ATOC 182 MidTerm

Lithosphere:

The rigid, solid outer layer of the Earth consisting of the crust and the uppermost solid mantle, split into moving tectonic plates

Asthenosphere:

The hotter, weaker, and partially molten layer of the upper mantle located directly beneath the lithosphere upon which tectonic plates float

Crust

The thin, rocky outermost layer of Earth, varying in thickness from about 3 miles (5 km) under ocean basins to 25 miles (30 km+) beneath continents

Subduction

The tectonic process in which one lithospheric plate moves under another plate and sinks into the mantle, forming deep ocean trenches and landward volcanic chains

Mid-Ocean Ridge:

A continuous underwater mountain chain formed along divergent plate boundaries, where magma erupts and cools to create new oceanic lithosphere

Seafloor Spreading:

The process by which new oceanic crust forms at mid-ocean ridges as tectonic plates pull apart, resulting in younger seafloor near the ridge and older seafloor further away toward abyssal plains

Ferromagnetic Minerals

Iron-bearing minerals within basaltic lava that become magnetized in alignment with Earth's magnetic field as the rock cools, recording past magnetic orientations and proving seafloor spreading

Marginal Sea:

A semi-enclosed sea located along the —— of an ocean basin that possesses distinct physical and chemical water mass characteristics (e.g., Labrador Sea

Abyssal Plain:

A vast, extremely flat region of the deep-ocean floor situated away from mid-ocean ridges, covered by thick sediment accumulations

Seamount:

An isolated submarine mountain of volcanic or tectonic origin rising from the seafloor that does not break the ocean surface

Guyot

A flat-topped seamount that formerly reached the sea surface, underwent wave erosion, and subsequently submerged into deeper water

Ocean Trench:

A narrow, steep-sided deep depression on the ocean floor produced along subduction zones where an oceanic plate dives beneath another plate

Fracture Zone:

Extensive linear fault zones that run perpendicularly across mid-ocean ridges, interrupting the continuity of the ridge axis

Echo Sounder:

An acoustic instrument operating since the 1920s that calculates ocean depth (D) by measuring the round-trip travel time (T) of a sound pulse traveling at speed (U) in seawater (D = U \X T / 2)

"Red" Clay (Pelagic Clay):

Deep-sea inorganic sediment composed of land-derived fine volcanic material and meteoric remains carried by winds, containing less than 30% biogenic material

Biogenic Ooze:

Deep-ocean sediment consisting of greater than 30% biogenic material derived from the microscopic skeletal remains of planktonic organisms

Turbidity Current:

A high-speed underwater avalanche of sediment and water flowing down continental slopes, depositing graded sediment layers^[11]

Turbidites:

Graded sediment layers produced by turbidity currents, characterized by coarse grains at the bottom transitioning smoothly to fine grains at the top

Methane Hydrate:

A solid lattice structure of water molecules trapping methane gas (CH4), formed within deep-sea sediments through bacterial decomposition

Polar Molecule:

A molecule such as water (H2O) with an asymmetrical charge distribution, possessing a weakly negative oxygen pole and weakly positive hydrogen poles

Dielectric Constant (k):

A physical parameter measuring a liquid's ability to polarize and hold charge internally, giving water its strong solvent power to dissolve salts

Salinity:

The total mass of dissolved inorganic salts in a given mass of seawater, dominated primarily by sodium (Na+) and chloride (Cl-) ions

Thermocline:

The ocean layer where water temperature decreases rapidly with increasing depth, separating warm surface waters from cooler deep waters

Halocline:

A subsurface layer in the ocean where salinity changes rapidly over a small depth interval

Density (p):

Mass per unit volume, (kg/m3) which in seawater is determined by temperature, salinity, and hydrostatic pressure

High Viscosity of Water:

The internal fluid friction resulting from hydrogen bonding and chain-like molecular structures, which facilitates momentum transfer from atmospheric winds to sea surface currents

Pressure (p)

Force applied per unit surface area ( p=F/S) conventionally expressed in oceanography in decibars ($\text{dbar}$), increasing linearly with depth

Solar Shortwave Radiation, (Qsw)

Infrared radiation emitted upward from the ocean surface proportional to its absolute surface temperature ( equation) acting as a cooling mechanism^[21]

Latent Heat Flux (Qlat)

Heat energy extracted from the ocean and transferred to the atmosphere during evaporation, manifesting as water vapor

Sensible Heat Flux ( Qsen)

Heat transferred directly between the ocean surface and the atmosphere via conduction and convection due to temperature differences

Freezing Point Depression:

The lowering of water's freezing temperature caused by dissolved salts; seawater with 35 PSU salinity freezes at $-1.91C rather than 0C

Brine Rejection & Deep Water Formation:

The process where salt is expelled from ice crystals during seawater freezing, producing cold, highly saline, dense water that sinks to initiate deep ocean circulation

Thermohaline Circulation:

