Our earth is one of the nine planets. All the nine planets orbit the sun. The center of the orbit is the sun. Without the sun, we cannot live. So what are the names of the nine planets?
We can easily learn their names by knowing their special features. The planet that is closest to the sun is Mercury while Pluto is the furthest planet from the sun.
The biggest of the planets is Jupiter. One planet has lovely rings around it. Its name is Saturn.
Between the earth and the sun are Mercury and Venus.
There is a planet between the biggest planet, Jupiter and us. Its name is Mars. So now we know seven planets! They are Mercury, Venus, Earth, Mars, Jupiter, Saturn and Pluto. We need to know the other two. They are twins! They are next to each other. They are close to the tiny planet Pluto. Their names are Uranus and Neptune.
So now we have all nine planets. In order they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
How do you remember the order? This will help.
My Very Educated Mother Just Served Us Nine Plates.
The beginning letter of each word is the planets first letter. (some say Pluto is a planet, others think it is not)
What is the Sun made of?
The Sun is a very big star. It is a million times bigger in size than the earth. It is the closest star to us. Many other stars are larger than the sun, but are so far away we cannot see them. This is why we see them as very tiny specks. The sun is the center of our solar System. We are in the forth planet known as Earth. It takes the earth a year to go round the sun.
The Sun is over a million times bigger than our earth. It is made of gases, the main ones being hydrogen and helium. These gases burn at very high temperatures; this is why we feel the heat. The sun is so far that it takes 8 minutes for the rays to reach us here. Without the sun’s heat, the oceans, the rivers and everything else would freeze and become like ice.
The Sun does not rotate around the earth. It is the earth that spins, which makes day and night for us. The sun provides the crops we plant with the light and heat they need to grow. Without the Sun, no food crops would grow. All plants and trees depend on the sun to grow.
How big is our earth?
The earth is like a very large football. It is spherical. So to understand the earth’s size, we need to measure the earth from one edge to the other. This is known as a diameter. Do you know what diameter means? The diameter is the distance through the center between the widest points of a sphere, for example a football has a diameter of about 22 centimeters. We measure it from one end to the other. So what is the diameter of the earth we live on? It is around 12 700 kilometers. If we could dig in our garden, then after 12 700 kilometers we would see the other end. So the earth is very big and heavy. This size includes everything we know of here, the farms, the mountains, the rivers and the oceans. Our planet has many layers. The main ones are the atmosphere and the hydrosphere.
How big are our oceans?
Our earth is covered with water or land. The very large amounts of water are known as oceans. The earth covering has more water than land. The surface area of land is 29 percent and the oceans cover the other 71 percent. To make it easy to remember, we say that three quarters of the earth is oceans. Oceans have salty water.
There are five oceans The Pacific, The Atlantic, The Indian, The Southern and The Arctic oceans. The largest of them is The Pacific Ocean. It covers the area between The Americas, Asia and Australia. The deepest point of the Pacific Ocean is 11 kilometers deep, though the average depth is four kilometers. The Pacific Ocean is so large that it covers almost a third of our earth. It is larger than all the land area combined. The pacific is a Portuguese name meaning peaceful, “The Peaceful Sea”.
The next largest ocean is The Atlantic Ocean which is about half the size of The Pacific Ocean. The Atlantic Ocean is surrounded by The Americas, Europe and Africa. Also not far behind is The Indian Ocean. It is surrounded by Africa, South Asia and Australia.
The other two oceans are just one tenth the size of The Pacific Ocean, in the South Pole and North Pole.
How to identify our Location?
We know where we are by comparing ourselves to another place. We say I am one kilometer from my school. The shops are two kilometers from school. So we need to place it on a paper so as to identify their locations. So where do we place the three? In a straight line, top to bottom, or across? We need to draw lines as a grid. Now we can place the house, the school and the shops as points on the grid. This becomes a map.
We have made imaginary lines of the whole world. Some run horizontally and some run vertically.
