Presentation on theme: "Weathering: Processes of Change"— Presentation transcript:
1Weathering: Processes of Change chemical weatheringmechanical weatheringmoving watererosionicedepositionwavesgravitywindglaciersAcidsabrasion
2How does weathering occur? EQ:How does weatheringoccur?
3Weathering Describe three ways abrasion occurs in nature. List three things that cause chemical weathering of rocks.Describe the similarity in the ways tree roots and ice mechanically weather rock.Describe five (5) sources of chemical weathering.
5Processes of Change (5)Weathering and erosion wear down, deposition fills in Earth’s surface.Weathering is the slow wearing away or breaking down of objects exposed to Earth’s atmosphereTwo kinds of weathering act on Earth’s surfaceMechanical weatheringChemical weathering
6WeatheringWeathering is the process by which rock materials are broken down by the action of physical or chemical processes.Mechanical weathering is the breakdown of rock into smaller pieces by physical means. (ice, wind, water, gravity, plants, animals)Chemical weathering is the process by which rocks break down as a result of chemical reactions. Water, weak acids, and air can cause chemical weathering.
7Mechanical Weathering (4) When objects are broken down into small pieces but their chemical makeup doesn’t changeWind and moving water are two main causes of mechanical weatheringRepeated changes in temperature (freeze, melt, freeze, melt again)
8Chemical Weathering (5) Material of an object is changedProduces underground cavernsStatue of Liberty needed repairs because of chemical weatheringExamples:Rust (oxidation)Acid rain precipitation
9Erosion (5) The natural moving of material from one place to another Erosion transports weathered rock materialCauses of Erosion:Moving waterGravityWindGlaciers (moving rivers of ice)Waves
10Deposition (5)Land torn down in one place is “deposited” in another placeGravity can cause a landslide moving mud, rock and soil down a hillWind erosion can move sand and deposit it in another areaGlaciers (rivers of ice) scrape rocks off the land and moves them downhill
11Glaciers will stop moving and even retreat and cut a steep U-shaped valley in the land
12Erosion caused by mountain rivers form V-shaped valleys
13Hurricanes create waves that erode beaches and cliffs
14Breaking of waves on a beach can wear it away Breaking of waves on a beach can wear it away. The larger the waves, the faster is the rate of erosion.
156 Agents of Mechanical Weathering 1. Water – as rocks and pebbles roll along the bottom of flowing water, they bump and scrape against each other, causing these rocks to become rounded and smooth.2. Wind – wind blows sand and silt against exposed rock eventually wearing away the rock’s surface.3. Gravity – rocks grind against each other during a rock slide, creating smaller and smaller rock fragments. Anytime one rock hits another rock, abrasion takes place.
16AbrasionAbrasion – the grinding and wearing away of rock surfaces through mechanical action of other rock or sand pebbles.The three ways that can cause abrasion are wind, water, and gravity.
18Frost Action4. Ice – water seeps into cracks during warm weather. When the temperature drops, the water freezes and expands, causing the ice to push against the sides of the crack. This causes the crack in the rock to widen eventually braking the rock apart.
20Plants and Animals5. Some plants can easily break rocks. The roots grow through existing cracks in rocks. The growth causes the root to expand, forcing the crack to widen. The force can eventually split the rock apart.6. Animals that live in the soil (moles, prairie dogs, insects, worms, gophers), cause a lot of weathering. By burrowing in the ground, these living creatures brake up soil and loosen rocks to be exposed to further weathering.
22Agents of Mechanical Weathering The breaking down of rock through physical means
23Flowing WaterAs rocks and pebbles roll along the bottom of flowing water, they bump and scrape against each other, causing these rocks to become rounded and smooth.
24WINDwind blows sand and silt against exposed rock eventually wearing away the rock’s surface.
25GRAVITYRocks grind against each other during a rock slide, creating smaller and smaller rock fragments. Anytime one rock hits another rock, abrasion takes place.
26ICEWater seeps into cracks during warm weather. When the temperature drops, the water freezes and expands, causing the ice to push against the sides of the crack. This causes the crack in the rock to widen.
