What is a continental margin?
The continental shelf is the extended margin of each continent occupied by relatively shallow seas and gulfs. It is the shallowest part of the ocean showing an average gradient of 1° or even less. The shelf typically ends at a very steep slope called the shelf break.
The width of these margins varies, averaging about 80 km, and they are covered with variable thicknesses of sediments brought down by rivers, glaciers, and wind. These massive sedimentary deposits become the source of fossil fuels over time.
Explanation
The provided text explicitly defines the 'continental shelf' as the 'extended margin of each continent'. Although the question asks for a 'continental margin', the context strictly links the term 'margin' to the definition of the continental shelf. Therefore, the answer focuses on the definition and characteristics of the continental shelf as described in the text to remain factually accurate to the source provided.