The horizontal lines start at the widest point of the earth, the equator. The equator is at zero. There are 90 lines north and 90 lines south. These are known as latitude lines, measured as degrees. At the ends, we have two poles. The North Pole at 90 degrees north. The South Pole at 90 degrees south. These latitudes are about 110 kilometers apart.
Then we have the vertical lines, known as longitude lines. Zero is located at a place in The United Kingdom called Greenwich. This Zero longitude is known as The Prime Meridian. We have 180 lines going west and 180 going east.
So now we say, Washington, USA is at 39 degrees north, 77 degrees west. That means Washington, USA is above the equator and west from the Greenwich, UK.
What are the 7 distinguished longitude lines?
We know that we made imaginary lines that run across. These lines are called latitude lines. There are seven important lines. They are important because they divide our earth into three main regions that have similar climates. They explain the position of the sun to different regions and this allows us to understand seasons and weather patterns.
At the very center of the earth is the equator. The equator is at the widest point on the earth. It is called latitude zero. The equator runs through a few countries, like Brazil, Ecuador, Kenya and Indonesia.
The other lines are the topical of cancer. It is 22.5 degrees north. The Tropic of Cancer runs through Bahamas, Taiwan, Bangladesh, Saudi Arabia and Algeria.
The other latitude found to the south of the equator is The Tropic of Capricorn. It is 22.5 degrees south.
It runs through Chile, Australia and South Africa.
The area between these two tropical latitude lines is known as The Tropics or Torrid Zone. It is a strip of about 5000 kilometers wide around the earth. We then have the Arctic Circle. Similar to the Tropic of Cancer, it is further north at 66.5 degrees north. It runs through Alaska, Greenland, Iceland, Russia and Finland.
There is a similar latitude line to the south, known as The Antarctic Circle. It is 66.5 degrees south. There are many islands it passes through.
The areas between the tropics and the arctics lines are known as Temperate Zones. They are around 4700 kilometers wide.
The last two latitude lines are at 90 degrees north and south. They are the North Pole and South Pole. The area between the arctics and the poles are known as Polar Circles or Frigid zones. They are around 2500 kilometers wide.
Why do we have seasons?
We now know the five geographical zones. The Torrid Zone, The North Temperate Zone, The South Temperate Zone, The North Frigid Zone and The South Frigid Zone.
The earth rotates on its self. This rotation is at a tilt. That means for six months of the year, the northern hemisphere is closer to the sun than the southern hemisphere. So what brings summer to the north and winter in the south. After the earth has moved half way around the sun, the opposite happens; the south becomes closer to the sun than the north. The changes are different in the geographical zones. The tilt of the earth gives us seasons. In the center torrid zones, there is not so much a change, as the sun is the same distance away. So we do not have any seasonal changes there. The
climate remains the same throughout the year. Day and night are more or less equal in time.
In the Temperate Zones, we notice a change between winter and summer. The Northern Temperate Zone gets cold in December while in June they get summer. The opposite happens to the southern hemisphere.
The Frigid zones see the greatest change. They have continues sun shine in the summer for six months and continuous darkness in the winter for six months.
What are the Solstices and Equinoxes?
These two explain how the suns rays are reaching and hitting the earth’s surface. They explain why we have seasons.
Equinoxes occur when the earth is passing the center of the sun. The axis of the earth to the sun is in a straight line. This makes the length of day and night equal everywhere on earth. The word equinox comes from the Latin words aequus (equal) and nox (night). This happens on approximately March 21st and September 21st each year. For the northern hemisphere, March 21st brings the beginning of spring. For the southern hemisphere it brings autumn.
During Solstices, the sun is at its greatest distance from the equator. The word solstice comes from the Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun stands still. It is when the day and nights are shortest or longest, depending in which hemisphere we are in. They occur on the December 21st and June 21st. They bring in summer or winter. On these solstices, the rays of the Sun shine directly on one of the two Tropics. During the June Solstice the rays of the Sun shine directly on the Tropic of Cancer. During the December Solstice the rays of the Sun shine directly on the Tropic of Capricorn.
What are the three ways to measure time?
