oceanography

What are tectonic plates?

Separate pieces that make up the Earth's crust.

What are the two types of crust?

Continental crust (less dense) and oceanic crust (more dense).

What percentage of Earth's surface is covered by oceans?

70%.

How much heat from greenhouse gas emissions have oceans absorbed since the 1970s?

Over 93%.

What are the four main ocean basins?

Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean.

Which ocean is the largest and has the greatest depth?

Pacific Ocean.

What is bathymetry?

Measurement of ocean depths and charting of the ocean floor's shape.

What instrument is primarily used for measuring ocean depth?

Echo sounder (sonar).

What are the three major topographic units of the ocean floor?

Continental margins, ocean basin floor, mid-ocean ridge.

What characterizes passive continental margins?

Found along most Atlantic coastal areas, not associated with plate boundaries, and experience little volcanism.

What is a continental shelf?

Flooded extension of the continent, varies in width, and contains important mineral deposits.

What are submarine canyons?

Deep, steep-sided valleys cut into the continental slope, often eroded by turbidity currents.

What are turbidity currents?

Downslope movements of dense, sediment-laden water.

What forms a continental rise?

Sediments accumulate at the base of the continental slope, creating a gradual incline.

What are deep-ocean trenches?

Long, narrow features that are the deepest parts of the ocean, primarily located in the Pacific Ocean.

What are abyssal plains?

Flat, sedimented expanses of ocean floor that make up 1/4 of Earth's surface.

What are seamounts?

Isolated volcanic peaks that may emerge as islands or sink to form flat-topped guyots.

What characterizes mid-ocean ridges?

An elevated position with extensive faulting and volcanic structures, forming the longest topographic feature on Earth's surface.

What is the most common type of sediment on the deep-ocean floor?

Mud.

What is terrigenous sediment?

Material weathered from continental rocks that is found in virtually every part of the ocean.

What is biogenous sediment?

Shells and skeletons of marine organisms, including calcareous and siliceous oozes.

What is hydrogenous sediment?

Minerals that crystallize directly from seawater, including manganese nodules and evaporites.

What resources can be found on the seafloor?

Oil, gas, sand, gravel, evaporative salts, and manganese nodules.

What is the role of the ocean in climate regulation?

Absorbs solar energy, releases heat, and supplies water vapor for rainfall.

What are the effects of the ocean on weather?

Shapes weather and climate by exchanging heat, moisture, and CO₂ with the atmosphere.

How do turbidity currents affect sediment distribution?

They transport sediments down submarine canyons to the deep sea.

What is the significance of understanding ocean processes?

Key to managing natural resources, addressing pollution, and exploring extraterrestrial life.

What percentage of seawater is made up of dissolved mineral substances?

About 3.5 percent (by weight)

How is salinity typically expressed in oceanography?

In parts per thousand (‰)

What is the average salinity of seawater?

3.5% or 35‰

What factors influence salinity in seawater?

Variations in rainfall and rates of evaporation

What are the primary sources of sea salt?

Continental weathering, outgassing from Earth's interior, and volcanic eruptions

What processes remove salts from seawater?

Biological uptake, chemical precipitation, and hydrothermal circulation

What causes a decrease in salinity?

Rainfall, river discharge, and melting ice

What causes an increase in salinity?

Evaporation and sea-ice formation

How does salinity vary with latitude?

High salinity near 25°-35° (dry subtropics), low near the equator and high latitudes

What happens to salinity during winter and summer in polar regions?

Winter: Sea ice forms, increasing salinity; Summer: Ice melts, adding freshwater, decreasing salinity

What is the impact of ocean acidity on marine life?

Acidic water dissolves CaCO₃, threatening corals, plankton, and shellfish

What chemical reaction occurs when CO₂ is absorbed by the ocean?

CO₂ + H₂O → H₂CO₃ (carbonic acid)

How has ocean pH changed since preindustrial times?

It has dropped by 0.1 and may drop by 0.3 by 2100

What is the thermocline?

A layer in the ocean where temperature drops rapidly with depth

What defines the density of seawater?

Density = mass/volume; it determines the vertical position of water masses

What factors control seawater density?

Salinity and temperature

What is the pycnocline?

A layer where density increases rapidly with depth, typically between ~300-1000 m

What are the three layers of the ocean structure?

1) Surface Mixed Zone, 2) Transition Zone, 3) Deep Zone

What is the role of high latitudes in ocean circulation?

Cold, dense surface water forms and sinks, initiating deep-ocean currents

What drives surface ocean currents?

Winds and land areas affecting the flow

What are thermohaline currents?

Currents driven by differences in temperature and salinity

What is the process of bottom water formation?

Water becomes dense enough to sink, forming North Atlantic Bottom Water (NABW) and Antarctic Bottom Water (AABW)

What happens during the return flow to the surface in ocean circulation?

Deep water rises through upwelling zones, carrying nutrients to surface ecosystems

How does temperature vary with depth in low latitudes?

Warm at the surface, drops rapidly to ~1000 m, then remains a few °C above freezing

What is the difference in temperature profiles between high and mid-latitudes?

High latitudes have a cold, uniform water column; mid-latitudes have a strong thermocline in summer