Continental Shelves

1
Continental Shelves

• Cover large area approx. 1/6 of the earths
  surface
• Ave. width is 40 nautical mile (1 n.m. 6000 ft)
• Ave. slope -- o07
• Ave depth 72 fathoms (a fathom 6 ft)
• Glaciated shelves
• -evidence of erosion by ice
• Nonglaciated shelves

2
Shelf Terms

• Shelf proper down to shelf edge or shelf break
• Continental slope from 132 m to 1400 m off the
  US Atlantic Coast. About 4 degrees
• Continental Rise 3000 4000 m lt1 degree
• Continental Shelf and Continentsl Rise
  Continental Margin

3
Shelf Profile
4
Shelf Seismic Profile
5
US Atlantic Coast Continental Shelf
6
Coastal Onlap

• Formed by a transgression, or rise in sea level
• Sediments seemed to a lap on the shelf
• Barrier island coasts a classic example

7
Coastal Offlap

• Sediments appear to lap off the continental
  shelf
• Formed by a regression or fall in sea level
• Deltas can be a good example of off lap
  sequences, especially during sea level low stands