The Realms of the Earth

Primary Realms	Sub Realms	Thick (Km)	Temp (°C)	Pressure (Kpa)	Density (Kg/m³)	Area (m²)	Cycles
Core	Deep Inner Inner Core Outer Core	cell3_1	cell4_1	cell5_1	cell6_1	cell7_1	cell7_1
Mantle	D Layer Lower Mantle Transition Zone Upper Mantle	cell3_2	cell4_2	cell5_2	cell6_2	cell7_2	cell7_1
Asthenosphere	------------------	cell3_3	cell4_3	cell5_3	cell6_3	cell7_3	cell7_1
Lithosphere	------------------	cell3_4	cell4_4	cell5_4	cell6_4	cell7_4	Rock
Hydrosphere	Cryosphere	cell3_5	cell4_5	cell5_5	cell6_5	cell7_5	Water
Atmosphere	Troposphere Stratosphere Mesosphere Thermosphere Exosphere	cell3_6	cell4_6	cell5_6	cell6_6	cell7_6	Air
Biosphere	Geosphere Anthroposphere	cell3_7	cell4_7	cell5_7	cell6_7	cell7_7	Life Energy

The realm of land is called lithosphere, the realm of water is called hydrosphere and the realm of air is called atmosphere.
The narrow zone where land, water and air meet is called biosphere. It is the fourth realm of the earth and it supports life.
One of the reasons for supporting life is that the earth has plenty of water on its surface. The first life on the earth is originated in water.
The outer solid layer of the earth is called crust or lithosphere. The word lithosphere comes from a Greek word Lithos which means rock. So, the crust or lithosphere is made up of rocks.
About one-third of the earth’s surface is occupied by land and the rest is covered with water
Vast land masses rising above the sea level are called continents.
There are seven continents in the world. They are Asia, Europe, Africa, North America, South America, Australia and Antarctica.
The continents are separated from one another by huge bodies of water called oceans.
The level of the oceans is all the same and this level of water is called the sea level.
About 250 million years ago, all the continents were joined to form one huge landmass called Pangea.
Asia is the largest continent in the world.
Europe and Asia continents form a single landmass. They are separated by the Ural Mountains and the Black Sea. These two continents are collectively known as Eurasia.
Africa is the second largest continent next to Asia. The equator passes through the middle of this continent. But the portion lying in the northern hemisphere is bigger than the part lying in the southern hemisphere.
North America and South America are connected by a narrow strip of land called the Isthmus of Panama. North America lies in the northern hemisphere while the South America lies in the southern hemisphere.
Australia is the smallest continent. It lies in the southern hemisphere. Since it is small and surrounded by oceans on all sides it is called Island Continent.
Antarctica is situated in the southernmost part of the earth. The South Pole lies in the centre of this continent. This continent is covered by thick ice all the year round and seen as snow-white. Therefore, it is also known as the White continent.
The Climate of Antarctica is not suitable for human habitation.
There are three Major Landforms of the earth. Highland region having pointed peaks are called mountains. Highland regions having flat summits are known as plateaus. Lowland regions of flat and level surface are called plains.
Mountains rise several thousand metres above the sea level. When such highlands form a long chain, they are known as mountain range. At some places, they may occur in a series of parallel ranges. The Himalayas in the north of India have three parallel ranges.
Young mountains are very high but old mountains are low and rounded. Old mountains become low and rounded because they have been eroded over the years.
The Himalayas and the Rockies are young mountains while the Aravallis and the Urals are old mountains.
Mountains are not suitable for human settlement because it is difficult to construct roads and railways in such highlands.
The highest point on the earth’s surface is Mount Everest (8,848 m) in the Himalayas (Asia).
Elbrus (5,633 m) is the highest peak in Europe.
Kilimanjaro (5,895 m) is the highest peak in Africa.
McKinley (6,194 m) is the highest peak in North America.
Aconcagua (7,022 m) is the highest peak in South America.
Kosciusko (2,230 m) is the highest peak in Australia.
Vinson Massif (4,897 m) is the highest point in Antarctica.
Plateaus look like a table and hence it is known as tableland.
The highest plateau in the world is the plateau of Tibet. It is often called the roof of the world.
Plateaus are moderately populated.
