|When working in the upper crust the maximum thermal gradient is generally assumed to be vertical. Direct measurement of underground temperature requires that a temperature-measuring device be lowered down a borehole. For the deep oceans, instruments take the form of thermistor-lined probes that penetrate the soft sediment on the sea floor. Near-surface temperature profiles record changes in surface temperature as deviations from equilibrium gradients. These deviations can be inverted to reconstruct the recent climatic history of the region.|
Colour versions of some of the figures from Chapter 3. Click on the figure for a larger version.
Figure 3.4. A cut-away view of a Bullard-type heat flow probe, showing thermistors positioned in contact with the steel casing. Thermistors are generally spaced about 25cm apart.
Figure 3.5. A cut-away view of a Ewing-type heat flow probe. Thermistor spacing is usually about 25cm.
Figure 3.6. A cut-away view of a Lister ‘violin bow’ heat flow probe (Horizontal scale expanded on inset).
Figure 3.12. Average sea surface temperature model (C). Modified after Boville and Gent(1998).