Day and Night
This is the simplest way, as the day changes to night and night to day because the earth is rotating. We get day because we are facing the sun, we get night because we moving away from the sun into the shadow. We also learn, as a section of the earth has sunshine, another is having darkness and night. This measuring is called solar time. The length of day and night differ in different parts of the word during different seasons. We can only value time in days. For someone a day would be just 8 hours, for another it could be 18 hours!
The Moons Phase
The moon changes its phase every 29 days. This is a cycle that can be recognized and thus, we get a moon month. We can see a New Month every month so we call it a Lunar Month. In ancient times they calculated days by this method.
As we learnt more about the sun, the moon and the orbits, we learnt that our earth rotates around the sun in 365 days. We also learnt about seasons and how and when they occur with precision. So we divided the day in 24 hours. Now we no longer use daylight and moon phases as a record of time. We have much more accurate manner to record time. We have complete 24 hours days!
Why do we have leap years?
Now we have learnt about our beautiful planet and we are able to calculate the times accurately, we notice a slight change to the time the earth orbits around the sun. It takes the earth a little longer than 365 days to orbit the sun. It takes an extra 5 hours, 48 minutes and 46 seconds. So we have decided that to make sure we are accurate we must add this to our calendar. In four years this works out to almost a day. So to make our calendar accurate, every four years we need an extra day. We add the extra day to February. This addition gives us a leap year and brings the days and year in accordance to our understanding of our solar system. The seasons, the days and nights are all matched up again. The Egyptians were the first people to think of adding a leap day to the calendar every four years. They noticed this change. Julius Caesar then adjusted the calendar. That was more than 2000 years ago.
Why have The International Dateline?
We know the earth is spherical, so where does the day begin? When is it the first minute of the day? We need to have a start point of the day somewhere on our planet. The date line in an imaginary line set at 180 degrees (longitude). It runs from North Pole to South Pole. It passes through the middle of the Pacific Ocean. On that line you have two days, the end of the previous one and the start of the new one. The date line is intended to run through the ocean. So, where it crosses land, the line is diverted to the ocean.
The International Date Line passes between The United States and Russia. Thus all of Russia is to the west of The International Date Line and all of The United States to the east. We have 24 hours in a day and 360 longitude lines, so for each 15 degrees of longitude crossed, the clock would need adjusting by an hour. This way of calculating time makes it easy for everyone.
What are The Earth’s Three Spheres?
We divide our planet into three spheres. Each sphere is categorized according to its physical characteristics. This makes it easy to study and understand our planet. The three spheres are:
It is made of all the earth’s gases. What is the atmosphere? What is air? When you blow air, you are blowing into the atmosphere! The atmosphere is a thin layer of gases that surrounds the earth. It protects us from space and has the necessary gases to protect us from the harmful rays of the sun. It carries our clouds for rain which we need for water. The atmosphere has the necessary gases for us to live, like oxygen. It has other gases like nitrogen and carbon dioxide to help planets grow.
It is the physical solid layer of the earth. This is where we live. It is between the Atmosphere and the Hydrosphere. The lithosphere is that cooled earth’s crust. This is the part on which we have built our homes, schools, stores and factories. It includes the farms, mountains and trees. All this land is known as the Lithosphere.
It is made up of all the earth’s water. Hydro is the Greek word for water. About seventy percent of the surface of the earth is covered by water. All life depends on water. So studying the hydrosphere is important. We need to understand oceans, rivers and clouds and how it affects us all. Everything related to water is in the hydrosphere.
What are the three layers of the atmosphere?
When we blow into the air, we are blowing air into the atmosphere. When we look up to the sky, we see far away. So what is the atmosphere? The atmosphere is made up of layers. It is about 9000 kilometers high. However, the higher you go the less the air you encounter. On earth, we have the most air which is always pressing on our heads! The air that is in our layer is known as the troposphere. It is just about 20 kilometers high.
The word troposphere stems from the Greek tropos for mixing. This area is always moving. We see winds blowing and clouds moving. Nitrogen makes up 78% of the gases and oxygen 21%. Each breathe we take, we take in nitrogen and oxygen.
