The term EARTH'S ___ LAYER is referring to the OZONE layer, which is a layer of gas in the Earth's atmosphere that absorbs most of the sun's ultraviolet radiation. It is composed of OZONE molecules and is located between 10 and 50 kilometers above the Earth's surface. The answer to this crossword puzzle is OZONE, which is a molecule made up of three oxygen atoms. The OZONE layer is important for protecting life on Earth from the harmful effects of UV radiation.