1. The Lithosphere

2. Weathering and Erosion Weathering is the chemical and physical processes by which rocks on or near Earth’s surface break down and change. Erosion is the removal and transport of weathered material from one location to another 1 on 1 Slide 2 What is the relationship between weathering and erosion?

3. Mechanical Weathering Mechanical weathering - process by which rocks and minerals break down into smaller pieces without changing their composition. Wears down rocks and minerals and does not involve any change in a rock’s composition. Can be caused by temperature and pressure

4. Temperature in Mechanical Weathering – In many places on Earth’s surface, water collects in the cracks of rocks and rock layers. – If the temperature drops to the freezing point the water freezes, expands, exerts pressure on the rocks, and may cause the rocks to split. – When the temperature then rises, the ice in the cracks of rocks and rock layers melts.

5. Pressure  Bedrock at great depths is under pressure from the overlying rock layers. When the overlying rock layers are removed, the pressure on the bedrock is reduced.  The bedrock surface, is then able to expand, and long, curved cracks known as joints can form that lead to exfoliation.  Exfoliation is the process by which outer rock layers are stripped away over time.  The roots of plants can also exert pressure causing rocks to split

6. Chemical Weathering Chemical weathering is the process by which rocks and minerals undergo changes in their composition as the result of chemical reactions Caused by: water, oxygen, carbon dioxide, and acids.

7. Water – Chemical reactions between rocks and water result in the formation of new minerals and the release of dissolved substances. – Water is an important agent in chemical weathering because it can dissolve many kinds of minerals and rocks.

8. Oxidation Oxidation is the chemical reaction of oxygen with other substances. Iron in rocks and minerals readily combines with oxygen to form minerals with the oxidized form of iron 1 on 1 Slide 8 What is the function of oxygen in combining with other substances like iron?

9. Carbon Dioxide – Carbon dioxide, which is produced by living organisms during respiration, contributes to chemical weathering – combines with water in the atmosphere, forms a weak carbonic acid that falls as acid precipitation. – Carbonic acid reacts with minerals such as calcite in limestone and marble to dissolve rocks and can also affect silicate minerals

10. Climate – major influence on the rate of chemical weathering. – The interaction between temperature and precipitation has the greatest effect on a region’s rate of weathering. – Chemical weathering occurs readily in climates with warm temperatures, abundant rainfall, and lush vegetation.

11. Rates of Weathering Physical weathering occurs readily in cool, dry climates – Physical weathering rates are highest in areas where water undergoes repeated freezing and thawing. – rocks and minerals in Asheville experience a higher rate of weathering than those in Phoenix

12. Rates of Weathering – The characteristics of rocks, including how hard or resistant they are to being broken down, depend on their type and composition. – In general, sedimentary rocks are more easily weathered than harder igneous and metamorphic rocks

13. Surface Area – Mechanical weathering breaks up rocks into smaller pieces. – As the pieces get smaller, their surface area increases. – The greater the total surface area, the more weathering that occurs.

14. Topography and other factors – Earth materials on level areas are likely to remain in place as they undergo changes. – Materials on slopes have a greater tendency to move exposing underlying rock surfaces and for weathering – Decaying organic matter and living plant roots release carbon dioxide, combines with water to produce acid, increases the weathering rate.

15. Erosion Deposition is the process of dropping materials in another location when the movement of transported materials slows down. Gravity is associated with many erosional agents, because the force of gravity tends to pull all materials downslope.

16. Erosion Rill erosion is the erosion by running water in small channels, on the side of a slope. Gully erosion is when a rill channel evolves to become deep and wide. Gullies, which can be more than 3 m deep, can be a major problem in farming and grazing areas.

17. Running Water water has more power to move large particles of weathered material than wind does. Swiftly flowing water can carry material over a greater distance.

18. Erosion and Formation of Deltas – Each year, streams and rivers carry billions of metric tons of sediments to coastal areas. – When a river enters a large body of water, the water slows down and deposits large amounts of sediments which form deltas. – The volume of river flow and the action of tides determine the shapes of deltas, most of which contain fertile soil.

19. Formation of Barrier Islands Ocean currents, waves, and tides carve out cliffs, arches, and other features – Sand along a shoreline is repeatedly picked up, moved, and deposited by ocean currents. – Sandbars form from offshore sand deposits and can become barrier islands. 1 on 1 Slide 19 Read Article on p. 176 Glencoe text, Shifting Sands, Is spending tax dollars to protect coastal structures a wise use of tax money? Debate this with your partner.

20. Wind Erosion major erosional agent in areas with low precipitation and high temperatures. can damage both natural features and human- made structures. Shore areas also experience wind erosion. relatively insignificant when compared to running water and glacial activity.

21. Wind Barriers – Planting wind barriers, or windbreaks, is one farming method that reduces the effects of wind erosion. – trees or other vegetation planted perpendicular to the direction of the wind. – can trap blowing snow, conserve moisture, and protect crops from the effects of the wind.

22. Formation of Soil Soil is essential to life on Earth.

23. Soil Soil is the loose covering of broken rock particles and decaying organic matter, called humus, overlying the bedrock of Earth’s surface. The four major types of soil are polar, temperate, desert, and tropical.

24. Soil result of chemical and mechanical weathering and biological activity over long periods of time. While all soils contain some organic matter, the amount varies widely among different types of soil.

25. Soil Composition Soil forms in layers. The parent rock is the solid bedrock from which weathered pieces of rock first break off. The smallest pieces of weathered rock, along with living and dead organisms, remain in the very top layer. Rainwater seeps through this top layer of materials, dissolves soluble minerals, and carries them into the lower layers of the soil.

