Our planet Earth is full of wonders and marvels. From nature and marine life in the oceans and rivers, mountains and waterfalls to the complicated yet miraculous structure of the human body. If we look around, or inside, we will always be in awe of the stunning arrangement of the system we live in.
The great set-up in which our planet Earth operates did not come into existence overnight. Previously on Learningmole.com, we have understood how the Solar System formed 4.5 billion years ago. Everything that we have now started as small as a speck of dust then evolved.
Today, we are going to look into one of these marvels of our planet which is so indispensable for life. Well, what I want to say is that we will not actually be here without it. Today, we are learning about the atmosphere of Earth.
What is the atmosphere?
Earth’s atmosphere is known as the thick layer of gases that wrap our planet. We may also call it air. Such a layer extends from the surface of Earth to 10,000 km above. That is the distance from Cairo, Egypt in Northern Africa to Cape Town in South Africa! That is an enormous distance!
It is interesting to mention here that although we say that the atmosphere’s height is 10,000 km above sea level, actually there is no dividing line between the last level of the atmosphere and the beginning of outer space. They only just merge into one another.
The atmosphere is as heavy as 5.5 quadrillion tons! That is a really big mass! And it is puzzling as well. We can imagine air as something light, very light actually it is almost weightless! But it is not. In fact, such a very heavy weight is literally above our heads and 66.6% of it is found at a height of 11 km from Earth’s surface.
But how does the atmosphere stay in place and wrap Earth? Why does it not escape to space? Well, it is Earth’s gravity that pulls the atmosphere down. This pulling action creates a force on Earth’s surface known as the atmospheric pressure.
Why is the atmosphere incredibly important?
We literally cannot live without the atmosphere. Not only because we need oxygen to breathe, but also because the atmosphere is responsible for so many essential aspects of life.
For example, the atmospheric pressure turns water vapor into liquid water. Such a process is called condensation. With liquid water, life on Earth is possible. That is the first reason why the atmosphere is very important to us.
Secondly, the atmosphere prevents the heat coming from the Sun from escaping back to space. This happens as the surface of Earth absorbs sunlight and radiates heat. But carbon dioxide absorbs such heat and traps it in the atmosphere. This warms the surface of Earth and makes it suitable for us to live on it. This is known as the greenhouse effect.
When the heat is locked in the atmosphere, it also keeps the night less cold which allows life on Earth. If there were no atmosphere at all, Earth would be so hot during the day and so cold during night that no living being would be able to survive.
The atmosphere also protects us from meteors. Meteors are small objects of rocks or metal that hit the Earth from outer space. They are a lot smaller than asteroids. Actually, they can be as small as a grain or as big as one meter-wide. When such meteors hit Earth, the atmosphere burns them before reaching the surface and causing any harm. When they burn, they create a ball of fire that we know as a shooting star.
📌 Yearly, an automobile size asteroid hits Earth but the atmosphere burns it before reaching the surface.
The atmosphere is also important because it protects us from the Sun’s harmful waves. These waves are called ultraviolet radiation. If anyone gets exposed to it, it will damage their skin cells and may also give them cancer. Luckily, we have the atmosphere to protect us.
In addition, the atmosphere has oxygen which we need to breathe and carbon dioxide which plants need to generate oxygen for us. That is why the atmosphere is very important for life on Earth.
Earth’s atmosphere is composed of 78% nitrogen (N), 20.95% oxygen (O2), 0.93% argon (Ar), 0.04% carbon dioxide (CO2), and little amounts of different other gases.
📌 All planets have an atmosphere, except Mercury.
Then how did the atmosphere form?
Well, let’s get a little back in time, 4.5 billion years back to be precise.
Earth’s atmosphere started once Earth settled as a big ball of rocks. Scientists believe that our atmosphere has passed by different stages to be what it is today. So let’s explore these stages one by one, from the very beginning to the present moment.
The very first stage of the formation of Earth’s atmosphere started 4.5 billion years ago. The atmosphere was mostly hydrogen (H) at the time with little amounts of water vapor, ammonia (NH3), and methane (CH4).
The second atmosphere
Around 3.5 billion years ago on Earth, there was an extremely intense series of volcanic eruptions that swept gases from the interior of Earth and released them into the atmosphere.
Simultaneously, Earth was bombarded by asteroids, rocks, and particles left over from the formation of the Solar System. These rocks failed to form planets on their own so they started hitting Earth. Such an event is known as the Late Heavy Bombardment and is believed to have lasted for about 700 million years.
These two events changed the then hydrogen-rich atmosphere significantly. The new atmosphere consisted of nitrogen (N), carbon dioxide (CO2), methane (CH4), and other gases. Nitrogen made up the major part of the atmosphere.
