Figure 2.10. Lava Color Temperature. The photograph is of lava flowing out from under the 3-cm-thick black, glassy crust of a pahoehoe flow from the Kilauea volcano on Hawaii. The field of view is approximately 1 m across. Standing next to it you can tell that basalt magma is hot, but how hot is it really? The color of the lava is a pretty good indicator of temperature. The higher the temperature, the more rapidly the atoms in the lava vibrate. Acceleration of charged particles and dipole oscillations caused by the atom movements produce thermal radiation. Most of the thermal radiation is infrared, but some is visible with colors that vary with temperature as approximated in the color bar (see Gavrin and Novak.) Blacksmiths use the color of hot metal as a guide to their work (see a blacksmith color guide).
