steady trickleof water falling into the pan and observefor 10 min. The washtub should catch theeroded CriticallyIn your Science Journal,draw a top view picture of the erosionpattern formed in the sand by the runningwater. Write a paragraph describing whatthe sand would look like if you had leftthe water running and ErosionMake the following Foldable to compare and contrast weath-ering and sheet of paper and drawoverlapping top sheet along the ovals as a Venn DiagramAs you read the Chapter , list the characteristics unique to weath-ering under the left tab, those unique to erosionunder the right tab, and those characteristicscommon to both under the middle 3 step 3 step 2 step 1 Preview this Chapter s contentand activities at Redondo/CORBIS530-S1-MSS05_G6_IN 8/17/04 3.

4 33 PM Page 259 Weathering Have you noticed potholes in roadways and broken concretein sidewalks? Holes in roads and broken sidewalks show thatsolid materials can be changed by nature. Earth is mostly rockwith three-fourths of its surface covered by a relatively thin layerof water, the oceans. The entire planet is surrounded by a rela-tively thin blanket of air, the atmosphere . Air and water con-tribute to the Weathering and Erosion of Earth s a mechanical or chemical surface process thatbreaks rocks into smaller pieces. Freezing, thawing, oxygen inthe air, and even plants and animals affect the stability of rockand cause rocks to weather, and sometimes to become Weathering When a sidewalk breaks apart, a large slab of concrete is bro-ken into many small pieces.

5 The concrete looks the same. It s justbroken apart. This is similar to mechanical Weathering of weatheringbreaks rocks into smaller pieces with-out changing them chemically. The small pieces are identical incomposition to the original rock, as shown in Figure o o fthe many causes of mechanical Weathering are ice wedging andliving and Soil Formation Identifyprocesses that breakrock apart. Describeprocesses that chemi-cally change rock. Explainhow soil forms when rocks break apartand change chemically. Soil is hometo many organisms, and mostplants need soil in order to grow. Review Vocabularyacid rain:acidic moisture, with apH below Vocabulary Weathering mechanical Weathering chemical Weathering soil topographyFigure 1 The forces of mechani-cal Weathering break apart : Explain that although weathered rock is the basic component of soil, the composition andtexture of soil and its fertility and resistance to Erosion are greatly influenced by plant roots and debris, bacte-ria, fungi, worms, insects, and other covers: (Detailed standards begin on page IN8.)

6 Indiana AcademicStandard : .. Describe that .. three-fourths of [Earth s] surface is cov-ered by a relatively thin layer ofwater, and .. is surrounded by arelatively thin blanket of air. What is this water and air?Jonathan Blair/CORBIS530-S1-MSS05_G6_IN 8/17/04 3:33 PM Page 260 SECTION 1 Weathering and Soil Formation261 Ice WedgingIn some areas of the world, air temperaturedrops low enough to freeze water. Then, when the temperaturerises, the ice thaws. This freezing and thawing cycle breaks uprocks. How can this happen? When it rains or snow melts, waterseeps into cracks in rocks.

7 If the temperature drops below freez-ing, ice crystals form. As the crystals grow, they take upmore space than the water did because when waterfreezes, its molecules move apart. This expansion exertspressure on the rocks. With enough force, the rocks willcrack further and eventually break apart, as shown inFigure wedging also causes potholes to form how ice wedging can break rock and AnimalsPlants and animals also causemechanical Weathering . As shown in Figure 3,plantscan grow in what seem to be the most inconvenientplaces. Their roots grow deep into cracks in rock wherewater collects.

8 As they grow, roots become thicker andlonger, slowly exerting pressure and wedging and prairie dogs also weather rock as doother animals that burrow in the ground. As they bur-row through sediment or soft sedimentary rock, animalsbreak rock apart. They also push some rock and sedi-ment to the surface where another kind of Weathering ,called chemical Weathering , takes place more 2 Over time, freezing water can break apart rock. Water seeps into cracks. The deeper the cracks are, thedeeper water can seep water freezes and expands,forcing the cracks to open ice melts.

9 If the temperaturefalls below freezing again, theprocess will repeat 3 Tree roots can breakrock & E. Thane/Earth Scenes530-S1-MSS05_G6_IN 8/17/04 3:33 PM Page 261262 Chapter 9 Weathering and ErosionChemical Weathering Chemical weatheringoccurs when the chemical composi-tion of rock changes. This kind of Weathering is rapid in tropi-cal regions where it s moist and warm most of the time. Becausedesert areas have little rainfall and polar regions have low tem-peratures, chemical Weathering occurs slowly in these 1summarizes the rates of chemical Weathering for differ-ent climates.

10 Two important causes of chemical Weathering arenatural acids and is chemical Weathering rapid in the tropics?Natural AcidsSome rocksreact chemically with naturalacids in the environment. When water mixes with car-bon dioxide in air or soil, for example, carbonic acidforms. Carbonic acid can change the chemical compo-sition of minerals in rocks, as shown in Figure carbonic acid is weak, it reacts chemicallywith many rocks. Vinegar reacts with the calcium car-bonate in chalk, dissolving it. In a similar way, whencarbonic acid comes in contact with rocks like lime-stone,dolomite, and marble, they dissolve.


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