WeatheringWeathering

SWBAT distinguish between SWBAT distinguish between weathering and erosion; identify the weathering and erosion; identify the

variables that affect the rate of variables that affect the rate of weatheringweathering

What do you think created the cracks in the rock to form?

Where did the smaller rocks come from?

Get your Lab notebooksGet your Lab notebooks

• In your group read through the discovery lab on page 153.

• Title and date your lab

• Send one person from your group to gather the supplies

• Complete the observe section in your lab notebook. Write your answers in complete sentences!!

WeatheringWeathering

• Weathering – The process that breaks down rocks on Earth’s

surface

• Erosion – The removal and transport of materials from one

location to another

• Mechanical weathering – Physical weather – the process by which rocks and

minerals break down into smaller pieces

Mechanical WeatheringMechanical Weathering• What are the 2 big factors in mechanical

weathering?– Temperature

• When water freezes it expands, which can expand cracks – Pressure

• Buried rock is under pressure. When the pressure is removed, it can expand creating cracks.

• Frost wedging – The repeated thawing and freezing of water in the

cracks of rocks • Exfoliation

– The process that strips away the outer layer of a rock

Chemical WeatheringChemical Weathering

• Chemical weathering – The process by which rocks and minerals

undergo changes in their composition as a result of a chemical reaction

Agents of Chemical WeatheringAgents of Chemical Weathering

Water

Oxygen

Carbon Dioxide

Acid Precipitation

Can dissolve many kinds of minerals and rocks. Acts as a medium for other reactionsCan combine with other substances to create reactions

When combined with water in the atmosphere it forms a weak acid that can dissolve certain rocks and mineralsCaused by the oxidation of sulfur dioxide and nitrogen oxides that are released in the atmosphere by human activities

Agents of Chemical WeatheringAgents of Chemical Weathering

• Water– Hydrolysis

• The reaction of water with other substances

• Oxygen– Oxidation

• The chemical reaction of oxygen with other substances

What affects the rate of What affects the rate of weathering?weathering?

• Climate– Precipitation, temperature, and evaporation

influence the rate of chemical weathering. – Chemical weathering happens in areas with

warm temperatures, abundant rain, and lush vegetation

– Physical weathering happens in cool, dry areas, where water is more likely to freeze and thaw repeatedly

What affects the rate of What affects the rate of weathering?weathering?

• Rock Type and Composition– Sedimentary are more easily weathered than

other types– Igneous rocks are harder and more resistant

to weathering

What affects the rate of What affects the rate of weathering?weathering?

• Surface Area – Mechanical weathering breaks rocks into

smaller pieces, increasing surface area– The more surface area, the more weather can

break it down

What affects the rate of What affects the rate of weathering?weathering?

• Topography and other variables– Materials on slopes are more easily eroded,

due to gravity– Decaying materials give off carbon dioxide

which when combined with water creates an acid that aids in weathering

In your GroupsIn your Groups

• Individually record the answers to questions 1-4 on page 161

• Turn in your individual work by the end of the period