Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.
17 2.11 Hydrothermal Vents
A whole new ecosystem reliant on the processes of plate tectonics was discovered on the deep seafloor of the Galapagos Rift in 1977. The deep sea submersible Alvin was exploring in 2500 m of water when it encountered unusually warm water. Following the temperature gradient, Alvin eventually discovered jets of superheated water coming from out of the seafloor at temperatures up to 350o C (the normal temperature for water at this depth would be 2-4o C). The water poured out of cracks in the crust, as well as through tall chimneys up to 20 m high and 1 m wide, and as it emerged it took on the appearance of thick black smoke, These fissures were named hydrothermal vents, and the chimneys “black smokers”.
Figure 2.11.1 A black smoker in the High Rise portion of the Endeavour hydrothermal vents (NOAA).
To create these vents, water percolates into the crust where there are plumes of magma close to the surface. The water gets superheated by the magma, then moves back to the surface through convection and is released through the vents. The hot water dissolves minerals from the surrounding rock, and as the water emerges and cools, the dissolved minerals and inorganic sulfides precipitate out as small particles and turn the water black, leading to the black “smoke” coming from the vents. Precipitation of these minerals also create the tall chimneys characteristic of many hydrothermal vents.
Since their original discovery in the Galapagos Rift, hydrothermal vents have been located across the globe along oceanic ridges where there is shallow crust and a lot of tectonic activity (Figure 2.11.2).
Figure 2.11.2 Distribution of hydrothermal vents (red dots) and their association with plate boundaries (By DeDuijn (Own work) [CC BY-SA 4.0], via Wikimedia Commons).
As unexpected as it was to discover these vent systems, even more surprising was the fact that they were teeming with life. The vents are surrounded by a diverse range of previously unknown organisms, including giant tube worms over 2 m long, crabs, shrimp, giant mussels, and mats of bacteria. How is it that such a diverse community can exist in the ocean depths, far removed from the sunlight that supports photosynthesis and primary production in most other ecosystems? The answer is that the water exiting the vents is rich in hydrogen sulfide (H2S), oxygen and CO2. The bacteria surrounding the vents use energy from the oxidation of sulfur compounds like H2S to form carbohydrates from CO2 and water. This is the process of chemosynthesis, and the bacteria are very productive as these reactions occur faster at high temperatures. The bacteria then represent the base of the food web, as other organisms eat the bacteria, or derive their energy from bacteria living symbiotically within their tissues. Watch the video below for more about hydrothermal vents.
It may seem odd to be discussing coral reefs in a section about geology, but due to the stony calcium carbonate skeletons secreted by many coral species, coral reefs are as interesting as geological features as they are biological ones. Corals grow best in warm, clear, tropical water, that is close enough to the surface for light to support photosynthesis by the algae living in the coral tissues. Because of this need for light, new coral will often grown on top of the stony skeletons of older corals.
In the 1830s Charles Darwin made some observations about different types of coral reefs, and hypothesized that they represent a progression from one form to the next. The types of reefs he examined were fringing reefs, barrier reefs, and atolls, which are associated with oceanic islands (Figure 2.10.1). Fringing reefs are reefs that are close to or are connected to shore. Barrier reefs are offshore reefs that are separated from the land by an expanse of water, such as a lagoon. Atolls are circular or oval reefs surrounding a lagoon, without any central land mass in the lagoon. Darwin speculated that reefs progressed from fringing, to barrier, to atolls as the land mass subsided. However, he had no explanation for how volcanic islands could sink. Today we know that Darwin was correct, and that islands can sink as oceanic crust subsides as it moves away from a spreading center, or as sea level rises as glaciers melt.
Figure 2.10.1 A fringing reef (left), barrier reef (center), and atoll (right) (Public domain, via Wikimedia Commons).
The progression starts with a fringing reef built against the shores of island (Figure 2.10.2). If sea level doesn't change or the land doesn't sink, many reefs will not progress beyond this stage. But if the land does subside, the corals would eventually sink too deep for light penetration and they would die. So as the reef gets deeper, the corals continue to grow upwards, at a rate of about 3-5 m per 1000 years, and eventually a lagoon develops between the reef and the island; the reef is now a barrier reef. If the land continues to subside until it is completely submerged, all that is left is a ring of coral that has been growing upwards around the central lagoon; an atoll.
Figure 2.10.2 Steps in the development of coral reefs (Steven Earle, "Physical Geology").
Modified from "Physical Geology" by Steven Earle used under a CC-BY 4.0 international license. Download this book for free at http://open.bccampus.ca
Written by Dr. Cristina Cardona.
With so many variables playing a role in the production of tides, it is understandable that not every place on Earth will experience exactly the same tidal conditions. There are three primary classifications for tides, depending on the number and relative heights of tidal cycles per day.
A diurnal tide consists of only one high tide and one low tide per day (Figure 3.7.1). "Diurnal" refers to a daily occurrence, so a situation where there is only one complete tidal cycle per day is considered a diurnal tide. Diurnal tides are common in the Gulf of Mexico, along the west coast of Alaska, and in parts of Southeast Asia.
Figure 3.7.1 A diurnal tide, with one high and one low tide per day (By NOAA [Public domain], via Wikimedia Commons).
A semidiurnal tide exhibits two high and two low tides each day, with both highs and both lows of toughly equal height (Figure 3.7.2). "Semidiurnal" means "half of a day"; one tidal cycle takes half of a day, therefore there are two complete cycles per day. Semidiurnal tides are common along the east coasts of North America and Australia, the west coast of Africa, and most of Europe.
Figure 3.7.2 A semi-diurnal tide, with two high and two low tides per day, each of roughly equal heights (By NOAA [Public domain], via Wikimedia Commons).
Mixed semidiurnal tides (or mixed tides), have two high tides and two low tides per day, but the heights of each tide differs; the two high tides are of different heights, as are the two low tides (Figure 3.7.3). The differences in height may be the result of amphidromic circulation, the angle of the moon, or any of the other variables discussed in section 3.6. Mixed semidiurnal tides are found along the Pacific coast of North America.
Figure 3.7.3 A mixed semi-diurnal tide, with two high and two low tides per day, each with a different height (By NOAA [Public domain], via Wikimedia Commons).
Figure 3.7.4 shows the distribution of the various tide types throughout the world.
Figure 3.7.4 Global distribution of the different types of tides (By KVDP (Own work) [Public domain], via Wikimedia Commons).
