<P> Earth 's atmosphere consists of a number of layers that differ in properties such as composition , temperature and pressure . The lowest layer is the troposphere , which extends from the surface to the bottom of the stratosphere . Three quarters of the atmosphere 's mass resides within the troposphere , and is the layer within which the Earth 's terrestrial weather develops . The depth of this layer varies between 17 km at the equator to 7 km at the poles . The stratosphere , extending from the top of the troposphere to the bottom of the mesosphere , contains the ozone layer . The ozone layer ranges in altitude between 15 and 35 km , and is where most of the ultraviolet radiation from the Sun is absorbed . The top of the mesosphere , ranges from 50 to 85 km , and is the layer wherein most meteors burn up . The thermosphere extends from 85 km to the base of the exosphere at 690 km and contains the ionosphere , a region where the atmosphere is ionised by incoming solar radiation . The ionosphere increases in thickness and moves closer to the Earth during daylight and rises at night allowing certain frequencies of radio communication a greater range . The Kármán line , located within the thermosphere at an altitude of 100 km , is commonly used to define the boundary between Earth 's atmosphere and outer space . The exosphere begins variously from about 690 to 1,000 km above the surface , where it interacts with the planet 's magnetosphere . Each of the layers has a different lapse rate , defining the rate of change in temperature with height . </P>
<P> Earth 's atmosphere consists of a number of layers that differ in properties such as composition , temperature and pressure . The lowest layer is the troposphere , which extends from the surface to the bottom of the stratosphere . Three quarters of the atmosphere 's mass resides within the troposphere , and is the layer within which the Earth 's terrestrial weather develops . The depth of this layer varies between 17 km at the equator to 7 km at the poles . The stratosphere , extending from the top of the troposphere to the bottom of the mesosphere , contains the ozone layer . The ozone layer ranges in altitude between 15 and 35 km , and is where most of the ultraviolet radiation from the Sun is absorbed . The top of the mesosphere , ranges from 50 to 85 km , and is the layer wherein most meteors burn up . The thermosphere extends from 85 km to the base of the exosphere at 690 km and contains the ionosphere , a region where the atmosphere is ionised by incoming solar radiation . The ionosphere increases in thickness and moves closer to the Earth during daylight and rises at night allowing certain frequencies of radio communication a greater range . The Kármán line , located within the thermosphere at an altitude of 100 km , is commonly used to define the boundary between Earth 's atmosphere and outer space . The exosphere begins variously from about 690 to 1,000 km above the surface , where it interacts with the planet 's magnetosphere . Each of the layers has a different lapse rate , defining the rate of change in temperature with height . </P>
what term do we use for the lowest layer of the atmosphere
what term do we use for the lowest layer of the atmosphere
troposphere
troposphere