Part of the Earth’s surface beneath the seas and the oceans; its topography is highly variable.
Underwater extension of the continent; it comprises the continental shelf, the continental slope and the continental rise.
Section of the continental margin extending from the coast of the continent to the continental rise; its depth is no more than 660 feet.
Ancient volcano whose summit has been cut off by erosion and then submerged.
Molten rock and gas under very high pressure that can reach extremely high temperatures.
Isolated mountain of volcanic origin featuring a pointed summit.
Extremely deep elongated depression bordering a continent or island arc; it occurs when one tectonic plate moves under another.
Volcano whose summit rises above sea level.
String of volcanic islands formed when two tectonic plates meet.
Rounded underwater rise of low elevation.
Mean water level observed for a given duration (day, month, year); it is used as a reference to define coastal features and calculate the elevation of topographical elements.
Group of underwater mountain chains criss-crossing the oceans; it is formed by an outpouring of magma.
A collective term for the vast landmasses and their submerged margins.
Deep valley that is frequently the extension of a river; it ends in a sediment buildup.
Slope of a few degrees that extends from the continental shelf; it is 660 to 6,600 feet deep.
Gently sloping section of the continental margin; it connects the continental slope to the abyssal plain.
Zone located at a depth of 6,600 to 20,000 feet; it covers most of the ocean floor.