The third planet from the Sun is your home. The Earth is the only known planet where life can survive. As far as we know, there is no other planet in the universe like Earth. We have a very narrow temperature range that allows water to remain a liquid. Life has developed over millions of years because of that liquid. What else makes us special? We have an atmosphere made up of nitrogen, a relatively inert gas. If we had clouds of sulfuric acid or methane, life may never have developed.
There are also huge landmasses on our planet. The rock plates that float across the surface are called tectonic plates. Those plates float on the mantle. The mantle is an area between the core and the crust. That mantle is basically filled with molten rock. It is kept in a liquid state because of the energy given off by the center (core) of the Earth. Scientists have also discovered that the pressure increases as you move towards the center of the planet. The core of the Earth has extreme temperatures and pressures that keep the iron and metals liquid and flowing.
The flowing metal in our planet helps create something called a dynamo effect. Dynamos create large magnetic fields. In the case of the Earth, the magnetic field protects our planet from space. The region of magnetic protection is called the magnetosphere and protects us from the solar winds and solar radiation. You can see where solar winds and the magnetosphere collide in the aurora borealis.
The structure of the planet is fairly simple to understand. Just as the atmosphere has layers, the upper layers of the Earth have layers. If you look at the outside of the planet, you can see that about 65% of the planet is covered by oceans of water. The rest of the 35% of the surface is made up of the continents.
Let’s look at the ocean zone first. Scientists break the floor of the ocean into three basic levels. The abyssal plain is the deep ocean floor. The mid-oceanic ridge is the middle layer. The final division is the ocean trench. The trench is the deepest part of the surface of the planet. Maybe you have already heard that the distance from the floor of the ocean to the top of a volcano in Hawaii is higher than any mountain above the surface. If you hadn’t heard, now you have. Cool! On the edges of the oceans are the continental slopes. They are the fringes of the continental plates.
Chances are, you’re on land right now. Scientists would say you are living on the sial. The sial is the part of the crust that is above water. It’s a continental plate floating over the globe. Right underneath the sial is the sima. The sima is the layer of the Earth’s crust that covers the entire planet. The sial is different in that it can begin and end where the plates do. You can think of the sima as the ocean floors. Under the sima is the mantle. When you consider the mantle is when you really start talking about the inner workings of the planet.
When you learn the layers of the Earth there really isn’t a lot to explain. It’s one of those memorization things. You might be wondering how all the layers came to be. When the Earth was forming billions of years ago, the matter came together. The densest matter moved to the center of the planet. The lighter rocks remained on the surface. When everything was done, the mantle wound up being about 2/3 the mass of the planet.
– Lithosphere (Sial and Sima)
– Asthenosphere (Molten Rock River)
OUTER CORE (Liquid Iron and Nickel)
INNER CORE (Solid Iron Compounds)
The basic idea behind plate tectonics is that there are eight major plates on the surface of the Earth. There are also bunches of minor plates. The plates are like the skin of the planet. They constantly move around the planet. When we say constantly moving, we’re talking centimeters each year. You couldn’t sit down and watch it happen. Or can you? You could watch it happen if you watched an earthquake.
They Really Float?
These plates make up the top layer of the Earth called the lithosphere. Directly under that layer is the asthenosphere. It’s a flowing area of molten rock. There is constant heat and radiation given off from the center of the Earth. That energy is what constantly heats the rocks and melts them. The tectonic plates are floating on top of the molten rock and moving around the planet. Think of it as ice floating at the top of your soda. When the continents and plates move it’s called continental drift.
Think of the molten rock in the asthenosphere, not as rock, but as a liquid. It has currents and it flows just like any other liquid. When the floating plates spread apart, it’s called a spreading center. When they are moving together, it’s called a subduction zone. When they are forced together, it is called a zone of convergence. One of the plates usually moves under the other in a zone of convergence. As the plate moves down into the asthenosphere it begins to melt. The place where they meet has a crack or a trench. Some of the deepest parts of the oceans are these trenches.
How do we back up these ideas? Scientists have traveled all over the Earth and found evidence that supports the ideas of plate tectonics. First, they looked at the continents. Ever notice how Africa and South America look like they could fit together? Scientists did. They cut up a map, moved the continents close together, and came up with a huge landmass called Pangaea (one super-continent).
Scientists also looked at the fossils (long-dead animal bones and plants) on the different continents. They found that fossils on Australia were similar to the ones in Southern Asia. They think the same plants once lived on the continents, but when they split apart, new plants developed. When they were digging, they also looked at the types of rocks. The West Coast of Africa has very similar rock formations to those on the East Coast of South America. They are too similar to be a coincidence.
