Final answer:
The average width of the continental shelves is approximately 70 kilometers (43 miles), which are the relatively shallow submerged fringes of continental crust extending from coastlines to the shelf break.
Step-by-step explanation:
The average width of the continental shelves is about 70 kilometers (43 miles). These shelves are the submerged portion of the continent's crust in relatively shallow water, often less than 180 meters (600 feet) in depth, and extend from the shoreline to the drop-off point marked by the continental shelf break. They can significantly vary in width but generally they provide an expanded area of relatively shallow water along the coastlines of continents.