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Soil and Weathering Mrs. Hoffman **Information taken and adapted from various websites. There are Two Types of Weathering Mechanical Weathering Chemical Weathering Mechanical Weathering This is an example of root pry. Root pry is when tree roots break rocks apart. Mechanical Weathering This is a result of ice wedging. Water freezes and thaws repeatedly and breaks rocks apart. Many potholes in streets are caused by ice wedging. Mechanical Weathering Animals burrowing into the ground to let in water and air is an example of organic activity. Mechanical Weathering This is a picture of abrasion. Abrasion is when rocks break apart rocks. A river can wear a pathway through rocks due to abrasion. Mechanical Weathering This is a picture showing gravity. A rock falling from a cliff is an example of gravity. Chemical Weathering Plant Acids: wearing away of rocks by the acids in plants. This is a picture of mosses wearing away a rock. Chemical Weathering This picture shows oxidation. Oxidation is caused by water and oxygen reacting with a material, such as iron, to form rust. Chemical Weathering Carbonation is when carbon dioxide is dissolved in water or an aqueous solution An example is rainwater passes through limestone into a cave and forms a stalactite. This is a picture of Indian Echo Caverns, which was formed by water flowing through cracks in the limestone bed. It formed about 440 million years ago. What kinds of weathering may occur in a wooded area like this? What kinds of weathering may occur in a wooded area like this? Some examples of weathering in this area may include: Organic Activity Root Pry Factors that Affect the Rate of Weathering Pollution Time Slope (Topography) Climate Type of Rock Factors that Affect the Rate of Weathering Pollution can speed up the process of weathering. This picture shows polluted water. Factors that Affect the Rate of Weathering Time can affect the rate of weathering. The photo shows Bryce Canyon, Utah. Notice the jagged pieces that formed from many years of weathering. Factors that Affect the Rate of Weathering Slope affects the rate of weathering. The greater the slope, the greater the chance for weathering to occur at a faster pace. Factors that Affect the Rate of Weathering Climate affects the rate of weathering. A cold, wet climate has strong mechanical weathering. A hot, wet climate has strong chemical weathering. Cold, Wet Climate Hot, Wet Climate Factors that Affect the Rate of Weathering Tombstones are often used as examples to show how the type of rock affects how fast or slow weathering occurs. Weathering can break rocks down into soil . . . Soil Scientists What does a soil scientist do? Looks at the properties of soil Considers land-use potential Determines if a Soil Sample is from Horizon A, B, or C Soil Competitions Sometimes soil scientists compete in local, regional, and national competitions with other teams Field Book for Describing and Sampling Soils Version 2.0 National Soil Survey Center Natural Resources Conservation Service U.S. Department of Agriculture September 2002 A soil scientist at work Soil Scientists Look at Soil Horizons Can you label the Soil Horizons? Litter Horizon A Horizon B Horizon C Scientists Look for Presence of Roots or Rocks NOTE: A rock is defined as being larger than 2 mm in size. Presence of Roots… Means the soil is likely to be from Horizon A or B Presence of Rocks… Means the soil is likely from Horizon B or C A few rocks with light soil means the soil is from Horizon B Many rocks with little soil means the soil is from Horizon C. Soil Texture Scientists use the Soil Types Key to determine if the soil is made from sand, silt, or clay Scientists ask if the soil is smooth, sticky, gritty, hard to squeeze, or able to form a firm ball. Why is Soil Important? Pretend that this apple is the planet Earth, round, beautiful, and full of good things. Notice its skin, hugging and protecting the surface.Water covers approximately 75% of the surface. Right away, cut the apple in quarters. Toss three quarters (75%) away. The three quarters (75%) you just removed represents how much of the earth is covered with water - oceans, lakes, rivers, streams. What is left (25%) represents the dry land. 50% of that dry land is desert, polar, or mountainous regions where it is too hot, too cold or too high to be productive. So cut that dry land quarter in half and toss one piece away. When 50% is removed, this is what is left. (12.5% of the original) Of that 12.5%, 40% is severely limited by terrain, fertility or excessive rainfall. It is too rocky, steep, shallow, poor or too wet to support food production. Cut that 40% portion away. You are left with approximately 10% of the apple. Peel the skin from the tiny remaining sliver. The remaining 10% (approximately*)- this small fragment of the land area - represents the soil we depend on for the world's food supply. This fragment competes with all other needs - housing, cities, schools, hospitals, shopping centers, land fills, etc., etc. And, sometimes, it doesn't win… How long does it take to form one inch of soil? In the time it took to form one inch of soil . . . New planets that could sustain life are discovered orbiting a neighborhood star1996 In the time it took to form one inch of soil . . . The Berlin Wall is torn down, signaling an end to the Cold War-1989 In the time it took to form one inch of soil . . . First "Earth Day" is observed-1970 In the time it took to form one inch of soil . . . British pop group The Beatles make their first recordings-1962 In the time it took to form one inch of soil . . . Korean War ends-1953 In the time it took to form one inch of soil . . . Ten million homes have television receivers1951 In the time it took to form one inch of soil . . . Jim Thorpe of the Sauk and Fox Tribes wins Decathlon and Pentathlon in Olympic Games, Sweden-1912 In the time it took to form one inch of soil . . . Lewis and Clark begin expedition to the American Northwest-1804 In the time it took to form one inch of soil . . . Benjamin Franklin is born - 1706 In the time it took to form one inch of soil . . . The toothbrush is invented by a Chinese dentist 1498 Remember it takes hundreds and even thousands of years to form one inch of soil! Celebrate Earth Day every day. . . The choice to help our Earth lies in your hands . . .