When The Ground Moves
Rumble rumble rumble! Have you ever been in an earthquake? Some people go through them all the time. In California there are dozens every day but they are usually very small. You tend to remember the big ones. Earthquakes are the breaking and cracking of the rocks inside the continental plates. The breaks happen after stress has built up in the surrounding area. There are usually very few or no quakes when the plates move slowly. When there is a fast movement of the plate, there is a snap (like breaking a cracker).
Changing The Landscape
More than buildings collapse when an earthquake hits. The land itself is totally changed. You can see scars across the landscape. Those scars appear when one block of land has moved compared to another. Roads often change their placement. They either become uneven or just crack. Streams can also change course. Sometimes rocks can fall and block the stream. Other times, the land is even lowered in certain areas. When it’s lower, it’s easier for the water to flow in the new direction.
Changes also happen on larger scales. Fault valleys and troughs can be created. These areas have large amounts of fracturing (the fracture zone is large). After the land has opened up, weather begins to act on the area and erosion follows. Slowly, new valleys are created.
Waves Across The Land
You might think, “If it only happens in one place, why can you feel them hundreds of miles away?” The crack happens where the quake starts. Ripples then move out in waves across the plate. Those waves are called seismic waves. Those waves shake everyone up within a specific area.
When scientists analyze an earthquake they look at several parts. They find out where the focus is. The focus is the exact point where the earthquake started. It is usually many miles/kilometers below the surface of the Earth. Scientists also look to see where the epicenter was. The epicenter is the point on the surface directly above the focus. When you think about the epicenter, try to remember there is actually a crack in the crust many kilometers below.
Built For Quakes
After an earthquake, you can turn on the television and see all sorts of footage showing buildings that didn’t quite survive. Buildings are built for up and down forces. If you jump on your floor a bunch of times your house will stay up. Earthquakes have forces that move side to side. Houses aren’t built for that direction of energy. When the Earth moves side to side, the house can’t wobble and it snaps. The walls collapse and roof falls in. Really tall skyscrapers are well designed for earthquakes. They are built to withstand strong winds. When strong winds happen, they can move side to side and sway if needed.
Look up in the Sky
What is the sky? What is air? What is the atmosphere? The atmosphere is just a thin layer of gases that surrounds the Earth. It can act many different ways and you need it to survive. Just as there are layers inside the Earth, there are also layers in the atmosphere. The layers interact, heat up, and interact with the top layer of the Earth’s crust. Sometimes you feel the atmosphere as a cool breeze. Sometimes it’s a really hot and humid day that seems to push on you from all sides.
Like an Envelope
If compared to the diameter of the Earth, the atmosphere is very thin. It is a coating of gases that protects the Earth and life on Earth from the vacuum and radiation of space. The thickness of the atmosphere is a balance between the gravity of the Earth and energetic molecules that want to rise and move towards space. The molecules become excited as energy from the Sun hits the Earth. If the Earth were much larger, the atmosphere would be thicker. The gravity of a larger planet would pull those gas molecules closer to the surface and pressure would increase.
The atmosphere is far more than just a layer of gases surrounding the Earth. It is a moving source of life for every creature of the planet. While the atmosphere is mainly composed of nitrogen (N2), it also contains gases such as oxygen (O2) and carbon dioxide (CO2) that plants and animals need to survive. It has specialized molecules like ozone (O3) that filter out harmful radiation from space. The atmosphere also protects us from the vacuum of space. Without the atmosphere, our world would be as barren and dead as the Moon or Mercury.
One result of the circulation of gases and particles is the climate of the planet. There is not one climate for the whole planet. Specialized climates are found in areas all over the planet. There is one type of climate over the equatorial Pacific Ocean and another type at the North Pole. The common trait of all of these Earth climates is the atmosphere.
The hot air from the equator eventually moves north or south to other climates. That warmer air combines with cooler air and mixing begins (and storms form). That constant mixing of the atmosphere helps to keep a stable system for the organisms of this planet to survive. Oxygen will never run out in one area of the planet, and the temperature will not skyrocket in another.
A Cozy Blanket Around The Earth
The atmosphere looks like a blanket of gas when you look at it from space or the ground. When scientists started to examine the atmosphere, they noticed that there were different parts and different layers. There are layers of different molecules, temperatures, and pressures. Overall, the atmosphere is made up of a few main molecules. The air above you is made of 78% nitrogen (N2), 21% oxygen (O2), 0.9% argon (Ar) and 0.04% carbon dioxide (CO2). That’s it. The rest of it is made of things called trace elements. Those trace elements include water vapor, ozone, and other particles and molecules floating around.
The thermosphere is the layer closest to space. There is a huge amount of energy in this layer. The source of that energy is the solar radiation from space hitting the thermosphere. There are very high temperatures because of all the excited atoms zipping around. Something interesting you should know is that even though the temperature is very high (very excited atoms), there is actually very little heat.
