Chapter 23 Vocabulary- The Ocean Floor
Read each definition, rewrite the definition IN YOUR OWN WORDS, and then draw a picture to
illustrate the definition.
Abyssal hill: One of a series of small rolling hills on the ocean floor that occur next to
continental margins or ridges.
Abyssal plain: A large flat area on the ocean floor, composed of sediments that originated
mostly on continents.
Active continental margin: A continental margin at which an oceanic plate is subducting under a
continental plate, characterized by the presence of a narrow continental shelf and a deep sea
trench., characterized by the presence of a narrow continental shelf and a deep sea trench.
Biogenous sediments: Sea-floor sediments that are composed mostly of the shells and
skeletons on living things.
Continental margin: The underwater part of the continental crust, which includes the
continental shelf and the continental slope.
Continental rise: A gently rolling undersea slope between a continental slope and an abyssal
plain.
Continental shelf: The flat or gently sloping submerged part of the continent; extends from the
shoreline out to the continental slope.
Continental slope: The steep boundary between the continental shelf and the continental rise.
Coral atoll: A ring-shaped coral island surrounding a central lagoon.
Core sampling: A technique that involves the use of a special hollow drill to remove cylindrical
samples from sediment or rock, so they can be analyzed for certain properties or features.
Deep-sea trench: A long, narrow, steeped-sided trough that runs parallel to continental margins
or volcanic island chains.
Echo sounding: A system that uses transmitted and reflected sound waves to measure
distances to the ocean floor; sonar.
Fracture zone: An area of ocean ridges that are broken by transform faults.
Guyot: A flat-topped seamount
Hydrogenous sediments: Sea-floor sediments, such as manganese nodules, that form when
chemical reactions cause minerals to crystallize from seawater.
Island arc: A volcanic island chain that forms along a deep-ocean trench.
Mid-ocean ridge: A long chain of mountains with a central rift valley that is located along a
divergent boundary on the ocean floor.
Passive continental margin: A continental margin that does not occur along a plate boundary.
Seamount: A cone-shaped undersea mountain of volcanic origin that rises high above the ocean
floor.
Submarine canyon: An undersea gully that cuts through the continental shelf and continental
slope.
Terrigenous sediments: Sea-floor sediments that came from eroded minerals that had
comprised continental rocks.
Turbidity current: An undersea landslide of mud and sand, triggered by earthquakes or by
gravity, that speeds down the continental slope carving out channels.