Waves, Tides, and Ocean Currents

UNIT 8STANDARDS: NCES 2.1.1, 2.1.3, 2.3.1LESSON 2

Lesson Objectives

In this lesson, you will learn about:– What causes tides, waves, and currents– What are neap and spring tides– What causes upwelling– What areas do upwelling occur

Ocean Movements: Waves

Waves

Characteristics

Wave Simulation

A rhythmic movement that carries energy through space or matter.

Crest: the highest point on a wave Trough: the lowest point on a wave Wavelength: distance between 2

equal points on a wave Amplitude: wave height above or

below the wave median Frequency: number of waves that

pass a point in a given time.

Wave Height

Depends on 3 factors

Wind Speed Wind direction Fetch: amount of water

available As waves reach shallow water,

they slow down because of the friction with the bottom.

The water behind the leading wave causes the wave height to raise.

When the wave collapses, it is called a breaker.

Tsunamis

Some waves that are not caused by wind. Earthquakes in, the ocean cause giant waves to form. So much energy is released by an earthquake that big waves rush across the ocean water. These waves are called tsunamis.Tsunamis cause great damage to islands and coastlines that they meet.

Tsunami strikes Ao Nang, Thailand

Tides

Tides

High Tide

Low Tide

The periodic rise and fall of sea level

The highest level the water reaches on the land

The lowest level the water reaches on the land

Tide Table Lab

Go to the Tide table lab in this unit. Graph the water level over time for the

24 hour period. Use curving lines to connect the points Estimate the approximate time of high

and low tides from the graph

Causes of Tides

Earth-Moon

Sun

The basic cause of tides are the gravitational attraction between the Earth, moon, and Sun.

Unbalanced forces cause bulges on the side of the Earth closest to the moon or sun. Lunar Tides

The Sun-Earth gravities also influence tides. Solar Tides

Even though the moon is smaller, lunar tides are twice as high as solar tides due to the closeness of the moon.

Spring Tide vs Neap Tides

Spring Tides happen when the moon and sun line up to pull on the water. These are the highest and lowest tides. They happen about every 14 days.

New moon = highest Full moon = lowest

Neap Tides happen when the sun and moon are at 90 degrees of each other. The sun pulls to the right on the water, while the moon pulls on the top or bottom to counter the solar tide.

Ocean Currents

Density Current

Surface Currents

Caused by more dense water settling to the bottom and less dense water rising.

Surface currents based on the direction of the prevailing winds.

In the northern latitudes, trade winds move the currents from east to west.

In the mid latitudes, westerlies move the current from west to east.

In the polar areas, polar winds push the water from east to west.

Ocean Currents

Thermal Current

As water in one part of the ocean cools, it becomes heavier than the warm water around it. The cooler water sinks and the warmer water rises.

The Gulf Stream is a massive temperature current. The Gulf Stream begins off the east coast of Mexico, south of Texas. The warm water flows from Mexico and South America along the east coast of the United States to northern Europe.

Gyres: Large system of rotating currents

If there were no land masses, the oceans would rotate east to west. But continents deflect the currents around.

Look at the overall currents

Upwelling

Definition

Origin

Benefits

Vertical movement of water.

Upward currents of ocean water.

Originate at the bottom of the sea and are COLD.

Generally on the west coasts of continents.

Abundant in nutrients and therefore support LOTS of marine life.

Section Review 8.2.1

Describe how water moves as a wave. What 3 factors determine wave height? What causes tides? Compare and contrast Neap and Spring tides. Why are the upwelling waters always cold? Predict the greatest fishing spots in the world

and WHY.