Heat happens when energy is transferred from one atom to another. In the thermosphere there is such a low pressure (the molecules are spread out) that there is very little heat transfer. The mesosphere is directly under the thermosphere. The mesosphere has a lower temperature and is the coldest of all the layers in the entire atmosphere.
The real importance of the stratosphere is the ozone layer. Scientists call it the ozonosphere. Those ozone (O3) molecules absorb large amount of UV (ultra-violet) radiation from the Sun. A chemical reaction takes place when an ozone molecule absorbs the UV radiation. The energy is then radiated as IR (infra-red) radiation, and that is what heats up the layer. Without the ozone, UV light would flood the surface of the Earth and the temperature of the stratosphere would be much cooler.
At the bottom of the atmosphere, where most of the life on the surface exists, is the troposphere. The troposphere is the only atmospheric layer that can support life. The higher layers have filtered out the harmful radiation, and there are large amounts of water vapor.
This is the layer where clouds develop, birds fly, and pollution collects. Yes, the troposphere is where humans most pollute the atmosphere. It’s right where we live. The pollution goes into the troposphere and rarely leaves until it falls to the ground or is mixed into the oceans. Some pollutants called CFC’s make it into the stratosphere and break down the ozone layer.
There are both global and local circulations of the air around us. Scientists have different terms for the circulation based on how large the air movements are. They say macroscale to describe wind currents that are on a global scale. Mesoscale describes storms like thunderstorms or blizzards. There are also winds and small circulations that only last for a few seconds. These smaller circulations are described with the term microscale.
Around The Neighborhood
Let’s talk about local winds first. Sometimes you’re outside of your house and you feel a breeze. There are very fast winds high in the atmosphere, sometimes moving at hundreds of miles per hour. The unequal heating of air masses creates those winds. Those air masses are actually a big chunk of warm air and a big chunk of cold air.
The unequal heating and temperature differences also create a pressure difference, and the warmer gases spread out because the molecules need more room. All of these differences cause the molecules of air to move from one area to another. That air movement is the wind. When you open a soda can you are hearing wind coming out (so to speak). The gas rushes out because of the difference in pressure.
Around The World
Let’s look at the larger winds of the Earth called global winds. What about the huge, monstrous winds that circle the globe? What about the trade winds that helped sailors cross the Atlantic and Pacific Oceans? Scientists use the term cells. There are enormous cells of wind that wrap around the Earth. The winds that blow in the cells are created by temperature and pressure differences but also because of the spin of the Earth. The effect of the spinning Earth is called the Coriolis Force.
A big part of circulation is due to temperature differences. Think about the Earth. It is warmer in the middle than on the top and bottom. The poles are colder than the equator. When warm winds want to move north, the cold winds need to move south and fill the empty space. Can you picture the cell being built? It’s a big rotation of the gas molecules in the atmosphere.
Greenhouse Effect – What Is It?
So you’re thinking its nice, comfortable and smells good in a greenhouse. It’s hundreds of happy plants and a bit humid. Don’t start thinking that the greenhouse effect for Earth would make such a nice place. It’s a term that scientists use to describe a slow increase in atmospheric temperature. That increase could be natural or accelerated by humans. It’s not always bad, but it does bring change. As with everything on Earth, there are cycles. Cold periods changing to warmer periods just happen in nature. For our discussion, the current greenhouse effect is changing the world we live in and it might not lead to happy plant times.
It Just Happens
As we mentioned, many things cause the greenhouse effect in our atmosphere. Our story starts with energy from the Sun. High energy radiation hits the Earth and the shorter (more energetic) wavelength energy makes it to the surface. As all of that electromagnetic radiation hits the surface, the land and water heat up. When something heats up, it means they are releasing long wavelength radiation (infrared). When that new form of energy is radiated, it all doesn’t leave the Earth. Most of it bounces around our atmosphere. The result is an increase in the atmospheric temperature.
Water vapor also plays a part in trapping that reflected heat energy. More water vapor in the atmosphere allows for more absorption. With that said, think about the larger picture of the planet. As water vapor levels increase, the temperature rises. As the temperature rises, the polar ice caps begin to melt. A portion of that additional water moves to the atmosphere and allows for more absorption. The higher temperatures also lead to more extreme weather including winter storms and tropical cyclones.
All of that natural absorption, radiation, and reflection is supposed to happen. Without it, the temperature of our atmosphere would be much lower and life would have a harder time surviving. But lately, that temperature has begun to increase. and only part of it is natural.
