Ecoregion
Connect wind, upwelling, and productivity
Use the Benguela Current as a case study linking physical transport with nutrient supply.
Ocean Literacy Principle 1
Earth has one big ocean with many features
Investigate how plate tectonics, seawater chemistry, circulation, and sea level connect one global ocean. Use maps, models, and evidence to explain mechanisms and compare change across timescales.
Guiding question: How do physical and chemical processes connect ocean regions and change the ocean over time?
NMEA grade band: Grades 9–12
Other grade bands are in preparation.
At a glance
What students should take away
Use evidence to explain how tectonics, seawater properties, and moving water shape a connected ocean, and distinguish short-term water-level changes from long-term sea-level change.
Learning goals
- Use seafloor evidence to explain plate movement and changes in ocean basins.
- Connect salinity, temperature, density, and carbonate chemistry to ocean processes.
- Distinguish currents, waves, tides, and the water cycle by their causes and effects.
- Explain why relative sea level varies across places and timescales.
Teach this principle
Why this matters
Students move from describing ocean features to explaining interacting mechanisms. Following energy, matter, and change helps connect geology, chemistry, physics, and marine ecosystems.
Explain basin formation
- Student task
- Compare a ridge and a trench on the ocean-features map, then inspect seafloor ages. Sketch a plate-boundary model and label the evidence supporting it.
- Ask the class
- How do the age patterns support an explanation of crust formation and recycling?
- Listen for
- New crust forms at ridges; plate movement and subduction explain patterns across a basin. Maps provide evidence rather than a direct view of the process.
Teaching resources
Connect water properties to processes
- Student task
- Compare temperature and salinity maps and predict relative density at the same pressure. Use the acidification card to explain why changing carbon dioxide also matters.
- Ask the class
- Why are temperature, salinity, and pH different measurements rather than interchangeable indicators?
- Listen for
- Temperature and salinity help explain density; pH describes acidity and is linked to carbonate chemistry. Each measurement answers a different question.
Distinguish forms of ocean movement
- Student task
- Trace a current and compare it with a tidal pattern. Draw separate explanations for a current, a wave, and a tide; connect upwelling to nutrient transport.
- Ask the class
- What drives each type of movement, and what is being transported?
- Listen for
- Currents transport water and its contents; waves transfer energy; tides follow gravitational and rotational cycles. Wind and density differences contribute to circulation.
Teaching resources
Explain a changing coastline
- Student task
- Compare three scenarios: a storm, a warming ocean with melting land ice, and rising coastal land. Predict relative sea-level change and propose observations that distinguish the causes.
- Ask the class
- Would one high-water observation demonstrate a long-term sea-level trend?
- Listen for
- Different mechanisms act over different timescales. Repeated measurements and a land reference help distinguish a trend from tides, storms, or land movement.
Teaching resources
Check understanding
Explain how warming could affect seawater density, circulation, and sea level. Which observations would support your explanation, and what would they leave uncertain?
Explore the concepts
Geologic featuresOcean basins change as lithospheric plates move; a vast ocean still has finite resources.
Plate motion creates and recycles seafloor.
The ocean covers about 70% of Earth’s surface. Its basins include the seafloor and its geological features, and differ in size and shape as Earth’s lithosphere moves. The lithosphere comprises seven major plates and many smaller plates. New oceanic crust forms at spreading ridges; older oceanic lithosphere is recycled at subduction zones.
Subduction carries older oceanic lithosphere down into the mantle, completing the creation–movement–recycling pathway.
Different processes act on different timescales.
Plate interactions help form ridges, trenches, rift valleys, seamounts, and islands. Earthquakes and eruptions can change features rapidly, while spreading and basin development continue over millions of years. The ocean’s size does not make its space or resources unlimited.
Tectonic activity both creates and destroys features such as islands. Diverging and converging plates produce different seafloor features.
Divergence produces spreading ridges and rift valleys. Convergence with subduction forms deep trenches and can produce volcanic island arcs; other volcanic islands and seamounts form above hot spots. The landform depends on the setting, not simply on the presence of moving plates.
Connected concepts in other principles
Properties of ocean waterSalinity, temperature, density, conductivity, freezing point, and pH influence physical conditions and marine life.
Salts and temperature affect seawater properties.
Salinity describes dissolved salts, including ions such as sodium, chloride, magnesium, calcium, and potassium. Together with temperature, it helps determine seawater density. At the same pressure, colder or saltier seawater is generally denser. Dissolved salts also affect electrical conductivity and freezing point.
Carbonate chemistry links ocean water and life.
Seawater is usually slightly basic. Dissolved carbon dioxide interacts with the carbonate system, which helps buffer pH changes. Adding carbon dioxide lowers pH and can reduce carbonate availability, affecting organisms that build calcium carbonate shells or skeletons. Buffering does not prevent all change.
