Unit E Lesson E4
Completion requirements
Lesson E4: Waves and Tides
Video Lesson
Why do coastline tide levels rise and fall each day? Why do water waves crash on beaches? Watch this video to learn more about waves and tides.
Lesson E4: Waves and Tides
Figure E.2.4.1 – Earth’s moon influences the ocean tides.
Figure E.2.4.2 – The strength of tides is determined by the alignment of Earth with the Sun and the Moon.
Spring and Neap Tides
The position of Earth’s moon is the main influence on ocean tides. However, the position of the Sun also affects the strength of tides.
The Moon rotates around the Earth once every 27 days. Twice during the Moon’s rotation, it lines up in a row with the Earth and the Sun. When the Moon, Earth, and Sun form a straight 180 degree angle, the Moon’s gravitational pull on the oceans is enhanced by gravitational pull from the Sun. This situation creates larger than average tidal ranges, called spring tides.
The position of Earth’s moon is the main influence on ocean tides. However, the position of the Sun also affects the strength of tides.
The Moon rotates around the Earth once every 27 days. Twice during the Moon’s rotation, it lines up in a row with the Earth and the Sun. When the Moon, Earth, and Sun form a straight 180 degree angle, the Moon’s gravitational pull on the oceans is enhanced by gravitational pull from the Sun. This situation creates larger than average tidal ranges, called spring tides.
Reading
and Materials for This Lesson
Science in Action 8
Reading: Pages 349–354
Materials:
Deep baking pan (9 x 13 inches), water, hairdryer with low and high settings, ruler.
Twice every 27 days, when the Moon and Sun form a 90 degree angle with the Earth, the Sun does not have as much gravitational pull on the oceans. This creates lower than average tidal ranges, called neap tides.
The Moon’s orbit around Earth is not a perfect circle. This means that sometimes the Moon is closer to Earth than at other times of year, causing even greater gravitational pull. Twice each year, a spring tide coincides with the Moon being slightly closer to Earth. This causes an extremely large tide called a king tide.
The Moon’s orbit around Earth is not a perfect circle. This means that sometimes the Moon is closer to Earth than at other times of year, causing even greater gravitational pull. Twice each year, a spring tide coincides with the Moon being slightly closer to Earth. This causes an extremely large tide called a king tide.
Figure E.2.4.3 – As the tide rises in Gorey, Jersey, water fills the coastline.
Watch More
Tides
Watch these videos for a review on tide formation.
Watch these videos for a review on tide formation.
Try It!
Make Waves
Try this simple experiment to learn how surface waves are generated in oceans.
Materials:
Try this simple experiment to learn how surface waves are generated in oceans.
Materials:
- Deep baking pan (9 x 13 inches)
- Water
- Hairdryer with low and high settings
- Ruler
Safety Warning
You must complete this activity with adult supervision.
This activity involves an electrical appliance near water. You can get a severe electrical shock if the hair dryer comes into contact with water. Keep the hair dryer a safe distance away from the water.
This activity involves an electrical appliance near water. You can get a severe electrical shock if the hair dryer comes into contact with water. Keep the hair dryer a safe distance away from the water.
Instructions:
- Fill the baking pan halfway with water.
- Wait for the water in the pan to be still.
- Aim the hairdryer at a 45-degree angle towards the water in one end of the pan. Keep the hairdryer approximately 30 cm away from the water.
- Turn the hairdryer on at its low setting for 20 seconds. What do you observe?
- Repeat steps 2–4, but change the hairdryer setting to high. What do you observe?
Questions:
Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.
The hairdryer caused air particles to move. When these moving air particles came into contact with the water in the pan, the air particles transferred some of their energy to the water particles. This transferred energy caused the water to start
moving as waves.
A faster air speed from the hairdryer created larger waves in the pan.
A hurricane is a storm with high speed winds. During a hurricane, you would expect to see large waves in the ocean, created by large amounts of energy in the high speed winds.