As with everything on our planet, we affect the environment. Related to the greenhouse effect, we are releasing many chemical compounds into the atmosphere that trap that longer wavelength energy (heat). When it is trapped and reflected back, the temperature increases. Fossil fuels are the easy culprit. All of our cars and power plants are spitting out emissions that spread through the atmosphere changing the way the Earth works. There are also many pollutants that are released into the air. It doesn’t happen as much in developed countries because of laws that are in place. Developing nations across the world need to generate income, so they often don’t think about the pollution. The problem is that the atmosphere of the world is shared and all of their pollution becomes our pollution after a few weeks. Chemical compounds such as carbon dioxide, methane, and ozone are big players in the greenhouse effect.
Astronomers studying our solar system believe that many other planets show signs of the greenhouse effect. Planets such as Venus have many gases in the atmosphere that permanently trap energy received from the Sun, further increasing their temperatures. If it can happen in our solar system, there is also reason to believe we will discover planets in other systems that show the same activity.
Welcome to something we like to call the hydrosphere! This is where we talk about the way water moves through the world. Water affects everything that happens in life. In Latin, “hydro” means water. Therefore, anything that scientists describe, when it comes to water, is a part of the HYDROsphere. That water may be at the bottom of the ocean or in the top layers of the atmosphere; it is all a part of the hydrosphere.
Water Water Everywhere
Water is in the air, on the land, between the rocks, and in every living thing. Water, in its purest form, is H20 (two hydrogen atoms and one oxygen atom). You will usually find ions or compounds floating around in it, but water is just one small molecule. As you’ll discover, it’s very busy. While water may move and carry other substances with it, you need to remember that pure liquid water is the thing that makes life on Earth possible.
Liquid water makes the Earth a special place. Our planet has a very nice temperature range that allows water to remain in its liquid state. If we were a colder object like Pluto, it would not matter how much water there was on the planet; it would all be frozen. On the other hand, if we were on a very hot planet, all of the water would be in a gaseous state. Water vapor and solid water are useless to the living organisms found on Earth. Since the hydrosphere includes all of the water on the planet, you will study all of the various states of water. There will be solids in the deep glaciers, liquids of the oceans, and the vapor state of clouds.
I Am Water, Hear Me Evaporate
So you’re a water molecule. Chances are you’ll stay a water molecule and won’t ever be broken down. The world likes to keep its water around. Imagine that you’re moving through the hydrologic cycle. You evaporate, fall as rain, and drain into a river. There’s not a lot of excitement. How much time does it take? Scientists think that if you are lucky enough to evaporate into a cloud, you spend about ten days floating around the atmosphere. If you’re unlucky enough to be at the bottom of the ocean or stuck in a glacier, you might spend tens of thousands of years without moving.
Where is Groundwater?
Groundwater is water that is under the ground. Okay. You’re done with the tutorial. If you want more, you should know that groundwater is extremely important. Civilization gets most of its water from groundwater sources. There is more groundwater under the surface of the Earth than in all the lakes and streams put together. Unfortunately, groundwater is also polluted more than any other source of fresh water.
How It Gets There
Groundwater starts life on the surface. When it rains and the water moves through the soil, it’s called infiltration. The area near the surface of the soil is called the zone of aeration. There are spaces between the dirt and rocks that allow the water to flow through easily. Eventually the water makes it to rocks where scientists say it percolates deeper into the Earth (yes, like a coffee pot). The area where the water winds up is called the zone of saturation. Different from the soil, the zone of saturation has very small spaces between the rocks. The spaces are so small they may even be the size of large molecules.
When the water can go no deeper, it creates an aquifer. An aquifer is an underground reservoir inside the rocks. When a farmer digs a well, they are digging into an underground aquifer. After they drill to the water table (the highest level of the aquifer), they are able to pump the water to the surface. As farmers pump too much water out of an aquifer, they find that the water table dips in that specific area. That dip in the water table is called a cone of depression.
We’re talking about humans pumping water out of an aquifer. There are two kinds of aquifers. One type you need to pump the water out of and another type in which the water is under pressure and moves towards the surface by itself. The pumping type is called unconfined. It has a layer of permeable (water can pass through) rock on top and nonpermeable (nothing can pass through) rock on the bottom. The water does not build up any pressure because it can expand and contract. The second type of aquifer is confined and called pressurized. It is sandwiched between two nonpermeable layers of rock. There is nowhere for the water to go when new water comes in and the pressure builds. The water eventually pushes up to the surface and creates springs and a type of freshwater called artesian water.
Let’s start with standing freshwater biomes, from a river to a lake or pond. The water doesn’t move very quickly here. It gives animals a chance to grow up. You’ll find larger fish, insects, and plants in this lake. Scientists divide lakes into two major levels, limnetic (the top), and profundal (the deeper part). They even have names for the shore (littoral) and the very bottom on the floor of the lake (benthic). You’ll find most of the activity in the limnetic zone. Fishermen often fish in the limnetic zone.
