The region of warm air over a city where temperatures are higher than in surrounding rural areas. It was the era of the steam engine, cotton gin, sewing machine, paper, telegraph, and railroad, and it saw the beginnings of many of our present industries. The process of checking, observing, or keeping track of something for a specified period of time or at specified intervals. Non-renewable resources can be used up completely or else used up to such a degree that it is economically impractical to obtain any more of them. Fossil fuels are examples.
Ozone absorbs much ultraviolet radiation and prevents it from reaching the Earth.
A layer of permanently frozen soil and rock. The active layer refers to that portion of the ground that freezes in winter and thaws in summer, usually less than 1 m in depth. The plant community in marine and freshwater situations that floats free in the water and contains many species of algae and diatoms. Any and all forms of water, whether liquid or solid, that fall from the atmosphere and reach the Earth s surface. A day with measurable precipitation is a day when the water equivalent of the precipitation is equal to or greater than 0.2 mm.