Select the correct answer.
The table presents the average day and night temperatures in five cities. It also reveals whether a city receives substantial rainfall (wet climate) or little rainfall (dry climate). Which city's rocks are likeliest to experience frost wedging, and why?
| City | Climate | Day Temperature (°C) | Night Temperature (°C) |
| :----- | :------ | :------------------- | :--------------------- |
| City A | dry | -11 | -30 |
| City B | wet | 5 | -4 |
| City C | wet | 14 | 6 |
| City D | dry | 26 | 17 |
A. City A because the consistently subzero temperatures would prevent water from melting and escaping rocks.
B. City B because it is a wet region and the temperature fluctuates around the freezing point.
C. City C because it receives plenty of rainfall and the weather is moderately cool.
D. City D because the hot and dry weather would cause rocks to absorb water.
Answer (1)
Frost wedging requires both water and freeze-thaw cycles.
City A and D are dry, making frost wedging unlikely.
City C's temperatures are consistently above freezing, preventing frost wedging.
City B has a wet climate and temperatures that fluctuate around freezing, making it the most likely to experience frost wedging. The answer is B.
Explanation
Understanding Frost Wedging We need to determine which city's environment is most conducive to frost wedging. Frost wedging occurs when water repeatedly freezes and thaws in the cracks of rocks, causing them to break apart. This process requires both water and temperatures that fluctuate around the freezing point (0°C).
Analyzing Each City Let's analyze each city:
City A: Dry climate with consistently subzero temperatures (-11°C and -30°C). The lack of water and consistently freezing temperatures make frost wedging unlikely.
City B: Wet climate with temperatures fluctuating around the freezing point (5°C and -4°C). This city has both the necessary water and freeze-thaw cycles for frost wedging.
City C: Wet climate with temperatures consistently above freezing (14°C and 6°C). The lack of freezing temperatures makes frost wedging unlikely.
City D: Dry climate with temperatures consistently above freezing (26°C and 17°C). The lack of water and freezing temperatures makes frost wedging unlikely.
Conclusion Based on the analysis, City B is the most likely to experience frost wedging because it has a wet climate and temperatures that fluctuate around the freezing point.
Examples
Frost wedging is a significant factor in landscape formation, especially in mountainous regions. For example, in the Rocky Mountains, water from snowmelt seeps into cracks in the rocks. During the night, this water freezes and expands, exerting pressure on the rock. Over time, this repeated freezing and thawing causes the rocks to fracture and break apart, contributing to the formation of talus slopes and other geological features. Understanding frost wedging helps us predict how landscapes evolve over time and how human activities might affect these processes.
