Our Earth

North America:
North America is the 3 largest continent according to its landmass. It is located at 7°12' north to 83°7' North latitude and 52°37' west to 172°27' East longitude, and has an area of 25.3 million sq.km (9.3 million sq. miles). The continent is bounded by The Atlantic Ocean in the east, The Paciﬁc Ocean in the west, The Arctic Ocean in the north, The Panama Canal and the Caribbean Sea in the south, and The Bering Strait in the north-west. It has 23 countries including the island nations of Central and Latin America with 16 territories.
The chief mountain chains here are the Rocky Mountain chain of approximately 4800km from North-South, Sierra Nevada, Sierra Madre and Appalachian Highland, Mt. McKinley (6194m) and Mt. Elbert (4399m). The rivers that ﬂow here are the Mississippi, Missouri, Arkansas, Rio Grande, St. Lawrence, Yukon and Colorado. There are some great lakes like the Great Bear, Great Slave, Superior, Huron, Michigan, Winnipeg and Ontario. The Niagara Falls is a world famous waterfall which straddles the international border between the Canada and United States. The Grand Canyon is the second deepest gorge in the world and is made by river Colorado. The Death Valley is the hottest place here with 150 sq. km. area and has an average temperature which does not fall below 50 C.

Climate and Vegetation:-

The factor aﬀecting the climate and vegetation of this continent are: latitude position, the Rocky Mountain Chain and coastal inﬂuence. Due to the inﬂuence of these factors, climate of North America greatly varies from one place to other places. There is extreme cold winter and very short summer with the maximum temperature of 10°C to 12°C. There is Tundra type of climate and vegetation called Taiga, with alpine forest consisting of soft wood. This forest is dense in Northwest and thinner towards East. The tall alpine trees are good in pulp and timber industries.

1. Central part of North America:

This region is cold in winter and hot in summer with less rainfall. About 150 mm annual rainfall takes place in this region. Vegetation consists of forest with scattered trees and large grass land which is called Prairies.

2. Southern-Lower part of North America:

It has mild winter and warm summer with adequate rainfall, due to coastal inﬂuence. It has coniferous forest.

3. The Northern Part:

The tundra type of climate is found in this part of North America. The climate is extremely cold throughout the year. The summer is very short and the winter is very long in this part. The temperature of this region varies from 0°C to 12°C. The climate in this part has been aﬀected by inﬂuence of longitude.

Physical Division

1. The Western Mountains:

The Rocky mountain chain is located in western part of North America. It is 4800 km which includes diﬀerent mountain ranges like, the Alaska Range, the Sierra Nevada, and Sierra Madre. The region is the main source of large perennial rivers, mines and tourists sites.

2. The Central Lowlands (Prairies):

It is a vast plain land which is very fertile and rich for cultivation and supported by the beautiful and large rivers for irrigation. It is favorable for wheat farming, cattle rearing, agro-based industrialization and networking of international market.

3. Eastern Plateaus (Highlands):

It is extended from the Hudson Bay in the North to the Gulf of Mexico in the South which includes Appalachian mountain. This is also called the Great Mississippi Plain because the Mississippi river and its tributaries ﬂow in the middle of the highland to the lowland.

South America:

South America is the 4 largest continent according to land mass. It has an area of 17.6 million sq. km (17,832,000 km ). It is location: 12°27' north to 55°59' south latitude and 34°41' west to 81°2' west longitude. It is bounded by The Atlantic Ocean in the east, The Paciﬁc Ocean in the west, The Panama Canal and Caribbean Sea in the north, and The Antarctic Ocean in the south. There are 12 countries with 4 territories in the region. It occupies 12% of the world's landmass. The Red Indians are the oldest natives of the continent.

