weathering this week we write it down if its in orange. photo: grand canyon, national park service

WeatheringThis week we write it down if it’s in

ORANGE.

Photo: Grand Canyon, National Park Service

What do you think made the hole in this rock?

Wind blows sand and other sediment against rocks. Little by little, it wears away the rock!

This is an example of mechanical weathering.

What do you think made the notch where the waterfall starts?

Water from the river wears away the rock, over thousands of years.

This is another example of weathering.

Photo: Yosemite Falls, National Park Service webcam

Weathering is the process that breaks down rock and other substances on Earth’s surface.

Part 1: Mechanical Weathering

Mechanical WeatheringForce of Mechanical Weathering

How it Works

Abrasion

Plant Growth

Animal Actions

Freezing and Thawing

Release of Pressure

Abrasion: Sand and other rock particles carried by wind and water grind away rock like sandpaper on wood.

Here we go again with wind and rock particles sculpting rock!

Photo: Delicate Arch, Arches National Park, National Park Service.

Plant Growth: Roots of trees and other plants grow in the cracks of rocks and pry them apart.

Perhaps you have seen this on sidewalks?

Photo source: Morguefile.com

Animal Actions: Animals dig in the soil and loosen and break apart rocks.


Ice Wedging: When water freezes it expands. Ice in the crack of a rock expands and makes the crack larger.

Perhaps you have seen a frozen bottle get cracked? Or cracks in the road? Why does that happen?

Whiteboard QuestionCHECK YOUR UNDERSTANDING!

Mechanical weathering in which rock is worn away by the grinding action of other rock particles is calledA. erosion.B. abrasion.C. ice wedging.

B. abrasion

Release of Pressure: When rocks reach Earth’s surface, reduced pressure can cause cracks and flakes in the rock.

Mechanical WeatheringForce of Mechanical Weathering

How it Works

Abrasion Sand and other rock particles carried by wind and water grind away rock like sandpaper on wood.

Plant Growth Roots of trees and other plants grow in the cracks of rocks and pry them apart.

Animal Actions Animals dig in the soil and loosen and break apart rocks.

Freezing and Thawing

When water freezes it expands. Ice in the crack of a rock expands and makes the crack larger.

Release of Pressure When rocks reach Earth’s surface, reduced pressure can cause cracks and flakes in the rock.

Your completed chart

should look like this!


Ice wedging causes mechanical weathering of rock by means of:A. plant growth.B. animal actions.C. freezing and thawing of water.

C. freezing and thawing of water

Chemical Weathering

Write it down if it’s in ORANGE.

Chemical weathering is the process that slowly breaks down rock with chemical changes, including changes in the minerals.

This rusty color is caused by oxidation in a wet climate.

Whiteboard Question CHECK YOUR UNDERSTANDING!

What kind of weathering causes the mineral composition of rocks to change?A. Chemical weathering.B. Mechanical weathering.C. General weathering.

A. Chemical weathering

Part 2: Chemical Weathering

Chemical WeatheringChemical weathering is___________________________________________________________________________________________________________

Force of Chemical Weathering

How it Works

Water

Oxygen

Carbon Dioxide

Living Organisms

Acid Rain

Water: Water is the most important cause of chemical weathering. When a rock dissolves in water, it mixes completely with the water.

This limestone cave was created by water dissolving the stone.


What made this old truck rusty?


Oxygen: Iron combines with oxygen and water in a process called oxidation. The result is rust. Oxidation of a rock makes it soft, crumbly and red or brown.

Rust happens to old vehicles, and to rocks.



Carbon dioxide: Carbon dioxide in the air dissolves in rainwater, becoming a weak acid called carbolic acid. Acids weather rocks such as limestone and marble.

Limestone.

Living organisms: Plants, and other living organisms such as lichen, release weak acids that slowly dissolve rocks.

Lichen growing on a rock will weather it.


Acid rain: Burning coal, oil, and gas for energy produces pollution. This pollution combines with air and water, to create acid rain, and fast chemical weathering.



A rock containing iron becomes soft and crumbly and reddish-brown in color. It probably has been weathered by:A. abrasionB. oxygen.C. acid rain.

B. oxygen

Chemical WeatheringChemical weathering is___________________________________________________________________________________________________________

Force of Chemical Weathering

How it Works

Water Water is the most important cause of chemical weathering. When a rock dissolves in water, it mixes completely with the water.

Oxygen A rock containing iron becomes soft and crumbly and reddish-brown in color. It probably has been weathered by

Carbon Dioxide Carbon dioxide in the air dissolves in rainwater, becoming a weak acid called carbolic acid. Acids weather rocks such as limestone and marble.

Living Organisms Plants, and other living organisms such as lichen, release weak acids that slowly dissolve rocks.

Acid Rain Burning coal, oil, and gas for energy produces pollution. This pollution combines with air and water, to create acid rain, and fast chemical weathering.

Your completed chart

should look like this!

Is it Chemical or Mechanical Weathering?

Final Whiteboard QuestionsAbrasion of a rock by blowing sand is an

example of __________________ weathering.Acid rain washing away the face of a statue

is an example of __________________ weathering.

True or False? Living things can cause both chemical and mechanical weathering.

A tree’s roots growing through cracks in a rock is an example of _________________ weathering.

mechanical

True

chemical

mechanical

Part 3: Rates of WeatheringWhat makes a rock weather fastest?


The most important factors for the rate (speed) of weathering are1. rock type; and 2. climate.

Rate of Weathering


Mechanical and Chemical Weathering Work Together

Mechanical weathering increases the surface area available for chemical weathering. Increased surface area usually results in faster chemical reactions (chemical weathering).

Photo source: Morguefile.comPhoto source: Morguefile.com

Mechanical and Chemical Weathering Work Together

A permeable rock weathers easily because it contains many small, connected air spaces

Which rock do you think will weather faster?


A permeable rock weathers easily because it:A. is made up of small particles.B. contains many small, connected air

spaces.C. is made up of many minerals.

B. contains many small, connected air spaces.

Which of these places would have faster weathering of rock? Why?

How Does Weather Affect Weathering?

Photo source: Morguefile.comPhoto source: Morguefile.com


Rainforests have warm, wet weather.

Wet climates with high temperatures speed up both mechanical and chemical weathering.




Granite lasts a long time when it is used for building in areas where the climate:A. is cool.B. has lots of acid rain.C. is hot and rainy.

A. is cool


The most important factors in determining the rate of weathering are:A. carbon dioxide and acid rain.B. animal actions and oxygen.C. rock type and climate.D. abrasion and acids from root plants.

C. rock type and climate

weathering this week we write it down if its in orange. photo: grand canyon, national park service

Documents

chemical weathering

water slide

mechanical weathering

mechanical weathering

water water

oxygen slide

abrasion slide

force of chemical weathering