7th Geography

I. Choose the correct answer

1. The major reason for the drought is the_______________ .

(a) Scarcity of rainfall (b) environmental degradation (c) A forestation (d) Industry

2. Tornadoes are common in

(a) India (b) Bangladesh (c) China (d) U.S.A

3. Landslides often occur in

 (a) Desert region (b) Forest region (c) Tundra region (d) Hilly region

4. The word Tsunami has been derived from

(a) Tamil (b) French (c) Japanese (d) Latin

5. Of the following which is not a natural disaster

(a) Nuclear explosion (b) Deforestation (c) Forest fire (d) Lightning

II. Match the following

1. Tornadoes – Rotating air 1

2. Molten rocks – Volcanic eruption 2

3. Landslide – Heavy rainfall 3

4. Drought – Scarcity of rainfall 4

5. Earthquake – Tsunami 5

III. Answer the following questions briefly

1. Define Mitigation.

Mitigation

It means “to make less severe”. Therefore, it can be defined as “taking action to reduce the effects of a hazard”.

2. What is Landslide?

Landslide

Landslide may be defined as the mass of rocks and debris move down a slope.

Debris flow is also known as mudslide.

3. Differentiate floods and droughts.

Drought

· Drought refers to the prolonged dryness of weather due to lack of rainfall.

· It is difficult to indicate the time of its onset and end.

4. Differentiate Tornadoes and Cyclones.

Cyclones

· The cyclones are the strongest winds generated by the meeting of the cold and warm fronts in the centre of low-pressure systems.

· When they are all formed over the sea and oceans they become violent due to the fact that there are no barriers to check these winds.

Tornadoes

· Tornadoes refer to the violently rotating columns of air.

· They extend from a funnel shaped cumulonimbus doud to the earth.

· Their width varies from a few meter to more than a 36 kilometer and it rotates at a speed between 64 km and 509 km per hour.

IV. Answer the following questions in detail

1. What do you meant by disaster? Explain the natural and man made disaster.

The disasters are broadly classified into Natural and Man- made. The natural disasters occur due to the natural forces whereas the man-made disasters occur due to human negligence, carelessness and ignorance.

2. Write about Tsunami and its effects on environment.

Tsunamis

v They are killer waves or Giant waves generated by earthquakes, volcanic eruptions or underwater landslides.

v It can raise to 15 metres or more in height. When earthquakes occur in the sea or ocean, the sea waves rise to several meters and may reach the coast within a few minutes.

v The danger period of Tsunami can continue for many hours after a major earthquake.

v Tsunami waves travel at a speed of 320 kilometer per hour and speed Increases when it approaches the continents.

A killer Tsunami hit South East Asian Countries on the 26^th December of 2004 killing more than 150000 lives.

v The emotional, economic and ecological toll of the disaster cannot be calculated. Many villages have lost entire generation.

v This was the biggest earthquake to hit the world in 40 years.

v No one could have thought that its effects would ripple worldwide overnight.

2. What are floods? List out the Mitigation measures of flood affected areas.

Floods

v Floods are a temporary inundation of overflow of water. They are caused due to very heavy rainfall, cyclones, melting of snow, tsunami or a dam burst.

v Floods are common features in Tamilnadu, Andhra Pradesh, and Orissa due to very heavy rainfall during the Northeast Monsoon season and in Mumbai during the Southwest Monsoon season.

v Floods destroy sewage system, pollute water, cause soil erosion, silt deposition, waterlogging, destruction to agricultural fields, livestock, damage to the fishing equipments, building structures and to the loss of life.

v Floods and droughts are the two problems caused due to the vagaries of monsoon.

Mitigation

v To avoid overflow of water, many channels are required, to drain, especially near the agricultural fields and low-lying areas.

v River embankment, desilting are needed especially in the ponds and lakes.

v Sand bags are to be kept in front of houses in the low-lying to block the water reaching inside.

v Afforestation is to b e encouraged to follow any one of the rain water harvesting methods.

v People from the low-lying areas are to be shifted to elevated areas.

v Students are to be trained to take part in the social activities at the time of floods.

3. What is called drought? Write about its effects.

Drought

v Drought refers to the prolonged dryness of weather due to lack of rainfall.

v It is difficult to indicate the time of its onset and end. According to the Indian Meteorological Department, the country is declared as drought-affected when overall rainfall deficiency is more than 10 % over a long period.

v The major reason for the drought is the scarcity of rainfall.

v Scarcity of rain can be listed due to failure of monsoons, vagaries of monsoons, deforestation, environmental degradation, high rate of evaporation, poor land management, overgrazing and soil erosion.

v The rainfed crops are mostly affected due to droughts.

v Other effects are:

(i) scarce drinking water supply,

(ii) shortage of food,

(iii) lack of water to the livestock,

(iv) nutrition deficiency diseases and

(v) soil erosion.