Plains are found along the sea coasts or in the river valley.
Rivers originating from mountains carry large amount of silt. They deposit the materials either in the sea or along their banks. These deposits are responsible for the formation of plains.
Silt deposits made by rivers are known as alluvium. Alluvial deposits form the most fertile lands. Thus, plains are suitable for agricultural activities. And plains are thickly populated.
The island of Mauna Kea in Hawaii is a submarine mountain. It is 10,203 m high if it is measured from the ocean bed – higher than Mt. Everest.
Water is collected in large depressions of the earth. Thus, oceans, seas, lakes, rivers are formed. These water bodies are collectively known as hydrosphere.
There are four oceans on the earth’s surface. They are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and the Arctic Ocean. The Pacific, the Atlantic and the Indian Oceans meet in the southern part of the earth to form the southern ocean.
The Pacific Ocean is the largest and the deepest in the world. The Mariana Trench, off the Guam Islands in the Pacific, is 11,022 m
The Atlantic Ocean is about half the size of the Pacific. It resembles the letter S in shape.
The Indian Ocean does not open out to the north because it is bounded by the continent Asia. Therefore, it is called half an ocean.
The Arctic Ocean is located around the North Pole. Being situated in North Frigid Zone, it remains frozen for most of the part of the year. This ocean is not important for trade and navigation.
Like the surface of the continents, the ocean floor has also mountain ranges and deep valleys.
The blanket of air surrounding the earth is called atmosphere. It extends up to 1,600 Km from the earth’s surface.
The atmosphere is made up of gases like nitrogen, oxygen, carbon-dioxide, argon, etc.
Nitrogen is the most dominant gas. It constitutes about 78 % of the atmosphere. It helps the living organisms to grow.
Oxygen, the life of human beings, constitutes about 21 %.
The remaining 1 % is made up of other gases like argon, carbon-dioxide, hydrogen, etc.
The air is very dense near the surface of the earth. It becomes thinner and less dense when we go high up in the sky. The atmosphere keeps us warm and protects us from the harmful effects of the rays of the sun.
Plants need carbon-dioxide for their survival. The air we exhale is carbon-dioxidewhich plants take in. the plants, on the other hand, release oxygen which we inhale. So, there is a cycle in the atmosphere which helps in maintaining the natural balanceon the earth.
Biosphere extends a few kilometres above and below the sea level. Human beings, plants, animals, birds, fishes and other microbes are found in this realm.
Human beings are called Man because they can make decisions based on reason. Thus, we often say Man is a rational animal.
All the realms of the earth are inter-related. When something happens to one realm that will affect other realms too. Therefore, we must try not to disturb the realms of the earth as much as we can.

A biogeographic realm or ecozone is the broadest biogeographic division of the Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided in ecoregions, which are classified in biomes or habitat types.

The realms delineate large areas of the Earth's surface within which organisms have been evolving in relative isolation over long periods of time, separated from one another by geographic features, such as oceans, broad deserts, or high mountain ranges, that constitute barriers to migration. As such, biogeographic realms designations are used to indicate general groupings of organisms based on their shared biogeography. Biogeographic realms correspond to the floristic kingdoms of botany or zoogeographic regions of zoology.

Biogeographic realms are characterized by the evolutionary history of the organisms they contain. They are distinct from biomes, also known as major habitat types, which are divisions of the Earth's surface based on life form, or the adaptation of animals, fungi, micro-organisms and plants to climatic, soil, and other conditions. Biomes are characterized by similar climax vegetation. Each realm may include a number of different biomes. A tropical moist broadleaf forest in Central America, for example, may be similar to one in New Guinea in its vegetation type and structure, climate, soils, etc., but these forests are inhabited by animals, fungi, micro-organisms and plants with very different evolutionary histories.

