IMS 3 - Continental Margin

Benioff zone

-         a deep active seismic area in a subduction zone

Continental shelf

-          avr. 80km wide, 130m deep

-          avr. inclination 0.1° (2m drop / km)

Continental slope

-          avr. 1500m deep

-          70m drop / km

-          Narrow, < 20km

Continental rise

-          Down slope of c. slope

-          Current pick up carry fine grained sediments (silt/mud)

-          Accumulation form large gentle slope

Abyssal plain

-          Broad flat featureless, thick sediment accumulation (deep-sea clay)

-          ~4000km below sea level

Accretionary prism

-          Sediments accreted onto non-subducting convergent plate boundary

Submarine canyon

-          Steep-sloped valley carved into the shelf and slope by a river

Abyssal hill (knoll)

-          Low, rounded hill less than 1,000 m tall; very common

Seamount

-          Underwater mountain (volcano)

Guyot

-          Flat-topped seamount caused by sea level erosion

Atoll

-          Coral reef ring remaining at sea level after an island has subsided