AbyssalHill Archipelago chain, cluster, or group of islands Atoll A ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. Backarc BackarcBasin Basin Bay Caldera Canyon Channel Channel Continent DrillHole Estuary A partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Fault Fjord FocusSite:Antarctic Antarctic Focus Site FocusSite:Arctic Arctic Focus Site FocusSite:GeoPRISMS GeoPRISMS Focus Site FocusSite:MARGINS Margins Focus Site FocusSite:Ridge2000 Ridge 2000 Focus Site Forearc ForearcBasin FossilRidge FractureZone Glacier Gulf Hemisphere Iceberg IceShelf Island Lagoon Lake Lake:Subglacial Margin MarineSanctuary Marine Sanctuary MountainRange NotApplicable Value will never be filled in. Cannot be known. NotProvided Information was not provided, but can be known Ocean OceanicPlateau Outcrop Outcrop Peninsula Plate Lithospheric Plate Rampart A wall-like ridge of rock fragments, earth, or debris Ridge RidgeAxis RidgeSlope Rift Rise relatively shallow area of ocean River Sea Seamount Shelf Slope SpreadingCenter Tectonic feature SpreadingCenterSegment Strait SubductionZone A type of convergent plate boundary where two tectonic plates move towards one another and one slides under the other TransformFault TripleJunction Vent VentCluster A hydrothermal complex with numerous hydrothermal vents. VentField VolcanicArc VolcanicCone Volcano