Changing Earth’s Surface What Processes Break Down Rock? Table of Contents 3.1 Rocks and Weathering Ms. De Los Rios 6th Grade

Vocabulary 3.1 Erosion is the process by which water, ice, wind, or gravity moves weathered particles of rock and soil. Sediment- Small, solid pieces of material that come from rocks or the remains of organisms; earth materials deposited by erosion. Deposition- Process in which sediment is laid down in new locations. Mechanical Weathering- The type of weathering in which rock is physically broken into smaller pieces. Chemical Weathering- The process that breaks down rock through chemical changes. Abrasion- The grinding away of rock by other rock particles carried in water, ice, or wind. Frost Wedging- Process that splits rock when water seeps into cracks, then freezes and expands. Oxidation- A chemical change in which a substance combine with oxygen as when iron oxidizes, forming rust. Permeable- Characteristic of a material that contains connected air spaces or pores, that water can seep through easily.

What Processes Wear Down and Build Up Earth’s Surface? Pg. 92 Weathering is the process that breaks down rock and other substances. Erosion is the process by which natural forces move weathered rock and soil from one place to another. What are agents or erosion?? And NO, not agent 007!!!  Gravity, moving water, glaciers, waves, and wind The material that gets carried away by erosion is called sediment. What makes up sediment?? pieces of rock or soil, or the remains of plants and animals.

Rocks and Weathering pg. 93 Cycle of Erosion and Deposition What are the steps in the cycle of erosion and deposition?

What Processes Wear Down and Build Up Earth’s Surface? Pg. 93 Deposition occurs where the agents of erosion deposit, or lay down, sediment. Deposition changes the shape of the land. Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface. Erosion and deposition are at work everywhere on Earth. As a mountains wears down in one place, new landform builds up in other places! The cycle of erosion and deposition is never-ending.

What Causes Weathering? Pg. 94 Physical weathering a type of weathering in which rock is physically broken into smaller pieces Types of Physical weathering Animal actions Freezing and thawing Plant growth Release and pressure Abrasion These are the natural agents of physical weathering Two types of weathering: Mechanical W. Physical W.

Mechanical Weathering pg. 94 Actions of animals Freezing and thawing, Plant growth Release of pressure Abrasion Animals burrow in the ground-moles, gophers, prairie dogs and some insects. Loosen the soil and break soil apart Water seeps into cracks in rocks and freezes and expands. The ice forces the rock apart. Wedges of ice in rocks widen and deepen cracks in the process called frost wedging. Plant roots enter cracks in rocks. As roots grow, they force the cracks apart. Even small plant root can pry apart cracked roots Erosion removes material from the surface of a mass of rock pressure, pressure on the rock is reduced. The released of pressure causes the outside of the rock to crack and flake off like the layers of onion. Abrasion refers to the wearing away of rock by rock particles carried by water, ice, wind, or gravity.

What Causes Weathering? Pg. 96 r. 1 P Chemical weathering A process that breaks down rock through chemical changes. Types of Chemical weathering Water Oxygen Carbon Dioxide Living organisms Acid rain These are the agents of chemical weathering. For example, the oxygen gas in air combines with iron in the presence of water in a process called oxidation. The product of oxidation is rust. Rust makes rock soft and crumbly.

Rocks and Weathering pg.96 Weathering and Surface Area The diagram shows what would happen if a rock cube broke into smaller cubes. Figure 2 By how much does the surface area increase? How would the rate of weathering change? ______________________________________________________________________________________________________________________________________________________________________________________

Agents of Chemical Weathering pg. 97 Oxygen- Carbon Dioxide- Living organisms- Acid rain- the oxygen gas in air combines with iron in the presence of water in a process called oxidation. The product of oxidation is rust. Rust makes rock soft and crumbly. Another gas found in the air, that causes chemical weathering when it dissolves in water. The result is a weak acid called carbonic acid. C. A. easily weathers some kinds of rocks, such as marble and limestone. as plants roots grow, they produce weak acids that slowly dissolve rock around the roots. Lichens- plantlike organisms that grow on rocks- also produce weak acids. Rainwater is naturally acidic. Burning coal, oil and gas for energy can pollute the air with sulfur, carbon, and nitrogen compounds. These compounds react with water vapor in clouds, making acids that are stronger than normal rainwater. These acids mix with raindrops and fall as acid rain. Acid rain causes rapid chemical weathering of rock.

The Old Man of the Mountain The Old Man of the Mountain was a rock formation in New Hampshire that looked like a face. But it collapsed suddenly on May 3, 2003. Mechanical and chemical weathering wore away rock behind the “chin” of the face, causing the whole face to fall.

How Fast Does Weathering Occur? Pg. 98 The most important factors that determine the rate at which weathering occurs are the type of rock and climate. Some rocks weather more easily because they are permeable. Permeable means that a material is full of tiny, connected air spaces that allow water to seep through it. Climate refers to the average weather conditions in an area. Both mechanical w. & physical w. occur faster in wet climates. Rainfall= chemical changes & freezing and thawing Human activities= producing more acid rain, increase rate of weathering.

Forces of _______________Weathering Rocks and Weathering Forces of _______________Weathering