Figure E.2.4.4 – Tsunami waves are much larger than normal waves.
Figure E.2.4.5 – Tsunami waves are dangerous because they move far inland.
Figure E.2.4.6 – Tsunamis cause damage to coastal communities.
Figure E.2.4.7 – Widespread flooding occurs after a tsunami reaches land.
The Biggest Waves
A tsunami is an abnormally large ocean wave. Tsunami is a Japanese word that means “harbor wave”. Earthquakes or underwater landslides in the ocean cause tsunami waves. It is difficult to sense tsunami waves in the deep open ocean. When the ocean becomes shallow near shore, the water rises up to form a huge wave that can travel far inland. Tsunamis usually consist of a series of several massive waves.
Some destructive tsunamis have occurred in recent years. In 2004, an earthquake off the coast of Sumatra, Indonesia, caused tsunami waves on coasts around the Indian Ocean. This tsunami destroyed buildings in many communities. Many countries around the Indian Ocean did not have tsunami warning systems, which led to the deaths of 230 000 people.
In 2011, a massive offshore earthquake in Japan caused a huge tsunami. Some tsunami waves were 40 meters high and travelled 10 kilometers inland. This tsunami damaged the Fukushima nuclear power plant, causing harmful radioactive substances to leak into the Pacific Ocean.
While scientists can’t predict the timing of earthquakes, they can predict tsunamis. Tsunami waves travel at a speed of 800 km/h. After scientists record an ocean earthquake, they can calculate the time that tsunami waves will reach different shorelines and warn people in advance.
There are some natural warning signs of an approaching tsunami. If you are close to the ocean and experience a large earthquake, a tsunami wave can arrive in 10 minutes. If you are on the beach and suddenly see all the water suddenly being sucked out to sea, a tsunami wave will arrive shortly. In both cases, you should run to higher ground immediately. If you visit or live in a tsunami zone, such as on the Pacific coast of British Columbia, you should be aware of the local tsunami evacuation routes.
A tsunami is an abnormally large ocean wave. Tsunami is a Japanese word that means “harbor wave”. Earthquakes or underwater landslides in the ocean cause tsunami waves. It is difficult to sense tsunami waves in the deep open ocean. When the ocean becomes shallow near shore, the water rises up to form a huge wave that can travel far inland. Tsunamis usually consist of a series of several massive waves.
Some destructive tsunamis have occurred in recent years. In 2004, an earthquake off the coast of Sumatra, Indonesia, caused tsunami waves on coasts around the Indian Ocean. This tsunami destroyed buildings in many communities. Many countries around the Indian Ocean did not have tsunami warning systems, which led to the deaths of 230 000 people.
In 2011, a massive offshore earthquake in Japan caused a huge tsunami. Some tsunami waves were 40 meters high and travelled 10 kilometers inland. This tsunami damaged the Fukushima nuclear power plant, causing harmful radioactive substances to leak into the Pacific Ocean.
While scientists can’t predict the timing of earthquakes, they can predict tsunamis. Tsunami waves travel at a speed of 800 km/h. After scientists record an ocean earthquake, they can calculate the time that tsunami waves will reach different shorelines and warn people in advance.
There are some natural warning signs of an approaching tsunami. If you are close to the ocean and experience a large earthquake, a tsunami wave can arrive in 10 minutes. If you are on the beach and suddenly see all the water suddenly being sucked out to sea, a tsunami wave will arrive shortly. In both cases, you should run to higher ground immediately. If you visit or live in a tsunami zone, such as on the Pacific coast of British Columbia, you should be aware of the local tsunami evacuation routes.
Watch More
Tsunamis
This video explains how tsunamis are caused.
This video explains how tsunamis are caused.
These two videos show some tsunamis and explain how scientists study tsunamis.
Figure E.2.4.8 – It is dangerous to swim at beaches with rip currents.
Figure E.2.4.9 – Rip currents move in the opposite direction to surf waves.