The patterns of distribution of living organisms in the world's biogeographic realms were shaped by the process of plate tectonics, which has redistributed the world's land masses over geological history.

The natural systems that we will encounter in the study of physical geography operate within the four realms, or spheres, of the Earth. These are the atmosphere, the lithosphere, the hydrosphere, and the biosphere.

The atmosphere is a gaseous layer that surrounds the Earth. It receives heat and moisture from the surface and redistributes them, returning some heat and all moisture to the surface. The atmosphere also supplies vital elements carbon, hydrogen, oxygen, and nitrogen that are needed to sustain life.

The outermost solid layer of the Earth, or lithosphere , establishes the platform for most Earthly life-forms. The solid rock of the lithosphere bears a shallow layer of soil in which nutrient elements become available to organisms.

The surface of the lithosphere is sculpted into landforms.These feature such as mountains, hills, and plains provide varied habitats for plants, animals, and humans.

The liquid realm of the Earth is the hydrosphere , which principally comprises the mass of water in the world ’s oceans. It also includes solid ice in mountain and continental glaciers, which, like liquid ocean and freshwater, is subject to fl ow under the influence of gravity. Within the atmosphere, water occurs as gaseous vapor, liquid droplets, and solid ice crystals. In the lithosphere, water is found in the uppermost layers in soils and in groundwater reservoirs.

The biosphere encompasses all living organisms of the Earth. Life-forms on Earth utilize the gases of the atmosphere, the water of the hydrosphere, and the nutrients of the lithosphere, and so the biosphere is dependent on all three of the other great realms.

Most of the biosphere is contained in the shallow surface zone called the life layer . It includes the surface of the lands and the upper 100 m or so (about 300 ft) of the ocean. On land, the life layer is the zone of interactions among the biosphere, lithosphere, and atmosphere, with the hydrosphere represented by rain, snow, still water in ponds and lakes, and running water in rivers. In the ocean, the life layer is the zone of interactions among the hydrosphere, biosphere, and atmosphere, with the lithosphere represented by nutrients dissolved in the upper layer of seawater.

The four realms of earth : lithosphere , hydrosphere , biosphere and atmosphere.

Lithosphere : the outer most solid layer of the earth that is composed of rocks and soil is known as lithosphere is also called the crust of the earth.

Hydrosphere:the hydrosphere contains all the water bodies in the world that cover about 71 per cent of the earth's surface.

Biosphere : the biosphere is the narrow zone where the lithosphere , the hydrosphere and the atmosphere come in contact with one another.this realm contains all the living organisms found on the earth.

Atmosphere : the atmosphere surrounds the earth as a layer containing a mixture of gases is held by the gravitational force of the earth.

PLANET EARTH

Introduction
Planet Earth is the third planet from the Sun. It is uniquely suited for plant and animal life. About 70% of our planet is covered with water. The continents and islands make up the remaining 30% that lies above sea level.

Interior layers of the Earth, USGS

Earth's interior
Scientists study the Earth's interior using earthquake waves. The lithosphere of our planet includes both the crust and the upper mantle. The boundary between the Earth's crust and the Earth's mantle is named the Moho boundary and is where the speed of earthquake waves change their velocity. The asthenosphere normally lies below the lithosphere. The rocks in this part of the mantle flow like a liquid and can break apart.

Earth's surface
The lithosphere is above the asthenosphere and includes the crust and part of the upper mantle. Scientists in the last century discovered our planet's tectonic plate boundaries using earthquake wave patterns. Iceland sets on top of two plates that are separating. The Iceland volcanoes frequently erupt because they are also sitting over a hot spot.

Earth's atmosphere
The Earth's is surrounded by gases that form our atmosphere. When solar energy from the Sun hits our poles people living near the north pole are able to view the northern lights.

