The diagram shows a research vessel using a fluxgate magnetometer to map an underwater volcanic rock formation. The instrument is towed behind the vessel, a...
Question 1 Report
The diagram shows a research vessel using a fluxgate magnetometer to map an underwater volcanic rock formation. The instrument is towed behind the vessel, away from the steel hull. It records small changes in magnetic field strength as the boat travels at constant speed. Basalt formed at different times can contain magnetic minerals. The scientist compares the readings with the Earth's background magnetic field to locate bands of rock with different magnetic properties.
(a) What does the magnetometer measure? [1]
(b) Which material in the ship could affect the readings if the instrument were too close to it? [1]
(c) When the instrument passes over strongly magnetic basalt, what happens to the reading? [1]
(d) Sketch why the instrument is towed behind the vessel rather than beside its steel hull. [1]
(e) What magnetic feature of Earth provides the background field? [1]
(f) Which control helps make distance on the map match time in the results? [1]
Answer Details
(a) The magnetometer measures magnetic field strength, or magnetic flux density [1].
(b) Iron or steel in the ship could affect the readings [1].
(c) Over strongly magnetic basalt, the reading changes from the background value, increasing or decreasing depending on the rock’s magnetic field direction [1].
(d) The instrument is towed behind because the steel hull has its own magnetic effect, which would distort the reading [1].
(e) Earth’s magnetic field provides the background field. Earth behaves approximately as a giant magnet [1].
(f) Keep vessel speed constant [1], so equal time intervals correspond consistently to distance travelled on the map.
Download The App On Google Playstore
Everything you need to excel in your exams
