The growth of plant roots and animal activity may result in ________________.

• erosion
• mechanical weathering
• chemical weathering
• abrasion

The definition of weathering is _______________________.

• the carrying away of rock
• the leaching of rock
• the breaking down of rock
• the permeability of rock

The agent of mechanical weathering in which rock is worn away by the grinding action of other rock particles is called _______________.

• plant growth
• oxygen
• abrasion
• ice wedging

The most important factors in determining the rate of weathering are _____________________.

• carbon dioxide and acid rain
• abrasion and acids from plant roots
• animal actions and oxygen
• rock type and climate

What kind of weathering causes the mineral composition of rock to change?

• mechanical weathering
• permeable weathering
• chemical weathering
• general weathering

Mechanical weathering is the removal of rock particles by gravity, wind, water, and ice.

• true
• false

Which of the following is a type of mechanical weathering?

• abrasion
• plant growth
• freezing and thawing
• all of the above

In the fall, Winston noticed a small crack on a boulder where he played in his backyard. The following spring, he saw that the small crack was much larger than he remembered. What most likely caused the change?

• gravity had caused the rock to shift
• acid rain had caused the crack to erode
• winds had caused the rock to break down
• water had frozen and thawed inside the rocks

What is the relationship between wind erosion and plant cover?

• More plants means less erosion
• More plants means more erosion
• There is no relationship
• Less plant cover means less erosion

When plants, animals, and other organisms die, they break down and become part of the soil. What is this part of the soil called?

• sand
• silt
• clay
• humus