Polar front
Air movement around our planet affects many parts of our life. Polar air flows down from the north pole creating the polar front. Warm air from the Caribbean meets the polar front air causing turbulent air that can create tornadoes in the great plains area of the United States.

The Earth's Layers Lesson #1

The Four Layers

The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier, denser materials sank to the center and the lighter materials rose to the top. Because of this, the crust is made of the lightest materials (rock- basalts and granites) and the core consists of heavy metals (nickel and iron).

The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The Outer and Inner Cores are hotter still with pressures so great that you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!!!!!!

The Crust

The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350 degrees Fahrenheit , at 1600 degrees F. rocks begin to melt.

The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, plastic mantle which is located below the crust. These plates usually move along smoothly but sometimes they stick and build up pressure. The pressure builds and the rock bends until it snaps. When this occurs an Earthquake is the result!

Notice how thin the crust of the Earth is in comparison to the other layers. The seven continents and ocean plates basically float across the mantle which is composed of much hotter and denser material.

The crust is composed of two basic rock types granite and basalt. The continental crust is composed mostly of granite. The oceanic crust consists of a volcanic lava rock called basalt.

Basaltic rocks of the ocean plates are much denser and heavier than the granitic rock of the continental plates. Because of this the continents ride on the denser oceanic plates. The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere. The layer below the rigid lithosphere is a zone of asphalt-like consistancy called the Asthenosphere. The asthenosphere is the part of the mantle that flows and moves the plates of the Earth.

The Mantle

The mantle is the layer located directly under the sima. It is the largest layer of the Earth, 1800 miles thick. The mantle is composed of very hot, dense rock. This layer of rock even flows like asphalt under a heavy weight. This flow is due to great temperature differences from the bottom to the top of the mantle. The movement of the mantle is the reason that the plates of the Earth move! The temperature of the mantle varies from 1600 degrees Fahrenheit at the top to about 4000 degrees Fahrenheit near the bottom!

Convection Currents

The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water.

Many geologists believe that the mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over. The next time you heat anything like soup or pudding in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust. The crust gets a free ride with these currents. A conveyor belt in a factory moves boxes like the convection currents in the mantle moves the plates of the Earth.

Outer Core

The core of the Earth is like a ball of very hot metals. (4000 degrees F. to 9000 degrees F.) The outer core is so hot that the metals in it are all in the liquid state. The outer core is located about 1800 milesbeneath the crust and is about 1400 miles thick. The outer core is composed of the melted metals nickel and iron.

Inner Core

The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place as a solid. The inner core begins about 4000 miles beneath the crust and is about 800 miles thick. The temperatures may reach 9000 dgrees F. and the pressures are 45,000,000 pounds per square inch. This is 3,000,000 times the air pressure on you at sea level!!!

Answer the following questions on a sheet of paper with your partner. If you need to look back to find the answers use the page titles located directly under the questions to help you. When you finish the questions click on the Earth icon to return the program to the beginning.

1. Name the four layers of the Earth in order from the outside to the center of the Earth.

2. What causes the mantle to "flow"?

3. What are the two main metals that make up the outer and inner core?

4. Describe in your own words how the Earth's layers were formed. "The Four Layers" will help you.

Introduction

Although humans spend every day on the crust of the earth, we tend to take for granted the incredible physical features that the earth displays. For example, downhill skiing would be impossible without hills and mountains. But why were these mountains formed? It is easy to assume that they were not formed for the sole purpose of downhill skiing. The strength of the earth's movements are amazing. Natural disasters such as earthquakes are caused by the movement and heat of material below the earth's surface. To understand the formation of physical features of the earth and natural disasters, we must probe beyond the surface of the earth. The inner layers of the earth do have an effect on our daily lives, and it is important to know what is beneath the surface that we live on and how it works.

