How can we use echoes?
A survey boat travels over the area where they are looking for gas. The boat pulls some equipment behind it that makes a loud 'bang'. It also tows a collection of special underwater microphones, called hydrophones. These hydrophones detect the echo bouncing back from the layers of rock.
The boat needs to sail across the area being investigated several times to build up a picture that the special scientists, called geologists, can study to look for the rock shapes.
It is important to know exactly where the boat is, so global positioning satellites (GPS) are used. This is also the system used for satellite navigation in cars.