Tidal Currents
The movement of water with the rising and falling tide creates tidal currents. As the tide rises, water flows into an area, creating a flood current. As the tide falls and water flows out an ebb current is created. Slack water, or slack tides occur during the transition between incoming high and outgoing low tides, when there is no net water movement.
The strength of a tidal current depends on the volume of water that enters and exits with each tidal cycle (the tidal volume or tidal prism), and the area through which the water flows. A large tidal volume moving through a large area may create only a weak tidal current, as the volume is spread over a wide area. On the other hand, a narrow area may produce a strong tidal current even if the tidal volume is small, as all of the water is forced through a small area. It follows that the strongest tidal currents will result from a large tidal range moving through a narrow area.
Tidal bores occur where rivers meet the ocean. If the incoming tidal current is stronger than the river outflow, the tidal bore appears as a wave, or moving wall of water that moves up the river as the tide comes in (Figure 3.7.5).
Figure 3.7.5 A tidal bore near Silverdale in the United Kingdom (Arnold Price [CC BY-SA 2.0], via Wikimedia Commons).
In many cases these tidal bores may move through a river or inlet for many kilometers, and if they are large enough they can form continually breaking waves that surfers can ride much farther and longer than a traditional ocean wave, such as the Severn Bore in England, shown in the video below.
Differential heating of the Earth's surface results in equatorial regions receiving more heat than the poles (section 6.1). As air is warmed at the equator it becomes less dense and rises, while at the poles the cold air is denser and sinks. If the Earth was non-rotating, the warm air rising at the equator would reach the upper atmosphere and begin moving horizontally towards the poles. As the air reached the poles it would cool and sink, and would move over the surface of Earth back towards the equator. This would result in one large atmospheric convection cell in each hemisphere (Figure 6.2.1), with air rising at the equator and sinking at the poles, and the movement of air over the Earth's surface creating the winds. On this non-rotating Earth, the prevailing winds would thus blow from the poles towards the equator in both hemispheres (Figure 6.2.1).
Figure 6.2.1 Hypothetical atmospheric convection cells on a non-rotating Earth. Air rises at the equator and sinks at the poles, creating a single convection cell in each hemisphere. The prevailing winds moving over the Earth's surface blow from the poles towards the equator in both hemispheres (Modified by PW from globe image by Location_of_Cape_Verde_in_the_globe.svg: Eddo derivative work: Luan fala! [CC BY-SA 3.0], via Wikimedia Commons).
The non-rotating situation in Figure 6.2.1 is of course only hypothetical, and in reality the Earth's rotation makes this atmospheric circulation a bit more complex. The paths of the winds on a rotating Earth are deflected by the Coriolis Effect. The Coriolis Effect is a result of the fact that different latitudes on Earth rotate at different speeds. This is because every point on Earth must make a complete rotation in 24 hours, but some points must travel farther, and therefore faster, to complete the rotation in the same amount of time. In 24 hours a point on the equator must complete a rotation distance equal to the circumference of the Earth, which is about 40,000 km. A point right on the poles covers no distance in that time; it just turns in a circle. So the speed of rotation at the equator is about 1600 km/hr, while at the poles the speed is 0 km/hr. Latitudes in between rotate at intermediate speeds; approximately 1400 km/hr at 30o and 800 km/hr at 60o. As objects move over the surface of the Earth they encounter regions of varying speed, which causes their path to be deflected by the Coriolis Effect.
To explain the Coriolis Effect, imagine a cannon positioned at the equator and facing north. Even though the cannon appears stationary to someone on Earth, it is in fact moving east at about 1600 km/hr due to Earth's rotation. When the cannon fires the projectile travels north towards its target; but it also continues to move to the east at 1600 km/hr, the speed it had while it was still in the cannon. As the shell moves over higher latitudes, its momentum carries it eastward faster than the speed at which the ground beneath it is rotating. For example, by 30o latitude the shell is moving east at 1600 km/hr while the ground is moving east at only 1400 km/hr. Therefore, the shell gets "ahead" of its target, and will land to the east of its intended destination. From the point of view of the cannon, the path of the projectile appears to have been deflected to the right (red arrow, Figure 6.2.2). Similarly, a cannon located at 60o and facing the equator will be moving east at 800 km/hr. When its shell is fired towards the equator, the shell will be moving east at 800 km/hr, but as it approaches the equator it will be moving over land that is traveling east faster than the projectile. So the projectile gets "behind" its target, and will land to the west of its destination. But from the point of view of the cannon facing the equator, the path of the shell still appears to have been deflected to the right (green arrow, Figure 6.2.2). Therefore, in the Northern Hemisphere, the apparent Coriolis deflection will always be to the right.
In the Southern Hemisphere the situation is reversed (Figure 6.2.2). Objects moving towards the equator from the south pole are moving from low speed to high speed, so are left behind and their path is deflected to the left. Movement from the equator towards the south pole also leads to deflection to the left. In the Southern Hemisphere, the Coriolis deflection is always to the left from the point of origin.
The magnitude of the Coriolis deflection is related to the difference in rotation speed between the start and end points. Between the poles and 60o latitude, the difference in rotation speed is 800 km/hr. Between the equator and 30o latitude, the difference is only 200 km/hr (Figure 6.2.2). Therefore the strength of the Coriolis Effect is stronger near the poles, and weaker at the equator.
Figure 6.2.2 The Coriolis Effect. Objects moving from the equator towards the poles (red arrows) move into a region of slower rotational speed and their paths are deflected "ahead" of their point of origin. Movement from high latitudes to low latitudes (green arrows) goes from a region of low speed to a region of higher rotation speed, and there is deflection "behind" their point of origin. In the Northern Hemisphere this deflection is always to the right from the point of origin, and in the Southern Hemisphere the deflection is always to the left (Modified by PW from globe image by Location_of_Cape_Verde_in_the_globe.svg: Eddo derivative work: Luan fala! [CC BY-SA 3.0], via Wikimedia Commons).