27AnimalsAnimals that live in the soil (moles, prairie dogs, insects, worms, gophers), cause a lot of weathering. By burrowing in the ground, these living creatures break up soil and loosen rocks to be exposed to further weathering
28PLANTSThe roots grow through existing cracks in rocks. The growth causes the root to expand, forcing the crack to widen. The force can eventually split the rock apart.
293 Agents of Chemical Weathering These (3) agents weaken the bonds between minerals grains of the rock.
303 Agents of Chemical Weathering 1. Water – can cause rock to be broken down and dissolve. Can take thousands of years to take place.2. Air – the process of oxidation is a chemical reaction in which an element (iron) combines with oxygen, causing rust.3. Weak Acids – Includes:acids in precipitationacids in Groundwateracids in living things
31Weak Acids Acids in Living Things Lichens, which consist Acids in Precipitationof fungi and algae, living Rain, sleet, or snowtogether, contribute that contains morechemical weathering acid than normalAcids in Groundwater(forming a karst feature,known as a cavern)
32Three Sources of Weak Acids Acid Precipitation – rain, sleet, or snow that contains a high concentration of acid. Normal precipitation is acidic, acid precipitation contains more acid than normal.Acids in Groundwater – carbonic acid or sulfuric acid reacts with rocks in the ground, causing a chemical reaction, eating away at the rock.Acids in Living Things – Lichens produce acids that slowly break down rock.
33Agents of Chemical Weathering These agents weaken the bonds between mineral grains of the rock.
34WaterCan cause rock to be broken down and dissolve. Can take thousands of years to take place.
35AIRThe process of oxidation is a chemical reaction in which an element (for example iron) combines with oxygen, causing rust.
36Acid Precipitation (weak acid) Rain, sleet, or snow that contains a high concentration of acid. Normal precipitation is acidic, acid precipitation contains more acid than normal.
37Acids in Groundwater (weak acid) Carbonic acid or sulfuric acid reacts with rocks in the ground, causing a chemical reaction, eating away at the rock. This is a karst landscape.
38Acids in Living Things (weak acid) Lichens produce acids that slowly break down rock by chemical means.
39SummaryWind, water, and gravity cause mechanical weathering by abrasion.Ice wedging is a form of mechanical weathering in which water seeps into rock cracks and then freezes and expands.Animals and plants cause mechanical weathering by turning the soil and breaking apart rocks.Water, acids, and air chemically weather rock by weakening the bonds between mineral grains of the rock.
40Quick CheckWhich of the following things cannot cause mechanical weathering?A. waterB. acidsC. windD. animals
41Quick Check Which of the following is a type of frost action? A. abrasionB. oxidationC. ice wedgingD. gravity
42Quick CheckWhich of the following types of chemical weathering causes a karst landscape, such as a cavern?A. lichensB. acid precipitationC. acids in groundwaterD. water
43Quick Check How do lichens slowly break down a rock? A. by abrasion B. by mechanical meansC. by ice wedgingD. by chemical means
44Quick CheckWhich of the following will most likely experience oxidation?A. tennis ballB. aluminum canC. wooden fenceD. Bicycle tire
45Quick CheckThe grinding and wearing away of rock surfaces through the mechanical action of other rock or sand particlesRain, sleet, or snow that contains a high concentration of acidsThe process by which rocks break down as a result of chemical reactionsThe breakdown of rock into smaller pieces by physical meansA chemical reaction in which an element, such as iron, combines with oxygen to form an oxideThe process by which rock materials are broken down by the action of physical or chemical processesa. mechanical weatheringb. oxidationc. weatheringd. acid precipitatione. abrasionf. chemical weathering
46Rates of Weathering What is differential weathering? How does surface area affect the rate of weathering?How does climate affect the rate of weathering?Why do mountaintops weather faster than rocks at sea level?
47Differential Weathering Differential weathering is a process by which softer, less weather resistant rocks wear away and leave harder, more weather resistant rocks behind.Hard rocks weather more slowly than softer rocks.
48Devils TowerDevils Tower appears as it does today because of differential weathering. As surrounding rock was worn away, the hard rock of the tower was exposed.