Deep-ocean circulation driven by density differences originating from surface variations in temperature ("thermo") and salinity ("haline")

Wind-Driven Circulation:

Upper-ocean surface currents generated by wind friction transferring momentum to the surface water, governed by friction and Earth's rotation

Coriolis Force:

An apparent force resulting from Earth's rotation that deflects moving fluids and objects relative to an observer on the surface

Ekman Transport:

The net directional movement of surface water resulting from the balance between atmospheric wind stress and the Coriolis force

Active Continental Margin:

: A continental boundary located along a tectonic plate boundary (typically a subduction zone) characterized by a narrow continental shelf, steep slope, deep ocean trench, and high earthquake/volcanic activity

Passive Continental Margin:

A continental margin located far from active plate boundaries (e.g., Atlantic coast), featuring a wide continental shelf, gentle slope, well-developed continental rise, and minimal seismic activity

Continental Shelf:

The gently sloping submerged edge of a continent extending from the shoreline to the shelf break, reaching a maximum typical depth of 130 meters

Continental Slope:

The steep gradient extending from the continental shelf break down to the deep ocean floor, with a maximum depth reaching around 4,000 meters

Continental Rise:

The thick sediment apron at the base of the continental slope on passive margins, formed by deep-sea fan deposits and turbidity current accumulations

Divergent Plate Boundary:

A region where two tectonic plates move away from each other (e.g., Mid-Ocean Ridges), allowing magma to upwell, cool, and form new oceanic lithosphere

Convergent Plate Boundary:

A boundary where tectonic plates move toward each other, leading to subduction (one plate sinking under another) or continental collision

Transform Fault:

A strike-slip fault plate boundary where adjacent tectonic plates slide past each other horizontally, offseting mid-ocean ridge segments

Paleomagnetism:

The study of Earth's ancient magnetic field preserved in iron-rich basaltic rocks as they cool below their Curie temperature at spreading ridges, proving periodic magnetic polarity reversals and seafloor spreading

Submarine Canyon:

V-shaped underwater valleys carved into continental slopes and shelves, created primarily by high-velocity turbidity currents carrying erosive sediments

Terrigenous (Lithogenous) Sediment:

Ocean sediment originating from land rock weathering, transported to the ocean via rivers, wind, glaciers, and turbidity currents

Hydrogenous Sediment:

Marine sediment precipitated directly out of seawater due to chemical reactions, such as manganese nodules and evaporite salts

Cosmogenous Sediment:

Deep-sea sediment formed from extraterrestrial debris, including cosmic dust particles and meteoritic tektites

Calcium Carbonate Compensation Depth (CCD):

The ocean depth below which the rate of calcium carbonate supply is equaled or exceeded by its rate of dissolution due to cold temperature and high pressure, preventing calcareous oozes from accumulating on deeper seafloors

Hydrogen Bonding:

Weak electrostatic attractions formed between the weakly positive hydrogen atom of one polar water molecule and the weakly negative oxygen atom of an adjacent water molecule

Specific Heat Capacity:

The amount of heat energy required to raise the temperature of 1 gram of a substance by 1°C; water's high specific heat allows oceans to absorb massive thermal energy without large temperature spikes, regulating Earth's climate

Latent Heat of Vaporization:

The large quantity of heat absorbed by liquid water during its transition to water vapor without a change in temperature, acting as a major atmospheric energy carrier through heat fluxes (Qlat)

Principle of Constant Proportions (Forchhammer's Principle):

The fundamental geochemical rule stating that while absolute salinity varies across ocean regions, the relative ratios of major dissolved ions ( Na+,Cl-…)

Practical Salinity Unit (PSU):

A dimensionless salinity scale based on measuring seawater's electrical conductivity relative to a standard potassium chloride (KCl) solution at 15ºC

Pycnocline:

A subsurface layer in the ocean where water density increases rapidly with increasing depth, acting as a strong barrier against vertical mixing between upper surface waters and deep waters

Albedo:

The percentage of incident solar radiation reflected back to space by a surface; liquid seawater has a low —— (absorbing most heat), while snow and sea ice have a high —- (reflecting most heat)

Evaporation minus Precipitation (E - P) Balance:

The net freshwater budget at the ocean surface; regions where evaporation exceeds precipitation (E > P) exhibit surface salinity peaks, whereas regions where precipitation exceeds evaporation (P > E) exhibit low surface salinity

Frazil Ice & Pancake Ice:

Early stages of sea ice formation; —— ice consists of needle-like crystals in turbulent surface water that aggregate into circular, flat disks with raised rims known as —- ice

Polynya:

Persistent, non-linear areas of open ocean water surrounded by sea ice, created by wind or upwelling, which serve as intensive ice factories generating dense, saline brine

Ekman Spiral:

The continuous change in direction and speed of water movement with increasing depth down the upper 50–100 m layer,

caused by the balance between wind stress, internal fluid friction, and the Coriolis force deflecting each deeper layer further to the right in the Northern Hemisphere