In the schematic, line P shows a 1-D geothermal profile. If the heat flow at the base of the mantle increases, which line will reflect the new geothermal profile?
Show Hint
When basal heat flow increases, the geothermal gradient becomes steeper, and the temperature at a given depth increases. Look for a geothermal profile shifted rightward.
Step 1: Understand the geothermal profile.
The geothermal profile shows how temperature increases with depth. Line P represents the current geothermal gradient. If the heat flow at the base of the mantle increases, more heat is being supplied from deeper regions. Step 2: Interpreting the effect of increased basal heat flow.
An increase in heat flow from the base leads to a steeper temperature gradient in the mantle. That means the temperature rises more rapidly with depth. On the graph, this would be represented by a geothermal profile that is shifted to the right (i.e., higher temperatures at the same depth). Step 3: Choosing the correct profile.
Among the profiles shown:
Line Q lies to the right of P, indicating a higher temperature at depth,
Lines R and S lie to the left of P, suggesting lower temperatures.
Thus, line Q correctly reflects the increased temperature gradient due to higher basal heat flow.