49The Shape of RocksWeathering takes place on the outer surface of rocks.The more surface area exposed to weathering, the faster the rock will be worn down.As the surface area increases, the rate of weathering also increases.If a large rock is broken into smaller pieces, weathering of the rock happens much faster.The rate of weathering increases because a smaller rock has more surface area to volume than a larger rock.More of the smaller rock is exposed to the weathering process.
51Weathering and Climate The rate of chemical weathering is faster in warm, humid climates than cold, dry climates because of oxidation.Oxidation happens when the temperature is higher and when water is present.Water increases the rate of mechanical (physical) weathering (ice wedging).Repeated changes in temperature (freeze, thaw, freeze, thaw) is a major factor in mechanical weathering.
53Weathering and Elevation Mountaintops weather faster than rocks at sea level because they are exposed to more wind, rain, and ice than rocks at sea level or lower elevations.The increase in wind, rain, and ice increases the effects of mechanical and chemical weathering. This increase in elevation causes peaks of mountains to weather faster.Gravity affects the rate of weathering:SteepnessRainwaterRemoval of sediment exposes new rock to weatheringAbrasionIncreased surface area of mountain
54Weathering and Elevation The Ice, Rain, and Wind that these mountain peaks are exposed to cause them the weather at a fast rate.
55Summary Hard rocks weather more slowly than softer rocks. The more surface area of a rock that is exposed to weathering, the faster the rock will be worn down.Chemical weathering occurs faster in warm, humid climates.Weathering occurs faster at high elevations because of an increase in ice, rain, and wind.
56Quick CheckWhat three factors determine the rate at which rock weathers?
57Quick CheckThe process by which softer, less weather resistant rocks wear away and leave harder, more weather-resistant rocks behind is calledA. mechanical weatheringB. chemical weatheringC. differential weatheringD. acid precipitation
58Quick Check Weathering takes place at different rates on the outer surface of rocks.on all rocks equally.inside the rocks.
59Quick Check Because of a large rock’s volume, it will weather unevenly.weather relatively quickly.not weather at all.weather relatively slowly.
60Quick CheckWhat is the average weather condition in an area over a long period of time called?_______________
61Quick CheckChemical weathering such as oxidation occurs more quickly in a climate that is ___________ and ________________.1.2.
62Quick Check Weathering occurs faster at high elevations because of an increase in wind but not ice or rain.an increase in ice and rain but not wind.a decrease in wind, ice, and rain.an increase in wind, ice, and rain.
63From Bedrock to Soil What is soil formed from? What is bedrock What is humus?What are soil horizons?
64The Source of SoilSoil is a loose mixture of small mineral fragments, organic matter, water, and air that can support the growth of vegetation.Bedrock is the layer of rock beneath soil.Parent rock is the rock formation that is the source of soil.Soil that is blown or washed away from its parent soil is called transported soil.Wind, water, and movements of glaciers can transport or move soil from one place to another.
66Soil Properties Soil is made from different-sized materials. Soil texture is the soil quality based on the proportions of soil particles.Soil texture can influence the ability of water movement through the soil.Soil structure is the arrangement of soil particles.Consistency describes a soil’s ability to be worked and broken up for farming.Infiltration is the ability of water to move through soil.
67Soil PropertiesSome soils are rich in nutrients, some are poor in nutrients.Soil fertility is the soil’s ability to hold nutrients and to supply nutrients to a plant.Humus is the dark, organic material formed in soil from the decayed remains of plants and animals.
69Soil Horizons Soil horizons are the horizontal layers of soil. The top layer of soil is called topsoil, containing more humus than the other layers of soil, rich in nutrients plants need to be healthy.Good topsoil is necessary for farming.
71Soil pH Soils can be acidic or basic. The pH scale, ranging from 0 to 14, is used to measure the acidity of a substance.7 is neutral; below 7 is acidic; above 7 is basic.Different plants need different types of soil.The right pH for a soil depends on the plants growing in it.
73Summary Soil (loam) is formed from the weathering of bedrock. Soil texture affects how soil can be worked for farming and how well water passes through it.The ability of soil to provide nutrients so that plants can survive and grow is called soil fertility.The pH of a soil influences which nutrients plants can take up from the soil.Different climates have different types of soil, depending on the temperature and rainfall.
