covalent bond

chemical bond that involves the sharing of electron pairs between atoms

ionic bond

chemical bond that involves the attraction between oppositely charged ions

hydrogen bond

a weak bond between two molecules due to the electrostatic attraction between a hydrogen atom in one molecule and an atom of oxygen, nitrogen or fluorine in the other molecule

halocline

a layer of water below the mixed surface layer where a rapid change in salinity can be measured as depth increases

thermocline

a layer between two layers of water with different temperatures

gradient

the rate of change in the y-axis value as the x-axis value increases

thermal insulator

a substance which reduces the rate of transfer of thermal energy

pycnocline

a layer of water between two layers of water with different densities

earthquake

a sudden release of energy inside the Earth that creates seismic waves

mid-ocean ridge

a mountain range with a central valley on an ocean floor at the boundary between two diverging tectonic plates, where new crust forms from upwelling magma

divergent boundary

where two tectonic plates are moving away from each other

convergent boundary

when two or more tectonic plates come together

subduction

the process where one lithospheric plate slides past below another at a convergent plate boundary

trench

a long, narrow and deep depression on the ocean floor with relatively steep sides

volcano

a mountain or hill with a crater or vent through which lava, rock fragments, hot vapour and gas are being forced from the Earth's crust

tsunami

a seismic sea wave created by an underwater earthquake or volcanic event

hydrothermal vent

an area where cold ocean water that has seeped into the Earth's crust is superheated by an underlying magma and forced through the vents in the ocean floor

transform boundary

when two plate are moving in an antiparallel direction, creating friction between them

abyssal plain

a flat, sandy region of the ocean floor found between trenches and the continental rise

semi-diurnal

occurring twice daily

diurnal

occurring daily

coriolis effect

a force that results from the Earth's rotation that causes objects or particles in motion to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere

thermohaline circulation

large-scale ocean circulation caused by density differences due to temperature and salinity changes in the world's ocean

downwelling

the downward movement of water in the sea due to density differences

community

all the different populations interacting in one habitat at the same time

competition

a relationship between two organisms where both species are negatively is affected as they are trying to use the same resource

food chain

a way to describe the feeding relationships between organisms

decomposers

bacteria and fungi which break down dead organic matter and release the nutrients back into the environment

food web

a way to show all the different feeding relationships in an ecosystem

trophic level

the position on organism occupies in the food chain or web

apex predator

an organism at the end of the food chain which has no natural predators

respiration

the process by which all living things release energy from their food by oxidising glucose

eutrophication

the process by which a body of water becomes enriched in dissolved nutrients that stimulate the growth of producers, usually resulting in the depletion of dissolved oxygen

marine snow

particles of organic material that fall from surface layers to the deeper ocean