||A low, outspread, relatively flat-to-gently sloping mass of loose material—shaped like an open fan or a segment of a cone—deposited
by a flow of water at the place where it issues from a narrower or steeper-gradient area into a broader area, valley, flat,
or other feature. Abyssal fans form at the mouths of submarine canyons, and fans are also the result of turbidities (that
is, gravity-driven, underwater avalanches).
||A long, narrow coral reef, roughly parallel to the shore and separated from it by a lagoon of considerable depth and width.
This reef may enclose a volcanic island (either wholly or in part), or it may lie a great distance from a continental coast
(such as the Great Barrier Reef). Generally, barrier reefs follow the coasts for long distances—often with short interruptions
that are called passes or channels. Three principle examples of this type of feature are Australia's Great Barrier Reef, the
New Caledonia Barrier Reef, and the Meso-American Barrier Reef system—although similar features exist elsewhere.
||A broad bend or curve in a generally open coast. Examples include the South Atlantic Bight and the Southern California Bight.
These are distinguished from Embayment/Bays by the shallower angle between the apex of the bight and the adjacent coasts,
although the term <i>Bay</i> has been used to name these features (e.g., Bay of Campeche).
||An area of the continental margin (between the shoreline and the continental slope) that is topographically more complex than
the continental shelf. This feature is characterized by ridges and basins, some of which are below the depth of the continental
||An area that lies at the deepest part of a continental or island margin between the continental slope and the abyssal plain.
The rise is a gentle incline (with slopes of 0.5° to 1°) and it has generally smooth topography—although it may bear submarine
||That part of the continental margin that is between the shoreline and the continental slope (or a depth or 200 meters when
there is no noticeable continental slope); it is characterized by its very gentle slope of 0.1°. Island shelves are analogous
to the continental shelves, but surround islands.
|Continental/Island Shore Complex
||This feature includes the land-water interface zone and contains geoforms across a diversity of scales. For CMECS, the supratidal
zone forms the landward limit of geoforms found within the shore complex setting. This setting does not include the land-water
interface along tidal rivers that may extend a considerable distance inland.
||That part of the continental margin that is between the continental shelf and the continental rise (if there is one); it is
characterized by its relatively steep slope of 1.5 - 6°. Island slopes are analogous to the continental slopes, but occur
||A water body with some level of enclosure by land at different spatial scales. These can be wide, curving indentations in
the coast, arms of the sea, or bodies of water almost surrounded by land. These features can be small—with considerable freshwater
and terrestrial influence—or large and generally oceanic in character.
||A long, narrow, glacially eroded inlet or arm of the sea. They are often U-shaped, steep-walled, and deep. Because of their
depth, they tend to have low surface-area-to-volume ratios. They have moderate watershed-to-water-area ratios and low-to-moderate
riverine inputs. Fjords often have a geologic sill formation at the seaward end caused by glacial action. This morphology—combined
with a low exchange of bottom waters with the ocean—can result in formation of hypoxic bottom waters.
||A large, water body almost completely surrounded by land. Salinities range from fresh through marine. The term <i>inland</i>
is used to describe situations where the water body is connected to an adjacent large water body by a narrow strait, channel,
canal, or river. Examples of this type of setting are the Mediterranean and Black Seas. The Great Lakes, due to their connectivity
to the Atlantic Ocean via the St. Lawrence River also fall into this category.
||This class of estuary tends to be shallow, highly enclosed, and have reduced exchange with the ocean. They often experience
high evaporation, and they tend to be quiescent in terms of wind, current, and wave energy. Lagoonal estuaries usually have
a very high surface-to-volume ratio, a low-to-moderate watershed-to-water-area ratio, and can have a high wetland-to-water
ratio. The flushing times tend to be long relative to riverine estuaries and embayments because the restricted exchange with
the marine-end member and the reduced river input lengthen residence times. As such, there tends to be more benthic-pelagic
interaction, enhanced by generally shallow bathymetry. Additionally, exchange with surrounding landscapes (often riparian
wetland and palustrine systems) tends to be enhanced and more highly coupled than in other types of estuaries.<br/><br/>Occasionally,
a lagoon may be produced by the temporary sealing of a river estuary by a barrier. Such lagoons are usually seasonal and exist
until the river breaches the barrier; these lagoons occur in regions of low or sporadic rainfall.
|Major River Delta
||The nearly flat, alluvial tract of land at the mouth of a river, which commonly forms a triangular or fan-shaped plain. It
is crossed by many distributaries, and the delta is the result of sediment accumulation from the river. Deltas are distinguished
from alluvial fans by their flatter slope. Examples of this feature include the Mississippi Delta, the Nile Delta, and the
Ganges Delta. All deltas are dynamic areas of mixed-water flow and salinity.
|Marine Basin Floor
||Basin floors refer broadly to the areas of the seafloor between the base of the continental margin (usually the foot of the
continental rise) and the mid-ocean ridge. Occasionally, this large region is subdivided into smaller basins based on local
||A mound-like or ridge-like elevated area on the seafloor; it may have a modest-to-substantial extent. Although submerged,
this feature can reach close to sea level (e.g., Bahama Banks).
||This class of estuary tends to be linear and seasonally turbid (especially in upper reaches), and it can be subjected to high
current speeds. These estuaries are sedimentary and depositional, so they may be associated with a delta, bar, barrier island,
and other depositional features. These estuaries also tend to be highly flushed (with a wide and variable salinity range)
and seasonally stratified. Riverine estuaries have moderate surface-to-volume ratios with a high watershed-to-water-area ratio—and
they can have very high wetland-to-water-area ratios as well. These estuaries are often characterized by a V-shaped channel
configuration and a salt wedge.<br/><br/>High inputs of land drainage can promote increased primary productivity, which may
be confined to the water column in the upper reach, due to low transparency in the water column. Surrounding wetlands may
be extensive and healthy, given the sediment supply and nutrient input. This marsh perimeter may be important in taking up
the excess nutrients that are introduced to the system. Physically, the system may tend to be stratified during periods of
high riverine input, and the input of marine waters may be enhanced by countercurrent flow.
||Basins occurring on the continental shelf formed by offshore faulting activity.
||The slope discontinuity (rapid change in gradient) of 3° or greater that occurs at the outer edge of the continental shelf.
This boundary generally occurs at a depth between 100-200 meters and forms the boundary between the Marine Offshore and Oceanic
||(a) A relatively long, narrow waterway connecting two larger bodies of water (or two parts of the same water body), or an
arm of the sea forming a channel between the mainland and an island (e.g., Puget Sound, WA). A sound is generally wider and
more extensive than a strait. (b) A long, large, rather broad inlet of the ocean, which generally extends parallel to the
coast (e.g., Long Island Sound, NY).
||A general term for all linear, steep-sided valleys on the seafloor. These canyons can be associated with terrestrial or nearshore
river inputs, such as in the Hudson or Mississippi canyons.
||Trenches in the physiographic setting subcomponent occur at a smaller spatial scale than the hemispheric-sized trenches in
the tectonic setting. Both types of trenches share similar morphology, but physiographic setting Trenches are not necessarily
associated with plate subduction.