The carbonate system also affects how much additional atmospheric carbon dioxide seawater can take up. As carbon dioxide is added, changes in carbonate chemistry reduce buffering capacity, so buffering neither guarantees stable pH nor unlimited carbon uptake. Coral reefs are one ecosystem affected by this chemistry.
Connected concepts in other principles
Ocean circulationWind, density differences, gravity, and Earth’s rotation produce different forms of ocean movement.
Wind-driven currents, gyres, and upwelling.
Winds transfer momentum to water; friction carries motion below the surface. Earth’s rotation deflects moving water through the Coriolis effect. Wind-driven Ekman transport can move water away from a coast, allowing cold, nutrient-rich water to rise and support productivity. Winds and continents organize major subtropical gyres, generally clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
In major subtropical gyres, cooler water generally flows toward lower latitudes along the west coasts of continents, while warmer water flows toward higher latitudes along east coasts. Productive upwelling regions include continental west coasts and waters around Antarctica.
Density differences connect surface and deep water.
Cooling and changes in salinity affect density. Dense water can sink beneath less dense water, creating layers and contributing to deep circulation. Circulation and mixing exchange heat, dissolved substances, particles, and organisms between regions, linking ocean conditions to ecosystems and climate.
Denser water tends to sink and less dense water to rise, with the densest water flowing near the seafloor beneath lighter layers. Water moving from equatorial regions toward the poles can cool, become denser, and sink. The global conveyor-belt model links circulation across ocean basins; changes in circulation can affect climate and ecosystems.
Temperature- and salinity-related density circulation is often called thermohaline circulation.
The water cycle connects ocean and atmosphere.
Evaporation moves water into the atmosphere; precipitation returns it to ocean and land. Runoff links land back to the ocean. These exchanges move water between reservoirs and can change ocean salinity.
Waves transfer energy.
Wind commonly generates surface waves. Water particles move mainly in orbits as wave energy travels; they do not travel across a basin with each wave. Waves can break when they become too steep, often as they enter shallow water. Seafloor displacement can generate tsunamis.
In deep water a wave can break when it becomes too steep. Near shore, breaking also depends on wave height relative to water depth: as a wave enters shallower water, its height can become too large for that depth.
Tides follow gravitational and rotational cycles.
The gravity of the Moon and Sun, together with Earth’s rotation, produces periodic water-level changes. Their relative positions influence tidal cycles, while basin shape and local conditions affect the tides observed at a coast.
Connected concepts in other principles
Sea levelSea level is the average height of the ocean relative to the land; it varies between places and over time.
Sea level varies locally and over time.
Winds and atmospheric pressure can raise or lower coastal water levels. Differences in sea-surface height help drive currents. Tectonics can change ocean-basin shape or the height of land, so relative sea level need not change equally at every coast.
Warming changes ocean volume.
Seawater generally expands as it warms and contracts as it cools. Melting land ice adds water to the ocean; growth of land ice stores water outside it. Human-driven warming contributes to sea-level rise. Distinguish these long-term changes from individual tides, waves, and storms.
Connected concepts in other principles
Teaching resources
Start here
Opportunity
Model a connected ocean
Trace how deep circulation exchanges water and properties between regions.
Explore this principle with the platform
Sources and curriculum alignment
Grades 9–12 conceptual alignment: Adapted from NMEA Ocean Literacy Scope and Sequence under CC BY-NC-SA 4.0.
Adapted from the NMEA Grades 9–12 Principle 1 CFD (2021, handbook page 59). Each explanation is mapped below to the sheet’s concept codes. Classroom tasks and platform links are Blue Biome teaching suggestions, not activities supplied by NMEA.
Source concepts and connections
The notes below paraphrase the English NMEA source. They also explain qualified adaptations and corrected references.
A · Plate motion creates and recycles seafloor.
- Basins include the seafloor and geological features.
- their size, shape, and features vary with lithospheric movement.
A1 · Different processes act on different timescales.
- The ocean is large but finite in space and resources.
A2 · Plate motion creates and recycles seafloor.
- Seven major plates and many smaller plates form the constantly recycled lithosphere.
A3 · Plate motion creates and recycles seafloor.
- Spreading ridges form new oceanic crust.
- subduction recycles older crust into the mantle.
- Subducted oceanic lithosphere returns to the mantle.
A4 · Different processes act on different timescales.
- Convergence and divergence determine seafloor features including islands, seamounts, trenches, ridges, and rift valleys.
- Plate boundaries create characteristic ridges, trenches, rifts and volcanic landforms.
A5 · Different processes act on different timescales.
- Seafloor change can be rapid during earthquakes or eruptions, or occur over millions of years through spreading.
A6 · Different processes act on different timescales.
- Tectonic activity continually creates and destroys features such as islands.
B · Salts and temperature affect seawater properties.
- Salinity, conductivity, freezing point, density, and pH affect ocean biological and physical characteristics.
B1 · Salts and temperature affect seawater properties.
