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Student Activity - Multibeam
Activity
How can we make a map of the sea floor that is kilometres below the surface of the water and that we can not see? Scientists on board the Tangaroa are tackling this challenge using technology called the ‘multibeam’. The multibeam measures the time it takes for a sound signal to reach the bottom of the sea floor and come back again, and from this it measures the water depth.
This activity allows you to build your own ‘sea floor’ and then simulate being in a boat and using the principle behind the multi-beam to determine if you can create a map of the sea floor.
Instructions
Materials
- cardboard box (such as a photocopy paper box)
- two sheets of cardboard cut the same size as the box (or two box lids)
- polystyrene or similar foam like structure
- dowel wood (height of the box plus 5 centimetres)
- ruler
- permanent marker pen
- paper
Instructions
- Cut the polystyrene into several square pieces and glue them to the cardboard. Make sure that you ‘build’ an uneven seafloor with mountains.
- On one of the cardboard sheets draw up a grid of 5x5 cm squares and punch holes big enough to allow the dowel to pass through in each square corner.
- On the second cardboard sheet draw up a grid of 2x2 cm squares and again punch holes in each corner.
- Prepare a template for each box lid. For this use two sheets of paper and draw the two grids (5x5 cm and 2x2 cm). These templates will be used to map your readings. You may find it easier to label each box lid with a number, name or symbol.
- Using a ruler and pen, mark the doweling rod every 1 cm from the bottom of the rod
- Label the doweling marks starting from the bottom in 0.7 intervals (0.0 is the end of the rod, 1 cm=0.7, 2 cm=1.4, 3 cm=2.1 etc.).
- Each of these numbers represents the time it takes to reach the seafloor and back to the surface, with each centimetre equalling 0.7 seconds (round trip) with equals approximately 500 metres.
- Follow the 'Multibeam sea floor survey' worksheet instructions to create a substrate map.
