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Weathering/Erosion/Deposition All roads lead to… LANDFORMS!! Let’s start with the foundation: Various landscape features are the result of several processes: Weathering Erosion Deposition Tectonics Glaciation Glaciation is primarily responsible for the various Landscape regions of NYS. But wait, there’s more . . . The driving force behind weathering, erosion and deposition is… The WATER or HYDROLOGIC Cycle The sun and gravity control this cycle. So, let’s start from the beginning. . . In the beginning, there was . . . Water And it was good. The Water/Hydrologic Cycle Evaporation Condensation Precipitation Infiltration Run-off Without these processes, weathering, erosion and deposition could not occur. So, now that we have a little background, let’s get started! Weathering Weathering is the breakdown of rocks. It occurs when rocks are exposed to agents such as water and air. These weathering agents can change the physical and chemical properties of rocks. As rocks are broken down, they are classified as sediments Sediments can be: boulders, cobbles, pebbles, sand, silt, clay and colloids Remember this . . . ? Types of weathering: Physical/Mechanical: Rocks are broken down into smaller pieces without changing the integrity or chemical composition of the rock. Chemical: Rocks are broken down and the chemical composition of the rock is changed. Physical Weathering: Frost action/Ice Wedging: The breakup of rock as the result of the expansion and contraction of water. Abrasion: The wearing down of rock as they rub and bounce against each other. Common in stream beds, windy areas and under glaciers. Exfoliation: The peeling away of surface sheets of rock. Common with shale, slate and mica. Chemical Weathering: Oxidation: When oxygen reacts with minerals. Remember ~ minerals are the building blocks of rocks and are composed of elements i.e. When oxygen combines with Iron (Fe), it forms iron oxide, more commonly known as . . . Rust! Hydrolysis: When water interacts with minerals. Hydro = water Lysis = Break Hornblende and feldspar often combine with water to form clay Carbonation: When carbon dioxide interacts with minerals. Causes the formation of: Stalactites (top) Stalagmites (bottom) Sink holes Karst Topography Weathering Rates: The rate at which material is weathered is dependent upon: Particle size/surface area (more surface area = more weathering) Mineral Composition (softer minerals = more weathering) Climate (warmer temperatures = more weathering) A quick review . . . The water/hydrologic cycle is chiefly responsible for weathering, erosion and deposition Weathering is the breakdown of rock materials by either . . . Physical means: frost wedging, abrasion, exfoliation or . . . Chemical means: oxidation, hydrolysis and carbonation. The rate of weathering depends on size, climate and mineral composition.