Because of the rotation of the Earth and the Coriolis Effect, rather than a single atmospheric convection cell in each hemisphere, there are three major cells per hemisphere. Warm air rising at the equator cools as it moves through the upper atmosphere, and it descends at around 30o latitude. The convection cells created by rising air at the equator and sinking air at 30o are referred to as Hadley Cells, of which there is one in each hemisphere. The cold air that descends at the poles moves over the Earth's surface towards the equator, and by about 60o latitude it begins to rise, creating a Polar Cell between 60o and 90o. Between 30o and 60o lie the Ferrel Cells, composed of sinking air at 30o and rising air at 60o (Figure 6.2.3). With three convection cells in each hemisphere that rotate in alternate directions, the surface winds no longer always blow from the poles towards the equator as in the non-rotating Earth in Figure 6.2.1. Instead, surface winds in both hemispheres blow towards the equator between 90o and 60o latitude, and between 0o and 30o latitude. Between 30o and 60o latitude, the surface winds blow towards the poles (Figure 6.2.3).
Figure 6.2.3 On a rotating Earth, there are three atmospheric convection cells in each hemisphere, leading to alternating bands of surface winds (red arrows) (Modified by PW from globe image by Location_of_Cape_Verde_in_the_globe.svg: Eddo derivative work: Luan fala! [CC BY-SA 3.0], via Wikimedia Commons).
The surface winds created by the atmospheric convection cells are also influenced by the Coriolis Effect as they change latitudes. The Coriolis Effect deflects the path of the winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Adding this deflection leads to the pattern of prevailing winds illustrated in Figure 6.2.4. Between the equator and 30o latitude are the trade winds; the northeast trade winds in the Northern Hemisphere and the southeast trade winds in the Southern Hemisphere (note that winds are named based on the direction from which they originate, not where they are going). The westerlies are the dominant winds between 30o and 60o in both hemispheres, and the polar easterlies are found between 60o and the poles.
Figure 6.2.4 The prevailing wind patterns of Earth (Modified by PW from globe image by Location_of_Cape_Verde_in_the_globe.svg: Eddo derivative work: Luan fala! [CC BY-SA 3.0], via Wikimedia Commons).
In between these wind bands lie regions of high and low pressure. High pressure zones occur where air is descending, while low pressure zones indicate rising air. Along the equator the rising air creates a low pressure region called the doldrums, or the Intertropical Convergence Zone (ITCZ)(convergence zone because this is where the trade winds converge). At 30o latitude there are high pressure zones of descending air known as the horse latitudes, or the subtropical highs. Finally, at 60o lies another low pressure region called the polar front. It should be noted that these high and low pressure zones are not fixed in place; their latitude fluctuates depending on the season, and these fluctuations have important implications for regional climates.
Doldrums? Horse latitudes? Trade winds?
These may seem like some odd names for these atmospheric phenomena, but many of them can be traced back to maritime traditions and lore.
The doldrums refer to regions of low pressure around the equator. In these areas, air is rising rather than moving horizontally, so these regions commonly encounter very light winds. The lack of wind could leave sailing ships becalmed for days or weeks at a time, which was not good for the morale of the ship's crew.
Like the doldrums the horse latitudes are also areas with light winds, this time due to descending air, which could leave ships becalmed. One explanation for the term "horse latitudes" is that when these ships became stranded they ran the risk of running out of food or water. To conserve these resources, sailors would throw their dead or dying horses overboard, hence the "horse latitudes." Another explanation is that many sailors received part of their pay before a voyage, and often spent it before departing. This meant that they would spend the first part of the voyage working without pay and in debt, a period called the "dead horse" time, which might last for a few months. When they started earning their pay once again, they had a "dead horse" ceremony and threw a pretend horse overboard. The timing of this ceremony often coincided with reaching the horse latitudes, leading to the association of the ceremony with the location. A third explanation is that a ship was referred to as "horsed" when winds were weak and the ship instead had to rely on ocean currents to move them. This could be a common occurrence in the high pressure zones around 30o latitude, so they were referred to as the horse latitudes.
The term trade winds may have originally derived from the terms for "track" or "path", but the term may have become more common during European exploration and commercialization of the New World. Mariners sailing from Europe to the New World could sail south until they reached the trade winds, which would then propel their ships across the Atlantic to the Caribbean. To return to Europe, ships could sail to the northeast until they entered the westerlies, which would then steer them back to Europe.
the flat seafloor of the deep ocean, typically beyond the limits of the continental slopes
abyssal zone
the region of the seafloor between 4000-6000 m
abyssopelagic zone
the deeper parts of the open ocean, between 4000 and 6000 m; also known as the abyssalpelagic zone
accretion (planetary)
the process by which solid celestial bodies are added to existing bodies during collisions
active continental margin
where the boundary between the continent and the ocean is also a tectonic plate boundary
aeolian
processes related to transportation and deposition of sediments by wind
albedo
the reflectivity of a surface of a planet (expressed as the percentage of light that reflects from the surface
amphidromic circulation
gyre-sized tidal patterns where a tidal crest rotates around an ocean basin
amphidromic point
the center point around which amphidromic circulation rotates; there is near-zero tidal range at the amphidromic point (also called a tidal node or amphidromic node
anoxia
conditions of zero or extremely low dissolved oxygen, usually below 0.5 mg/L
Antarctic Bottom Water
water at abyssal depths in the ocean that forms from the sinking of dense cold water adjacent to Antarctica
anthropogenic
resulting from the influence of humans
aphotic zone
depths beyond 1000 m where there is no light penetration
arch
a rock weathering remnant in the form of an arch (typically along a coast and resulting from wave erosion)
asthenosphere
the part of the mantle, from about 100 to 200 km below surface, within which the mantle material is close to its melting point, and therefore relatively weak
atmospheric wave
a wave formed in the atmosphere at the boundary between air masses of different densities
atoll
a ring-shaped carbonate (or coral) reef or series of islands
backshore
the region of the beach above the high tide line, which is only submerged under unusually high wave conditions
backwash
the wash of wave water down the slope of a beach
bar-built estuary
an estuary created when a sand bar or barrier island cuts off the estuary from mixing completely with seawater
barrier island
a long, thin island parallel to the shore, created through the deposition of sand
barrier reef
a reef that forms a barrier to waves along a coast; it is separated from land by a lagoon
barycenter
the center of mass in the Earth-moon system around which they rotate
basalt