The next layer above the troposphere is The Stratosphere. This is where we get the ozone layer that protects our planet. This layer protects us from Ultra violet rays of the sun. Airplanes fly near this layer because there are less wind movements. There are no clouds here. This layer is around 40 kilometers wide.
The third layer up is The Exosphere. It is around 10 000 kilometers high. It has only hydrogen and helium gases. The moon is in this sphere.
After this there is emptiness, which we call space.
Why is the sky Blue?
You look everywhere you notice the lovely blue sky. How does it become blue? Are you able to reach the sky?
The reason why the sky is blue is that there are particles in the air that act like prisms. Light is made up of many colors. You notice these colors in the Rainbow! The different rays of the colors have different wave lengths. Red has the longest and blue has the shortest wave lengths. Orange, yellow and green are in between. The atmosphere has billions of tiny particles in it. So when the rays come towards the earth, they get reflected by the particles, and since blue has the shortest wave, we see its reflection the most. Blue is scattered more than other colors because it travels a shorter distance. This reflection is everywhere this is why we just see this blue reflected light. As the rays come lower down to earth, all this scattering mixes the colors together again so we see whiter and less blue. The blue bounced around more than the other colors of light, so we see more blue in the sky. No, we can never touch the sky! The sky is just the blue light that is reflected.
What is Weather and Climate?
The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short term of time,
and climate is how the atmosphere behaves over longer periods of time. The weather is for the conditions closer to us. Like rain, snow, winds and storms. The daily temperatures and cloud cover. These weather patterns change daily or weekly.
Climate is the long term affects. We see a trend and can predict the outcome at some future date. Today’s climate is different to the climate our grand parents may have experienced. Example, a few years ago, there was greater amounts of snow. In some places the spring comes earlier. Migrating birds have also changed their routine. All of this is due to climate changes.
An easy way to remember the difference is that weather includes sunshine, rain, flooding, winds, hail, snow, sleet, freezing rain, blizzards, cloud cover, ice storms, thunderstorms, heat waves and more. Weather is what you do get, like a nice hot day with a few clouds.
Climate is what you expect in a more distant future, like a very hot summer or very cold winter. Scientists define climate as the average weather for a particular area and region over a long time period, usually taken over 25 years. Therefore, the climate refers to an average pattern of weather.
Where does our earth’s heat come from?
The earth remains warm. It neither freezes up nor get over heated. So where does this heat come from? The heat comes from the sun! The sun is millions of kilometers away. Sun rays take eight minutes to reach us. Imagine how far it is? The sun is burning hydrogen and helium continuously. The sun creates this massive amount of heat by what scientist call nuclear fusion. This fusion produces so much heat. All humans together cannot create that much heat in a lifetime that the sun creates in just one second. The sun is a million times greater than earth. We get just a very tiny amount of the total heat the sun releases. Even so, it is enough to keep our planet warm. It helps us grow and helps the plants too. If there was too much heat, we would be unable to bear it. If it were too little, we would freeze. The oceans would become blocks of ice.
The air in our atmosphere regulates the heat. It protects the harmful rays reaching earth. The heat in the earth is reflected back to earth by the atmosphere. The atmosphere acts like a nice warn blanket for all of us!
What causes the wind to blow?
The atmosphere gets warm from the rays of the sun. The earth begins to warm up. The thing to note is that, the rays of the sun do not heat up the earth equally. It will warm up certain areas more than others. So the effect is that in some areas, the air gets warmer than in other areas. Warm air weighs less than cold air and warm air rises. When warm air rises, the colder air replaces it. Warm air goes up, cold air moves across to replace it. This movement of air where it rises and gets replaced causes the winds to blow. This is a continuous cycle. The warm air goes to colder places, and then it comes down again. We cannot see the wind, but most certainly see its affect. We see it with the clouds, the rain and sand storms. This movement of air balances the different temperatures of air. The wind masses covers hundreds of kilometers and often over thousands of kilometers. It can move from the poles all the way to the equator.
How are clouds made?
