As indicated in one of my posts the atmosphere is a mixture
of nitrogen (78%), oxygen (21%), and other gases (1%) that surrounds Earth.
High above the planet, the atmosphere becomes thinner until it gradually
reaches space. It is divided into five layers. It is thickest near the surface
and thins out with height until it eventually merges with space. Most of the
weather and clouds are found in the first layer.
The atmosphere is an important part of what makes Earth livable.
It blocks some of the Sun's dangerous rays from reaching Earth. It traps heat,
making Earth a comfortable temperature. And the oxygen within our atmosphere is
essential for life.
The 5 layers are:
·
TROPOSPHERE
·
STRATOSPHERE
·
MESOSPHERE
·
THERMOSPHERE
·
EXOSPHERE
TROPOSPHERE
It is the first layer above the surface of the Earth.
Weather occurs in this layer. The troposphere starts at Earth's surface and
goes up to a height of 12 km ( 7 miles) above sea level. Most of the mass
(about 75-80%) of the atmosphere is in the troposphere. The troposphere is the
lowest layer
of Earth's atmosphere.
STRATOSPHERE
The stratosphere is
the second layer, as one moves upward from Earth's surface of the atmosphere.
The stratosphere is above the troposphere
and below the mesosphere.
Many jet aircrafts fly in the stratosphere
because it is very stable. The top of the stratosphere occurs at 50 km (31
miles) altitude. Ozone,
an unusual type of oxygen
molecule that is relatively
abundant in the stratosphere, heats this layer as it absorbs energy from
incoming ultraviolet
radiation from the Sun. Temperatures
rise as one moves upward through the stratosphere. This is exactly the
opposite of the behavior
in the troposphere in which we live, where temperatures
drop with increasing altitude.
MESOSPHERE
The mesosphere is
above the stratosphere
layer. The layer above the mesosphere is called the thermosphere.
The mesosphere starts at 50 km (31 miles) above Earth's surface and goes up to
85 km (53 miles) high. Meteors or rock fragments burn up in the mesosphere.
THERMOSPHERE
The space
shuttle and the International
Space Station both orbit Earth within the thermosphere The thermosphere is
directly above the mesosphere
and below the exosphere.
It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to 621
miles) above our planet. Much of the X-ray
and UV
radiation from the Sun is absorbed in the thermosphere. The auroras (the Southern and Northern Lights)
primarily occur in the thermosphere. Charged particles (electrons, protons, and
other ions) from space collide with atoms and molecules in the thermosphere at
high latitudes, exciting them into higher energy states. Those atoms and
molecules shed this excess energy by emitting photons of light, which we see as
colorful auroral displays.
EXOSPHERE
The atmosphere merges
into space in the extremely thin exosphere.
This is the upper limit of our atmosphere. The exosphere
is almost a vacuum. The "air" is very, very thin there. When air is
thin, it doesn't transfer much heat to objects in the air, even if the air is
very, very hot. The region where atoms and molecules escape into space is
referred to as the exosphere. The exosphere is on top of the
thermosphere. It extends from
the exobase, which is located at the top of the thermosphere
at an altitude of about 700 km above sea level, to about 10,000 km
(6,200 mi; 33,000,000 ft.).
Between the
layers there are boundaries. The boundaries are the tropopause, top of the
troposphere; the stratopause, top of the stratosphere; the mesopause, the top
of the mesosphere; the exobase, the top of the thermosphere.
Within the 5
layers there are secondary layers. Some of them are- ozone layer, ionosphere,
homosphere and heterosphere.
The Earth’s atmosphere, commonly called air, is not a vast homogeneous
expanse. It is layered. It has 5 layers. The atmosphere has been so layered as
to make the Earth livable. The first layer, from the surface of the Earth, the troposphere,
makes 75-80% of the mass of the whole atmosphere. The exosphere, the upper
limit of our atmosphere merges into space. The troposphere is where you and I
hang out; that is where humans hang out. Humans are tied to the troposphere.
Reference:
windows2universe.org
en.wikipedia.org
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