While Earth was dealing with the crazy volcanoes we mentioned earlier around 3.5 billion years ago, the very first form of life on Earth appeared. It was a microorganism known as anaerobic bacteria. It lived in the ocean and did not require oxygen to survive. Well, this makes sense because the atmosphere had no oxygen in the first place.
Over hundreds of millions of years, some bacteria evolved until they obtained the ability to produce energy using photosynthesis, just like plants. This bacteria is called Cyanobacteria and is now found everywhere on Earth.
Cyanobacteria started absorbing carbon dioxide (CO2) from the atmosphere. With the help of water and sunlight, it could produce sugars to use for energy and released oxygen (O2) as a waste product.
This oxygen was then released into the ocean. But the anaerobic bacteria (remember them from above?) were allergic to oxygen. And with all this newly produced oxygen, the ocean was full of toxins for the poor anaerobic bacteria which killed them all.
Scientists called this event the first mass extinction in history. It is also called The Great Oxygenation event or The Oxygen Catastrophe. This is one time when oxygen played the bad guy.
Anyways, oxygen (O2) also oxidized the materials in the ocean, notably iron. So, when the ocean was full of oxygen, it started to be released into the atmosphere and accumulated. It also reacted with methane (CH4) to form carbon dioxide (CO2). As Cyanobacteria reproduced fast, it absorbed a great amount of carbon dioxide from the air and released more and more oxygen.
With Cyanobacteria absorbing carbon dioxide (CO2) from the air and oxygen (O2) reacting with methane (CH4), the amounts of these two greenhouse gases decreased significantly. Consequently, there was nothing to keep Earth warm so the temperature went down so much that Earth became very cold. Many believe that this was the beginning of the first ice age.
Though, oxygen remained active. About 600 million years ago, and as oxygen (O2) accumulated in the air, it started to absorb the ultraviolet radiation coming from the Sun. This caused the oxygen molecule (O2) to split into two atoms (O and O). Such single atoms then combined with oxygen molecules (O2) to form ozone (O3).
Ozone (O3) piled up and formed a band that shielded the entire Earth. This shield absorbed all the ultraviolet radiation and prevented it from reaching Earth’s surface. Such an act enabled life to be possible on the surface of Earth and not just exclusive to the oceans.
Since then, the levels of oxygen (O2) in the atmosphere varied until they reached a steady percentage of more than 15%, then reached its peak of 30% around 280 million year ago. Scientists do not know why oxygen levels fluctuated. But it finally reached a steady level at 21% of the atmosphere.
So now we understand how our atmosphere came to be 78% nitrogen, 20.95% oxygen, and 0.04% carbon dioxide.
Layers of the atmosphere
We mentioned before that the atmosphere extends from the surface of Earth to 10,000 km up. Despite this great distance, the atmosphere is nowhere near bulky! In fact, the atmosphere is composed of five different layers. Each layer has a different length and many many different features. Let’s explore them one by one.
The troposphere is the first layer of the atmosphere. It extends from the surface of Earth to several kilometers up in the sky. This thickness changes based on where you are. For instance, if you are at the north or south poles, the troposphere will extend to only 6 km. But if you are at the equator, the troposphere is 18 km thick. So the average thickness of the troposphere is 13 km, from the surface of Earth up. The troposphere contains 75% of the mass of the whole atmosphere as well.
Because it starts from the surface of Earth, the troposphere contains the greatest amount of water vapor. This is because water vapor stems from oceans, seas, lakes, rivers, as well as plants. Water vapor then creates clouds which in turn drive rain and snow. That is why the weather phenomena happen in the troposphere.
The troposphere is also known for having air turbulence. The hot surface of Earth heats the air above it. But the warmer air is more buoyant than the cool air so it floats higher pushing the cool air down toward the surface. The hot surface then heats the cool air which goes up letting the air which is now cooler go down. This air movement is called turbulence.
📌 In fact, the troposphere is called troposphere because the word ‘tropo’ means rotation in Greek. It refers to the rotation of air, turbulence, which occurs in this layer.
When it comes to temperature, we find it changes just like the thickness of the troposphere. At the equator, the temperature ranges from 20°C on the surface to −75°C at the end of the troposphere. At the poles, the temperature starts from 0°C to −45°C at the end of the layer. The poles are icy, you know!
So the higher we go, the lower the temperature gets. But at some point, the temperature ceases to decrease with height. This is exactly where the troposphere ends and where the tropopause starts.
The tropopause is the boundary between the troposphere and the second layer of the atmosphere, the stratosphere. In this pause layer, air temperature does the exact opposite. It increases the higher we go (we will know why in a bit). That means the warmer air is above the cooler air. That is why the tropopause is called the inversion layer.