Salty And Fresh Water Mixing
Estuaries are the regions where the freshwater meets the saltwater. They will always be found near the coast. Fresh and saltwater mix constantly in estuaries. This mixing allows huge amounts of marine life to exist. It turns out that this is a great area for fish to lay their eggs. The water is quiet and still and when the fish are tiny, they can hide in the cloudy (brackish) water. When you look around you will see all sorts of birds such as cranes and storks and insects who lay their eggs near the still water also.
Right Around The Coasts
The intertidal zone is where the waves hit the coast. Tides are controlled by the gravity of the Moon. The Moon causes them to move up and down each day. As they rise and fall they leave a patch of coast under the water when the tide is high. The same area is dry and exposed when the tide lowers. It’s usually very rocky here with lots of algae and small creatures. You can walk around when the tide is low and find sea urchins, sea stars, and all sorts of birds and insects looking for food with you.
Next to the intertidal zones are subtidal zones. This zone is always under water along the coasts of continents. You can find coral reefs and most of the world’s fish in this region. You’ll also find larger fish because they have more room to swim and more little fish to eat. There are also huge sandy plains in this subtidal region. Because of all of the waves and activity, there is a lot of oxygen in the water to support the wildlife.
Deep In The Ocean
There comes a point where the floor of the ocean just drops away. Now you are in the deep ocean biome. Scientists break this biome into three layers. At the surface is the euophotic zone. There is a large amount of sunlight and oxygen but very few nutrients. They all fall to the bottom of the ocean. You’ll find many small organisms that are photosynthetic. As we move down, we get to the bathyal zone. The light is very dim. No little organisms are found here, just some fish who feed on the organisms at the surface. At the bottom of the ocean is the abyssal zone. This zone is pitch black, with no producers, little oxygen, extremely cold, and high pressure. There are living organisms down there. They usually feed on the dead stuff that falls from the surface layers. Then, of course, there are the predators that swim through the murky depths.
A Big Ball of Life
The biosphere is all about life. Physical geographers use the term biosphere to describe our living world. This is where all of the trees, bugs, and animals live. The biosphere extends to the upper areas of the atmosphere where birds and insects can be found. It also reaches deep into the ground at a dark cave or to the bottom of the ocean at hydrothermal vents. The biosphere extends to any place that life (of any kind) can exist on Earth.
The biosphere is the one place where all of the other spheres of the planet work together. Think about the interactions for a second. The land interacts with the water (hydrosphere). The land interacts with the air (atmosphere and climates). The land even interacts with forces deep inside the Earth and the energy coming to the Earth from space. All of those forces work together to create our living world.
Big, Small, and the Smallest Factors
Many factors affect the biosphere and our life here on Earth. There are large factors such as the distance between the Earth and the Sun. If our planet were closer to the Sun, it might be too hot to support life. If we were further away, it might be too cold. Even the tilt of the Earth is important. Seasons and seasonal climate changes are direct results of the tilt of the Earth towards or away from the Sun.
Smaller factors are also act on the biosphere. If you were to look at a piece of land that was only one square mile, you would find influential factors such as climate, daily weather, and erosion. These smaller factors change the land and the organisms must react accordingly. Even though humans are able to control their environment, they are still vulnerable to weather and earthquakes.
The smallest of factors in the biosphere work on a molecular level. Chemical erosion is a great example of a landscape changing one molecule at a time. Oxidation and reduction reactions happen all the time, changing the composition of rocks and organic materials. It’s not just chemistry at work on the molecular level. Tiny organisms such as bacteria and single-celled organisms are constantly working to break down materials (organic and inorganic) and change the world.
An Ecological System
The word ecosystem is short for ecological systems. An ecosystem includes all of the living organisms in a specific area. These systems are the plants and animals interacting with their non-living environments (weather, Earth, Sun, soil, atmosphere). An ecosystem’s development depends on the energy that moves in and out of that system. As far as the boundaries of an ecosystem, it depends upon how you use the term. You could have an entire ecosystem underneath a big rock. On the other hand, you could be talking about the overall ecosystem of the entire planet (biosphere).
An ecosystem can be as small as a puddle or as large as the Pacific Ocean. That ecosystem includes every living and non-living thing in the area. It is several small communities interacting with each other.
Let’s look at a puddle example. You might start by looking at the temperature, depth, turbulence, sunlight, atmospheric pressure, weather patterns, wind, nutrients, etc. Those are just the non-living things in the ecosystem of a puddle. When you add on all the living interactions, you have a good idea how complex an ecosystem can be. Even a puddle is an amazing place.
Scientists discuss some general ecosystem types. They call them biomes. A biome is a large area on the Earth’s surface that is defined by the types of animals and plants living there. A biome can be partially defined by the local climate patterns. You may also have more than one type of biome within a larger climate zone. Here is a short list of possible biomes.