The major rivers in the continent are The Amazon River, which is the biggest, widest and second longest river of the world, Parana River, San Francisco River, Orinoco River, Paraguay River, etc. The mountain ranges here are the Andes Mountain Range, which is the longest mountain range of the world that stretches 7,000 km nearly along the coast from north to south, the Brazilian Highland, the Guiana Island, Mt. Aconcagua, which is the highest peak in South America and has a height of 6960m, Mt. Cotopaxi, Mt. Khinbozaro, Mt. Corupuna, etc.

The Titicaca Lake is the largest lake at the highest altitude, 160 km, lies along the Peru-Bolivian border. The Atacama Desert is the driest place in the world. The Cape Horn is the wildest and stormiest place of the world. The Amazon forest is the largest rainforest of the world.

South America has some unique physical features. They are divided into three physical regions:

1. The Andes Region:

The region lies to the West of the continent. Andes Mountain Chain is the longest mountain chain of the world which lies in this region. It stretches about 7200 km from Venezuela in the north to the Southernmost part (Cape Horn) of Chile in the South. The altitude of the mountains decreases from north to south. The Atacama Desert also lies in this region. Similarly, Lake Titicaca, the largest fresh water and Navigable Lake, situated at the highest altitude also lies here. The major peaks are Mt. Aconcagua, Mt. Cotopaxi, Mt. Chimborazo, Coropuna, etc. is also located in this region.

2. The Central Lowland Region:

The Central lowland lies in between Western Mountain Region and Eastern Highlands. It has covered almost half territory of South America. They are drained by river Orinoco in the North, river Amazon and its tributaries in the center, and Parana-Paraguay River has formed a fertile plain in the Pampas. It has provided irrigation facility to the Pampas Grassland for cultivation.

3. The Eastern Highlands Region:

The Eastern Highlands consist of two major highlands. There are Guiana Highlands in the South and Brazilian Highland in the North-East. These Highlands are older than Andes. To the Southeast part of Brazilian Highlands, there lies a fertile plain. Major cities of Brazil are also located here

Africa:

Africa is the world's second largest and second most popular continent. There are 53 countries, 12 territories and 4 autonomous regions in this continent. The Victoria Falls is in Africa, which is the World's most beautiful fall. Among the Mountains and Mountains ranges, Atlas is the largest mountain range and Ginsberg Kilimanjaro is the highest mountain.

There are several lakes like Lake Victoria, the second largest freshwater lake in the world, and the Lake Tanganyika, the world's second largest lake in terms of volume as well as the second deepest lake. Congo, Zambezi, Zaire, Nile, and Niger are the famous rivers of Africa. Physical Division

The continent can be physically divided into three types, deserts, lowlands and highlands. The deserts are sandy and hot with temperatures very high all year long in some places. The lowlands are ﬂats and the highlands are the areas which are tall and hilly.

Climate and Vegetation

The climate of Africa ranges from tropical to subarctic on its highest peaks. Its northern half is primarily desert or arid while its central and southern areas contain both savanna plains and very dense jungle (rainforest) regions. In between, there is a convergence, where vegetation patterns such as Sahel and Steppe dominate. Africa is the hottest continent on earth and 60% of the entire land surface consists of dry lands and deserts like Sahara, Namibia and Kalahari. Population The continent has population with mostly dark skin tone due to the extreme hot climate. They have oily skins, broad lips and curly hairs. There are more than 800 tribes that reside here and each tribe has their own historical and cultural aspects. Most of the African countries are aﬀected by misunderstandings, violence and civil wars. The area also has limited exposure to the developed world and natural disasters like famine and hunger are prevailing. The Nile River originates from Victoria Lake as White Nile and later turns into the Blue Nile after reaching Egypt. Due to the Nile River, the basin is very fertile and appropriate for agriculture. The Sudanese live in The North, Arab Masai in Central Africa, and Bushman in the Southern parts. The main export of the continent is coﬀee, animal products, doves, radium, uranium, gold, tropical fruits, etc.

