OCS Test 2

Wave

Energy moving through water.

Wave crest

The highest part of a wave.

Wave trough

The valley between crests.

Wave height

The vertical distance between a crest and a trough.

Wavelength

The horizontal distance between crests.

Disturbing force

The force that causes waves by putting energy into the water.

What is the disturbing force for capillary waves?

Wind.

Capillary wave (ripple)

A small wave with a short wavelength (up to about 1.7 cm), caused by a slight disturbance such as a gentle breeze. It has smooth, rounded crests and V

What causes wind waves?

Wind blowing over the water’s surface.

What disturbing forces can create tsunamis?

Landslides, volcanic eruptions, and seafloor faulting associated with earthquakes.

Three primary factors influencing wind waves

Wind speed, wind duration, and fetch.

Wind speed and wave size

Higher wind speeds create larger waves.

Wind duration and wave size

The longer the wind blows, the larger the waves can become.

Fetch

The distance of open water over which wind blows; a longer fetch allows larger waves to develop.

Why can hurricanes create large waves?

Very strong winds blow for many days over large expanses of open ocean, creating a large fetch.

What usually causes a tsunami?

A large displacement of ocean water, usually from an underwater earthquake.

Tsunamis compared with wind

driven waves

Tsunami wavelength

Extremely long, sometimes hundreds of kilometers.

What is tsunami wavelength related to?

The size of the underwater disturbance.

Example of a tsunami

producing disturbance

How can an earthquake create a tsunami?

It suddenly moves a large area of Earth’s tectonic plates, displacing hundreds of cubic kilometers of water and creating a wave that extends through the entire depth of the ocean.

Why can tsunamis develop long wavelengths in deep water?

The disturbance forms in deep ocean water, spreading wave energy through the entire water column.

When do capillary waves become wind waves?

When their wavelength is greater than 1.73 cm (0.68 inch).

Typical wind

wave height in the study guide

Common open

ocean wind

What happens when a wind wave enters shallow water?

When the water is shallower than half the wavelength, the wave grows taller and then crashes toward shore.

What causes a wave to break nearshore?

The depth to the seafloor becomes smaller than half the wavelength.

Maximum open

ocean wave height

When can a wave break in the open ocean?

When its height exceeds the 1:7 wave

What happens to excess wave energy?

It becomes turbulence and whitecaps.

What drives tides?

Gravity, especially the gravitational forces of the Moon and Sun.

What is a tide?

A regular, periodic rise and fall of sea level; a visible vertical shift of the ocean.

Tides compared with waves: time scale

Waves are short

Tides compared with waves: cause

Tides are driven by gravity; waves are driven by wind or another disturbance.

Tides compared with waves: movement

Tides are a vertical displacement of the ocean; waves are caused by a disturbance of the ocean surface.

Tides (definition)

Periodic changes in ocean surface height caused by the gravitational forces of the Moon and Sun.

Tides as forced waves

Tides are huge, shallow

Isaac Newton and gravity

Newton determined that heavy bodies attract each other more strongly than light bodies do.

What causes tides in the ocean?

The gravitational attraction between the ocean and the Moon and Sun.

Why does the Moon affect tides more than the Sun?

Although the Sun is millions of times bigger than the Moon, it is much farther away; the Moon has about twice the influence on tides compared with the Sun.

Gravity and centrifugal force in the Earth–Moon system

Gravity pulls Earth and the Moon toward each other, while centrifugal force keeps them apart.

Why do Earth and the Moon not crash into each other or fly apart?

They remain in a stable orbit.

The ocean’s two tidal bulges

One bulge faces the Moon, and the other is on the opposite side of Earth.

Tide on the side of Earth facing away from the Moon

The centrifugal force is greater than the Moon’s gravitational force there, so the ocean bulges away from the Moon on that side.

Tide on the side of Earth facing the Moon

The Moon’s gravitational attraction is greater than centrifugal force there, so the ocean bulges toward the Moon.

Spring tide

Occurs when Earth, Moon, and Sun are in a line. Lunar and solar tides add together, producing higher high tides and lower low tides.

Spring tides: tidal heights

High tides are very high and low tides are very low.

When do spring tides occur?

Every two weeks, when the Moon is new and when it is full.

Does “spring tide” refer to the spring season?

No. Spring tides do not mean the spring season.

Neap tide

Occurs when the Moon, Earth, and Sun form a right angle; the Sun’s gravitational pull is at 90° to the Moon’s.

What happens to the Moon’s tidal effect during a neap tide?

Some of the Moon’s effect on the tide is diminished by the Sun’s pull acting at a right angle.

Neap tides: tidal heights

High tides are not very high, and low tides are not very low.

When do neap tides occur?

About every two weeks, a week after a spring tide.

Moon and Sun forces during a neap tide

Their gravitational pulls are not in the same direction.

Diurnal tidal cycle

One high tide and one low tide.

Semidiurnal tidal cycle

Two high tides and two low tides of approximately equal height.

Mixed semidiurnal tidal cycle

Two high tides and two low tides of different heights.