Figure E.2.4.10 – To escape a riptide, stay calm and swim sideways out of the outflow.
Rip currents are also called riptides, but they are not actually tides. When waves break on a beach, the wave water sometimes flows into a low spot, and back out into the ocean. This outward flowing water is a rip current.
Rip currents are dangerous because they can carry people far out to sea. Rip currents often move faster than a person can swim. Weak swimmers who get caught in a rip current risk drowning far from shore. Strong swimmers can sometimes exit a rip current by swimming parallel to the shore, out of the current.
Rip currents can be hard to spot. Sometimes they appear as a break in the waves. It is dangerous to swim on a beach that warns of rip current danger, especially when there is no lifeguard present.
Watch More
Rip Currents
Watch this video to learn more about rip currents.
Watch this video to learn more about rip currents.
Connections
Figure E.2.4.11 – Surfing is a popular ocean sport.
Figure E.2.4.12– Waves carry surfers to shore.
Figure E.2.4.13 – Even dogs can catch a wave on a surfboard. Photo by Frank Kovalchek.
>> Catching a Wave
Surfing is a popular ocean sport. Surfers balance on a surfboard while they are pushed towards shore by a wave.
Experienced surfers enjoy the challenge of surfing on large, fast, curling waves. Waves curl when the ocean quickly becomes shallow near shore. Friction between the water and the ocean floor causes the bottom of a wave to slow down. The top of the wave keeps moving faster and further ahead than the bottom. This makes the wave curl over and crash.
To catch a wave, a surfer paddles out to sea on their surfboard. They look for a wave swell and start paddling into shore, so they can travel in sync with the wave. The surfer then stands up and shifts their weight on the surfboard to stay balanced as they ride the wave into shore.
Watch More
Surfing
How do massive surf waves form? Watch this video to learn more.
How do massive surf waves form? Watch this video to learn more.
Figure E.2.4.14 – Tide pools form in rock depressions at low tide.
Figure E.2.4.15 – Interesting marine organisms live in tide pools.
Figure E.2.4.16 – Sea anemones live in tide pools.
Tide Pools
Tide pools form when an outgoing tide leaves behind saltwater puddles in rocks. Tide pools are a difficult habitat for most marine organisms because their conditions are constantly changing. Water moves in and out of tide pools several times each day. When the tide goes out, the Sun quickly heats up the water in a tide pool. This heat also causes water to evaporate from the tide pool, increasing its salinity.
Despite these extreme living conditions, some organisms thrive in tide pools. Sea stars, sea anemones, barnacles, and mussels all cling to the rocks in tide pools.
Tide pools form when an outgoing tide leaves behind saltwater puddles in rocks. Tide pools are a difficult habitat for most marine organisms because their conditions are constantly changing. Water moves in and out of tide pools several times each day. When the tide goes out, the Sun quickly heats up the water in a tide pool. This heat also causes water to evaporate from the tide pool, increasing its salinity.
Despite these extreme living conditions, some organisms thrive in tide pools. Sea stars, sea anemones, barnacles, and mussels all cling to the rocks in tide pools.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit E Lesson 4 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
More large storms occur in the winter. Large storms have fast winds, which create bigger ocean waves. Larger waves create faster, more desirable surfing rides.
Tsunami waves are caused by underwater earthquakes or landslides that transfer large amounts of energy to deep ocean water. Large storm waves are caused by strong winds transferring energy to the surface water of the ocean.
Tide times are determined by the positions of the Moon and Sun relative to Earth. The Moon has a predictable orbit around Earth, which enables us to make accurate predictions about tide times. The timing of surface waves cannot be predicted,
because surface waves are dependent on wind and weather patterns, which change every day.
You would expect to see the tide go out further than usual, in a spring tide. During a full moon, the Moon, Earth, and Sun line up in a row. This creates a larger gravitational pull and a larger tidal range.
Waves in the ocean travel long distances. Waves can be created by wind far away from shore, and travel through the ocean to crash on the shore, even on still days.