The stratosphere is the second layer of the atmosphere after the troposphere. It starts from the end of the tropopause and extends for 35 km higher. Temperature in this layer ranges from −51°C to −3°C at the end of this layer.
Wait! −51°C is colder than −15°C! That means the temperature at the beginning of the layer is colder than the end. That also means the higher we go, the warmer it gets, just like the tropopause! So why does this happen? Why does the temperature increase with height?
Well, this is due to the ozone layer, the guardian angel that protects Earth from the dangerous ultraviolet radiation coming from the Sun.
Do you remember how ozone forms? Yes, that happens when an oxygen atom (O) combines with an oxygen molecule (O2). Scientists have found that ozone is better at absorbing ultraviolet radiation. And this absorption heats up the stratosphere.
As the temperature rises the higher we go, this creates different layers of temperature along the stratosphere. That is why it was called stratosphere because strato means layer.
Because these layers have ascending temperatures, warmer air is always above the cooler air and this is exactly where they should be. So air is stable where it is; it does not move. As a result, there is no turbulence in the stratosphere.
📌 Because there is no turbulence, airplanes like to fly in this region of the atmosphere. Since there is not much air resistance, planes can fly faster and burn less fuel.
What is interesting is that some birds such as rüppell’s vulture and bar-headed geese can fly as high as in the stratosphere!
And just like the tropopause, there is the stratopause at the end of the stratosphere. It acts like a border between this layer and the next one, the mesosphere. The stratopause stretches for about 5 km.
Now with the third layer of the atmosphere: the mesosphere. This layer extends from the stratopause at a height of 50 km from surface level to around 80-85 km above. That means the mesosphere is around 35 km thick.
Since the mesosphere is the third layer, it is the middle one. That is why it is called meso because meso is a Greek word that means middle.
Leaving the ozone layer behind, the temperature goes back to its first behavior. It decreases with altitude. The mesosphere has an average temperature of −85 °C. At the end of the mesosphere, there is the mesopause which marks the end of this layer and the beginning of the layer after.
The mesopause extends for 15 km; from 85 km from sea level to 100 km. It is the coldest region on the planet since its temperature is −143°C. And because it is very high in the sky, sometimes it is referred to as near space.
The mesosphere is where meteors burn, resulting in meteor showers or shooting stars. When meteors and small asteroids enter the mesosphere, they collide with the air. This collision is called friction which generates fire (just like when you grind two rocks against each other fast to get fire).
So the mesosphere protects us from dangerous bodies coming from space.
Given that it is so high in the sky, planes cannot fly in the mesosphere. Satellites are not located there as well because they orbit Earth at a much higher level. And even though scientists can send rockets, they can only study the mesosphere for a few minutes.
As a result, we do not know much about the mesosphere. Unfortunately. That is why the mesosphere got its nickname: ignorosphere!
Thermosphere is the fourth layer of the atmosphere. It starts from the mesopause and extends for a thickness of 513 km. That is by far the thickest layer we have studied so far. It is called thermo which refers to heat.
Like the stratosphere, the thermosphere absorbs the Sun’s highly energetic radiation which creates heat within the layer. Sometimes, the temperature can reach 2000°C and even more. The temperature also increases with higher altitudes.
The International Space Station (ISS) resides in this region and orbits Earth. This station is a cooperative project between five different countries in which scientists stay in orbit and study space.
Space shuttles and satellites also orbit Earth from the thermosphere. Space shuttles are rockets that can be used multiple times to travel to and from space. They are used to deliver astronauts to the International Space Station. They can also stay in orbit for some time so scientists can study different features of space.
One of the most successful and popular space shuttles is Discovery, developed by NASA, which stayed in work for 27 years from 1984 until it retired in 2011.
If the temperature of the thermosphere can get to as high as 2000°C, why then did the International Space Station, nor space shuttles and satellites not melt?
That is a good question! To answer it, we need to learn how heat is transferred.
For liquids and gases, heat is transferred by a process called convection. Any gas has atoms or molecules and they are free to move because the distances between them are large. When we heat a gas, the molecules take the heat energy and they start to move faster.
As molecules go crazy from here to there, they collide with other molecules and give them some of this energy. And there you go, heat is transferred.
When distances between atoms or molecules increase so much, we call the gas less dense or thin. And the air in the thermosphere is very thin.
Keeping this in mind, let’s get back to the thermosphere and look into what happens in it:
- Molecules absorb the ultraviolet radiation and get so energetic.
- The temperature of the molecules rises so much, sometimes it reaches 2000°C.
- Molecules move around so fast trying to collide with other molecules to give them energy but they find no one because other molecules are so far-distant.
- Eventually, heat stays inside the molecules and is never transferred.