a volcanic rock that makes up much of the oceanic crust
bathyal zone
the region of the seafloor from the shelf break to 4000 m
bathymetry
pertains to measuring the depths of the ocean
bathypelagic zone
the moderately deep parts of the open ocean, between 1000 and 4000 m
baymouth bar
a spit that extends across the mouth of a bay
beach face
the area of a beach between the high and low tide lines
Beaufort scale
a 0-12 scale describing the wind conditions at sea, often reflected in wave heights
benthic
refers to the environment of the seafloor
benthos
refers to the community of organisms living on or in the ocean floor
berm
a flat area of a beach in the backshore area (above the high tide level)
big-bang theory
the theory that the universe started with a giant expansion approximately 13.77 billion years ago
biogenous sediment
sediment created from the remains of organisms
blocky iceberg
iceberg with a flat top and steep sides, but their length to height ratio is not as great as it is for a tabular iceberg
blowhole
a hole in the ceiling of an arch or sea cave through which water is ejected when waves approach
body wave
a seismic wave that travels through rock (e.g., a P-wave or an S-wave)
boulder
a sediment with a grain diameter of at least 256 mm
boundary currents
ocean currents whose properties are influenced by the presence of a coastline
Boyle’s Law
the volume of a gas is inversely proportional to the pressure
brackish
seawater of low salinity; part fresh water, part seawater
breaker
an unstable wave that has collapsed
breakwater
a structure built offshore in order to deflect the energy of waves
buffer
a solution that moderates changes in pH when acids or alkalis are added to it
calcareous sediment
sediments composed of calcium carbonate, often from the shells of marine organisms
calving
when ice breaks off of the front of a glacier and collapses into the water
capillary waves
small ripples that form on the water surface under light winds; their restoring force is surface tension
carbonate compensation depth
the depth in the ocean (typically around 4000 m) below which carbonate minerals are soluble
Carboniferous
a geologic period that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period, 298.9 Mya
celerity
the speed of a wave
chemosynthesis
the creation of organic compounds using the energy from inorganic chemical reactions
chip log
a device for determining a ship’s speed at sea, by measuring the rate at which a line is unspooled when cast overboard
clay
sediment particle that is less than 1/256 mm in diameter
climate feedback
a process by which the physical effects of a climate forcing can have other effects (either negative or positive) on the climate
climate forcing
a mechanism, such as a change in greenhouse gas levels, that forces the climate to change
coastal plain estuary
an estuary formed when sea level rises and submerges a river valley (also known as a drowned river valley estuary)
coastal straightening
the tendency for an irregular coast to be straightened over time by coastal erosion processes
cobble
sediment particle that is between 64 and 256 mm in diameter
coccolithophore
photosynthetic algae that makes its test (shell) out of calcium carbonate
compensation depth
the depth where the rate of photosynthesis equals the rate of respiration
conduction
the transfer of heat through direct contact
conservative ions
ions whose proportions are the same regardless of overall salinity; the major ions in seawater
constructive interference
where the interaction of multiple waves creates waves larger than any of the component waves
continental crust
the Earth’s crust underlying the continents (as opposed to ocean crust)
continental drift
the idea that the continents have moved over the surface of the Earth over geological time
continental margin
the region of transition from the land to the deep sea floor, i.e. between continental and oceanic crust
continental rise
the area at the bottom of the continental slope, where it transitions to the abyssal sea floor
continental shelf
the shallow (typically less than 200 m) and flat sub-marine extension of a continent
continental slope
the steeper part of a continental margin, that slopes down from a continental shelf towards the abyssal plain
convection cell
a rotating region in a fluid in which upward motion of warmer, low density fluid in the center is balanced by downward motion of cooler, denser fluid at the periphery
convergent boundary
a plate boundary at which the two plates are moving towards each other
core
the metallic interior part of the Earth, extending from a depth of 2900 km to the center
core-mantle boundary
the boundary, at 2900 km depth, between the mantle and the core
Coriolis Effect
the tendency for the path of moving bodies (e.g., ocean currents) to be deflected on the surface of the Earth, to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
cosmogenous sediment
sediment derived from extraterrestrial sources
crest
the highest point on a wave
Cretaceous
a geologic period that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 mya
crust
the uppermost layer of the Earth, ranging in thickness from about 5 km (in the oceans) to over 50 km (on the continents)
deep water wave
a wave above a water depth greater than half of its wavelength
delta
large, often triangular accumulation of sediment near the mouth of a river
denitrification
where nitrate is converted to molecular nitrogen through a series of intermediate nitrogen oxide products
density
mass per unit volume of a substance (e.g., g/cubic cm)
destructive interference
where the interaction of multiple waves creates waves smaller than any of the component waves
diatom
photosynthetic algae that make their tests (shells) from silica
diatomaceous earth
powdery sediment composed of silica diatom tests
differentiation
the un-mixing of a magma, typically by the physical separation of minerals that crystallize early and settle towards the bottom
dinoflagellate
photosynthetic algae characterized by the presence of flagella and a cellulose test (shell)
discoaster
an extinct form of single-celled algae that produced calcareous tests that can still be found in some marine sediments
diurnal tide
a tidal cycle with only one high and one low tide per day
divergent boundary
a plate boundary at which the two plates are moving away from each other
doldrums
areas of low pressure and weak winds along the equator
domed iceberg
iceberg with a rounded top
downwelling
process by which surface water is forced downwards
drowned river valley estuary
an estuary formed when sea level rises and submerges a river valley (also known as a coastal plain estuary)
drydock iceberg
iceberg with a water-covered channel running through it
dysphotic zone
depths of the water column where there is some light penetration, but not enough to support photosynthesis; corresponds to the mesopelagic zone, 200-1000 m. Also known as the twilight zone
ebb current
current created by an outgoing tide
eccentricity
in the context of Milankovitch Cycles, the degree to which the Sun is offset from the geometric center of the Earth’s orbit
eddy
a rotating water mass
Ekman spiral
where each layer of water is deflected relative to the layer above it, forming a spiral that extends down to about 100 m
Ekman transport
bulk transport of water due to the Ekman spiral; the net movement Ekman transport is 90 degrees relative to the wind direction
El Niño
a periodic climatic situation in which warm water extends all or most of the way to the eastern edge of the equatorial Pacific
El Niño-Southern Oscillation (ENSO)
the fluctuating atmospheric conditions that lead to the localized ocean warming of El Niño
electron
a sub-atomic particle of essentially no mass and a single negative charge