A cloud is a huge amount of very tiny and very light droplets of water which float in the air. The clouds are made from the water from the earth. When water warms up, it becomes a vapor. This vapor is all around us. As the air warms up, the vapor rises in the atmosphere. This rising makes the vapor colder. At a certain height, this vapor condenses and again becomes tint droplets of water. These droplets are not so heavy to fall as rain or not so warm that they remain vapor. Therefore, we see them as clouds. The collection of these tiny droplets is what we know as clouds. You may have seen air planes fly through them so easily. The whiteness is a result of the reflection of the light since they are big enough to reflect light.
So why are some clouds gray then? It is because the clouds are thick and instead of reflecting white light, they are now coming under the shadow of the other clouds. This shadow makes it appear gray to us. The clouds keep collecting the condensed vapor till it becomes too heavy. When it becomes very heavy, it drops down as rain. This cycle of heat, water evaporation, vapor rising, clouds and rain is known as the hydrologic cycle.
What causes lightning?
Lightning comes from clouds. So how and why do we get lightning? The clouds droplets are moving about as the air rises. As they do this, they keep knocking each other. The rubbing and knocking causes an electrical charge. An example of this charge may occur when you rub a balloon. Do you notice that there is static electricity? The same happens to these droplets of clouds. When this happens continuously, the whole cloud is charged with electricity. The clouds become positively charged but they reach a level where they require a negative charge from the bottom of its self.
When the positive charges above the cloud meet the negative charge from below it, it sparks. This spark is lightning. Sometimes it needs the earth to neutralize it. The charge connects to the cloud from items that are closest to the cloud. Mountain tops, tall buildings and single trees.
We see the lightning before we hear it. This is because light travels faster than sound. It is estimated that each lightning flash is 5 kilometers long and just a few centimeters wide and lasts less than a second. So lightning is the meeting of electrical charges in the cloud due to the friction of the water droplets in the clouds.
What Is Water?
Water is the most important product for life on the planet. We refer to all the water on earth as the hydrosphere.
The hydrosphere (from Greek hydōr for water and sphaira for sphere) in geography describes the combined mass of water found on, under, and over the surface of our planet. It includes the oceans, the lakes and the rain.
Do you know how water is made? Water is made by having two gases mixed together. The two gases are hydrogen and oxygen. You may have heard water being referred to as H2O? This is because each molecule of water has two atoms of hydrogen and one atom of oxygen. This gives us H2O.
The earth’s covering is made up of 70% water.
Water has many unique qualities that allow us to live. It changes in a very short temperature range from solid at 0 degrees to gas at 100 degrees. So in just a short 101 degrees range we can have water in all three states. Solid, liquid and gas!
When you place ice in a drink, what happens? It floats. In this solid state water floats on liquid water! Why is this so unique? This protects all the fish and species in the water. By freezing and floating, the water underneath remains liquid. This ice layer protects the fish and also saves the other remaining water below from freezing. Imagine what would happen if all the water froze?
Water also easily becomes a vapor, so the clouds carry water to other parts of the earth. How could we ever live without water?
What is The Biosphere?
You know biology is the subject about life. So biosphere is about the place (sphere) where we find life! This is the area where we find all living species, like plants, birds, animal and microbes.
Any place that has life as we know it is in the biosphere. We need to know of this biosphere because it affects all of us. We learn about erosion and deforestation. We need nutrients. The earth needs to replenish all these so that all the living species can grow. We need bacteria and fungi to break down organic matter. We need plants. We breath in oxygen with every breathe, so we need a supply of oxygen from nature. All these cycles, big and small determine the existence of our earth. All this is part of the biosphere.
The use of man-made fertilizers causes a very great impact on biosphere. Fertilizers increase the amount of nitrogen, phosphorus, and other nutrients that organisms can use for growth. These extra nutrients drain into the lakes and rivers. The chemicals damage lakes, making the algae to overgrow and also kill fish.
The use of fuel in cars and air planes with land clearing increases carbon dioxide levels in the atmosphere. This may cause global warming. So we need to understand the biosphere to understand the effects of our actions.
What are food chains?
Food chains show us how we need each other to survive. We have generally three groups that can help us understand how living species rely on each other. They are producers, consumers and decomposers.