In fact, if we go to the thermosphere, we would feel cold rather than hot! That is why astronauts at the International Space Station never melt.
As the ozone layer is within the stratosphere, the ionosphere is a layer within parts of the mesosphere and it takes the entire layer of thermosphere as well as some parts of the exosphere (the fifth and last layer of the atmosphere).
The ionosphere extends for a distance of 917 kilometers! It is called ionosphere because it is ionized. To understand what ‘ionized’ means, we need to go back to the very first chemistry lesson: atoms and molecules.
An atom is the smallest particle there is. A molecule is made of two or more atoms connected together. An atom has a nucleus, protons, electrons, and neutrons. Protons and neutrons are inside the nucleus while electrons orbit the nucleus.
Protons have a positive charge but neutrons, you guessed it, are neutral. It means they have no electric charges. Meanwhile, electrons have a negative charge. And they spin around the nucleus in an orbit, just like Earth orbits the Sun.
Each atom is neutral because it has an equal number of protons (+) and electrons (-). These two opposite charges cancel each other so the atom stays neutral.
When the number of electrons and protons is unequal, the atom is called an ion. Ions are electrically charged. If the number of electrons is higher than the number of protons, ions are negatively charged and vice versa. They are positively charged if the protons are more than the electrons.
Back to our topic..
We have mentioned in the thermosphere that gases in this layer absorb the ultraviolet waves from the Sun. This tremendous energy pushes an electron or two out of their
atom which turns it into a positive ion. These free electrons collide with other atoms and make them negative ions.
This ionization process makes the oxygen and nitrogen molecules in the thermosphere produce free electrons and light. Oxygen gives out green and red light. Nitrogen glows blue and purple. This light can be seen from Earth and we know it as aurora.
If you live anywhere in Norway, Sweden, Alaska, or Canada, you will be able to see auroras.
📌 Since the ionization process is activated by the highly energetic radiation from the Sun, the thickness of the ionosphere changes dramatically during the day and at night.
The exosphere is the outermost layer of the atmosphere and the largest in distance as well. It extends from the thermopause, which marks the end of the thermosphere, for 9300 km!
In this part of the atmosphere, the air is so thin. This means that there are great distances between gas molecules so they do not collide with each other. The gases in this layer are mostly hydrogen and helium.
The exosphere is hence the perfect home for satellites because they can orbit Earth without any problems of friction or disruption since the air is very thin.
We cannot mention the atmosphere without discussing the weather. Weather is a very distinctive feature of Earth’s atmosphere and it dramatically affects how we live on this planet as well as the development of humanity in general.
When we think of weather, we know we are referring to how hot or cold a day is and whether or not it is rainy or windy. Well, this is pretty correct. Weather is caused by changes in the air temperature, air pressure, and how much water vapor is in there. That is why most weather phenomena happen within the troposphere.
Why does weather happen?
To understand how changes in the air temperature, pressure, and amount of water vapor determine the weather events we are familiar with, let’s study the lifecycle of water vapor.
We can define humidity as how much water vapor there is in the air. Heat from the Sun causes water from rivers, lakes, oceans, seas, and even dew on leaves to evaporate. Water then turns into its gas state and becomes vapor. When we feel it is too humid, this is because there is so much water vapor in the air.
We have learned before that in the troposphere, the higher we go, the colder it gets. So when water vapor goes high in the air where it is cooler, it starts to condense on teeny-tiny particles such as dust, salt crystals, and ash, which act as surfaces to the water vapor.
So water vapor condenses and goes back to its liquid state, water. Well, it actually forms water droplets. Water droplets then accumulate and form a cloud. Sometimes, if it is too cold (temperature is usually 0°C or lower), water droplets turn into ice crystals and form an ice cloud.
So if clouds are pure liquid water or ice in the form of droplets, why do they not fall down from the clouds? How can clouds float in the air?
Well that is a good question. Let’s know how this happens.
Everything on the surface of the planet as well as the atmosphere that extends for 10,000 km above is pulled down by Earth’s gravity. And for an object to fall down, it must also have a mass. The heavier an object is, the faster it falls back to Earth. And vice versa. That is why a rock reaches the ground so fast but a balloon takes longer.
Those water or ice droplets in the clouds are so tiny. Their weight is so small that Earth’s gravity does not affect them. And because the air is dense, it pushes them up so they float in the clouds. As a result, they do not fall back to Earth.
Clouds grow at different altitudes from Earth’s surface. Based on where they are in the atmosphere, they can be classified in three different categories. Low-level Clouds form at ground level to almost 2 km up. Mid-level Clouds start at a height of 2 km and have a range of 5 km (to 7 km up). High-level Clouds start at altitudes of 5 km up to 12-13 km.
