The Atmosphere

Our Atmosphere is a wonderful thing.  The atmosphere creates weather, provides us with protection from the sun, and is the reason for the wonderful Northern Lights.  Face it, without an atmosphere life on Earth couldn't exist.  But what exactly is the atmosphere?  And what are all those layers about, it's not like the atmosphere is a giant cake or something!  Well lets just hold off on the cake thing for a little while and focus on the first half of this query.  What is the atmosphere.


The atmosphere is a collection of gasses that surrounds the Earth like a blanket.  What gasses are in the atmosphere you ask?  Well you may be surprised that the atmosphere is mostly Nitrogen (N).  In fact it is almost 79% Nitrogen.  Then comes Oxygen (O) at around 20%.  So what about all the horrible Carbon Dioxide (CO2) that causes global warming?  That's only about 0.04% of our atmosphere.  Even Water Vapor makes up more of the atmosphere, about 1% to be more exact.

These gasses all play a very important role in providing a safe and sustainable place for life to form.  Without Carbon Dioxide the plants and trees could not exist.  Without the plants and trees making oxygen we could never exist.  There are 3 primary stages in the formation of our atmosphere.  The first stage would have been a basic "outer space" layer.  This first layer would have been mostly Hydrogen (H) and wasn't very useful in protecting our planet.

The second version was formed primarily by volcanoes.  The volcanoes that exist on a much hotter Earth (See primitive Earth coming soon) spewed out tons and tons of Carbon Dioxide.  In addition to the volcanoes the Earth was being bombarded by asteroids.  This set the stage for the first 'real' atmosphere to be formed.  This version contained much more carbon dioxide then today, but it also held a much more important nitrogen.  Since the nitrogen didn't freely float away it helped to start shielding the Earth from the space.

The third and final version of our atmosphere includes oxygen.  This oxygen is the result of life on Earth, primarily started by algae in the vast oceans.   The algae uses photosynthesis to make food.  As you may remember from biology class plants used photosynthesis to take in Carbon Dioxide and release Oxygen.  As the atmosphere gained oxygen it became more and more like we know it toady.  Weather events were born, and life was able to evolve and expand.


So now that the boring history lesson is over lets talk about something more interesting...cake.

Sorry about that...So you have an idea of what the atmosphere is made of.  Let's consider those elements the makings of a cake.  Nitrogen is like Flour.  And Oxygen is your Sugar.  Water Vapor can be the Vanilla Extract, and Carbon Dioxide is your...mmmm cake...I mean your cocoa powder.  So why I am prepping you to think cake?  Because I think cake is a great way to think about the layers of the atmosphere!

The atmosphere is broken down into 4 layers (much like a cake).  Each of these layers is very specific in its temperature gradient, distance from the Earth, and its role in making our atmosphere sustain life.  For the rest of this explanation I am going to cake flavors to help guide you in your wondrous (educational) journey.



Lets start with the base of our cake, the Earth's Surface.  Think of the surface as the plate in which we will build our cake.  Yes I know the surface of Earth is very uneven, but compared to the thickness of our layers, it is hardly worth worrying about.  On our plate lets add the first layer of cake.  The Troposphere, lets call it the Chocolate Layer.

The Troposphere is were most of the action is.  This is were a majority of our weather events come from.  This is also where you will fly in an airplane. Typically the troposphere is between 30,000 ft tall (at the poles) and 56,000 ft tall(at the equator).

This layer is primarily heated by the Earth's surface meaning that it is  warmest at the bottom of this layer, and gets colder as you travel up in height. This is very important in the creation of weather.   

The icing that is between the troposphere and the next layer of cake will be called the Tropopause.  I'll let you decide what flavor your icing is (but I prefer chocolate mousse to remind you that it shares part of the name as the layer of cake below it).

Before we dive into our next layer I have to ask.  Have you ever noticed the top of a thunder storm is flat?  That is because the cloud that contains the thunderstorm (a cumulonimbus) is so tall that it is hitting the next layer of the atmosphere, the stratosphere.

As you can see to the left, our next layer of cake will be the Strawberry flavored Stratosphere. This layer works much in opposite of the Troposphere in that very little weather goes on.  This next layer increases our atmosphere to about 170,000 ft total.  About the only man made objects in the Stratosphere are weather balloons and some super-sonic jets.

Unlike the Troposphere, this layer actually increases with temperature as you travel up due to the ozone layer.  The ozone layer collects ultra violet (UV) radiation.  This radiation gets trapped in the ozone layer and causes it to heat up, and thus makes the Stratosphere warmer as you travel upwards.
The boundary between the Stratosphere and our next layer is called the Stratopause.  The layer of icing will be a creamy Strawberry Whip with fresh strawberries.  Once again the icing shares its flavor with the cake because they share the same root name.

If you haven't left me to go eat some cake then prepare for our third layer.  A tangy Lemon Meringue will be used as a metaphor for the Mesosphere.  The only notable events that occur in the mesosphere is the creation of 'shooting stars'.  As I've discussed earlier, shooting stars are actually small meteorites that 'burn up' in our atmosphere on their way to Earth.

The Mesosphere extends our atmosphere up to about 260,000-280,000 ft.  Once again in this layer temperature will decrease with height.  The very top of the Mesosphere marks the coldest place on Earth and averages around -120 degrees Fahrenheit!

And now for a layer of icing to represent the Mesopause.  Lets go with lemon creme, not quite the same but again similar enough to help you remember the shared traits.


The Final layer in our cake will be a Vanilla layer of Thermosphere.  This is the final layer of our atmosphere and is by far the thickest.  This layer takes our atmosphere out between 220 and 500 miles!  That's roughly 1,100,000 - 2,600,000 ft.  The Thermosphere is the layer in which the international space station orbits.

In the Thermosphere the temperature once again increases with height.  This time however the increase is not caused by a direct warming effect. It is instead due to a lack of molecules.  The 'air' in this layer is so thin that molecules can fly around for miles before colliding.

Our final icing layer before we put the fondont on the cake is the cookie crumble.  Why not a vanilla?  Because the boundary that separates the Thermosphere from the exosphere (or just plain outerspace) is called the exobase.  Since the name is completely different so is the filling.

So there you have our four layer cake.  It probably wont taste very good, but we weren't making it to taste good, we were making it to help you understand the atmosphere just a little bit better.  Once we compile our cake we will notice the four layers all have a fairly distinct boundary.  And that each layer has alternating temperature profiles.  Meaning the first layer zigs, as it cools off with height.  Then the second layer zags, as it gains heat from the ozone layer.  Our third layer zigs again as it reaches colder and colder temperatures with height.  And our top piece makes the final zag as it extends to the edge of what we consider the atmosphere.

And what happens once you pass the exobase?  Well from here the temperature climbs in a very steady, straight line kind of way as you near the sun.

So overall we have learned a lot about the atmosphere in this single entry.  We have covered how the atmosphere was born, and why it is important to life on Earth.  Then we got a little nerdy (and hungry) discussing the different layers of the atmosphere.  We defined the four major layers, and the boundaries between them..  Now the next time you look up into the sky you will know, that there are more particles of gas then you can ever count, and each one of them is doing something that keeps you and I alive on this planet.