– Tropical Rainforest (Think about Brazil)
– Tropical Savanna (Think about Africa)
– Desert (Think about the middle east)
– Mediterranean Woodland (Think about coniferous forests)
– Mid-latitude Grassland (Think about Oklahoma)
– Mid-latitude Deciduous Forest (Think about the east coast of North America)
– Tundra (Think about frozen plains of Alaska)
– Ice Caps (Think about the poles)
Biomes don’t just start and stop when they border each other. They all have transition zones that have characteristics of both sides. That zone is like a blending of two biomes. Scientists call it an ecotone. Ecotones can happen at the edges of forests, deserts, and mountain ranges. They are often easy to see because one type of world (many trees) changes quickly into another type (the cliffs of a mountain). While an ecotone on the ground may not cover a large area of land, climate transition zones between biomes are often very large.
Another Link in the Food Chain
Everyone plays a specific role in the food chain of life. You might be a human thinking they are king of the hill or you might be a bacterium under the feet. You are very important to the survival of the system no matter what role you play.
As you study more about ecosystems and cycles in life, you will see the terms food chains and food webs. They describe the same series of events that happen when one organism consumes another to survive. Food web is a more accurate term since every organism is involved with several other organisms. Cows might be food for humans, bacteria, or flies. Each of those flies might be connected to frogs, microbes, or spiders. There are dozens of connections for every organism. When you draw all of those connecting lines, you get a web-like shape.
Producers are the beginning of a simple food chain. Producers are plants and vegetables. Plants are at the beginning of every food chain that involves the Sun. All energy comes from the Sun and plants are the ones who make food with that energy. They use the process of photosynthesis. Plants also make loads of other nutrients for other organisms to eat.
There are also photosynthetic protists that start food chains. You might find them floating on the surface of the ocean acting as food for small unicellular animals.
Consumers are the next link in a food chain. There are three levels of consumers. The levels start with the organisms that eat plants. Scientists named this first group of organisms the primary consumers. They are also called herbivores. They are the plant eaters of the chain. It might be a squirrel or it might be an elk. It will be out there eating plants and fruits. It will not eat animals.
Secondary consumers eat the primary consumers. A mouse might be a primary consumer and a cat might be the secondary. Secondary consumers are also called carnivores. Carnivore means “meat eater.”
In some ecosystems, there is a third level of consumer called the tertiary consumer (that means third level). These are consumers that eat the secondary and primary consumers. A tertiary consumer could be a wolf that eats the cat and the mouse.
There are also consumers called omnivores. Omnivores can either be secondary or tertiary consumers. Humans and bears are considered omnivores: we eat meat, plants, and just about anything.
The last links in the chain are the decomposers. If you die, they eat you. If you poop, they eat that. If you lose a leaf, they eat it. Whenever something that was alive dies, the decomposers get it. Decomposers break down nutrients in the dead “stuff” and return it to the soil. The producers can then use the nutrients and elements once it’s in the soil. The decomposers complete the system, returning essential molecules to the producers.
Break It Down
Erosion is the process that breaks things down. As far as we’re concerned, erosion is the breakdown of the continents and the land around you. The overall effect of breaking down and weathering the land is called denudation. Denudation is the process of erosion. In nature, large things are broken down into smaller things. Boulders become sand. Mountains are rained on and become hills. The pieces of the mountain become smaller pieces and go down the sides of hills. Weathering and erosion always happen in a downhill direction.
Erosion is an easy idea to understand. If you see a rock, pull it out of a mountain. Then throw it down on the ground. You are now a part of the erosion of that mountain. You have taken a big object (a mountain) and started to make little objects out of it (a rock). When that rock hit the ground, it could have cracked and made some tiny pieces of rock (sand). Erosion is just that easy. When it rains, the same process happens. Rocks are washed down a mountain or down a stream. Soils are washed away. The ocean beats against a cliff and breaks it apart. They are all examples of denudation.
Mass wasting can happen two ways:
1) mechanical, similar to breaking a rock with a hammer; and
2) chemical, similar to pouring acid on a rock to dissolve it.
A surefire way to tell what is happening is to check the color of the rock. If a boulder breaks because of frost, you won’t see a color change. If you see rock that has been near the ocean, you may observe color changes because it is oxidizing.
Does Erosion Build Things Up?
Erosion happens at the tops of mountains and under the soil. Water and chemicals get into the rocks and break them up through those mechanical and chemical forces. Erosion in one area can actually build up lower areas. Think about a mountain range and a river. As the mountain erodes, the river carries sediment downstream towards the ocean. That sediment slowly builds up and creates new wetlands at the mouth of the river. The swamps of Louisiana are good examples of sediment carried by the Mississippi River and collected at the end.