There are 5 physical divisions of Africa . they are as follows:

1.The Atlas Mountain

2.The Central Plateau

3.The High Plateau

4.The Great Rift Valley

5.The Nile and Zaire Basins

Temperate Zone:

The Mediterranean region is found in the countries bordering the Mediterranean Sea like Central California, Central Chile, Cape Province, South Western and Western Australia. It extends between latitudes 30° and 45° North and 30° and 40° South of the equator. The seasons experienced in this region are hot dry summer and mild wet winter. The average temperature varies from 20°C to 26°C in summer and 5°C to 15°C in winter. The rainfall is moderate, of about 65 cm to 70 cm annually. The Westerlies winds blow from sea to land in this region and bring rainfall.

The vegetation in this region is not luxuriant because of moderate rainfalls. The trees have hardwood, spongy barks, thick leathery leaves and long roots. Most common trees are oak, walnut, almond, chestnut, ﬁg, etc. Shrubs like myrtle, lavender and rosemary are also found in this region.

The wildlife is less and limited in this region. Native animals include deer, rabbits and numerous small rodents.

Birds tend to have short wings and long tails to make it easier to ﬂy. Temperate Grassland Climate The temperate grassland climate can be found between the Rocky Mountains in the west to the Great Lakes Region in the east in North America, Uruguay and Argentina in South America, between the Black Sea and the Caspian Sea in the west to Lake Balkhash and parts of North China in the East. It also extends between the Drakensberg Mountain and the Namibian Desert in South Africa and Murray-Darling basin of Australia.

The temperate grassland climate extends between 45° and 60° North and 30° and 40° South of the equator. It is also known as a continental type of climate. The climate is extreme with very cold winters and fairly hot summers. In summer, the temperature rises up to 24°C, and lowers in winter to about 0°C. There is moderate rainfall of 25 cm to 65 cm in the early summer season. The winter precipitation is in the form of snow.

There is not suﬃcient rainfall for trees to grow, so the vegetation is less as compared to other regions. Trees like willow and poplar are most commonly found. Short grasses grow everywhere. In places with rainfall more than 50cm, rich carpet of grass suitable for cattle rearing can be found. And where less that 50 cm of rain falls, stiﬀ grass suitable for only sheep and goats can be found.

Wildlife is comprised of animals which are found underground. Rodents like prairies dogs, hamsters, moles are found. Birds like ostrich, rhea, emu, etc. are not good ﬂiers but have strong, powerful legs to outrun predators. Antelopes, donkeys, horses, wolves, in Eurasia, bison, rabbits, prairies dogs in North America, kangaroo and dingo dogs in Australia are found. Temperate Oceanic Climate

The temperate oceanic climate can be found in St. Lawrence basin in North America, northern China, Manchuria, Korea and northern Japan. This climate does not occur in the Southern Hemisphere. It can be found between 45°N and 60°N latitude and 40°S and 50°S in the eastern part of the continents of North America and Asia. The temperature in the winter ranges from 9°C to 7°C, and in the summer from 15°C to 24°C. In the summer, rainfall occurs in the north-east Asia but not in North Korea and North Japan. The rainfall which is mainly cyclonic varies from 50 cm to 100 cm.

The natural vegetation here is mixed type of forest. At higher altitudes, coniferous forests are found. The main coniferous trees found there are spruce and pine. At lower altitudes, there are deciduous forests.

The wildlife consists of bears, foxes, beavers and squirrels. Temperate Monsoon Climate

The temperate monsoon climate can be found in North and South China, Southern Japan and Korea, South East USA, South Brazil and North Argentina, south-east coastal region of Africa and New South Wales and Queensland of Australia. It can be found between 30° and 45° North and 30° and 40° South of the equator. The area experiences warm moist summer and cool dry winter. The summer temperature varies from 21°C to 27°C and the winter temperature varies from 5°C to 12°C. The rainfall varies from 75 cm to 125 cm and occasionally aﬀected by hurricanes.

