Weathering Part 1

In your journal:

Main title: Weathering  

The Earth's land surface is always changing. Rocks or minerals are constantly breaking apart or wearing away. This process is called Weathering.

Subtitle:

Constructive and Destructive Processes 

• Wind and water wear Earth's surface down (Destructive processes) in some places, and build it up (Constructive processes) in others. The continuous movement of wind and water changes the size of mountains over millions of years.

These processes build up mountains (constructive) and carve out canyons

(destructive) . They create many other kinds of landforms, like deltas and dunes.

Slow rivers deposit sediments when they enter a larger body of water, like an ocean, forming a delta (constructive process). The end of the river is called the "mouth" of the river.

Winds are natural forces that shape sand dunes. Scientists use models to observe and predict how sand dunes form.

Flowing waters in a river current can carve canyons.

Multiple Select

Weathering is an example of a _____________ process.

• destructive

• constructive

• heat

Multiple Choice

A landform example of a destructive weathering process is _____________

• canyon

• river

• mountain

• delta

Subtitle:

Weathering and Its Effects 

Everything around you changes over time. Brightly painted walls and signs slowly fade. Shiny cars become rusty. Things made of wood dry out and change color. These changes are some examples of weathering. The physical and chemical processes that wear down landforms on Earth's surface are called weathering. 

Subtitle: Physical Weathering

Physical weathering (also called mechanical weathering) occurs naturally when rocks break into smaller pieces (destructive process). During mechanical weathering, the chemical makeup, or composition, of a rock is not changed. It's a physical change- not a chemical change.

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​Discuss:

​Which picture shows a rock that has undergone a physical change? A chemical change? Which one shows both?

​A

C

​​B

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A piece of soft stone such as sandstone undergoes physical weathering, the smaller pieces that result are still sandstone.

• Large boulders break into smaller rocks.

• Both large rocks and small rocks were once a part of the Earth's solid rock layer (Crust).

Fill in the bubbles with these phrases: smaller pieces, break down, weathering, change the chemical makeup of a rock

​Discuss by filling in the blanks.

Multiple Select

The chemical makeup, or composition, of a rock ______ changed by physical weathering.

• is

• is not

​Discuss:

​Physical weathering or chemical weathering?

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​A

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​B

Physical weathering is caused by the pushes and pulls of nature:

• wind,

• flowing water,

• moving ice,

• plants and animals, and

• gravity can all cause rocks and minerals to break down. 

Multiple Choice

Rocks and minerals break down and change into smaller pieces of sediment is an example of______________

• mechanical weathering

• pressure

• oxidation

• erosion

Multiple Select

These agents can cause weathering. (Check all that apply)

• glaciers

• wind

• waves

• river currents

• digging or burrowing

Sub-subtitle: Ice Wedging 

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• One of the most effective weathering processes is ice wedging-also called frost wedging.

• When liquid water enters cracks in rocks, and the temperature reaches 0°C, the water freezes. Water expands as it freezes, and the expansion widens the crack.

• Repeated freezing and thawing can break apart rocks. Ice wedging usually happens in the spring season. Why?

• Ice wedging will happen in mountainous areas.

• Ice wedging is identified by finding cracks in rocks, like boulders.

Ice/frost wedging usually happens in cold, mountainous regions. Why?

Multiple Choice

What type of physical weathering has happened to this rock?

• Unloading

• Frost Wedging

• Thermal Expansion

• Abrasion

Multiple Choice

Water in small cracks in rock expands when it freezes, eventually breaking off parts of the original rock. This is weathering by _______________.

• Abrasion

• Unloading

• Thermal Expansion

• Ice Wedging

Sub-subtitle: Abrasion

Currents can carry loose fragments of rock. The pieces tumble and grind against one another into smaller and smaller pieces. At first, the rocks are rough, then get smoothed by the friction.

Sub-subtitle: Abrasion

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• River currents, glaciers, wind, waves, and burrowing animals cause abrasion by grinding away rocks by friction or impact.

• Abrasion is mechanical weathering in which rock is worn away by the grinding action of other rock particles carried by the air.

Discuss:

How can be gravity help in causing abrasion?

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​Gravity changes the landscape on Earth by producing landslides and avalanches.

What force works with glaciers to form this kind of abrasion?

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Rocks break into smaller rocks called sediment. Mechanical weathering

In rivers, rocks hit each other, cracking them and giving them rough edges. Over time, water and other rocks smooth them and they become rounded.

​Discuss:

​Physical weathering or chemical weathering?

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​A

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​B

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Sub-subtitle: Plants 

Plants can cause weathering by applying pressure from the inside of rocks. Imagine a plant growing into a crack in a rock. As the plant grows, roots not only get longer, they also get wider. The growing roots push on the sides of the crack. Over time, the rock breaks into smaller pieces.

Roots can break through concrete sidewalks.

Trees can grow through cracks in rocks, breaking them apart.

Plant weathering is also known as biological weathering. Why?

Sub-subtitle: Animals 

Animals such as moles, rabbits, and foxes that burrow through soil and loose rock can break down rocks as they dig. Animals that live in soil, like worms, can create holes in the soil where water enters and causes weathering. 

Discuss:

Why are animal and plant weathering also called "biological weathering"?

Burrowing causes weathering.

Multiple Choice

What animal creates weathering on rocks?

• Birds

• Snakes

• Rabbits

• Fish

​Discuss:

​Physical weathering or chemical weathering?

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​A

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​B

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Poll

Where does soil come from?

• The ocean

• Mountains

• Weathered rocks

• Underground

Parent rock is also known as bedrock. Weathered bedrock plays an important part in soil formation.