Oceans
What is the largest ocean on Earth?
Ocean trench (example: Mariana Trench)
What causes most surface ocean waves that you see at the beach?
Wind blowing across the surface of the water.
What two astronomical bodies primarily cause Earth's tides?
The Moon and the Sun (the Moon has the larger effect).
What is the name for the relatively flat, gently sloping area at the edge of the continent that lies under the shallow sea?
Continental shelf.
What is the main salt found in seawater?
Sodium chloride (table salt).
What term describes the deepest parts of the ocean floor, such as the Mariana Trench?
Ocean trench (example: Mariana Trench)
What part of a wave is the highest point called, and what is the lowest point called?
Crest (highest) and trough (lowest).
What is the term for a tide with the greatest difference between high and low tides, which occurs when the Sun, Moon, and Earth are aligned?
Spring tide.
What is a mid-ocean ridge?
A mid-ocean ridge is an underwater mountain range formed where tectonic plates move apart and magma rises to create new seafloor.
What word describes the total amount of dissolved salts in seawater (its "saltiness")?
Salinity.
Name two major factors that affect ocean water temperature.
sunlight (solar heating), latitude, depth, ocean currents, and wind-driven mixing.
What is wave period?
The time it takes for two successive crests (or troughs) to pass a fixed point.
How many high tides and low tides does a typical coastal location experience each day? (Explain briefly why.)
Most coastal locations experience two high tides and two low tides each lunar day (about 24 hours 50 minutes) because the Earth rotates under two tidal bulges caused mainly by the Moon.
What is the deep, narrow valley on the ocean floor formed by tectonic plate subduction called?
An ocean trench (example: Mariana Trench).
Besides salts, name two other dissolved substances commonly found in seawater.
Examples: dissolved gases (like oxygen and carbon dioxide), nutrients (nitrates, phosphates), and trace elements (iron, silica).
What is the global circulation pattern that moves warm and cold water around the world's oceans, sometimes called the "conveyor belt"?
Thermohaline circulation (also called the global conveyor belt).
Describe how waves change as they move from deep water into shallow water near the shore (list at least two changes).
In shallow water waves slow down, wavelength shortens, wave height increases (they steepen), and they may break as they interact with the bottom.
Describe how the shape of a coastline or the ocean floor can change the local tide range (give one example).
A funnel-shaped bay (like the Bay of Fundy) can concentrate tidal energy and amplify tidal range; a wide shallow continental shelf can also increase local tide heights.
Describe how seafloor spreading at mid-ocean ridges helps explain the movement of tectonic plates.
At mid-ocean ridges, magma rises and forms new oceanic crust; this pushes older crust away from the ridge, which helps drive plate motion and explains how continents shift over long times.
Explain how freshwater input (from rivers or melting ice) and evaporation change local salinity. Give one classroom-friendly example.
Freshwater input from rivers or melting ice lowers local salinity; evaporation removes water and increases salinity. Classroom example: mix a small amount of freshwater into a saltwater cup to show salinity decrease; leave a shallow tray of seawater to evaporate a bit (carefully) to show salinity increase.
Explain how salinity (saltiness) and temperature together affect the density of seawater and how that influences vertical movement of water (upwelling or sinking).
Warmer water is less dense; saltier water is more dense. Colder, saltier water tends to sink while warmer, fresher water tends to rise. These density differences drive vertical movement: sinking forms deep water masses; upwelling brings deep, nutrient-rich water to the surface.
Explain what constructive and destructive interference are when two wave trains meet, and give one real-world effect each could have on the shoreline.
Constructive interference: crests line up and combine, making larger waves (can increase erosion and stronger surf). Destructive interference: a crest meets a trough and they cancel, reducing wave height (can reduce energy reaching the shore).
Explain why spring tides and neap tides occur in terms of the relative positions of the Sun, Moon, and Earth, and include how each affects tidal range.
Spring tides occur when the Sun, Moon, and Earth are aligned (new and full moons), so their gravitational forces combine and tidal range is larger. Neap tides occur when the Sun and Moon are at right angles (first and third quarter), so their forces partially cancel and tidal range is smaller.
Explain how features of the ocean floor (such as trenches, ridges, and continental shelves) influence ocean currents and marine habitats (give two specific effects).
Examples of influences: (1) Trenches and ridges can steer deep ocean currents, changing water temperature and nutrient distribution; (2) Continental shelves provide shallow habitats that support large fisheries and kelp/seaweed beds; underwater canyons can concentrate nutrients and support rich marine life.
Describe how dissolved oxygen, nutrients (like nitrates and phosphates), and temperature together influence where different kinds of marine organisms can live (give two specific examples).
Examples: (1) Dissolved oxygen is higher in colder water and near the surface from photosynthesis — fish that need lots of oxygen prefer cooler, well-mixed waters; (2) Nutrient-rich upwelled water supports plankton blooms that feed many fish, while warm, nutrient-poor surface water supports different, often lower-productivity communities.