Weathering The breakdown do the materials of Earths

Weathering • The breakdown do the materials of Earth’s crust into smaller pieces.

Mechanical Weathering

Photo A What has caused these stones to become smooth? Photo B

Photo A Abrasion by water (a type of Mechanical weathering) Photo B

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

http: //geology. com/rock-tumbler/rocktumbler-grit. shtml

TUMBLING GRIT: Silicon Carbonate is harder than the rocks you are tumbling and will therefore smooth off the rough edges. This is used to smooth the rocks out. As these tiny rocks hit the larger rocks and are tumbled together, it makes the rocks smooth and round. http: //geology. com/rock-tumbler/rocktumbler-grit. shtml

Rocks before they are tumbled. . And after they are tumbled. The Tumbling causing abrasion to happen. http: //geology. com/rock-tumbler/rocktumbler-grit. shtml

Sea glass

Sea glass starts out as broken glass.

Water causes abrasion of the sea glass as the water causes the sand glass to tumble against each other.

Sea glass: now the glass is smooth and round because of the abrasion of sand against the glass.

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

Answer: Abrasion

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 A. What type of weathering causes this? B. What agent?

National Geographic Photos A. Mechanical weathering B. Wind blowing sand against the rock, causing abrasion

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

A. What type of weathering causes this? B. What agent? http: //www. cbc. ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler. html

A. Mechanical weathering B. Gravity, which causes rocks to tumble Into each other as they fall, which breaks them apart more by abrasion http: //www. cbc. ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler. html

http: //www. cbc. ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler. html

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.

What type of weathering is this? What agent causes this?

Mechanical weathering: ice wedging

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.

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 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

Question Time 1. For each question, tell what type of mechanical weathering is happening. 2. Write on dry erase board the agent causing the weathering. 3. Discuss with your partner & explain how that agent caused what you see in the picture.

What agent of mechanical weathering is at work here? How?

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.

What agent of mechanical weathering is at work here? How?

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

What agent of mechanical weathering is at work here? How?

What agent of mechanical weathering is at work here? How?

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.

Ice- Wedging

What agent of mechanical weathering is at work here? How?

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

Animals

What agent is at work here? What type of weathering?

Mechanical weathering Tree roots

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.

Temperature Change Cold causes rock to contract (shrink). Heat causes rock to expand (grow slightly).

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.

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 1000 s 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

• Some groundwater 3. Acids in contains weak acids Ground water 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.

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

What type of weathering are these National Geographic Photos lichens causing on the rock? What agent of weathering?

Mechanical weathering National Geographic Photos Agent: acids in living things (they dissolve the minerals in the rock)

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.

What type of weathering is happening here? What agent is at work?

Chemical Weathering Water dissolves the minerals in the rock

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

What type of weathering caused the changes to this statue? What agent is at work?

Chemical weathering acid precipitation

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.

What type of weathering is at work here? What agent created the cave?

Chemical weathering Acids in groundwater

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.

What type of weathering caused this? What agent?

Sinkholes caused by chemical weathering. Agent: acids in groundwater

What type of weathering and what type of agent has caused the rust on these metal objects?

Chemical weathering Agent: air. Oxygen in the air causes oxidation, which causes rust.

What type of weathering caused this rock to split in half? What agent of weathering?

Mechanical Weathering Agent: Ice wedging Water gets into the crack, freezes, and expands, pushing the rock apart. When the water thaws (melts) and then freezes and does this over and over again, it causes the rock to break apart.

What type of weathering caused this statue to become worn down? What agent of weathering?

Mechanical Weathering Wind blows sand against the statue, causing abrasion. Remember, sand is just broken down rocks and minerals.