Which statement best describes how frost wedging accelerates mechanical weathering in temperate climates?

Which statement best describes how frost wedging accelerates mechanical weathering in temperate climates?

• A. Water enters cracks, freezes, and expands, widening cracks and breaking rock apart; repeated freeze-thaw cycles accelerate fragmentation.
• B. Wind erosion enlarges cracks.
• C. Solidification of rock reduces cracks.
• D. Chemical weathering from acids.

Answer: (A)

Frost wedging drives mechanical weathering by turning a small crack into a bigger one through the action of freezing water. In temperate climates, moisture enters cracks, freezes, and expands—about 9%—which pushes the crack walls apart. When temperatures rise and the ice thaws, the material remains stressed and the crack stays wider. Repeating this freeze-thaw cycle slowly widens cracks and eventually pieces of rock break off. This is a physical breakup of rock, not a chemical change, which is why it accelerates mechanical weathering specifically in environments that swing between freezing and above-freezing temperatures. The other processes described don’t produce the same cycle of cracking: wind erosion removes material rather than prying rocks apart, solidification doesn’t create widening cracks, and chemical reactions from acids change minerals rather than split the rock.

Frost wedging drives mechanical weathering by turning a small crack into a bigger one through the action of freezing water. In temperate climates, moisture enters cracks, freezes, and expands—about 9%—which pushes the crack walls apart. When temperatures rise and the ice thaws, the material remains stressed and the crack stays wider. Repeating this freeze-thaw cycle slowly widens cracks and eventually pieces of rock break off. This is a physical breakup of rock, not a chemical change, which is why it accelerates mechanical weathering specifically in environments that swing between freezing and above-freezing temperatures. The other processes described don’t produce the same cycle of cracking: wind erosion removes material rather than prying rocks apart, solidification doesn’t create widening cracks, and chemical reactions from acids change minerals rather than split the rock.