Final answer:
Small dimples or circular depressions on asphalt shingles are often caused by under-driven nails.
Step-by-step explanation:
Small dimples or circular depressions on asphalt shingles are often caused by under-driven nails. When nails are not driven deep enough into the shingle, it creates a depression or dimple in the surface. This can occur during the installation process if the nails are not properly driven into the shingles.
Under-driven nails can be a result of improper installation or lack of care during the roofing process. These small dimples can sometimes be seen on the surface of the shingles, indicating that the nails have not been driven securely into the material.