i think is most likely the answer
together with the crust, we call it the lithosphere. below the lithosphere is a layer of upper mantle called the asthenosphere. this is made up rock that is fluid and can move. it is this fluidity that powers the movement of the tectonic plates of the earth's crust.
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if you are not aware what emissivity is defined as the ratio of the energy radiated from a material's surface to that radiated from a blackbody (a perfect emitter) at the same temperature and wavelength and under the same viewing conditions. it is a dimensionless number between 0 (for a perfect reflector) and 1 (for a perfect emitter).
it is the measure of how an object radiates heat.
the higher the emissivity “ε” the higher the temperature it emits. the perfect emitter of heat is called a “black body.”
a black body has an emissivity ε measure of 1.
for the emissivity of
therefore, water would emit more heat than of the sand.