The areas with high summer temperature and heavy rainfall favor luxuriant evergreen vegetations. Deciduous type of forest is found in places with moderate rainfall and temperature. Pines and cypress are found in highlands and mountains. The area is well suited for grass, ferns, bamboos and palms. Mulberry trees thrive best in the region.

The region is densely populated with diﬀerent types of animals. Many types of birds and animals thrive in mountains and swamps with unique adaption suited for seasonal life. The bald eagle, nightingale, cardinals and hawks are some of the birds. Most common animals are squirrels, bear, beavers, foxes, deer, rats, snake and wolves.

Equatorial Climate

This region lies between 0° to 5° latitude in both hemispheres. Equatorial climatic region is found in Amazon Basin and Guinea Coast in South America, Congo Basin and Guinea Coast in Africa, Malaysia and East Indies. The equatorial region is rich in various species of wild birds and animals. About 90% of the living species of the world are found here.

As we know equatorial climate is near from the sun, the direct sun rays fall over there, which causes extreme hot throughout the year. The average temperature of this region is 27°C throughout the year. Days and night are equal and there is no change in season. The heavy convectional rainfall (evaporation in land) takes place everyday throughout the year the noon.

The forest found in this region is dense evergreen forest due to hot and wet climate (rainfall). The trees are tall with hard wood and broad leaves. The main species of the tress are Mahogany, Rose wood, Sal, Bamboo, Rubber, etc.

Major characteristics: 1. Equatorial regions have hot and wet climate because of the nearness of the sun. 2. These regions do not experience any season as they have hot and wet climate throughout the year. 3. There is dense evergreen forest with tall, big and hard wood trees because of the everlasting hot and wet climate throughout the year. 4. Conventional rainfall occurs almost in every afternoon with lighting and thunder throughout the year. 5. The forest in this area is called "Rain forest" or "Evergreen Forest" as they remain green throughout the year. 6. 90% of wild species are found here.

Tropical Grassland Climate

Tropical grassland climatic region is found between 5° to 20° Latitudes in both hemispheres. This region is situated between the hot desert in the north and equatorial climate in the south. Brazilian Highlands, parts of Bolivia, Paraguay and Argentina in South America, Sudan, Senegal, Queensland of Australia, Cuba, Jamaica and Paciﬁc islands in Central America are the major areas found in this region.

Generally, there are only two types of seasons found in this region i.e. summer and winter. The summer is hot and the temperature during the summer is 32°C. The rainfall varies from 50 cm to 150 cm during summer because of the inﬂuences of trade wind. The winter is cold and dry with the average temperature of 14°C. Due to less rainfall, very little number of about trees grows here.

As the land is fertile there because of the humus grass, the land has been covered by the tall and dense grasses which are about 10 ft. tall. The elephant grass is about 4m tall. They have long roots which help them to take the required minerals for their growth and development. Umbrella shaped and scattered trees are only found there because of dry land. The climate of this region can support to grow thick and long grasses, scrubby bushes and shrubs. Few numbers of umbrella-shaped and swollen trunk trees are found here but they survive due to less rainfall that occurs there. This region is called Savanna in Africa.

The savanna climatic zone is home of carnivorous and herbivorous animals. Millions of animals of diﬀerent species such as lions, tigers, rhinoceros, zebra, elephants, giraﬀe, etc. are found here. That is why this region is called Zoo of the worlds. It is also the home of many birds like ostrich, emus, etc. These birds live on the land where there are few trees. These birds are large and heavy and have long necks and legs which give them a wider range of vision.