Tidal pattern on the US Pacific Coast (as stated in the study guide)

Mixed diurnal: two high tides and two low tides a day of different heights.

Tidal pattern on the US Gulf Coast (as stated in the study guide)

Diurnal: one high tide and one low tide a day. The enclosed ocean basin rocks, affecting the tidal pattern.

Tidal pattern on the US East Coast (as stated in the study guide)

Semidiurnal: two equal high tides and two low tides a day.

Small tidal range

Not much difference between high and low tide; occurs in enclosed areas such as the Mediterranean and the US Gulf Coast.

Great tidal range

The eastern Bay of Fundy near New Brunswick, Canada, has a tidal difference of up to 15 meters (50 feet) between high and low tide.

Rachel Carson’s observations of tidal ranges

In “The Edge of the Sea,” Rachel Carson documented many tidal ranges throughout US Gulf and Atlantic coastal areas.

Tidal bore

A steep wave that moves upstream in some rivers exposed to large tidal fluctuations, formed by the incoming tide crest at an enclosed river mouth.

How does a tidal bore form and move upriver?

A confined river mouth forces the tidal wave toward land faster than the theoretical shallow

Tidal bore size and speed

Most are less than 1 meter (3 feet) high, but some reach 8 meters (26 feet) and move at 11 meters per second (25 miles per hour). Their danger is reduced by predictability.

Where are tidal bores common?

The Amazon, the Ganges Delta, and England’s River Severn.

Intertidal zone

The area between the high

Emergence and submergence in the intertidal zone

Intertidal organisms are alternately exposed to air (emergence) and covered by water (submergence).

How are organisms distributed within the intertidal zone?

Species that tolerate different amounts of exposure sort into horizontal bands; each zone contains organisms adapted to that habitat’s conditions.

Tide pool

A small pool of ocean water trapped in a rock basin when the tide goes out.

Why are tide pools important habitats?

They provide shoreline habitat for organisms such as sea stars, sea anemones, and crabs, which are adapted to being underwater and exposed to air as tides change.

Tidal range at Grand Isle, Louisiana

Very small, sometimes less than a foot between high and low tide, because the Gulf is enclosed and protected.

Where do tide pools and intertidal zones occur?

On beaches where there is a large difference between high and low tide.

Louisiana coast compared with Oregon coast tidal ranges

Louisiana has a small difference between high and low tide, while some locations on the Oregon coast have very large differences.

Main forces behind tides and waves

Gravity drives tides; wind and other disturbances drive waves.

Photosynthesis

The process by which organisms use light energy to make carbohydrates (food).

Marine primary producers

Organisms such as phytoplankton that use sunlight and carbon dioxide to make carbohydrates (biomass).

Photosynthesis equation

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ (carbohydrates) + 6O₂.

Chlorophyll

A molecule used by photosynthetic organisms to perform photosynthesis.

What does phytoplankton include?

Photosynthesizing algae (diatoms, dinoflagellates, radiolarians, foraminifera, and coccolithophores) and photosynthetic bacteria such as cyanobacteria.

Primary productivity on land compared with the ocean

The amount of primary productivity on land and in the ocean is about equal.

Phytoplankton and oxygen

Phytoplankton releases oxygen into the atmosphere and ocean as a byproduct of photosynthesis.

Cyanobacteria and early oxygen production

Cyanobacteria, the first primary producers, released oxygen into the environment as a byproduct of producing carbohydrates.

Diatoms and global production (study

guide figure)

Dinoflagellates

Algae that can be bioluminescent and can create harmful algal blooms (HABs) called red tides.

Coccolithophores

Single

Why is the Sun important to life?

The Sun produces enormous energy that powers the growth of nearly all living things.

How do primary producers convert sunlight?

Chlorophyll captures light energy in primary producers (certain bacteria, algae, and vascular plants) and converts it to chemical energy.

What is the energy from photosynthesis used to build?

Carbohydrates (food) that store energy.

How do primary producers use carbohydrates?

They use the carbohydrates they produce for their own energy.

How do consumers obtain carbohydrates made by primary producers?

Consumers eat primary producers or other organisms that contain those carbohydrates.

Light energy and photosynthesis

Light energy powers the synthesis of carbohydrates that store energy; this process is photosynthesis.

Where is chlorophyll located in photosynthetic cells?

Chlorophyll is in the thylakoids, which are in the granum; these structures are inside the chloroplast.

Food web

A group of organisms linked by feeding relationships; energy flows from primary producers to consumers.

Primary productivity: phytoplankton vs. vascular plants

The study guide says primary productivity levels are similar for ocean phytoplankton and vascular plants on land.

Average phytoplankton count in one liter of ocean water

About one million phytoplankton cells.

Diatoms and ocean organic material

Diatoms make up nearly half of the organic material in the oceans.

Diatom contribution to marine primary production

Diatom photosynthesis is responsible for 40% of marine primary production, according to the study guide.

Diatoms compared with rainforests

The study guide says diatom photosynthetic productivity is equivalent to the photosynthetic productivity of all rainforests.