Eocene
a geological epoch lasting from 56 to 33.9 million years ago
epicenter
the location on the surface vertically above the location (i.e., “hypocenter” or “focus”) where an earthquake takes place
epipelagic zone
the upper layer of water (0 to 200 m) in areas of the open ocean
estuary
a partially enclosed body of water where seawater is diluted by freshwater input
euphotic zone
the upper regions of the ocean where there is enough light to support photosynthesis; approximately 0-200 m; also called the photic zone
eustatic sea level change
sea level change related to a change in the volume of the oceans, typically because of an increase or decrease in the amount of glacial ice on land
evaporites
hydrogenous sediments that form when seawater evaporates
fast ice
ice sheets that are attached to land
fault
a boundary in rock or sediment along which displacement has taken place
fecal express
small particles reach the seafloor much faster when incorporated into large fecal pellets than if they sank on their own
feedback
a process by which the physical effects of a climate forcing can have other effects (either negative or positive) on the climate
Ferrel Cell
the atmospheric convection cells between 30 and 60 degrees latitude
fetch
the distance over which wind blows to form waves
firn
the granular transitional state between snow and ice within a glacier
fjord
a deep, U-shaped estuary that was carved out by advancing glaciers
flood current
current created by an incoming tide
flushing time
the time it would take for all of the fresh water in an estuary to be replaced by runoff of new water
focus (earthquake)
the actual point below surface at which an earthquake takes place (equivalent to hypocenter)
foraminifera
a single-celled protist with a shell that is typically made of calcium carbonate
foreshore
the part of a beach between the high tide and low tide lines
frazil
small, needle-like crystals in the first stages of sea ice formation
frequency
the number of waves that pass a point in a given amount of time
fringing reef
a reef adjacent to a shoreline where there is either a very narrow back reef area or none at all (in which case the reef is effectively attached to the shore)
frost line
in the context of planetary systems the boundary beyond which volatile components (e.g., water, carbon dioxide, methane, ammonia etc.) are frozen
Ga
(gigaannus) billions of years before the present
galaxy
a gravitationally-bound system of stars and interstellar matter
gas giant
a large planet composed mostly of hydrogen and helium (e.g. Jupiter)
geostrophic flow
circular currents created from the balance between gravity- and Ekman-driven flow
giant impact hypothesis
the theory that the Moon formed when a Mars-sized planet (Theia) collided with the Earth at 4.5 billion years ago
gill rakers
tiny hairs in fish mouths that extract plankton from the water
glacial groove
scratches and grooves carved into bedrock from rocks carried by moving glaciers
glacial ice
ice formed from the accumulation and compression of snow into glaciers
glacial period
a period of Earth’s history during which glacial ice was present over a sufficient extent to have left recognizable evidence
glacier
a long lasting (centuries or more) body of ice on land that moves under its own weight
granite
an igneous (formed from cooling magma) rock that comprises much of the continental crust
granule
a sedimentary particle ranging in size from 2 to 4 mm in diameter
grease ice
an accumulation of frazil to create a slushy consistency in sea ice formation
greenhouse effect
in the context of climate, the ability of an atmosphere to absorb infrared radiation due to the presence of greenhouse gases
greenhouse gas
a gaseous molecule with 3 or more atoms that is able to absorb infrared radiation
groin (groyne)
a man-made structure extending from the shore built to deflect the energy of waves
groin field
a series of groins along a beach
gross primary production
the total amount of organic material created by primary producers
groundwater
water that lies beneath the surface of the ground
Gulf Stream
the major surface current flowing northwards along the Atlantic coast of the U.S. and Canada
guyot
a flat-topped seamount (also called a tablemount)
gyre
a large circular ocean surface current
hadal zone
the region of the seafloor below 6000 m
Hadley Cell
the atmospheric convection cells between the equator and 30 degrees latitude
hadopelagic (hadalpelagic) zone
region of the open ocean with water depths greater than 6000 m
halite
NaCl, a mineral also known as table salt
halocline
where there is a dramatic change in salinity over a small change in depth
hard stabilization
the building of physical structures to prevent the erosion of beaches and shorelines
harmful algal bloom (HAB)
when phytoplankton appear in very high concentrations with potentially hazardous consequences such as mass die-offs or toxicity
headland
a point of land extending out to sea
heat budget
the balance between the amount of heat entering and leaving the Earth
heat capacity
the amount of heat needed to change a substance’s temperature by one degree
Henry’s Law
as the pressure increases, a fluid will contain more dissolved gas
high pressure
in atmospheric terms, a region of descending air, increasing the atmospheric pressure. Winds blow away from high pressure zones
highly stratified estuary
a deep estuary with some mixing at the surface, but little mixing at depth
homolosine projection
a map projection where area is retained, but there are interruptions to the continents or oceans
horse latitudes
areas of high pressure and weak winds around 30 degrees latitude in both hemispheres
hot spot
the surface area of volcanism and high heat flow above a mantle plume
hydrogen bond
a weak bond between two molecules due to the electrostatic attraction of a proton in one molecule to the negative polar end of the other molecule
hydrogenous sediment
sediments formed from the precipitation of dissolved substances
hydrological cycle
the cycling of water through the ocean, atmosphere, lakes, organisms, and other reservoirs
hydrothermal vent
area of the seafloor where superheated water seeps out of the crust
hypocenter
the actual point below surface at which an earthquake takes place (equivalent to focus)
hypoxia
a condition with low dissolved oxygen, usually defined as oxygen levels below 2 mg/L
ice field
an area covered by ice floes
ice floe
a relatively large piece of floating sea ice
ice giant
a planet that is comprised mainly of gases heavier than hydrogen and helium, including oxygen, carbon, nitrogen, and sulfur (e.g., Uranus and Neptune)
iceberg
a large, floating piece of glacial ice
ichthyology
the study of fish
inner core
the solid metal mass at the center of the Earth, extending 1200 km from the center
insolation
a measure of the intensity of solar energy at a specific location or time (expressed in W/square m)
Intergovernmental Panel on Climate Change (IPCC)
an international body established in 1988 by the UN’s World Meteorological Organization and the UN Environment Program to prepare periodic reports on the status of global climate change and its mitigation
intermediate wave
a wave in a water depth between 1/2 and 1/20 its wavelength
internal wave
waves that form below the surface at the interface between water masses of different densities
intertidal zone
the region of a coast between the high and low tide lines. Also called the littoral zone
Intertropical Convergence Zone
the area near the equator where the northeast and southeast trade winds converge; known for weak winds, it is also called the doldrums
ion
an atom or molecule that has either gained or lost electrons and has thus become charged
island arc