Natural Resources And Recycling
The Earth is a closed system. For our examples, we need to think that nothing comes in (except energy) and nothing goes out (except energy). Even the amount of energy that moves in and out of the Earth is equal. If more came in than was released, we would heat up. If the Earth gave off more energy than it received, we would cool down. The smarties in the crowd are saying “What about meteorites?” Yes. There are small amounts of matter hitting the Earth from space. On the other hand, we are sending more satellites and spacecraft into orbit. A little is being lost too.
The big point of this section is to look at the idea that humans have a finite amount of material on this planet. We call these materials natural resources. Not only are humans using these materials, but nature is using them too. The difference between humans and nature is that nature doesn’t waste. Materials are cycled through the ecosystems of the Earth and reused whenever possible. There have been points in time where nature runs out of things and it adjusts, changing ecosystems or the types of organisms that survive. Think about water for a second. Many places used to have large freshwater lakes with thriving communities. Over thousands of years, those lakes dried up and some even became deserts. Nature didn’t just give up, with the change in environment, new organisms began to thrive and the ecosystem changed.
Humans may be doing that as we speak. We use natural resources, but don’t return them to the system. They may wind up in landfills or at the bottom of the ocean. If we have a finite amount of resources, there is always the possibility that we will run out. Nature will continue. The organisms that survive will change. But we might not be one of them. Don’t worry about it this afternoon. We have plenty of stuff for a long time.
In The Forests
Forests are an easy starting point. These are dense ecosystems with a large amount of plant life. Types include tropical and temperate forests. Some have a lot of rain and others have seasonal moisture. Humans like the land and the trees. Realtors say location-location-location when they talk about homes. They know that there is only a specific amount of space in an area that people can live. Unfortunately for forests, they are sometimes sacrificed for our needs.
We like the timber. We build houses and all sorts of stuff from wood. The big worry of many people is not timber, it’s the fact that many forests are being cut down to increase the amount of farmland. What happens when you lose forests? Well, there’s less timber. There’s also a complete change in the ecosystem. Forests absorb heat and cool areas. They also release oxygen into the atmosphere and help purify the air. When you clear-cut a forest the temperatures can increase, wind patterns can change, and (many would argue) it’s less beautiful. But there’s always a trade-off. We need more food. More farmland=more food. As with all of our discussions of natural resources, management of the resources is the key to success.
In The Mountains
Are they just big hunks of rock? No way. Mining operations see mountains as the source of their ore. They might be looking for iron, silver, gold, diamonds. whatever. All mining requires a hole in the mountain, blowing up part of the mountain, or maybe making a deep hole in the ground. We use the mountain loosely. Think of it as the surface of the Earth. As with forests, there are only so many areas with easy mining opportunities. If humans use up all of those locations, the cost of getting those resources will go up. There’s also the problem of destroying the surrounding area. Not only do some mining operations leave big holes in the Earth, but also the process of mining often collects toxic materials in the rocks. Those pollutants are left over and poison the surrounding area. There are ways to use these resources, but intelligent management is the key.
In The Water
Oceans, water, puddles. All areas with water are natural resources. The most direct connection to you is drinking water. Aquifers exist under the surface and wells pull that freshwater out for you. If humans take out more water than goes in, they will run out of water. An even worse situation would happen if the water were accidentally poisoned (maybe mining or farming). If you look at all of the water on Earth, there isn’t a lot of freshwater. That’s what makes it so important. Saltwater provides other things we need including food. Fishing is a huge industry that needs to be managed so we don’t over fish the oceans. If we do, there won’t be enough fish left for the world. We’ll say management again, but you need to understand there aren’t easy answers.
You might think of competition as a baseball game or maybe two wolves fighting over a piece of meat. The real competition of your future will come from people competing for natural resources. There will always be at least three groups involved. You will hear about business and companies that want to take as many natural resources as they can in order to have a more successful business. Many of them will not be thinking long term, especially in developing nations. You will also hear about environmental extremists who want to keep the Earth exactly as it is. They might want to lock out all industry from using any more natural resources. They often think that because they are willing to sacrifice certain pleasures in life, everyone should. And then there will be those in the middle. People who think long-term and want to preserve the environment but know that business will need some of the resources. The environmental managers will plan for plans such as reforestation and fisheries to replenish the oceans.
There will be no easy answers. Just know that when it comes to natural resources you need to think long-term. The Earth and nature will adjust. It’s the people that might not be happy with the results.
First a definition… What the heck is a climate? Is it weather? Is it the rain? Is it a hot day in August? Yes, yes and yes, but only in one place at a time. Climate is the atmospheric condition in a certain location near the surface of the Earth. Is the Aurora Borealis (Northern lights) a climate? No. Is there such a thing as a global climate? Yes. Kind of. It’s all of the climates of the planet added up. If the Earth were getting hotter you would have to say, “All of the global climates are increasing in temperature.”