Plants are producers because they make their own food by using the heat of the sun. They are at the start of the food chain. Plants use the process of photosynthesis to grow. They depend upon the sun’s heat. Plants also make many other nutrients and vitamins for other organisms to eat.
Animals are consumers because they eat plants and other animals. Animals that eat other animals for survival are known as predator. The one killed and eaten is known as the prey. Each is dependent upon the other. The producers have to be the most in the food cycle as all animals depend on them. We need plants and crops for the survival of all species.
Decomposers are nature’s recyclers. They are chiefly the micro-organisms such as bacteria and fungi. These decomposers break down bodies of dead organisms and release compounds that can be used by producers, the plants. These compounds can include phosphorus, nitrogen, and magnesium which plants need to grow. Decomposers produce chemicals, called enzymes that digest dead material.
Food cycles can also be presented as food webs.
What are carbon, oxygen and nitrogen cycles?
Carbon is a gas and is the bases of life. Plants are made with 99% carbon. Human beings are made of carbon gas and need it to survive. Carbon gas is recycled continuously. Plants use it in the photosynthesis process. They take in carbon dioxide and water. They process it and use the light from the sun to produce sugars, starch and give out oxygen. The animals eat the sugar and starch and take in oxygen. The animals breathe out carbon dioxide into the atmosphere so the plants can use it to survive. So animals take in oxygen whilst plants take out oxygen. Animal and plants exchange oxygen for carbon dioxide.
The nitrogen cycle is when nitrogen is in the soil as nitrates. These nitrates are useful to bacteria and algae. The plants use the nitrates to grow. These plants are eaten by animals. The nitrogen returns to the earth through poop and dead organisms. Once in the soil, the plants use the nitrogen again.
What are Biomes?
Biomes are very unique in the ecosystem. They exist in specific places only. Factors like rainfall, temperature and altitude all decide what type of life can be supported. They have different climate patterns. Some are dry and some wet.
To make it easier to understand, biomes are dived into five types, forest, desert, aquatic, grassland and tundra
Forest Biome. The forest biome is the largest of all and has many types of plants, trees, animals and insects. The main contents to make it stand out are lots of trees! The major characteristic of the forest biome is its trees. The Amazon is a good example.
Desert Biome- This is the opposite of the forest biomes. The desert’s main feature is that it has very little trees or vegetation! The desert biome has one major, distinguishing characteristic, it has very little vegetation. The temperature is extreme. The Sahara desert of Africa is very hot during the winters and warm during the rest of the year. The Antarctica too is a desert. These deserts are extremely cold. No vegetation can grow there.
Aquatic Biome refers to places covered with water.
Then there are grassland biomes. They have little vegetation but not many trees.
Tundra Biome- They are found in north and south poles. These are the coldest places on earth.
These are the types of biomes that exist. They have unique weather and vegetation patterns.
Why the Temperature difference?
Why do we have different temperatures on land and on the ocean? We have great changes of temperature between day and night on the land compared to those at sea. Why does this happen?
It happens because the heat absorbing qualities of water and land are different. On the earth, the land will adsorb the heat from the sun, but that absorption is just on top. The bottom of the land does not absorb much heat. Whereas with the ocean, the water is moving, so much more of the suns heat is absorbed. At night, the land loses its heat quickly but the ocean loses its heat slowly. The temperature at sea will change less during day and night compared to the temperature changes on land. The closer to the ocean you are, the warmer you feel. This is because the air pressure is greater by the seaside. This greater pressure retains more heat than higher up on land, where air pressure is less.
The oceans water gains more heat. This heat slowly moves to the poles. The transfer of heat by water is slower than it is in air. So this slower movement keeps heat longer in the oceans and releases it slowly.
What is The Greenhouse Effect?
The greenhouse effect is about the air in the atmosphere. The atmosphere has two important functions. It protects us from dangerous rays from the sun and stops the heat from the earth moving into the atmosphere.
There is always a natural balance between the two.
