Marine Provinces and Ocean Floor Topography Flashcards

Vocabulary flashcards covering marine provinces, bathymetric mapping methods, continental margins, deep-ocean floor features, mid-ocean ridges, and hydrothermal vent types.

Bathymetry

The measurement of ocean depths and the charting of the shape or topography of the ocean floor.

Echo Sounder (Sonar)

The primary instrument for measuring ocean depth, invented in the 1920s, which calculates depth by reflecting sound waves off the ocean floor.

Sounding

A historical method of measuring ocean depth using a line attached to a heavy weight, first performed by Poseidonus in $85\text{ B.C.}$

Fathom

A unit of water depth measurement equal to $1.8\,m$ ($6\text{ feet}$).

Hypsographic Curve

A curve showing the relationship between the height of land and the depth of the ocean across Earth's surface.

Topographic Provinces of the Ocean Floor

The three major structural regions of the ocean floor: continental margins, ocean basin floor, and mid-ocean ridge.

Passive Continental Margins

Coastal margins found along most areas surrounding the Atlantic Ocean that are not associated with active plate boundaries, experiencing little volcanism and few earthquakes.

Continental Shelf

A gently sloping, flooded extension of the continent that varies in width from $70\,km$ to $150\,km$ and contains oil deposits.

Continental Slope

A relatively steep structure with a slope of $1^\circ$ to $25^\circ$ that marks the seaward edge of the continental shelf and forms the boundary between continental and oceanic crust.

Submarine Canyons

Deep, steep-sided valleys cut into the continental slope, some of which are seaward extensions of river valleys and most of which are eroded by turbidity currents.

Turbidity Currents

Underwater downslope movements of dense, sediment-laden water that erode submarine canyons and deposit turbidites displaying graded bedding on deep-sea fans.

Continental Rise

A gradual incline found in regions where deep-ocean trenches are absent, composed of thick accumulations of sediment deposited by turbidity currents forming deep-sea fans at the base of the continental slope.

Active Continental Margins

Coastal margins where the continental slope descends abruptly into a deep-ocean trench, characterized by subduction zones, accretionary wedges, volcanism, and earthquakes.

Accretionary Wedge

An accumulation of deformed sediment and scraps of ocean crust formed at subduction zones along active continental margins.

Abyssal Plains

Extensively level places on the ocean floor extending from the base of the continental rise, formed by thick sediment deposits from suspension settling.

Seamounts and Guyots

Isolated underwater volcanic peaks formed near oceanic ridges, where guyots represent flat-topped submerged volcanic features.

Deep-Ocean Trenches

Long, relatively narrow features forming the deepest parts of the ocean where subducting lithospheric plates plunge into the mantle, closely associated with volcanic arcs.

Mid-Ocean Ridge

An interconnected underwater mountain range spanning over $70{,}000\,km$ ($43{,}000\text{ miles}$) and covering $23\%$ of Earth's surface, characterized by elevated topography (~$2.5\,km$ above seafloor) and extensive faulting.

Ridge vs Rise vs Rift

Distinctions based on spreading rate and elevation: a ridge is slow-spreading and below sea level; a rise is fast-spreading and below sea level; a rift is slow-spreading and above sea level.

Pillow Lavas

Basaltic lava structures with pillow-like shapes formed when molten basalt erupts underwater and rapidly quenches.

Warm Water Vents

Hydrothermal vents on the seafloor with water emission temperatures below $30^\circ\text{C}$ ($86^\circ\text{F}$).

White Smokers

Hydrothermal vents discharging water at temperatures ranging from $30^\circ\text{C}$ to $350^\circ\text{C}$ ($86^\circ\text{F}$ to $662^\circ\text{F}$).

Black Smokers

Hydrothermal vents discharging dark, mineral-rich water at temperatures exceeding $350^\circ\text{C}$ ($662^\circ\text{F}$).