- Salinity measures salts, including magnesium, sodium, calcium, chlorine, and potassium.
- salinity and temperature determine density.
Adaptation notes (English)
Use chloride rather than elemental chlorine for seawater ions, and land ice for melt that adds ocean water. These are scientific wording clarifications, not additional CFD branches.
Read the explanationB2 · Carbonate chemistry links ocean water and life.
- Ocean pH is slightly basic and is affected by dissolved carbonate ions.
B3 · Carbonate chemistry links ocean water and life.
- pH balance matters to marine ecosystems including coral reefs and to the ocean’s response to additional atmospheric carbon dioxide.
- Carbonate buffering affects pH and further atmospheric carbon uptake; coral reefs are an affected ecosystem.
Adaptation notes (English)
Restore the link between carbonate buffering, lower pH and future carbon uptake capacity.
Read the explanationC · Wind-driven currents, gyres, and upwelling.
- Ocean water is continually moving.
C1 · Wind-driven currents, gyres, and upwelling.
- Wind-driven and density-driven currents circulate ocean water.
C2 · Wind-driven currents, gyres, and upwelling.
- Coriolis, prevailing winds, continents, and other currents direct wind-driven surface currents into gyres.
C3 · Wind-driven currents, gyres, and upwelling.
- Surface currents influence subsurface currents through Ekman forces.
C4 · Wind-driven currents, gyres, and upwelling.
- The diagram gives opposite gyre rotation by hemisphere and links colder water to continental west coasts and warmer water to east coasts.
Adaptation notes (English)
Qualify rotation and boundary-current directions as major subtropical gyres; the unqualified statement does not describe all gyres.
Read the explanationC5 · Wind-driven currents, gyres, and upwelling.
- Prevailing winds and Coriolis can move surface water offshore, replaced by nutrient-rich water from below.
C6 · Wind-driven currents, gyres, and upwelling.
- Upwelling supports high productivity, especially along continental west coasts and around Antarctica.
C7 · Density differences connect surface and deep water.
- Temperature and salinity variations drive thermohaline circulation and density layering.
C8 · Density differences connect surface and deep water.
- Saltier or colder water is denser.
- denser water tends to sink and less dense water to rise.
C9 · Density differences connect surface and deep water.
- Densest layers flow near the seafloor with less dense water stratified above.
C10 · Density differences connect surface and deep water.
- Water moving from equatorial regions toward the poles cools, becomes denser, and can sink.
C11 · Density differences connect surface and deep water.
- The thermohaline conveyor-belt model links water movement within and among ocean basins.
- Temperature and salinity influence density-driven thermohaline circulation.
C12 · Density differences connect surface and deep water.
- Interbasin mixing transports heat, solids, gases, dissolved substances, and organisms.
C13 · Density differences connect surface and deep water.
- Circulation changes affect climate and ecosystems.
C14 · The water cycle connects ocean and atmosphere.
- The water cycle exchanges water between ocean and atmosphere.
C15 · Waves transfer energy.
- Waves transfer energy over long distances with little horizontal movement of water.
C16 · Waves transfer energy.
- Wind friction produces waves.
- earthquakes can generate tsunamis.
C17 · Waves transfer energy.
- Waves break when too steep in deep water or large relative to depth near shore.
- Deep-water steepness and wave height relative to shallow-water depth can cause breaking.
C18 · Tides follow gravitational and rotational cycles.
- Tides are periodic rises and falls of surface water level.
C19 · Tides follow gravitational and rotational cycles.
- Solar and lunar gravity and Earth’s rotation produce tides.
C20 · Tides follow gravitational and rotational cycles.
- Tides vary cyclically with the relative positions of Moon, Sun, and Earth.
D · Sea level varies locally and over time.
- Sea level is the average height of the ocean relative to land.
D1 · Sea level varies locally and over time.
- Sea level differs between places and changes over time.
D2 · Sea level varies locally and over time.
- Atmospheric pressure and prevailing winds affect regional sea level.
D3 · Sea level varies locally and over time.
- Sea-surface height differences help set currents in motion.
D4 · Sea level varies locally and over time.
- Lithospheric movement changes basin volume and land height.
D5 · Warming changes ocean volume.
- Temperature changes affect ice growth or melt and seawater expansion or contraction.
Adaptation notes (English)
Use chloride rather than elemental chlorine for seawater ions, and land ice for melt that adds ocean water. These are scientific wording clarifications, not additional CFD branches.
Read the explanationD6 · Warming changes ocean volume.
- Human effects on global climate affect sea level.
Concept pathways (English)
Geologic features: Ocean basins change as lithospheric plates move; a vast ocean still has finite resources.
Properties of ocean water: Salinity, temperature, density, conductivity, freezing point, and pH influence physical conditions and marine life.
Ocean circulation: Wind, density differences, gravity, and Earth’s rotation produce different forms of ocean movement.
Sea level: Sea level is the average height of the ocean relative to the land; it varies between places and over time.