long chains of volcanic islands found along convergent tectonic plate boundaries
isostasy
the equilibrium position reached by a block of crust floating on the underlying fluid mantle
isostatic sea level change
the effect on relative sea level of a vertical movement of the crust resulting from a change in the mass of the crust (e.g., from losing or gaining ice)
isotope
forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei
jetty
a long structure built to protect a harbor from filling with sand due to longshore transport
Jovian planet
a gas giant
ka
(kiloannus) thousands of years before the present
kinetic energy
the energy that an object possesses due to its motion
knot
one knot (kt) = 1 nautical mile per hour = 1.15 mph = 1.85 kph
La Niña
a periodic climatic situation in which colder than normal water extends throughout the equatorial Pacific
land breeze
winds blowing from land towards the ocean
Langmuir circulation
corkscrew circulation patterns formed parallel to strong winds; they only extend a few meters below the surface
latent heat of fusion
the heat required to change a substance from solid to liquid; 80 cal/g in the case of ice melting to water
latent heat of vaporization
the heat required change a substance from liquid to gas; 540 cal/g to turn water into vapor
latitude
the distance north or south of the equator, measured as an angle from the equator
Laurentide Ice Sheet
the continental glacier that extended across central eastern North America during the Pleistocene, covering most of Canada and a significant part of the United States
lithification
the conversion of unconsolidated sediments into rock by compaction and cementation
lithogenous sediment
sediment derived from preexisting rock
lithosphere
the rigid outer part of the Earth, including the crust and the mantle down to a depth of about 100 km
littoral drift
the movement of sediment along a shoreline resulting from a longshore current and also from the swash and backwash on a beach face (another name for longshore transport)
littoral zone
the region of a coast between the high and low tide lines. Also called the intertidal zone
longitude
measurement of distance east or west of the prime meridian, expressed as an angle
longshore bar
an offshore deposit of sand parallel to the shoreline
longshore current
the movement of water parallel to a shoreline produced by the approach of waves at an angle to the shore
longshore transport
the movement of sediment along a shoreline resulting from a longshore current and also from the swash and backwash on a beach face. Also known as littoral drift
low pressure
in terms of the atmosphere, a region of rising air, lowering the atmospheric pressure. Winds blow towards low pressure regions, which are often characterized by precipitation from rising, cooling, condensing air
low tide terrace
another name for the beach face
lysocline
the depths where the rate of calcium carbonate dissolution increases dramatically over surface waters
Ma
(Megaannus) millions of years before the present
magma
molten rock typically dominated by silica
magnetic dip
the angle of the magnetic field within a rock, relative to the horizontal; may be used to infer the latitude where the rock was first formed
magnitude
a measure of the amount of energy released by an earthquake
major ions
the six ions that comprise over 99% of the ions in the ocean (chloride, sodium, sulfate, magnesium, calcium, potassium)
manganese nodule
spherical accumulations of manganese and other metals that form slowly through precipitation on the seafloor
mantle
the middle layer of the Earth, dominated by iron and magnesium rich silicate minerals and extending for about 2900 km from the base of the crust to the top of the core
mantle convection
movements in the mantle from rising and sinking mantle material as it heats and cools
mantle plume
a plume of hot rock (not magma) that rises through the mantle (either from the base or from part way up) and reaches the surface where it spreads out and also leads to hot-spot volcanism
maturity
how long sediment particles have been transported by water or other vectors
meander
the sinuous path taken by a current, such as the Gulf Stream
Mercator projection
a map projection where latitude and longitude are both represented as straight, parallel lines intersecting at right angles
mesopelagic zone
the upper middle zone of the open ocean extending from 200 to 1000 m depth
Mesozoic
the geological era from about 252 to 66 million years ago
meteoroid
a fragment of either stony or metallic debris in space
methane hydrate
a combination of water ice and methane in which the methane is trapped inside “cages” in the ice
mid-ocean ridge
an underwater mountain system along divergent plate boundaries, formed by plate tectonics
Milankovitch cycles
millennial-scale variations in the orbital and rotational parameters of the Earth that have subtle effects on the Earth’s climate
mixed interference
where the interaction of multiple waves creates both constructive and destructive interference and an irregular surface pattern
mixed layer
the topmost layer of the ocean, where winds, waves, and currents mix the water so that conditions are relatively constant; approximately the top 100 m
mixed semidiurnal tide
a tidal cycle with two high and two low tides per day, each of different heights
Mohorovičić discontinuity (Moho)
the boundary between the crust and the mantle
nautical mile
a distance equal to one minute of latitude; equivalent to 1.15 land miles or 1.85 km
neap tide
the period of minimum tidal range when the Earth is perpendicular to the sun and moon
nearshore
the part of a beach from the low tide line to the depth where wave action is no longer influenced by the bottom, i.e. to where the depth exceeds the wave base
nebula
a cloud of interstellar dust and gases
negative feedback
a process that results in a decrease in that process (in the context of climate change it is a process that reduces the change in climate, such as the enhanced growth of vegetation in response to an increase in atmospheric carbon dioxide)
neritic
the marine pelagic province from the low tide line to the shelf break
net production
total primary production minus the organic compounds used up by respiration by the producers
new production
primary production supported by nutrients brought in from outside of the local ecosystem
nilas
a thin surface sheet of sea ice
nitrification
the biological oxidation of ammonia or ammonium to nitrite followed by the conversion of the nitrite to nitrate
nitrogen fixation
the process of converting atmospheric nitrogen gas into nitrogenous compounds like ammonia
non-conservative ions
ions in seawater whose proportions fluctuate with changes in salinity
non-tabular iceberg
an iceberg with any shape other than tabular
North Atlantic Deep Water
deep Atlantic Ocean water that has descended in the far north of the basin in the area between Scandinavia and Greenland
nutrient
in the context of primary production, substances required by photosynthetic organisms to undergo growth and reproduction
nutrient-like element
elements that have a similar vertical profile to nutrients; low amounts at the surface, increased abundance at depth
obliquity
in the context of Milankovitch Cycles, the angle of the tilt of the Earth’s rotational axis with respect to the plane of its orbit around the Sun
ocean acidification
where the overall pH of the ocean declines, likely due to an increased amount of carbon dioxide in the ocean
oceanic
the marine pelagic province representing the open ocean regions, i.e. beyond the neritic zone
oceanic crust
the Earth’s crust underlying the oceans (as opposed to continental crust)
offshore
the beach zone beyond the nearshore region
oolite