74Quick Check a. soil b. transported soil c. parent rock d. bedrock 1.Soil that is blown or washed away from its parent rock2. The layer of rock beneath the soil3. A rock formation that is the source of mineral fragments in the soil4. A loose mixture of mineral fragments, organic material, water, and air that can support vegetationa. soilb. transported soilc. parent rockd. bedrock
75Quick Check Soil quality based on the proportions of soil particles The arrangement of soil particlesAbility of water to move through soilSoil’s ability to be broken up for farminga. soil structure b. infiltration c. consistency d. soil texture
76Quick CheckWhat is soil’s ability to hold nutrients and to supply nutrients to a plant?Soil structureSoil textureSoil horizonsSoil fertility
77Quick CheckWhat do we call the removal of substances from soil due to water passing through it?WedgingInfiltrationErosionleaching
78Quick CheckWhat is the layer of soil that often contains the most humus?HorizonParent rockTopsoilbedrock
79Quick Check What is soil that has a pH below 7 called? Neutral Acidic Basicmidpoint
80Quick Check What is the correct pH for growing plants? 7 Above 7 Below 7It depends upon the plant
81EQ: How can we conserve our soil? Soil ConservationEQ: How can we conserve our soil?
82The Importance of SoilSoil provides minerals and other nutrients to plants.Without nutrients, plants cannot grow.All animals get their energy from eating plants or eating animals that eat plants.If plants do not get their nutrients from the soil, animals cannot get their nutrients from the plants
84Housing and Water Storage Soil provides a place for animals to live.The area where plants and animals live is called a habitat.If the soil disappears, then so does the habitat.Soil stores water for plants.Without soil to hold water, plants cannot get the moisture of nutrients they need to survive.
85Soil Damage and Loss Soil loss is a serious problem around the world. Soil damage and loss can come from overuse or poor farming techniques.Plants cannot grow in soil that is infertile.Without plants to hold soil in place the area can become a desertDesertification and land degradation
86Providence Canyon in Georgia, has suffered soil erosion from the cutting of forests for farmland.
87Soil Erosion Without plants, soil can be blown or wash away. If soil is left unprotected, it can be exposed to erosionErosion is the process in which water, wind, or gravity transports soil or sediment from one location to another.By taking care of vegetation, you also take care of the soil.
88Soil Conservation Techniques Contour Farming – to prevent erosion on a hill, the rows of plants act as a series of dams instead of a series of rivers.Terracing – on a steep hill, terracing changes the a steep hill into a series of smaller, flatter fields.No-till Farming – the practice of leaving old stalks, providing cover from rain.Cover Crops – crops that are planted between harvests to replace certain nutrients and prevent erosion.
90SummarySoil is important for plants to grow, for animals to live in, and for water to be stored.Soil erosion and soil damage can be prevented by no-till farming, contour plowing, terracing, using cover crop, and practicing crop rotation.
91Quick CheckIn your own words, what is the definition of soil conservation?
92AnswerSoil conservation is a method used to protect soil from erosion and nutrient depletion.
93Quick CheckIn your own words, what is a definition for erosion?
94AnswerErosion is a process by which soil is moved or transported from one location to another location by wind, water, or gravity.
95Quick CheckPracticing which of the following soil conservation techniques will replace nutrients in the soil?Cover crop useNo-till farmingTerracingCountour plowing
96Quick CheckWhat are three (3) important benefits that soil provides?
97Answer Soil importance: provides minerals and nutrients to plants, provides housing for animals,stores water.solid surface to walk upon
98Quick CheckList five (5) methods of soil conservation, and describe how each helps prevent the loss of soil.
99AnswerCrop rotation – slows down nutrient depletion, because different crops use different nutrientsContour Plowing – plowed rows across a slope act as a series of dams to prevent erosionTerracing – prevents erosion by diving a hillside into a series of flat fieldsNo-till Farming – prevents erosion from water runoff by leaving cover over the soilCover Crops – prevents erosion from water runoff by providing cover for the soil