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Weathering: Mechanical or Chemical?. (Take notes as we go through the slide show.). What is Mechanical Weathering?. The process that breaks rocks into different shapes and smaller pieces. (Changes the rock’s physical appearance).
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Weathering:Mechanical or Chemical? (Take notes as we go through the slide show.)
What is Mechanical Weathering? The process that breaks rocks into different shapes and smaller pieces. (Changes the rock’s physical appearance)
TEMPERATUREHeating & cooling cause rocks to expand and contract. Temperature changes cause outer layers of rock to crack .Exfoliating is when the outer layers of rock crack and break off .
Changes in Temperature cause Exfoliation Mechanical (Physical)
FROST ACTIONLiquid water seeps into cracks and expands when frozen causing small cracks to widen and open up
Frost Action: Freezing and Melting of Water (Ice Wedging) Mechanical (Physical)
ORGANIC ACTIVITYAnimals scratch and dig on the surface breaking rocksPlant roots break up soil, even asphalt and concrete
Organic Activity: Animals Breaking Down Rocks Mechanical (Physical)
Organic Activity: Tree Roots Cracking Cement (Root-Pry) Mechanical (Physical)
GRAVITY • Gravity can pull loosened rocks down hills or mountains in a landslide, when mixed with water, it is a mudslide
Gravity:Landslide Mechanical (Physical)
ABRASION • Wind carrying particles smooth rocks on the surface • Water carrying particles smooth rocks in rivers/oceans
Abrasion: Wind & Sand Mechanical (Physical)
What is Chemical Weathering? The process that changes the mineral composition or chemical makeup of the rocks. Minerals can be added or removed from rocks. OR Minerals in the rocks can be broken down.
WATER • Water can dissolve most types of minerals that hold rocks together – these rocks are said to be soluble which means able to dissolve
Water & Oxidation Chemical
OXIDATION • Oxygen chemically combines with other elements such as Iron making iron oxide or rust (orange/brownish new material)
Oxidation: Rust Chemical
CARBONATION • When carbon dioxide dissolves into water it is called carbonic acid – think about a carbonated beverage like soda – this can dissolve rocks but is too weak to harm people or plants. It can dissolve limestone or soft rocks
Limestone Caves Chemical
SULFURIC ACID • Sulfur dioxide is a byproduct of burning fossil fuels and it combines with water too to form acid rain • Acid rain affects marble statues, paint, and metal
Acid Rain Chemical
Acid Rain Chemical
PLANT ACIDS • Plants produce weak acids that break down rocks – lichens or mosses break down rocks and can form soil • Also, some plants such as cactus produce acids to prevent other plants from growing too close to them
Plant Acid: Lichen Creates an Acid Chemical
What Factors Affect the Rate of Weathering? • COMPOSITION of the rock – what the rock is made up of 2. CLIMATE where rock is found 3. Amount of TIME rock is exposed to the Earth’s surface 4. Amount of EXPOSED SURFACE AREA – smaller pieces allow for more rock surfaces to be exposed
Mechanical vs. Chemical Mechanical: GO FAT Chemical: COWS P Carbonation Oxidation Water Sulfuric Acid Plant Acids • Gravity • Organic Activity • Frost Action • Abrasion (wind) • Temperature
ROCKS • Hard solids made from one or more minerals. • IGNEOUS • SEDIMENTARY • METAMORPHIC
MINERALS • Natural, non-living solid with a chemical composition (elements from the periodic table) and a crystal structure • Have Differences in : • Color Crystal Shape • Luster (reflecting light) Fracture • Density Streak