a small (approximately 1 mm) sphere of calcite formed in areas of tropical shallow marine water
ooze
a sediment composed of >30% biogenous material
outer core
the layer of the inner Earth extending 2300 km from the top of the inner core to the bottom of the mantle, composed of fluid metal alloys
outgassing
where dissolved substances in magmas are released as gases when the pressure is reduced
overturning
the vertical cycling within a body of water, where denser water sinks and less dense water floats to the surface
oxygen minimum layer
region of ocean depths where dissolved oxygen is at its lowest level; usually around 1000 m for the open ocean
p-wave
a seismic body wave that is characterized by deformation of the rock in the same direction that the wave is propagating (compressional vibration)
pack ice
free-floating ice floes
Paleocene
a geological epoch that lasted from about 66 to 56 million years ago
paleomagnetic
past variations in the intensity and polarity of the Earth’s magnetic field
Paleozoic
the geologic era lasting from 541 to 252 million years ago
pancake ice
small, rounded, thin pieces of sea ice that will freeze together to form an ice floe
Pangaea
the supercontinent that existed between approximately 300 and 180 Ma; it contained all of the modern continents combined into a single land mass
partially mixed estuary
where salinity increases from the head to the mouth, but there is also a slight increase in salinity with depth at any point; also called a slightly stratified estuary
passive continental margin
a boundary between a continent and an ocean at which there is no tectonic activity (e.g., the eastern edge of North America)
pebble
a sedimentary particle ranging in size from 2 to 64 mm (includes granule)
pelagic
relating to the open ocean
period
the time it takes for a complete wave to pass a given point
Permian
a geologic period which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya
Phanerozoic
the eon on the geological time scale covering time from the beginning of the Cambrian period 541 million years ago to the present, and comprising the Paleozoic, Mesozoic, and Cenozoic eras
phase change
the change of state between a solid, liquid, or gas
photic zone
the upper regions of the ocean where there is enough light to support photosynthesis; approximately 0-200 m; also called the euphotic zone
photosynthesis
the production of organic compounds from carbon dioxide and water, using sunlight as an energy source
physiographic projection
map projection presenting bathymetry or altitude data as a 3D relief map
phytoplankton
drifting, usually single-celled algae that undergo photosynthesis
picoplankton
planktonic bacteria
pinnacled iceberg
an iceberg with one or more tall spires
planisphere projection
map projection that keeps latitude horizontal, but shows some convergence of longitude
plankton
an organism that cannot swim effectively, so it drifts with the currents
plate
a region of the lithosphere that is considered to be moving across the surface of the Earth as a single unit
plate tectonics
the concept that the Earth’s crust and upper mantle (lithosphere) is divided into a number of plates that move independently on the surface and interact with each other at their boundaries
plunging breaker
a breaking wave on moderately-steep beaches that curls over on itself as it breaks
Polar Cell
the atmospheric convection cells between 60 degrees latitude and the pole
polar easterlies
the dominant wind bands between the poles and 60 degrees latitude
polar front
the boundary between the polar cell and the Ferrel cell around the 60 latitude in each hemisphere
polar molecule
a molecule where the electrons are not distributed equally, leading to a charge imbalance across the molecule; portions of the molecule are slightly positive while other portions are slightly negative
polar wandering path
a path of varying magnetic pole positions defined by paleomagnetic data (in fact it is now understood that the continents have wandered, not the poles, so a more appropriate terms is “apparent polar wandering path”)
polyna
an area of persistent open water in areas otherwise covered with ice
positive feedback
a process that results in an increase in that process (in the context of climate change it is a process that enhances the change in climate, such as the reduced reflectivity of the Earth’s surface when ice melts)
ppm
parts per million
ppt
parts per thousand
practical salinity unit (PSU)
a unitless measure of salinity equal to parts per thousand
precession
in the context of Milankovitch Cycles, the variation in the direction at which the Earth’s rotational axis is pointing
pressure ridge
jagged ridges created from colliding and buckling ice floes
primary production
the synthesis of organic compounds from aqueous carbon dioxide by plants, algae, and bacteria
protoplanetary disk
a rotating cloud of gas and dust surrounding a young star
pycnocline
a region in the water column where there is a large change in density over a small change in depth
quartz
a mineral composed of silicon and oxygen atoms in the ratio of 1 Si:2 O; one of the most abundant minerals in the Earth's surface
radiation
the emission of energy in the form of electromagnetic waves
radiolaria
microscopic (0.1 to 0.2 mm) marine protozoa that produce silica shells
rain shadow
arid conditions behind a mountain range, as rising air on the other side of the mountain caused rain, leaving only dry air to descend back down the mountain
reef
a mound of carbonate formed in shallow tropical marine environments by corals, algae and a wide range of other organisms
regenerated production
primary production resulting from the recycling of nutrients within an ecosystem
remnant magnetism
magnetism of a body of rock that formed at the time the rock formed and is consistent with the magnetic field orientation that existed at that time and place
residence time
the average amount of time an element will remain in the ocean before being removed
restoring force
the force that opposes a wave-generating force and attempts to return the sea surface to the still water level
ridge push
the concept that at least part of the mechanism of plate motion is the push of oceanic lithosphere down from a ridge area
rift valley
a valley created when crust subsides along a divergent plate boundary
rip current
a strong flow of water outward from a beach
rogue wave
an exceptionally large wave arising among a series of smaller waves
rule of constant proportions
the major ions in seawater are always found in the same proportions, regardless of overall salinity
runoff
flow of water down a slope, either across the ground surface, or within a series of channels
s-wave
a seismic body wave that is characterized by deformation of the rock perpendicular to the direction that the wave is propagating
salinity
the concentration of dissolved ions in water
salt wedge estuary
an estuary with mostly fresh surface water, and a wedge of seawater intruding along the bottom
sand
a mineral or rock fragment ranging in size from 1/16th to 2 mm
saturation
the amount of a substance currently dissolved in the water, relative to the maximum possible content
scarp
a short, steep wall carved out by wave action between the foreshore and the berm of a beach
scavenged element
elements whose vertical profiles show high abundance at the surface and declining concentrations at depth as they are removed by sinking particles
sea breeze
winds blowing from the ocean towards the land
sea cave
a shallow cave formed on a rocky shore by wave erosion
sea cliff
a coastal escarpment that is typically eroding inland as a result of wave action
sea ice
ice formed from the freezing of seawater
sea stack
a prominent rocky island that is a remnant of the erosion of a headland