When clouds form at or near ground level, they are called fog. Usually fog forms at a height lower than 15 m. When it is higher than that, it is a cloud.
When water droplets in a cloud get so large and heavy that the air cannot carry them anymore, they get subjected to Earth’s gravitational pull and they fall back down to the surface of Earth. This falling water is called precipitation.
Precipitation includes different types, some of which are very familiar to us and others may sound a little bizarre:
Each one of those takes specific conditions to form. So let’s discuss them one by one.
Drizzle vs. Rain vs. Sleet
Precipitation includes different types which depend on either the size of the water droplets or the conditions at which they form. If the water droplets falling from the clouds have a diameter of less than 0.5 mm, they are called drizzles.
If the droplet’s size is 0.5 mm or bigger, it is called rain. Rain can be light, moderate, or heavy based on its intensity. When sunlight passes through rain droplets, light is scattered to its seven colors which we collectively call the rainbow.
If the temperature where the cloud is located is 0°C or lower, droplets of drizzle or rain turn into ice as they fall. These icy balls are usually less than 0.76 cm in diameter and we call them sleet.
Sometimes during the formation process of clouds and when the temperature gets very low, usually below 0°C, water vapor condenses directly to ice crystals without going through its liquid form. These ice crystals accumulate to form an ice cloud.
Then, ice crystals absorb more water vapor and freeze it. The result of this is the formation of more crystals onto one another. These crystals are called snow clusters or aggregates which then fall to the ground forming the familiar white snow blanket.
While ice crystals are fairly clear, these resultant snow clusters are white. This is because the snow clusters reflect light in all directions until it goes out of it. The reflected light includes all colors which together look white.
Typically, as the ice crystals aggregate to form clusters, they would cluster in 6-armed symmetrical or almost symmetrical hexagon shapes. These perfect shapes have confused scientists for years. Finally, we understood that they are mainly influenced by the chemistry of water.
Water (H2O) consists of two atoms of hydrogen (H) and one atom of oxygen (O2). Usually oxygen has a negative charge and the hydrogen atom has a positive charge. This is called a water molecule. When water becomes ice, these water molecules start to attract each other and stick together.
The negative charge of oxygen attracts the positive charge of hydrogen and they result in a beautiful hexagon shape. This is called a hydrogen bond.
When ice crystals absorb water vapor which freezes onto them, these crystals take the shape of the hydrogen bond in ice. That is why snowflakes have a hexagon shape.
We mentioned that snowflakes form in ice clouds. Every cloud is subject to different conditions of temperature and humidity. The difference between such conditions controls the shape of each snowflake. It is even said that every snowflake is unique, that no two snowflakes are alike.
Sometimes the conditions are so severe that they diminish the hexagon shape altogether and make snowflakes completely irregular.
When snowflakes become heavy, they fall to the ground.
Graupel vs. Hail
Sometimes, clouds get so cold, around −40°C, but water droplets in them stay in their liquid state. In this case, they are called supercooled water droplets. When snowflakes fall through one of these supercooled clouds, the supercooled water droplets stick to the surface of the snowflake and then freezes.
These frozen water droplets then accumulate on top of the snowflake until the beautiful hexagon shape of the snowflake is no longer identified. These frozen droplets are called graupel. Graupel is usually 2–5 mm in diameter.
And these supercooled clouds are called cumulus clouds.
Thunderstorms, which we will discuss in a bit, cause air to move up, pushing graupel so it does not fall to ground. So more water droplets from the supercooled clouds stick to and freeze onto the graupel causing it to grow. When the graupel gets so heavy that the air cannot hold it anymore, it falls down to the surface and is then called hail.
Clouds form in different types, shapes, and colors that are determined based on the conditions at which they form. One of them is the very common cloud type we are all familiar with. It looks puffy, fluffy, and cotton-like. These clouds are called cumulus clouds.
Cumulus clouds create a different, bigger, and taller type of cloud called cumulonimbus. Such clouds accumulate upward and they look like towers of clouds. That is why they are called the kings of clouds.
Cumulonimbus clouds form at a height of 200 to 4,000 m and they grow upward to a maximum of 12 km from the surface of Earth. Some of these clouds were even found to grow to an altitude of 21 km! That means these towering clouds exceed the troposphere itself and even grow in the stratosphere. How gigantic!
The temperature of the cumulonimbus clouds is usually way below 0°C and can sometimes reach −30°C. Due to such low temperatures, they have ice crystals.
Wind causes these ice crystals to move up and down fast so they collide with each other. Remember the ionization process? These collisions cause electrons to be knocked off their molecules to make them positively charged. Then free electrons collide with other ice crystals and make them negatively charged.
Moving air causes the positive charges to go to the top of the cloud and the negative ones go to its bottom. It also acts as a barrier between them so they do not attract each other.
