Weathering

DEFINITIONS WEATHERING - Brainstorm: 1) What is it? 2) What can cause it? 3) How does weathering change the surface of the Earth? - Possible Causes: Have students discuss these questions as a class. Then have the students choose an appropriate definition to write. (Guide them to correct definition). The write down some of the possible causes that the students think cause weathering.

WEATHERING Weathering= the breaking down of rock into smaller and smaller pieces. Is weathering constructive, destructive, or both? Why? -Weathering is destructive- it “tears down” rocks and landforms.

2 Types of Weathering Mechanical 2) Chemical Brain-storm WEATHERING 1) What can cause each type of weathering? WEATHERING Mechanical 2) Chemical Breaking down rocks by physical means; pieces do not undergo a chemical change Chemical breakdown of rock and minerals into new substances Possible causes:

MECHANICAL WEATHERING 1. ANIMALS Little animals also help weathering by burrowing and digging through the ground.

MECHANICAL WEATHERING 2. Ice Wedging – when water gets into cracks of a rock, freezes & thaws over & over again & splits the rock

MECHANICAL WEATHERING Ice

MECHANICAL WEATHERING 3. PLANT GROWTH Roots of plants also push into the rocks and break them apart. They act like wedges and push the rocks apart.

MECHANICAL WEATHERING 4. RELEASE OF PRESSURE/Exfoliation- as erosion moves sediment from the surface, pressure is reduced. The outside of the rock begins to flake off

MECHANICAL WEATHERING NONLIVING CAUSES 5. Abrasion- sediments carried by wind, water, or ice wear away rock by hitting & scraping against other rock

Abrasion Wind sandstone shapes eroded by coastal winds  Sandblasting

Abrasion WATER - rubs fragments against each other and wears away the surface of the rock by abrasion. The faster the water, the greater the erosion

Abrasion Ice- Glaciers The glacier gouges out chunks of rock and leaves scratches on the rock called striations

CHEMICAL WEATHERING CHEMICAL WEATHERING the chemical breakdown of rock and minerals into new substances

CHEMICAL WEATHERING Water is considered to be the universal solvent. It dissolves many things – including rock Over time, water can break down even hard rock like granite

CHEMICAL WEATHERING 2) Oxygen Oxidation (rust) is a chemical reaction in which an iron combines with oxygen.

CHEMICAL WEATHERING creates Carbonic Acid that 3) Carbon Dioxide (CO2) -CO2 mixing with water creates Carbonic Acid that slowly dissolves limestone. (Acid in groundwater) -Caves

CHEMICAL WEATHERING 4) Living Organisms Acids from decaying plants or fungi such as lichens breaks down rocks

CHEMICAL WEATHERING 5. ACID PRECIPITATION is rain or snow that contains more acids than normal due to air pollution. The acid “dissolves” and “eats away” the rock

WEATHERING How does weathering change the surface of the Earth?

Mechanical Weathering Living Plant Roots of plants also push into the rocks and break them apart Animal burrowing and digging through the ground Non-living Ice (glaciers) -water gets into cracks of a rock, freezes & thaws over & over again & splits the rock -scratches on the rock called striations Wind wears away the surface of the rock by abrasion Water rubs fragments against each other and wears away the surface of the rock by abrasion.

Chemical Weathering Living Plants Acids from decaying plants or fungi such as lichens breaks down rocks Non-living Water universal solvent. It dissolves many things – including rock Acid rain rain or snow that contains more acids than normal due to air pollution. -acid “dissolves” or “eats away” the rock Ground-water CO2 mixing with water creates Carbonic acid that slowly dissolves limestone Oxidation chemical reaction in which an element combines with oxygen to form an oxide

FORCES THAT CAUSE Weathering Plants Ice - (Glaciers) Water Acid rain 1) Mechanical 2) Chemical Living Nonliving Plants Ice - (Glaciers) Water Acid rain Wind Groundwater Animals Oxidation

Interactive Weathering How are materials from the earth broken down?