Convective cooling cools rocks much more rapidly than heat conduction. hydrothermal circulation represents convective cooling at
ocean ridges and is well known from things like black smokes, but only occurs close to the spreading ridge axis. when geophysicists measure the geothermal gradient in areas along ridges where there is no hydrothermal activity, the thermal gradient is far below what you would predict theoretically, but near hydrothermal vents it is far more than you would predict. why would this be?
When geophysicists measure the geothermal gradient in areas on the ridges where there is no activity hydrothermally, the gradient is far below than what is predicted theoretically, but when measured near hydrothermal vents it is more than what is predicted. This is because most of the heat is being carried through convection by hydrothermal systems so that the average gradient when measured far from the circulation would be depressed or lower.
The speeds of sound depend upon the temperature of the medium. As the temperature increased in the afternoon, the speed of sound increases. Then the time taken by reflected sound will be less than 0.1 sec in the afternoon. And to hear an echo the time gap between an original sound and reflected sound must be at least 0.1 sec. That is why the student could not hear the echo at all in the afternoon.