There are many types of climates across the Earth. You live in one of them or one the border between two. Every year as the seasons change, your climate changes a bit. It might get warmer or colder. You might have more or less rain. You might have more or less sunlight that changes all of that other stuff.
Scientists have broken down the world’s climates into a few types:
– Polar: Ice Caps
– Polar: Tundra
– Subtropical: Dry Summer
– Subtropical: Dry Winter
– Subtropical: Humid
– Subtropical: Marine West Coast
– Subtropical: Mediterranean
– Subtropical: Wet
– Tropical: Monsoon
– Tropical: Savannah/Grasslands
– Tropical: Wet
What Makes A Climate?
Several factors go into making a climate. Those factors also affect what the climate will do. Scientists can then make observations and predictions of what will happen in certain climates. If it’s hot today and a storm is coming in, you can guess it will get cooler. More specifically, if it’s summer where you live, hot and humid, you might be able to guess that you’ll have thunderstorms in the evening. These factors usually happen in the atmosphere in the area you are looking at. There is more water vapor in the air if it is humid. If there is a lot of wind, something is making that wind speed up. It could be a series of mountains, or you could be near the ocean.
As we move into these factors, you need to understand that they all affect each other. Examples would show you that higher temperatures might increase evaporation of water that would then increase humidity.
The temperature changes throughout the day. At mid-day the temperature gets hot, the land heats up, and air rises. In a coastal area when the air rises, it is replaced by cool air from the ocean. This creates a breeze. When evening comes, the ground cools and the air over the ocean is warmer. The breeze shifts to move towards the ocean.
Atmospheric pressure is another important factor. There are large masses of high and low pressure across the Earth. There are also small changes in air pressure that affect you locally. In the borders between high and low pressures you will find storm fronts or smaller changes in weather: temperature, humidity, or cloud cover.
The number of clouds and the amount of dust and smog affect local climates by changing the temperature. Increased cloud cover decreases the amount of energy hitting the Earth from the Sun. This decrease in energy lowers temperatures. In an extreme example, something called nuclear winter covers the entire planet with clouds. With no sunlight getting through, the plants begin to die.
Humidity is a measure of the water vapor in the surrounding air. As humidity increases, the chances of rain also increase. You see, the air can only hold so much water vapor before it says, “Whoa! I can’t do it anymore!” Then it needs to rain. Thunderclouds can be created and violent storms can dump huge amounts of water on the land.
Wind speed is that last factor we will cover. When we talked about temperature we discussed on-shore and off-shore winds. Sometimes these can be nice slow breezes and other times very fast and destructive. You may also encounter situations near the base of mountains where changes in temperature create winds that reach 80 miles per hour.
The most moist and warm of all the climates on the planet is the tropical rainforest climate. This climate experiences daily thunderstorms. The storms are called convectional because they are caused by the surface heating up during the day, and the high humidity creates thunderclouds. With the high amount of rain, the trees never lose their leaves. They are evergreen. The trees also have big broad leaves to catch the Sun’s light. The trees are very high and their branches create a canopy. That canopy lets very little light reach the ground, and there are very few plants on the surface. You will find bacteria and small animals on the ground that break down the plant material that falls. Go to Brazil to see these forests.
Marine West Coast
The marine west coast climate is characterized by a mild winter and a cool summer. Because these areas are so close to the ocean, the temperatures generally remain within specific ranges. Much of Europe is classified as this climate type. When you say mild, you have to consider the extremes of temperatures that can happen at the same latitudes. Even though you can expect a reasonable temperature range, there is always unpredictable weather (day-to-day occurrences). Sometimes you get a lot of fog, and other times you get a strong frost at the end of spring. Those frosts make the growing seasons shorter than for most other places.
Mediterranean dry summer climates have very wet winters and dry summers. Maybe you’ve been to California or to places in Europe. Even though they are thousands of miles apart, they have very similar climates. They are kept cool (in summer) because of the ocean currents that move past their coastal areas. They get most of their rain for the year (70%) in the winter months. The rest of the year is generally very dry. In California the local plants are considered to be drought resistant because most of the water has gone by April and May. They have to survive until November when the rains begin again.
The subarctic climate type is the last stretch of land before you get to the polar regions. Subarctic climates are more seasonal than many other climates. Because they are at such high latitudes, their day length also changes a lot (very short in winter, long in summer). Sometimes the Sun comes up at three in the morning! A characteristic of these areas is that they may have had glaciers on the land thousands of years ago. The glaciers cut through the landscape and even now, there are very few plants and very thin soil.
-To understand better this topic, enjoy the following activities and videos:
http://www.youtube.com/watch?v=lwwioJhQzeg Planet Earth (Views From Space)