Bathymetry is the study of the ocean floor. And it creates a lot of maps! These maps record the changing depths of the ocean and are often beautiful to look at. Why not make your own?

Concentric coloured blobby shapes.

You will need

  • Notebook with blank pages
  • Pencil
  • Scissors
  • 10 coloured pencils or markers


Handle scissors with care.

What to do

  1. Open your notebook and turn 9 pages. The blank page on the left will make the bottom of your map.

    Spiral bound notepad open with blank pages.
  2. In the centre of this blank page, draw a blobby shape about 4 centimetres in diameter. It doesn’t have to be exact.

    Small blobby shape drawn on left page of an open spiral bound notepad.
  3. Cut out your newly drawn shape. You will need to start at the page’s edge and cut into the paper until you get to the shape. It’s okay if you can’t cut it out perfectly.

    Cutting page with scissors.
  4. Lie the notebook down again and make sure the page you just cut is on the left. Trace the cut-out shape onto the paper below.

    Tracking the blobby shape onto the next page.
  5. Turn back one page so the hole is now on the right, and there’s a traced outline on the left page.

    Open spiral bound notepad with blobby shape on left page and cut out blobby shape on the right.
  6. On the left page, draw a larger shape around the traced outline. Your new shape should not cross the old shape. Try varying the distance between the new shape and the old shape. You can also exaggerate the curves of the old shape in the new shape.

    Two blobby shapes, one drawn inside the other.
  7. Repeat steps 3-6 until you have at least 5 pages with shapes cut out.

    Many concentric blobby shapes cut out on subsequent pages.
  8. Time to add colour! Pick as many markers or coloured pencils as you have cut-outs. Arrange them in the order you’d like the colours to appear. We made a rainbow starting with purple.

    6 different coloured marker pens.
  9. Turn all the way to your first cut-out shape. It should be on the right side of the notebook.

    Cut out blobby shapes in the notebook.
  10. Lightly trace the shape onto the page below. This will show you where to colour in.

    Tracing the cut out shape on the page below.
  11. Turn the page so you can see your new trace and colour it in with your preferred marker. The colouring in should be messy and outside the lines! If you’re using markers, rip out and put a page or two underneath the page you’re colouring to prevent the colour from bleeding.

    Colouring the traced shape with purple marker pen.
  12. Flip back two pages so you can see two uncoloured pages on the right side.

    Coloured blob viewed through bigger cut out blob.
  13. Repeat steps 10-12 until all your pages with cut-outs are coloured in. Voila! You’ve made a seafloor map.

    Concentric coloured blobby shapes.

What’s happening

What lies beneath the waves? Just as land has peaks and valleys, the ocean floor has many variations, too. This includes mountains, volcanos, trenches, and even shipwrecks! The variations we see on land are called topography but the variations underwater are called bathymetry. Bathymetry comes from Greek words “bathus” meaning deep and “metry” meaning measure. People who study bathymetry make beautiful maps, much like the one you just created!

Colourful concentric shapes mapping an underwater volcano, each colour representing a different depth of water.

A beautiful bathymetric map of the underwater Ruby volcano

Credit: NOAA, Public domain, via Wikimedia Commons

Bathymetric maps are very colourful, for good reason. Each colour represents a different depth of water, so dark blues and purples might be deep trenches, while underwater mountains appear orange or red. In your model, you can see how different colours represent deeper and deeper layers in your notebook. With a real bathymetric map and a notebook, you can make a 3D model of the real ocean floor!

We still don’t know much about the ocean floor. Although some areas are shallow and near to a harbour, most of the ocean is hundreds of kilometres from shore, and thousands of metres deep. We can use satellites to scan the ocean floor from space, but this can only spot enormous features, like entire mountain ranges. Only now are we starting to develop the technology needed to map the ocean floor in great detail.

Real-world bathymetry

CSIRO’s research vessel, RV Investigator carries a cutting-edge bathymetry machine. And it has a really cool name: multibeam echosounder! As the name suggests, the device aims multiple sound waves at the ocean floor and listens for their echoes. While listening, the device measures the time it takes for the sound to bounce off the bottom of the ocean and travel back to RV Investigator. A longer time means a deeper part of the ocean floor. As the ship travels, the device creates a detailed bathymetry map of the ocean floor below.

Measuring the ocean floor is helping many kinds of scientists answer new questions. For example, RV Investigator recently helped marine archaeologists identify a shipwreck. Climate scientists on RV Investigator mapped the ocean floor to better understand ocean currents. They will use bathymetry to ask whether the shape of the ocean floor impacts currents and therefore the temperature of Antarctica. The scientists hope their study will allow governments to make better decisions on climate change. Not bad for an underwater map!

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