4. Write about the seismic zones of India.

India is divided into four seismic zones. They are listed in the following table:

V) Fill in the blanks

1. A hazard is an EVENT .

2. India is divided in to FOUR seismiczones.

3. In India Tsunami warning centre has been set up at HYDERABAD.

4. Debris flow is also known as MUDSLIDES

5. Avalanches occur on the high and high LATITUDE AND ALTITUDE

I. FILL IN THE BLANKS

1.The Greek world klimal’ refers to ——–

Inclination.

2. The temperature on the earths surface decrease at the rate of 6.5^oC for every 1000 meter.

3. EI Niño means the ————— in Spanish

Christ child.

4. The —————- is a metropolitian are which is significantly warmer than its surrounding areas.

Urban heat Island

5. The——— is the boundary between the troposphere and stratosphere.

Tropopause

6. The equational low-pressure belt is called a ——-

A battle of calm

7. The air in horizontally motion is called a—–

Wind

8. The name of the local wind which blows over that desert is—Loo

9. The study of the science of lightning is called ——–

Fluminology

II. Choose the correct answer:-

1. In the tropical regions paddy is a major crop.

2. During nino period the temperature rises rapidly once in three to eight years along the coast of a peru and equadar.

3. The difference between maximum and minimum temperature of the day is called diurnal range of temperature.

4. Barometer is an instrument used to measure the atmospheric pressure.

5. Subtropical high-pressure belt is called horse latitudes.

6. In Ionosphere layer the sun’s rays is ionized.

7. Cumulus clouds are associated with rainfall, thunder and lightning.

8. Convectional type of rainfall is also called 4’O’ clock rainfall.

9. The average air pressure at the sea level is 1013 millibars.

10. The nimbus clouds are vertical clouds

Match the following

1. Global Warming — human influences

2.Thermometer —- instrument measuring temperature

3. Anemo meter — instrument showing of wind

4. Eye of the cyclone —- vaccum

5. Thunderstorms — weather factory.

IV. Write short answers:

1. Differentiates weather and climate:

Weather:

Refers to the physical state of the atmosphere within 24 hours destroyed by weather elements

Climate:

Climate is commonly defined as the weather averaged over a long period of time and over a large area.

The standard averaging period is 30 years

2. What are the advantages and disadvantages of meeting warm of and cold ocean currents.

Advantages:-

· The meeting places of warm and cold ocean currents are the areas of major fishing grounds.

· Because the conditions are suitable for the formation of dense fog and low clouds.

Disadvantages:-

· At that same time these areas are dangerous for shipping as they are suitable for the formation of dense fog and low clouds.

3. List the mechanisms by which the earth receives the solar radiation.

· Radiation in the atmosphere.

· Conduction overland.

· Convection in the water bodies.

4. What are the scales to measure Temperature?

· Celsius.

· Fahrenheit.

· Kelvin.

5. Differentiate Isobars and isohyets.

Isobars:-

The imaginary lines joining different places with the same pressure on a map are known as isobars.

Isoyetss:-

The imaginary lines that join different places having same amount of rainfall on a map are known as Isohyets.

6. Define ferrels law:-

· All moving objects including winds and oceans currents tend to get deflected towards right in the northern hemisphere and left in the southern hemisphere due to the rotation of the earth.

· This changeless principle is called the ferral1s law (or) coriollis force.

7. What are planetary winds?

· The winds that blow from a particular direction throughout the year are known as the planetary winds.

8. What is lightning? How they formed?

Lightning can be defined as the atmosphere discharge of electricity.

It is formed by the meeting of the positive and negative charges in the clouds containing ice.

9. What is weather factory?

· The thunderstorms are Accompanied by many weather element, meteorologists refer them to as weather factory.

· The formation of thunder Stroms ranges from 4 to 20 km.

10. Differeentite equable and extreme type of climate.

Equable climate:-

· The coastal areas experience the cool, wet air from the sea throughout the year which modifies the weather along coast to have uniform weather both in the winter and summer.

· This condition is said to be an equable climate or maritime climate.

Extreme climate:-

· The land absorbs and loses heat quickly an empty experience warm and dry air.

· They are very hot in summer and very cold in winter.

· This condition is said to be extreme type of climate or conditional climate.

V. Brief answers.

1. What are the factors determining weather and climate?

Explain EL nino.

The following factor determine weather and climate.

· They are latitude, altitude, ocean currents from the sea, direction of prevailing winds.

EL Nino:

· EL Nino is one of the reasons for the failure of the monsoon.

· In Spanish EL nino means ‘The Christ child’.

· It is formed around Christmas time and continues for a six months.

· During this period, once in five or six years the temperature rises rapidly. A low pressure system is formed along the coast of Peru and Equador.

· It attracts winds from all directions.

· So, the trade winds become very weak over the pacific Ocean and Indian ocean.

· These winds are deflected and cause a prolonged dry period in India.

· The other effects of EL nino are experienced in other areas too.

· They are bush fire and drought in Australia, famine in Indonesia and forest fires in Brazil and south East Asia.

