Refresh your memory of the White Mountain scene, as recalled here in a color composite.
Three broad geological categories dominate the scene: dark volcanics, alteration products derived from these, and the limestone mountain. The Landsat thermal Band 6 image greatly simplifies the apparent scene content.
The warmest areas (shown in lighter tones in keeping with the convention that hot areas display in whites and light grays, and cold areas are in dark tones) are from the volcanics, most of which are dark basalts. These rocks are imperfect black bodies that absorb much of the solar radiation and re-emit it as strong radiators. The altered zones appear mostly in dark tones, implying that they absorb less solar energy, so that they have lower radiant temperatures. The limestones, in the field grayish surfaces with superficial brownish-red alteration, appear as moderately light tones, which are hard to distinguish from the volcanic expressions.
For experimental reasons, operators activate Thematic Mapper Band 6 on Landsat occasionally at night to obtain thermal images. One example, a full scene acquired at 9:32 P.M. on August 22, 1982 shows the familiar east half of Lake Erie (left lake), and the western part of Lake Ontario (top lake).
The land appears moderately cool (darker tones), with little detail, although the cities of Buffalo, NY (east tip of Lake Erie), and Toronto (top center) and Hamilton, Ontario (west end of Lake Ontario; locally hot because of steel mill effluents) may be discernible on a computer monitor from street patterns and slightly lighter (warmer) tones. A mottled pattern of variably warmer bands characterizes Lake Ontario. These bands relate to thermal overturning effects (thermoclines), which are possible in this deeper (237 m [777 ft]) lake. Lake Erie is uniformly "hot" because its shallowness (less than 67 m [220 ft]) inhibits this type of circulation. Warm rivers, such as the Niagara connecting the two lakes, stand in contrast to the land.