What is the innermost layer of the atmospherewhat is the innermost layer of the atmosphere extending 17 km above sea level at the topics and about 7 km above the earth's north and south poles

The innermost layer of the atmosphere is TROPOSPHERE.

Explanation:

Atmosphere - The gaseous  surroundings of earth is known as atmosphere. On the basis of variations in temperature, atmosphere has several layers as follows-

Troposphere- It is the innermost layer of the earth. extending 17 km above sea level at the  equator and about 7 km above the earth's poles.Weather phenomenon occurs in this layer.It is known as troposphere because of vigorous air current.

Stratosphere- It is the second layer above troposphere.It extends approx  50 km above the earth surface.Ozone is also found in this layer. ozone plays very important role in maintaining thermal balance.

Mesosphere- It is the third layer of earth surface.Extending approx 50 to 85 km above the earth.Here temperature remains low.And at the top of this layer i.e, mesopause has the coldest temperature.

Thermospher- Temperature in this region is slightly high because  of absorption of solar light.

Exosphere- It is the outer most layer of earth. Any particle or object in this layer if moving very fast can escape to the space. The exopause boundary of exosphere is approx 250-500 km above the surface. This is the transition layer between earth atmosphere and space