Major Characteristics: 1. Tropical Grassland (Savanna) regions are known as Zoo of the Worlds as thousands of wildlife is inhabited in these regions. 2. These regions experience two reasons, cold and dry winter and hot and wet summer. 3. The rainfall varies from 50cm to 150cm because of the inﬂuence of trade winds, which causes more rainfall towards equatorial region and less towards deserts. 4. The land has been covered by long grasses with long roots to absorb water from the deep underground. 5. Very less trees having swollen trunk, long roots and umbrella shaped are found because of less moisture. Tropical Desert Climate

Tropical hot desert lies between 20° and 30° latitudes especially, in the northern hemispheres. Most of the deserts lie on the western sides of the continents because of dry trade winds that blow to the western parts of the continents. Sahara and Kalahari deserts in Africa, Arabian, Iranian and Thar Deserts in Asia, Arizona and Mexican deserts in North America, The great Australian desert in Australia etc. are the major areas found in this region. The climate of tropical desert is very hot throughout the year. The daytime temperature may rise up to 49°C and the night temperature fall to 10°C. The rainfall is unreliable as the trade wind blocks the rainfall.

Natural vegetation is very poor in the desert region. Most of the desert vegetation has long roots to collect water from the deep surface. Cactus and thorny plants are the major natural vegetations. They have capacity to store the water into their stem and leaves. So, it can survive in the hot desert.

Most of the desert animals are small and move about only in the cool hours of night or early in the morning. Kangaroo Rat eats the leaves of the cactus to get water required for their survival. They live in the burrows during the days and come out at night to eat the leaves of the vegetation found there. And other animals like rats, lizards, snakes also live in the bushes where they can avoid heat. They go for hunting at night and survive by hunting the living creatures found in the desert. Camels are the ship of the desert and are the best example of adaptation to the desert condition. Their skin is very thick so, they can survive extreme heat. They store water in the hump, so they can survive for 6 months without drinking water. They have ﬂat feet therefore they can walk easily on the sand. Desert fox gets liquid from the small creatures as they kill and get the blood required for their survival.

Oasis is the place or area where water is found in the desert. Date palm is found in this region. It is tall enough and is the important tree of this region. Its stem is used for timber, leaves for roof, bark for making ropes and mats. It also gives juicy fruits.

Major Characteristics: 1. This region has very harsh climate, as it is very hot and dry throughout the year. The temperature reaches about 45 C in the day time and falls to 10 C at night. 2. The trade winds block rainfall here and the bare rock and sand causes temperature to rise up in the day time. At night, it is too cold because the bare rock and sand cool down very fast. 3. Thorny plant with long roots to absorb underground water, thorny leaves to prevent the loss of moisture and thick ﬂeshy stems and prickles to store water are found in this region. 4. About 5% of the world population lives in this region. Bushmen of Kalahari, Bindibu of Australia, Bedouins of Arabia are the typical inhabitants of these regions. Some of them have nomadic life and involved in hunting and gathering and caravan trading etc. Tropical Monsoon Climate The tropical monsoon climate extends between 5° and 30° latitude. It covers most of India, Bangladesh, Sri Lanka, Myanmar, Thailand and other parts of Asia and Northern Australia. In summer, the rain bearing winds blow from sea to land, and dry winds blow from land to sea in winter. The annual temperature ranges from 32°C in summer and 15°C in winter. It is characterized by hot wet summer and cold dry winter. Rainfall varies from 25cm to 300cm from place to place.

The natural vegetation mostly comprises of deciduous forest, but others are also present. The vegetation also varies according to the rainfall. Evergreen forests are found in areas with rainfall over 200cm, deciduous forests in areas with 100cm to 200cm rainfall, and tall grasses and thorny shrubs in areas with less than 100cm rainfall.

Evergreen trees like leak, rubber, bamboo etc are found here. The deciduous forests like Sal, Acacia, Eucalyptus, etc. are present and the soil is highly favorable for agriculture. There are varieties of wildlife and existence of diﬀerent species of animals, birds etc. Wild animals like leopards, tigers, monkeys, etc are found in this region. Species of birds like peacocks, hornbill, parrot, etc. are abundant. Reptiles like snakes, alligators, crocodiles, lizards, etc. are also found in this region.