26. Soil Composition The parent bedrock determines what kinds of minerals a soil contains. The parent rock and climatic conditions of an area determine the length of time it takes for soil to form.

27. Soil Profile – Horizon A contains high concentrations of organic matter and humus. – Horizon B contains subsoils that are enriched with clay minerals. – Horizon C, below horizon B and directly above solid bedrock, contains weathered parent material

28. Topography – The topography of a region affects the thickness of developing soil. – Soils on slopes tend to be thin, coarse, and infertile. – Soils formed in lower areas, such as in valleys, are thick and fertile.

29. Soil Types

30. Soil Texture Particles of soil are classified according to size as being clay, silt, or sand, with clay being the smallest and sand being the largest. affects its capacity to retain moisture and ability to support plant growth. 1 on 1 Slide 30 Can you predict three things that will have an impact on soil fertility?

31. Soil Fertility Factors: – Availability of minerals and nutrients – Number of microorganisms present – Amount of precipitation available – Topography – Level of acidity

32. Soil Color – A soil’s composition and the climate in which it develops are the main factors that determine a soil’s color. – Topsoil is usually dark-colored – Red and yellow soils may be the result of oxidation of iron minerals. – Yellow soils are usually poorly drained and are often associated with environmental problems. – Grayish or bluish soils are common in poorly drained regions where soils are constantly wet and lack oxygen

33. Rock Formation Igneous Metamorphic Sedimentary

34. Formation of Magma – The main factors involved in the formation of magma are temperature, pressure, water content, and mineral composition. – Temperature generally increases with depth in Earth’s crust, a phenomenon known as the geothermal gradient.

35. Igneous Rocks Igneous rocks are rocks that are formed from the crystallization of magma. Lava is magma that flows out onto Earth’s surface.

36. Igneous Rocks Extrusive igneous rocks are fine-grained igneous rocks that cool quickly on Earth’s surface Intrusive igneous rocks are coarse-grained igneous rocks that cool slowly beneath Earth’s surface (granite is an example)

37. Classifying Igneous Rocks Igneous rocks are classified as intrusive or extrusive and further by mineral composition Physical properties such as grain size and texture serve as clues for the identification of various igneous rocks. 1 on 1 Slide 37 What influence will cooling location have on the size of the crystals (grains) of igneous rock, i. e intrusive vs. extrusive?

38. Classifying Igneous Rocks Felsic rocks, such as granite, are light-colored and have high silica contents. Mafic rocks, such as gabbro, are dark-colored, have lower silica contents, and are rich in iron and magnesium. Intermediate rocks, such as diorite, have some characteristics of both felsic and mafic rocks.

39. Sedimentary Rocks Sediments are pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation. When sediments become cemented together, they form sedimentary rocks. The formation of sedimentary rocks begins when weathering and erosion produce sediments.

40. Metamorphic Rocks Metamorphic rock forms when high temperature and pressure combine to alter the texture, mineralogy, or chemical composition of a rock without melting it. The high temperatures ultimately are derived from Earth’s internal heat.

41. Metamorphic Rocks cont. The high pressures can be generated in two ways: – From vertical pressure caused by the weight of overlying rock – From the compressive forces generated as rocks are deformed during mountain building

42. The Rock Cycle Metamorphic rocks are formed by the changing of other rocks. Any rock can be changed into any other type of rock. The rock cycle is the continuous changing and remaking of rocks 1 on 1 Slide 42 Devise a chart that shows how one type of rock can turn into another type of rock. Use these terms, igneous, sedimentary, metamorphic, sediment, magma

43. The Rock Cycle

44. Mass Movements Mudflows Mudslides Landslides Creep Slump

45. Mass Movements Downward movement of loose sediments and weathered rock resulting from the force of gravity. Climatic conditions determine which materials and how much of each will be made available for mass movement. occur on slopes and range from slow motions to sudden slides, falls, and flows.

46. Variables that influence mass movements – The material’s weight resulting from gravity, which works to pull the material down a slope – resistance to sliding or flowing – A trigger, such as an earthquake

47. Creep Creep is the slow, steady, downhill flow of loose, weathered Earth materials, especially soils. effects usually noticeable only over long periods of time.

48. Mudflows – swiftly moving mixtures of mud and water. – can be triggered by earthquakes, common in volcanic regions. – common in sloped, semi-arid regions that have intense, short rainstorms

49. Landslide A landslide is a rapid, downslope movement of Earth materials that occurs when a relatively thin block of loose soil, rock, and debris separates from the underlying bedrock. – common on steep slopes, especially when soils and weathered bedrock are fully saturated by water.

50. Slump mass of material in a landslide rotates and slides along a curved surface. – may occur in areas that have thick soils on moderate-to-steep slopes. – common after rains and leave crescent- shaped scars on slopes.

51. Avalanche landslides that occur in mountainous areas, usually on slopes of at least 35°, with a lot snow – usually occur when snow has melted, and then refrozen into an icy layer. – Snow that falls on top of this crust builds up – A vibrating trigger, even from a single skier, can send start an avalanche

52. Glacier large, moving mass of ice. form near Earth’s poles and in mountainous areas at high elevations. The weight of the top layers exerts downward pressure that forces the accumulated snow below to recrystallize into ice. currently cover only about 10 percent of Earth’s surface.

53. Types of Glaciers Valley glaciers are glaciers that form in valleys in high, mountainous areas. Continental glaciers, also called ice sheets, are glaciers that cover broad, continent-sized areas. most powerful erosional agent because of great size, weight, and density

54. Evidence of Glaciers grind out parallel scratches into the bedrock. Small scratches are striations, and the larger ones are grooves. Scratches and grooves provide evidence of a glacier’s history and establish its direction of movement.