As the ionization process continues, the negative charges at the bottom of the cloud grow magnificently. Right at this moment, they get so strong that they overcome the air barrier. So they start to attract the positive charges whether those within the cloud itself or the positive charges of the ground.
These two opposite charges move toward each other. Once they touch, the negative charges from the cloud begin to move quickly towards positive ones and a sudden flash of light bursts into the air caused by this discharge of electricity. This light is actually a very strong electric current and we know it as lightning.
The tremendous amount of negative charges is called a stepped leader because it is the one that leads the whole lightning process.
Lightning bolts are also tremendously hot, reaching a temperature of 27,760°C! That is five times hotter than the surface of the Sun!
This immense heat causes the air to expand quickly. When the expanding air moves, it makes a sonic shock sound which we know as thunder.
Thunderstorms are usually accompanied by extreme rainfall, sleet, and hail.
We might define wind as the movement of air, and this is fairly correct. But how does the air move in the first place? Well, just like something as gigantic as thunderstorms was initiated by tiny water droplets, wind is existent because of air pressure.
We have understood that air is made of different gases. We have nitrogen (N), oxygen (O2), aragorn (Ar1), and little amounts of carbon dioxide (CO2), water vapor and other gases.
The molecules of these gases have weight. Since all molecules are pulled down by Earth’s gravity, their weight presses on the air or surface below them. When the number of molecules increases, this pressing force increases in return. So the pressure increases.
And vice versa, the fewer the molecules, the lower air pressure gets.
Temperature affects air pressure. Heat causes gas particles to move faster and away from one another so their number in a given area decreases and makes the pressure low. Also altitudes change air pressure. The higher we go, the fewer the air molecules. So pressure is low.
When there are two places with high and low pressures, air would always try to equalize itself. So the air molecules of high pressure move towards the lower pressure areas to balance the pressure out. This movement is the wind.
The bigger the difference in air pressure between different places, the faster the wind blows.
Wildfires are an extreme weather event in which fire burns plants, kills animals, pollutes the air, causes people to leave their homes, and sometimes even kills them.
Scientists could track back wildfires to 420 million years ago. They started after plants appeared on Earth. In this section, we are going to discuss how wildfires occur, how they change the atmosphere, and whether or not they have any good sides.
Wildfires happen randomly and unexpectedly. They can start from a small dwarfing spark of a leftover cigarette or by a lightning strike. Wildfires are usually initiated with the presence of three main components: heat or flame, fuel, and oxygen. And all three of these are available in the forest.
High temperature evaporates water and makes plants, trees, grass, bush, and everything in the forest dry. Fire cannot happen if the plant has water. So dry plants are a perfect fuel for the fire. Secondly, oxygen and we already have plenty of it in the atmosphere. So what is missing? Well, we need a spark to start a fire.
The majority of wildfires are ignited by, unfortunately, people. The carelessness of people to be fair. The spark or flame which starts wildfires could be something as trivial as a cigarette leftover or when someone forgets to put out the fire they lit as they were camping in the woods.
So the tiny spark fires the poor dry plant which then reacts with oxygen in the air. As a result, fire is magnified and gases and smoke are released.
Nature itself can also cause wildfires. They occur by the extreme heat coming from the Sun, lightning strikes, volcanoes, and the wind as well.
Heat? Can heat by itself start a fire? Yes. Yes, it can. Here is how.
Every substance has a temperature called autoignition temperature. When this temperature is reached, a substance can react with oxygen (O2) and burn spontaneously without an external source of flame or spark.
Lightning strikes can also initiate wildfires because they generate very strong electric current. But if the lightning is accompanied by rain, wildfires fail to start because the rain puts out any fires.
Volcanoes can also start wildfires using their lava. Lava is burning rocks that spread over long distances. It is extremely hot, reaching, sometimes, a temperature of 1200°C. When they reach dry grass land for instance, their tremendous heat can start a fire.
The wind also has a hand in spreading wildfires over long distances. Since it provides the fire with a bigger supply of oxygen, the wind helps the wildfire magnify and pushes it to different places. The stronger the wind blows, the faster the wildfire spreads.
📌 If the air is very humid, wildfires are less likely to happen because the water in plants will not allow the fire to happen.
But are wildfires any good?
Since wildfires started to happen ever since plants appeared on Earth, the environment, by some means, could survive through them. In other words, wildfires in and of themselves are a part of nature.
But how could nature evolve with the presence of wildfires given the destruction they leave behind? Well, that is a good question. Let’s break the answer down.
Fire clears the forest from the dead organisms that can badly affect other living organisms. When plants die or rot, they fall on the ground and build up a shield that prevents organisms in the soil from accessing their food which they get from outside such as the atmosphere. This shield also prevents small plants from growing.
