Section II Question 28 from the 2002 HSC Examination
Summary: (a) Describe Earth’s current magnetic field. Using a diagram of magnetic anomalies of the oceanic crust, explain the origin of the pattern on either side of the mid-ocean ridge. (b) Recount the steps involved in gravity data reduction. Using a diagram of the surface height and gravity anomaly curve in a region, propose reasons for the difference in anomaly at two marked locations. Predict the variation in orbital path for a satellite moving West to East across the region. (c) Using a graph of travel time for P and S waves, at different surface distances from an earthquake epicentre, contrast the properties of P and S waves; account for the absence of S waves at distances greater than 11 000 km from the epicentre, and assess the application and advantages of geophysical methods in mineral exploration.