Now due to mans own development, we are burning many fuels that affect the atmosphere’s air make up. With tonnes of new gases we emit into the atmosphere, the atmospheres protection is weakened and therefore more dangerous sun rays reach us. These rays become part of our atmosphere and do not leave. Since so much of these rays enter the earth, the atmosphere gets warmer, the oceans gets warmer and the ice caps begin to absorb them.
This absorption makes the oceans rise and makes the polar ice caps melt. The result is we have extreme weather patterns.
So which gases are the main causes of atmosphere damage? They include fossil fuels. They are the fuel that we use in cars and air planes and many power plants that generate electricity for us. The whole world as a single body needs to reduce the emission of these harmful gases.
What is weathering?
Weathering is the process where rock is broken down, gets dissolved or worn away into smaller and smaller pieces. We notice over time rocks break up. So how did all this happen to a rock that was so hard before? There are several ways this is done: By mechanical, chemical or organic weathering processes. Mechanical weathering physically breaks up rocks. Examples of mechanical weathering include freeze thaw, frost action or frost shattering. Water gets into cracks or joints in bedrock. It acts as a wedge. When the water freezes due to the cold, it expands and the cracks are opened a little wider. Over many years pieces of rock are split off the rocks face and big boulders are broken into smaller rocks and gravel. The same process happens with salt, which is known as salt wedging.
Another form of weathering is by expansion and contraction. During the hot days, the rock expands. At night it cools down and contracts. Over time it weakens the surface of the rock and then it falls off. Similarly, plants grow on the rocks and the roots of these plants break the rock. All these forms are known as weathering.
What is erosion?
Erosion is where soil and rocks are moved by wind, water, snow or other natural agents. Water is one of the main causes of erosion. It can be by means of rain, floods, rivers or waves. Every rain drop is chipping the earth slowly! When the river flows, it takes soil along with it! Have you seen the force at which the oceans batter the shore lines? Every strike is weakening the earth. The water’s force is gradually breaking up the earth.
The wind too carries soil and dust. It then deposits the soil further away. This repeated thousands of times, creates great soil movement.
The snow too, just like water causes the soil and earth to move. The great snow movement cause glazier erosion.
These three factors cause much of the erosion.
Humans are contributing to erosion by cutting more and more trees. This weakens the soil. Trees hold the soil together and protect the soil from being washed away. The more we cut them, the less the soil is protected and the greater the erosion.
The best example of erosion is the Grand Canyon. The Colorado River has been eroding the Grand Canyon for many millions of years.
What is deforestation?
The clearing of forests by logging, cutting trees or burning is called deforestation.
Agriculture use is the leading cause of deforestation. Many people who are subsistence farmers grow just enough food to feed themselves and their families. They cut more and more trees which they use as fuel. The trees may also be cut for ranching purposes as it is done in Arizona. In some cases deforestation is caused by fires that man cannot control.
The affects of deforestation
Deforestation affects the animal and the ecosystem. Many species of trees are being lost to deforestation. Some of trees lost used to provide ingredients for medicines. Also, as trees take-in carbon dioxide and release oxygen, the balance in the atmosphere is affected. With no trees, the free flow of rain water causes floods. Trees can suck up water and create vapor. Unfortunately, this does not happen nowadays. Many countries are trying to plant more trees and protect the present forests.
Why do Earthquakes happen?
Earthquakes are usually caused when rock under the earth suddenly breaks along a weak point. When two blocks of rock are rubbing against each other, they stick a little causing some form of friction. They don’t just slide against each other smoothly. After a while, the rocks break because all the pressure accumulated must be released. This breaking of the earth is what causes an earthquake. The pressure on the rocks has no other escape route.
The area underground where the rock breaks is called the focus of the earthquake. The place right above the focus is called the epicenter of the earthquake. Earthquakes happen every day around the world. But most of these earthquakes are minor and we can not even feel them.
Earthquakes are measured using a Richter scale. When the reading on the scale is greater than 7, it can cause great damage. If it is under 3, it may not be noticed.
The effect of an earthquake is that it can damage buildings, cause floods or start fires. Earthquakes cannot be predicted.