So the fire burns this dead shield and gives the soil an open window to the atmosphere so it can breathe. Also when these dead plants burn, they turn into ash which is usually full of nutrients for the soil. So the soil quickly absorbs the ash to become healthy and fresh.
A healthy soil is a fertile soil. Farmers need fertile soil to grow vegetables and fruit which we need to have a healthy diet.
Another good side of wildfires is that they help some plants and insects to grow. I know this sounds strange but here is how.
When the holiday season is approaching, people start to buy or cut down trees to decorate as Christmas trees. Well, there are different types of Christmas trees, one of them is called pine trees (pineapples come from the same family by the way).
In order for new pine trees to grow, their seeds must go into the soil. But unfortunately, the seeds are stuck inside thick and stiff pitch cones and only fire can melt the pitch and allow the seed to come out.
Another benefit of wildfire is gained by a type of butterfly called karner blue (it is blue) which requires fire to come to existence. A baby butterfly is usually called a carter pillar and it has to go through a process called metamorphosis in order to grow into an adult butterfly. Yet, its food is a plant called wild lupine which does not flourish without fire.
But still, wildfires are detrimental
Despite the benefits wildfires bring to some species, they are still dangerous because they burn large areas of plants and vegetation and kill animals that live in these forests. Not only plants and animals are affected but the atmosphere and therefore us as well.
As fire burns forests, it releases large amounts of smoke, carbon dioxide (CO2), and nitrogen oxides (NO). Smoke causes air pollution in the area of wildfire as well as very distant areas because it travels so far. Smoke causes health problems to people.
Carbon dioxide (CO2) is a greenhouse gas which traps the heat inside Earth’s atmosphere and prevents it from escaping to space. This, as we will see in the next section, puts our planet in danger.
Effects of human activity on the atmosphere
As we discussed earlier, the atmosphere has been evolving since the formation of Earth. It responded to the changes our planet was subjected to until it made our life on Earth possible. But, did we return the favor? Well, not quite.
In order to understand how human activity affects the atmosphere and puts our beloved planet in danger, we need to hop into a time machine and go back to 18th-century Britain.
In the mid-18th century, Britain started using machines in factories rather than people. Machines enabled the production of incredibly large amounts of products such as textiles. For the machines to work, they needed power and their power was fossil fuels.
What are fossil fuels?
Well, when animals and plants die and get buried, their bodies decompose into smaller and smaller pieces. These pieces are then mixed with the soil and with the heat from inside Earth; they turn into fuel over time. Well, I mean over millions and millions of years. And they are called fossil fuels.
When fossil fuels burn, they give out energy so humans started to use them as an energy source for the machines.
As time went by and as more technological changes were introduced to societies, the usage, and then burning, of fossil fuels increased dramatically. And now we depend on them to provide the essential needs for life. For example, we burn fossil fuels to have electricity, heat homes, and run cars and factories.
The most common types of fossil fuels are coal, natural gas, and oil. When these fuels burn, they mainly release carbon dioxide (CO2), nitrogen oxides (NO), and methane (CH4). These gases changed the planet dramatically. They caused air pollution and global warming which may one day be responsible for the drowning of our cities.
Besides burning fossil fuels, humans also burn waste in order to get rid of it. Fire releases smoke and chemicals that pollute the air and cause serious health problems. And let’s not forget sprays, paints, and perfumes that harm the atmosphere and magnify air pollution.
The gases from burning fossil fuels, smoke, and the chemicals released to the air all change the composition of the air we breathe, resulting in air pollution which causes serious health problems to humans, animals, and plants.
For example, nitrogen oxides (NO) create smog. Smog looks exactly like fog. Although fog is made of tiny water droplets and caused completely by nature, smog on the other hand is human-made fog containing harmful gases. It is called smog because it is part smoke and part fog.
On the one hand, nitrogen oxides are helpful in creating the ozone gas which we are now familiar with. Though ozone blocks the Sun’s harmful ultraviolet radiation, it is helpful only when it is in the stratosphere layer, up there. But when ozone is in the troposphere, we can breathe it.
Inhaled ozone can cause many health problems especially for kids and old people as well as those who have asthma because it causes shortness of breath, chest pain and coughing.
Carbon dioxide (CO2) and methane (CH4) which are released from burning fossil fuels are greenhouse gases. That means they lock the heat coming from the Sun in the atmosphere, precisely in the troposphere, and prevent it from going back to space.
The more greenhouse gases there are in the atmosphere, the more heat is trapped inside. This increasing heat is one of such threats that endanger our planet and we know it as global warming.
Global warming increases the temperature which makes summers longer and winters shorter. This high temperature also causes wildfires to happen more frequently which in turn release large amounts of smoke and harmful gases as discussed above.
