Introduction to Terminology Describing the Topography of the Ocean Floor:

• Definitions of terms and annotated images of features from lectures
• abyssal plain
• passive continental margin with shelf, slope and rise
• fracture zone
• mid-ocean ridge or spreading ridge
• lateral ridge
• deep sea trench
• island chains and seamounts
• triple point junction

Images	Definitions	Images
	abyssal plain: flat ocean-basin floor extending seaward from the base of the continental slope and rise, typically 4-6km deep continental margin: zone separating continents from the deep sea floor.  passive, if seismically inactive. continental shelf: zone bordering a continent from shoreline to depth where a marked change in deoth occurs (shelf break). continental slope: relatively steep downward slope from shelf to depth. continental rise: gentle slope at the base of the continental slope. fracture zone: linear zone of irregular bathymetry associated with fault zones and offsetting mid-ocean ridges. mid-ocean ridge (MOR): spreading ridge at divergent plate boundary. lateral ridges: volcanic ridges often separating ocean basins that are not divergent plate boundaries seamounts: isolate volcanic peaks that rise >1km above the ocean floor, often in island chains formed by 'hot spots.' trenches: long, deep and narrow depressions of the sea floor with relatively steep sides that are associated with subduction zones. triple point junction: a point where three plates meet

---

Department of Geological Sciences, 
1001 E. Tenth Street, Bloomington, IN 47405-1403
Phone: (812) 855-5582  Last updated: 6 October 2002
Comments: simon@indiana.edu
Copyright 2000, The Trustees of Indiana University