Polar Zone:

Siberian Climate:

This climate region stretches between 60°N and 70°N latitudes in the northern part of the continents. The main areas of this climate are southern Alaska, northern Canada, parts of Norway, Sweden, Finland, northern Siberia tot the south of the coastal parts. This climate is not found in the Southern Hemisphere. Climate Summer is warm and short, about two or three months long. Winter is severely cold and lasts for six or seven months. The summer is merely warm and winters very cold with extreme temperatures ranging from -35°C to -45°C. As the region lies very far from the equator, the sun rays are extremely slanting. Annual rainfall is about 40 cm. This rain is cyclonic rain. Water remains in the freezing state for months.

Vegetation The natural vegetation of this climate is the evergreen coniferous forest which is called 'Taiga' in Russia. The species of the trees are spruce, pine, maple, ﬁr and cedar. They are cone-shaped with short and drooping branches. Their leaves are like a needle so that they can prevent water loss. Their shallow roots absorb enough water when there is ice-melting. The wood of the trees is soft and very useful. It is used for making pulp for paper, matches, plastics, etc.

Animals Very few animals live in this cold dry climate. They are small, sturdy and have short tails and ears. The body is covered with thick fur which protects them from cold. The main species of wild beasts are bear, beaver, squirrel, minx and lynx.

Tundra Climate

Position and Distribution The Tundra climate region is located beyond 60°N and 70°N latitudes around the pole in the Northern Hemisphere. The chief areas of this climate are the northernmost parts of Canada, Alaska, north-west Scandinavia, Iceland, Greenland and Siberia. Climate There is severely cold throughout the year. The temperature goes down below the freezing point. In some places it is below -35°C. Summer is short not more than three months long. Winter lasts for nine or ten months. Sun rays are very slanting. Rainfall occurs in summer and is not more than 25 cm. Heavy snowfall occurs in winter.

Vegetation Due to biting cold and snowfall, trees and plants do not grow there. However, in the southern part birches, shrubs and willows are seen. In the northern parts only moss and lichen are found. They can survive in the extreme cold. They grow when the snow melts in summer.

Animals The wild animals found in this climate are reindeer, caribou, polar bear, musk ox and arctic fox. These animals have thick fur which keeps them warm. Whales, seals and some other ﬁshes are also found. In the Antarctic coasts, penguins are found.

Earthquake
The shaking or jerking motion of the earth surface vertically or horizontally is called an earthquake. The Hypocenter is the point inside the earth where the earthquake originates. The Epicenter is the point on the earth surface that is vertically above the hypocenter.
The seismic waves are the ways or the vibration traveled in a diﬀerent direction from the epicenter. A seismograph is an instrument that measures the intensity, origin and speed of the earthquake. The intensity of an earthquake is measured in Richter scale.

Causes of earthquake:
1. The adjustment of the continental plates inside the earth by colliding causes tremor at the hypocenter.
2. A volcanic eruption.
3. Large deposition of soil by the rivers causes huge pressure on the earth.
4. Underground bombs testing

Eﬀects of earthquake:
1. Destruction of the building, roads, electricity supply, etc.
2. Aﬀects on human and animal lives.
3. Causes landslides and mudslides.
4. Cracking the earth’s crust.
5. Formation of the lake, small hills etc\

Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, usually a sea or ocean. Tsunamis are often barely visible when they are in the deep sea. This makes tsunami detection in the deep sea very diﬃcult. A tsunami can travel at well over 970 kph (600 mph) in the open ocean. A tsunami may be less than a foot (30 centimeters) in height on the surface of the open ocean. But the powerful shockwave of energy travels rapidly through the ocean as fast as a commercial jet. Once a tsunami reaches shallow water near the coast, it is slowed down. The top of the wave moves faster than the bottom, causing the sea to rise dramatically.

Causes of Tsunami:
1. Earthquake
2. Volcanic Eruption
3. Underwater Explosions
4. Meteorite

Impacts Eﬀects of Tsunami:
1. Flooding
2. Devastating of property.
3. Loss of lives
4. Basic infrastructures destruction