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Supported by Trinity House

When tides collide

Find out what makes the highest high and the lowest low in this game of tidal flow.
Plan a session with this activity

You will need

  • A4 paper
  • A4 card
  • Pens or pencils
  • Acetate sheets or old plastic wallets
  • Marker pens
  • Paper fasteners
  • Length of rope (optional)
  • Cookies (optional)
Spring and neap tides template
PDF – 88.8KB

Before you begin

  • Check out this info from National Geographic to get a quick overview of the topic of tides.
  • The following instructions involve using the ‘Spring and neap tides template’ to make a model, but you could also make a similar template from scratch.

 

Make a model system

  1. Explain to everyone that they’ll be making a model of the tidal system on Earth. Give out the templates you’ve made, or the ‘Spring and neap tide templates’, if you’re using these. Everyone will need craft materials too. Cut out the Earth and draw a little person on the circumference. This will be the point from which you’ll be seeing the tides.
  2. Cut out the rectangle showing the moon and its tidal effects. Use a paper fastener to attach the Earth to the cross marked on the moon template.
  3. Rotate the Earth and see how the tides ebb and flow during the day. Have everyone imagine they’re standing where they drew the person. They should see a high and a low tide twice a day.
  4. Cut out the rectangle showing the sun and its tidal effects. Use a paper fastener to carefully attach it underneath your Earth and moon, using the cross as a guide.
  1. Keep the sun card still and rotate the moon to see the effects of the tides again. When the sun and moon are in line with each other, the effects will add together and the result is the two highest high tides of the month. These are the spring tides.
  2. Rotate the moon, so that it’s at a right angle to the sun. The sun and moon’s gravity will cancel out and the result is the smallest difference between high and low tide. These are the neap tides.
  3. Get a sheet of paper, place it underneath the model and mark out the position of the moon for the spring and neap tides.
  4. See if you can work out which phases of the moon would be visible for each spring and neap tide and draw the phase onto the paper where you marked the moon.

Act it out

  1. Explain that as a group you’ll now be making a moving picture of the tides. Everyone should get into a big circle and join hands. Ask for a volunteer from the group to stand in the middle to act as ‘Earth’.
  2. Explain that the rest of the group will act as the sea. The further away from the Earth they are, the higher the tide is on that side of the Earth.
  1. When the person leading the activity calls ‘flow’, everyone should step as far away from the ‘Earth’ as they can, still keeping hold of the person next to them. This is the high tide.
  2. Call ‘ebb’ and everyone should step as close to the ‘Earth’ as they can – this is the low tide. Have a couple of goes until everyone understands what we mean by tidal ebb and flow.
  1. Everyone should start in a circle, at an equal distance from the ‘Earth’. Ask another person to volunteer to be your ‘moon’ and stand at one end of the space. Explain that the moon’s gravity will affect the tide on Earth. Ask everyone on the side closest to your ‘moon’ to take two big steps towards it, still holding hands. The Earth should also take one step towards the moon.
  1. See what the tides look like now and where the sea is highest and lowest. It won’t be the same on different sides of the earth. Ask the ‘Earth’ to spin around on the spot, like it would over the course of a day. They should call out whether they see high or low tide and see how the tide ebbs and flows from high to low and back again. As the Earth rotates during one day, it should see two high and two low tides.
  2.  Now ask the ‘moon’ to circle the space and orbit your ‘Earth’. Everyone holding hands and acting as the sea should move with the moon to show how the tide would ebb and flow during a month.
  3. The sun’s gravity also affects the tide, so ask for one more volunteer to stand at one end of the space and act as your ‘sun’. To start, make sure the ‘sun’ and ‘moon’ are in line with each other.
  4.  Explain that like the moon, the sun’s gravity also affects the tides, but it’s only about half as strong. Repeat the action from step 5 to show the moon’s effect, then ask everyone closest to the sun to take an extra half a step forward.
  1. Try again with your ‘sun’ at a right angle to your ‘moon’. Get everyone to show the effect of the moon and sun’s gravity again. This time, you should notice that the high tide is made lower by the effect of the sun, which is pulling the sea in another direction. This is known as the neap tide.
  2.  Have some fun and see if everyone can follow the movement of both the ‘moon’ and ‘sun’ as they move around the space. See if the group can work out the best positions for the sun and moon to make the highest high tide, the lowest low tide, or the smallest difference between high and low tide.

Reflection

In this activity, everyone needed to work closely and coordinate their movements to get an accurate picture of the tides around the world. See how everyone found this experience. Did anyone find it easier or more difficult being joined together to complete the task? This activity is a great way to show that when you’re working in a team, one person’s actions can have a big impact on the group as a whole.

Did the group manage to have a go with both your ‘moon’ and ‘sun’ moving around the space at the same time? It’s a lot to think about, so clear communication was important too. Everyone needed to talk to each other so that they all moved the correct way at the right time. See if anyone has any tips to share with the group on what they’ve learned about working together in this activity.

Safety

Scissors

Supervise young people appropriately when they’re using scissors. Store all sharp objects securely, out of the reach of young people

All activities must be safely managed. Do a risk assessment and take appropriate steps to reduce risk. Always get approval for the activity and have suitable supervision and an InTouch process.