sea state
describes the current wave conditions in an area
seafloor spreading
the formation of new oceanic crust by volcanism at a divergent plate boundary
seamount
a submerged mountain rising from the seafloor
seawall
a wall built against a sea cliff or dune to prevent erosion from wave action
sediments
unconsolidated particles of mineral or rock that settle to the seafloor
seismic
pertaining to earthquakes
seismology
the study of vibrations within the Earth
semidiurnal tide
a tidal cycle with two high and two low tides per day, each of roughly equal heights
shallow water wave
a wave in water with a depth less than 1/20 of the wavelength
shelf break
the boundary between the continental shelf and continental slope, where the angle of the seafloor begins to get steeper
significant wave height (Hs)
the mean height of the largest one-third of the waves in a wave spectrum
silica
a form of the mineral quartz
siliceous sediment
sediment dominated by particles of silica, often from the shells of marine organisms
silt
sedimentary particles ranging is size from 1/256th to 1/16th of a mm
slab pull
the concept that at least part of the mechanism of plate motion is the pull of oceanic lithosphere down into the mantle
slack tide
period of little water movement between an incoming and outgoing tide
slightly stratified estuary
where salinity increases from the head to the mouth, but there is also a slight increase in salinity with depth at any point; also called a partially mixed estuary
snow line
in astronomy the radius around a star at which represents the boundary between gases (or liquids) and solids
SOFAR channel
range of depths around 1000 m where sound travels the slowest, so sound waves are refracted back into the channel and can be propagated long distances
solar system
a star and the planets surrounding it
solar wind
a stream of ionized (charged) particles away from the Sun
solubility
the amount of a dissolved substance that water can hold under a particular set of conditions, which are usually defined as 0 degrees C and 1 atmosphere of pressure
sonar
acronym for sound navigation and ranging; a method of using sound echoes to detect objects
sorting
how uniform the particles of a sediment are in terms of size
sounding
a single measurement of ocean depth
specific heat
the heat required to raise the temperature of 1 g of a substance by 1 degree C
spherule
a microscopic piece of space dust
spilling breaker
a breaker on relatively flat beaches that slowly increases its height and collapses
spit
a sand or coarser deposit extending from shore out into open water
splash wave
a wave formed when something falls into the ocean and creates a splash
spring tide
the period of maximum tidal range when the moon, sun and Earth are aligned
stable gas
unreactive gases that dissolve in seawater
steady state
where a system shows no net change, as input equals output
still water level
where the water surface would be if there were no waves present and the sea was completely calm
storm surge
an area of high water that moves with storm systems
subducted
when part of a plate is forced beneath another plate along a subduction zone
subduction zone
the sloping region along which a tectonic plate descends into the mantle beneath another plate
subittoral zone
the region of a coast from the low tide line to the end of the continental shelf
supralittoral zone
the region of a coast above the high tide line
surf beat
an irregular surface wave pattern caused by mixed interference
surf zone
the near-shore zone where waves are breaking into surf
surface tension
where a cohesive layer forms on the water surface due to attraction between water molecules
surging breaker
waves that break on steep beaches with a very sudden increase in height and sudden collapse right on the beach
swash
the upward motion of a wave on a beach (typically takes place at the same angle that the waves are approaching the shore)
swell
regular, long-period waves that have sorted themselves based on speed
tablemount
a flat-topped seamount (also called a guyot)
tabular iceberg
flat-topped, steep-sided iceberg with a length greater than five times the height
tectonic estuary
an estuary formed from flooding following the tectonic subsidence of land
tectonic plate
a region of the lithosphere that is considered to be moving across the surface of the Earth as a single unit
tektite
solidified glass fragments ejected during meteorite impacts
terrestrial planet
a planet with a rocky mantle and crust and metallic core (e.g., Earth)
terrigenous sediment
referring to sedimentary particles that originated on a continent
test
the shell-like hard parts (either silica or carbonate) of small organisms such as radiolarians and foraminifera
thermal expansion
the increase in the volume of a body water as its temperature rises and its density decreases
thermocline
a region in the water column where there is a dramatic change in temperature over a small change in depth
thermohaline circulation
deep ocean circulation driven by differences in water density
tidal bore
a wave that moves up a river with an incoming tide
tidal day
the amount of time between a tide on one day and the same tide the following day
tidal range
the difference in height between the high and low tides
tidal volume / tidal prism
the volume difference of an area between low and high tides
tombolo
a sand or coarser deposit connecting an island or rocky prominence to a larger body of land
trade winds
prevailing wind bands between the equator and 30 degrees latitude
transform boundary
a boundary between two plates that are moving horizontally with respect to each other
transform fault
a type of fault in which two pieces of crust slide past one another
trough
the lowest point of a wave (10.1)
tsunami
a long-wavelength wave produced by the vertical motion of the floor of the ocean, typically related either to an earthquake or other submarine seismic event
turbidity current
a current moving down downhill along the bottom, driven by the weight of the sediment within it
twilight zone
depths of the water column where there is some light penetration, but not enough to support photosynthesis; corresponds to the mesopelagic zone, 200-1000 m. Also known as the dysphotic zone
upwelling
process by which deeper water is brought to the surface
vertically-mixed estuary
estuary with complete mixing of fresh and salt water, where salinity is constant at all depths in a particular location but increases towards the estuary mouth; also called a well-mixed estuary
water mass
a volume of seawater with a distinctive density as a result of its unique profile of temperature and salinity
wave base
the depth of water that is affected by the sub-surface orbital motion of wave action (approximately one-half of the wavelength)
wave height
the distance between the crest and trough of a wave
wave steepness
the ratio of wave height to wavelength
wave-cut platform/terrace
a nearly-horizontal bench of rock eroded by waves within the surf zone
wavelength
the distance between the crests of two waves
weathering
a range of processes taking place in the surface environment, through which solid rock is transformed into sediment and ions in solution
wedge iceberg
iceberg with a steep face next to a more gradually sloping side
well-mixed estuary
estuary with complete mixing of fresh and salt water, where salinity is constant at all depths in a particular location but increases towards the estuary mouth; also called a vertically-mixed estuary
westerlies
the dominant wind bands between 30 and 60 degrees latitude in each hemisphere
western intensification
currents on the western side of a gyre are faster, deeper, and narrower than currents on the eastern side
