Weathering The breakdown do the materials of Earth’s crust into smaller pieces. p?id=3204

Mechanical Weathering

Abrasion The grinding and wearing away of rock surfaces through the mechanical action of other rock or sand particles. Caused by wind, water, & gravity.

tumbler-grit.shtml

TUMBLING GRIT: Silicon Carbonate is harder than the rocks you are tumbling and will therefore smooth off the rough edges.

Rocks before they are tumbled.. And after they are tumbled.

Sea glass

How did the pebbles get this way? Why are they not sharp?

Flowing Water As rocks and pebbles roll along the bottom of flowing water, they bump and scrape against each other, causing these rocks to become rounded and smooth.

2. Water River carries rocks and pebbles that bump and scrape against each other, eventually wearing them down. (This makes them smooth & rounded).

National Geographic Photos

WIND wind blows sand and silt against exposed rock eventually wearing away the rock’s surface.

3. Wind Blows and silt across exposed rock, wearing down the rock’s surface.

3. Gravity Rocks pulled down and falling on top of each other – Ex. Rockslide (rocks falling down a mountain or cliff )

GRAVITY Rocks grind against each other during a rock slide, creating smaller and smaller rock fragments. Anytime one rock hits another rock, abrasion takes place.

Frost Wedging

Frost Heaving

ICE Water seeps into cracks during warm weather. When the temperature drops, the water freezes and expands, causing the ice to push against the sides of the crack. * This causes the crack in the rock to widen.

5. Plants Roots grow into cracks in the rocks. As the roots grow, they press on sides & break apart the rock – Ex. Tree roots breaking up sidewalk

PLANTS The roots grow through existing cracks in rocks. The growth causes the root to expand, forcing the crack to widen. The force can eventually split the rock apart.

6. Animals Burrowing animals loosen sediment & push it to the surface. This exposes it to other forces of weathering. Ex. Rabbits, worms, ants, coyotes, & mice

Animals Animals that live in the soil (moles, prairie dogs, insects, worms, gophers), cause a lot of weathering. By burrowing in the ground, these living creatures brake up soil and loosen rocks to be exposed to further weathering

Chemical Weathering

CHEMICAL WEATHERING Process by which rocks break down as a result of chemical reactions.

CHEMICAL WEATHERING chemical reactions Process by which rocks break down as a result of chemical reactions. Dissolve minerals in rocks or change them into different minerals.

Agents of chemical weathering 1. Water 2. weak acids (acid precipitation, acids in ground water, acids in living things) 3. air. These agents weaken bonds between the mineral grains of rock.

Water Can cause rock to be broken down and dissolve. Can take thousands of years to take place.

1. Water Dissolves minerals from a rock over a long period of time (sometimes 1000s of years).

2. Weak Acids Include 1.acid precipitation 2.acids in ground water 3.acids in living things

2. Acid precipitation Where does acid rain come from? Rain, sleet, or snow, that contains a high concentration of acids. Small amounts of nitric or sulfuric acids from volcanoes. Air pollution from fossil fuels (coal & oil) give off gases & combines with water to form acid rain.

Acid Precipitation ( weak acid) Rain, sleet, or snow that contains a high concentration of acid. Normal precipitation is acidic, acid precipitation contains more acid than normal.

Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering

3. Acids in Ground water Some groundwater contains weak acids like carbonic & sulfuric acid. These weak acids react with rocks, causing a chemical reaction. Ex. When groundwater touches limestone, it dissolves limestone to form caves over thousands of years.

Acids in Groundwater (weak acid) Carbonic acid or sulfuric acid reacts with rocks in the ground, causing a chemical reaction, eating away at the rock.

Carbon Dioxide CO 2 dissolves in rain water and creates carbonic acid Carbonic acid easily weathers limestone and marble

Karst Topography A type of landscape in rainy regions where there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams. Created by chemical weathering of limestone

Features of Karst: Sinkholes

Features of Karst: Caves

Features of Karst: Disappearing Streams

National Geographic Photos

Acids in Living Things (weak acid) Lichens produce acids that slowly break down rock.

4. Acids in Living things Lichens produce acids that slowly break down rock Roots and decaying plants release acids that dissolve minerals, thus weakening the rock.

AIR The process of oxidation is a chemical reaction in which an element (iron) combines with oxygen, causing rust.

5. Air oxidation Oxygen in the air reacts with iron, causing it to rust. This process is called oxidation. A chemical reaction in which an element (iron) combines with oxygen to cause rust. Causes aluminum cans, bikes, & cars to rust. Water speeds up this process.