Another serious consequence of high temperature is that it causes water to evaporate at a higher rate. More water vapor means more and more clouds. Then, we have more heavy rains which cause floods, kill plants, damage the soil and make it unsuitable for growing plants anymore. Floods also damage people’s homes and drown them.
On the other hand, evaporation also causes drought. It sucks the water from plants making them dry, evaporating all water from Earth’s surface, making it water unavailable for the animals who live there. Animals hence leave those areas and look for other places where water is available. Sometimes during this relocation process, animals may die and disappear from Earth altogether. They go extinct.
However, the most serious outcome of the rising temperature is causing the ice in the north and south poles to melt. The resulting water then moves towards oceans and seas increasing their water level. When the water levels increase beyond certain points, it can flood our cities.
Increasing the levels of carbon dioxide (CO2) in the atmosphere is not just serious for humans, but also for fish. When oceans absorb carbon dioxide (CO2) from the atmosphere, it makes it hard for the corals to form their homes, the reef, and may cause the existing ones to dissolve in the ocean.
This also makes food for fish less available which affects their life cycle. And since millions of people depend on fish in their diet, they will be badly affected as well.
So what can we do?
Global warming imposes serious threats on our planet and we have to take action in order to minimize them and help make our planet a safer place for us and for the upcoming generations. Here are some actions which we can take every day to help save our planet.
Since energy from fossil fuels is used to generate electricity to run our home appliances, we can help burn less fuel when we save power. Here are some steps to do that.
- Switching off lights when not in use.
- Reducing the temperature of the heating or cooling systems.
- Choosing energy efficient appliances.
- Using LED light bulbs.
- Pulling the plugs.
- Carpooling: instead of having five individuals in five cars, we can have five individuals in one car. Thus power consumption is reduced to 20%. Bingo!
- Walking and cycling: they are even healthier and more fun
Throw less food
When we throw food away and it goes rotten, it produces methane which is a greenhouse gas that intensifies global warming. We can minimize food waste by buying the exact amounts of food we eat and not more than that.
Buying less food also saves energy. This is because a lot of energy is used to grow, process, package, and ship the food to distant places.
When we recycle, then we do not need to buy a lot of stuff. This in turn reduces their production and hence less fuel is burned.
Many of the devices we cannot live without anymore such as mobile phones and laptops emit carbon (C) during their manufacturing process. This carbon reacts with oxygen (O2) to produce carbon dioxide (CO2). This causes an increase in the global warming level.
When we use these devices efficiently, unplug them when not in use, and get them repaired instead of buying new ones, we are helping save our planet.
Water requires a huge amount of energy to clean, purify, pump, and heat. So when we use less water, in turn we use less energy.
Our atmosphere is one of the millions of miracles we are surrounded by. It is one thing that has started life on Earth, making me write this article to you now and making you able to read it. It has formed, changed, evolved, and transformed to be the way it is now, just like we grow from clumsy toddlers to full-grown and independent adults.
In this long journey in our earthly atmosphere, we demonstrated how important it is and dived into the history of its formation and evolution which started 4.5 billion years ago. In this section, we have learned that the atmosphere has passed by three main stages: earliest, second, and third atmospheres which created the structure it has now.
Then we studied this structure in detail and looked into each of the five layers starting from the troposphere where we breathe and live and experience weather, the stratosphere where our guardian angel, the ozone layer, resides, the mesosphere which burns meteors, the thermosphere where the International Space Station, space shuttles, and satellites are, and finally the exosphere which extends so far up until it dissolves in outer space.
Through this journey of the layers of the atmosphere, we introduced many different concepts such as how heat is transferred, what an atom is and what its components are, how ions form in the ionosphere, and how they create the beautiful aurora light as well.
Then we moved to study weather closely and learned how a small process such as the evaporation of water is responsible for a great deal of weather conditions such as humidity, cloud formation, rain and snow falls, and thunderstorms. And we also learned how lightning and thunder occur.
Next, we discussed how the wind forms and where it comes from as well as wildfires, how dangerous they are, and what part humans have in starting them.
Lastly, we moved to how we, humans, have caused the atmosphere to suffer by burning fossil fuels to run machines and how this expanded as technology developed. Burning fossil fuels creates air pollution and global warming which threaten our life. At the very end, we finished with some small actions which when carried on by every one of us, we can help preserve our beloved atmosphere and our planet as well.
So when you take a deep breath, or see a puffy fluffy cloud in the blue sky or extend your hand to feel the drizzles, remember that you are a part of this great, extremely accurate, complex, and beautiful system and that we need to preserve it in order to continue living happily and healthily, and allow our planet to continue evolving.