The Composition of the Earth

The earth contains three layers of different composition. The innermost is the core, the densest of the three layers. It is a spherical mass, composed largely of metallic iron, with smaller amounts of nickel and other elements. The middle layer is the mantle, made of dense, rocky matter. The outermost layer of the earth is the crust, which is the thinnet of the three layers. The core, mantle and crust are different sections of the earth because of the different composition they have.

Differing Physical Properties of the Earth

The earth also contains layers of differing physical properties. Examples of these properties are rock strength and solid versus liquid. Changes in physical properties differ from changes in composition because physical properties are controlled by temperature and pressure. These different properties divide the mantle and crust into three strength regions.

Mesosphere

The lower part of the mantle where rock is very highly compressed is called the mesosphere. It is located from the core-mantle boundary to a depth of about 350 km. The pressure in the mesosphere is so great that even though the rock is hot, it is solid and considerably more rigid than the rock on top of it.

Asthenosphere

The asthenosphere is the next layer within the mantle. It has the same chemical composition of the mesosphere but differing physical properties. In the asthenosphere, the balance between temperature and pressure is such that rocks have little strength. The rocks in the asthenosphere are weak and easily deformed, like butter or warm tar. The asthenosphere is also known as the "low velocity" zone of the mantle because seismic waves slow down as they pass through it. This property tells us that the asthenosphere is composed of partially molten rock slushlike material consisting of solid particles with liquid occupying spaces in between. Although the asthenosphere represents no more than six percent of the mantle, the mobility of this layer allows the overlaying lithosphere to move.

Lithosphere

The lithosphere is the top layer of the physical properties divisions. It begins at the uppermost level of the mantle and includes the entire crust. It ends with the surface of the earth. In the lithosphere, the rocks are cooler, stronger, and more rigid than the asthenosphere. It is rock strength that differentiates the lithosphere from the asthenosphere. The differences in strength between rock in the lithosphere and rock in the asthenosphere is a function of temperature and pressure. The lithosphere has a chemistry composition far different from the planet as a whole. Although rich in silicon like the mantle, it has far higher iron and magnesium contents and far lower aluminum, sodium, and potassium contents. (See figure 1).

(Picture taken from The Dynamic Earth: An Intorduction to Geology.)

Figure 1: Division of the earth.

Types of Crust

There are two types of crust that make up the surface of the lithosphere. One is oceanic crust and the other is continental crust. The ocean crust portion of the Earth's outer skin is fundamentally different in composition from the continental portion.

Continental Crust

The continents are constructed largely of rocks called granite, the ocean floor consists of rocks called basalt. The chemical composition of these two types of rocks is surprisingly different. The granitic crust is composed mostly of the elements aluminum and sodium along with potassium. Feldspar and quartz are the chief minerals in granite. A mica, either muscouite or biotite, is usually present, and many granites contain scattered bits of hornblende. Granite is intrusive igneous rock that is formed when magma solidifies within the crust or mantle. Another difference in granite and basalt is age. The granites of the continents range back to about 3.8 billion years but the ocean's basalts rarely exceed .1 billion years of age. This is because the oceanic crust is constantly being renewed with molten material that climbs upward from the mantle.

Oceanic Crust

The ocean basins take up 71 percent of the earth's surface, and the average depth of the oceans is 3.7 km. The other 29 percent of the earth's surface is continents, which have an average height of .8 km above the earth's surface. The reason that the continents stand higher than the ocean basins is that the oceanic crust is more dense (3.2 g/cm3) than the continental crust (2.7 g/cm3). Because the lithosphere is floating on the asthenosphere, those portions of the lithosphere capped by the lighter continental crust stand higher than those capped with oceanic crust. In contrast to granite, the chemical composition of basalt is closer to the composition of the mantle, with larger amounts of iron and magnesium than granite. Basalt is extrusive igneous rock, which is formed from the solidification of lava. The minerals pyroxine and olivine make up over fifty percent of b asalt.

