Name: __________________________ Date: ___________________ Pd. ________
Rocks and Weathering Worksheet
Objectives:
Students will…

determine what causes mechanical and chemical weathering and how fast weathering occurs
Introduction:
Weathering is the process that breaks down rock and other materials at Earth’s surface. The
forces of weathering break rocks into smaller and smaller pieces. The forces of erosion carry the
pieces away. Erosion is the movement of rock particles by wind, water, or ice. Weathering and erosion
work together continuously to wear down and carry away the rocks at Earth’s surface.
The type of weathering in which rock is physically broken into smaller pieces is called mechanical
weathering. These smaller pieces have the same composition as the rock they came from. Mechanical
weathering breaks rock into pieces by freezing and thawing, heating and cooling, growth of plants,
actions of animals, and abrasion. In cool climates, the most important force of mechanical weathering
is freezing and thawing. Water expands when it freezes, and acts as a wedge. This process is called ice
wedging. Heating and cooling can cause rocks to crack. Plant roots can pry apart cracked rocks. Rock
particles carried by wind, water, and ice can wear away rocks in the process called abrasion. Animal
actions, such as burrowing, can break apart rocks in the soil.
Chemical weathering is the process that breaks down rock through chemical changes. The
agents of chemical weathering include water, oxygen, carbon dioxide, living organisms, and acid
rain. Chemical weathering produces rock particles that have a different mineral makeup from the
original rock. Chemical and mechanical weathering often works together. As mechanical weathering
breaks rock into pieces, more surface area becomes exposed to chemical weathering.
Water is the most important agent of chemical weathering. Water weathers rocks by dissolving
it. The oxygen in air is an important cause of chemical weathering. Iron combines with oxygen in the
presence of water in a process called oxidation. Rock that contains iron oxidizes, or rusts. Another gas
found in air, carbon dioxide, combines with rainwater to form carbonic acid. Carbonic acid easily
weathers marble and limestone. Plant roots produce weak acids that slowly dissolve any rock around the
roots. Lichens also produce a weak acid that weathers rock. Acid rain causes very rapid chemical
weathering.
The most important factors that determine the rate at which weathering occurs are type of
rock and climate. Some types of rock weather more rapidly than others. For example, limestone
weathers easily because it is permeable, which means that it is full of air spaces that allow water to
seep through it. Both chemical and mechanical weathering occurs faster in wet climates. Chemical
weathering occurs more quickly where the climate is both hot and wet.
Fill in the blanks in the table below.
Agent
Type
Description
1. ______________________
Mechanical
Rock particles wear away rock
2. ______________________
Chemical
Forms from coal, oil, and gas burning
Freezing and Thawing
3. _________________
Breaks rock by ice wedging
Carbon dioxide
4. _________________
Forms carbonic acid in water
5. ______________________
Chemical
Weathers marble and limestone
6. ______________________
Mechanical
Burrowing in the ground breaks rock
Plant Growth
7. _________________
Roots pry apart cracks in rock
Living Organisms
8. _________________
Produce weak acid that weathers rock
Oxygen
9. _________________
Causes rust on some rock
10. ______________________
mechanical
Sun or forest fire causes rock to crack
Answer the following questions.
11. How does erosion differ from weathering?
12. What factors determine the rate of weathering?
Fill in the blank to complete each statement.
13. ________________________________ is the movement of rock particles by wind, water, or ice.
14. _______________________ means that a material has spaces that allow water to seep through it.
15. The process that breaks down rock and other materials at Earths’ surface is called ____________
16. The grinding away of rock by other particles is called ___________________________________
17. The process by which ice widens and deepens cracks in rocks is called _______________________