Plates of the Earth

The lithosphere is not a continuous layer. Instead, the lithosphere is divided up into a number of huge plates that move in relation to one another. Some plates carry continents with them, while others carry only oceanic crust. Plates move over the surface of the earth about as rapidly as human fingernails grow. Although this may seem slow, the progress of plates over millions of years has been considerable. Many have moved as far as 500 or even 1000 kilometers in ten million years. It is believed that at the begining of the earth, the continents were all locked into a huge landmass, called Pangea. They broke apart and gradually drifted to their present positions. The plates are currently drifting sideways at rates up to 12cm a year. However, it is not just the continents that move, it is the lithosphere also.

Figure 3

Plate Tectonics

The motion of the earth's plates is called plate tectonics. Tectonics is derived from a Greek word "tekton" which means "carpenter" or "builder". Tectonics is the study of the movement and deformation of the lithosphere. Plate tectonics is the only hypothesis ever proposed that explains all of the earth's major surface features on the continents and ocean basins.

Motion of the Plates

What is the cause behind the motion of the plates? We know that the asthenosphere and the lithosphere are closely bound together. If one part moves, the other part must move with it. We know that the lithosphere must have kinetic energy in order to move, and the source of this kinetic energy is the earth's internal heat. The mantle is solid rock, but is subject to convection currents when a local source of heat causes a mass of rock to become heated to a higher temperature than surrounding rock. The heated mass expands, becomes less dense, and rises slowly. To compensate for the rising mass, rock that is cooler and denser must sink downward. The rate at which heat reaches the earth's surface can be accounted for only if convection in the mantle brings heat from the deep interior. It is hard to imagine how convection motions alone are responsible for moving entire plates. Most scientists believe that the lithosphere movement is due to a number of reasons and convection is only one of them. However, convections the process that keeps the asthenosphere hot and weak by bringing up heat from the mantle. Therefore, convection is essential for plate tectonics.

Plate Boundaries

Divergent

(

Figure 3

Convergent

Transform

Figure 4:

Summary

(Picture taken from The Dynamic Earth: An Introduction to Geology. 3rd ed., page 32.)

Figure 5

Closing Thoughts and Comments

Glossary

Andesites

Asthenosphere:

Basalt:

Continental Drift

Mesosphere

Lithosphere

Seismic Waves

Granite

Plate Tectonics

Divergent Plate Boundaries

Convergent Plate Boundaries

Convection

Subduction zones

Subduction

How is the asthenosphere different from the lithosphere?

Question Date: 2013-01-21

Answer 1:

The difference between asthenosphere and lithosphere is how the materials in these layers can flow. Rocks in the lithosphere are "rigid", meaning that they can bend but they cannot flow. Rocks in the asthenosphere are "plastic", meaning that they can flow in response to deformation. Even though it can flow, the asthenosphere is still made of solid (not liquid) rock; you can think of it kind of like Silly Putty. What determines whether rocks act in a rigid manner (bending or breaking) or a plastic manner (flowing) is temperature. Deep in the Earth, hot rocks (above about 1300°C) can flow, whereas cold rocks cannot. The lithosphere is broken up into rigid plates that ride on top of the flowing asthenosphere. In terms of chemical composition, there is no difference between the upper part of the asthenosphere and the lower part of the lithosphere. In fact, if the upper part of the asthenosphere cools down it becomes part of the lithosphere.

In addition to layers with different mechanical properties (lithosphere vs. asthenosphere), we can talk about layers with different chemical composition. The outer most layer of the Earth is the crust, which varies in thickness from about 7-70 km. Below that is the mantle, which of made up of denser rocks than the crust. At a depth of almost 3000 km, you reach the core, which is made of iron and nickel and is even denser than the mantle. The lithosphere is made up the crust plus the very upper part of the mantle, whereas the asthenosphere is only upper mantle material.

The Realms of Earth

PLANET EARTH

MORE PLANET EARTH LINKS

The Earth's Layers Lesson #1

The Realms of Earth

PLANET EARTH

MORE PLANET EARTH LINKS

The Earth's Layers Lesson #1

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