2. What are the heat zones of the earth? Explain any one of them with a neat diagram.

· The temperature reduces with increasing latitude.

· Based on this, the earth is divided into Torrid, Temperate, Frigid zones.

Torrid zone:

· The places between the tropic of cancer and the tropic of capricorn.

· It receives vertical Sun rays all round the year.

· So they are hotter than the other zones.

3. What is called land breeze and sea breeze? With a Diagram.

Land breeze:

· During the night time the land becomes cooler than the adjoining of water bodies. So, there is a high pressure on the land and the low pressure on the water body.

· Hence cool dry breeze blows from the land towards the sea in the early morning.

Sea breeze:

· During the daytime the land becomes warmer than the adjoining of water bodies.

· As a result, a low pressure on the land and a high pressure on the water body formed.

· This leads to the cool wet breeze from the sea to blow towards land in the late evening.

5. What are the types of rainfall? Explain conventional rainfall.

Rainfall is classified into 3 types namely,

a. Convectional rainfall

b. Relief or Orographic rainfall

c. Cyclonic rainfall.

Convectional rainfall:

· The equatorial regions receive vertical sunrays and hence become hot.

· The hot air temperature reduces gradually, the air gets cooled and formed clouds.

· When the clouds reach the dew points, they cause rainfall.

· This is known as convectional rainfall. It is known as convectional thunder and lightning.

· Usually it occurs around 4’o clock rainfall.

Orographic rainfall (or)Relief:

· The winds that below from the sea contain a lot of moisture.

· When the moisture laden winds from the sea climb the hill slope the winds become cool causing heavy rainfall in the wind- ward side.

· Then these winds descend on the lee ward side of the mountains and cause low to no rainfall.

Cyclone rainfall.

· The warm air from the hot area is further heated and moves upward.

· Hence a low pressure area is developed and attracts air from the adjacent high pressure areas.

· The raising air gets cooled and condensation take place.

· This brings heavy rainfall in the low pressure areas. Eg. Coast of Tamil Nadu, Andhra Pradesh and Orissa.

8.Write a note on Thunderstroms?

· Thunderstroms are produced by cumulonimbus clouds.

· They are usually of short duration. They are accompanied by lightning, thunder, strong wind guests. Heavy rain and sometimes hail.

· The thunderstorms are accompanied by many weather elements, meteorologists refer them to as weather factories.

The formation of the Thunderstroms ranger from 4 to 20 km.

9. What are clouds? Explain any one of them.

· A cloud can be defined as a mass of small water droplets or ice crystals formed in the atmosphere.

· Clouds are formed by very minute suspended water particles present in the atmosphere.

· According to the shape and altitude the clouds are classified as cirrus, stratus, cumulus and nimbus.

Nimbus clouds:-

· These are vertical clouds. They are thick dark on gray or black clouds.

· They are vertical clouds.

· They cause continuous rainfall so they are known as storm or rain clouds.

10. What are the layers of Atmosphere? Explain any one of them with a diagram.

· The atmosphere of the earth is divided into four major layers.

· They are Troposphere, stratosphere, Ionosphere, Exosphere.

Exosphere:

· The exosphere is the upper most layer of the atmosphere.

· The main gases within it are the lightest gases mainly hydrogen and helium.

· This layer is sometimes considered a part of outer space.

I. Choose it.

1.Oxidation process is better known as Rusting

2.Meanders are formed in the Valley course.

3.Beaches are features of waves.

4.Pedestal rock is also called as Mushroom rocks.

5.Barchan is related to Depositinal features.

II Fill in the Blanks:-

1. Weathering can also be termed as gradation.

2. Two caves approach one another are called arch.

3. The fan shaped alluvial feative formed by a river at its lower course called as delta.

4. The government of India banned the tanneries around Tajmahal.

5. The fine dust deposited by wind beyond the desert limit are called loess.

III Match it:-

1.Salt crystal growth — Holoclasty

2.Ox-bow lakes — Plain Course

3.Spits — Depositional features by waves

4.Moraines — Glacial depositions

5.Seifs — Wind depositions.

IV. Short answers:-

1. Write a brief note on weathering.

Weathering is a process of disintegration or decomposition of rocks

weathering is a complex interaction of physical, chemical and biological process that after the rocks of the crust.

Weathering can be classified into physical, chemical and biological weathering.

2. Name the Erosional landform produced by a river.

The gorges, canyons and v-shaped valleys are formed by a river.

River also produces waterfalls, meanders, river cliffs, valley course, delta, ox-bow lakes.

3. How are cirques formed?

The arm shaped, chair like depression formed by plucking of glacier is known as cirque.

4.What are longitudinal dunes?

They are long narrow ridges of sand and cover over a hundred miles, lying parallel to the direction of the prevailing wind.

5. Define the process of Rusting.

This is the process where the metals present in the rocks combine with O₂ and water to form oxides. These oxides make the rock weak and it consequently crumbles from smaller rock particles. This process is known as rusting.

V Distinguish:-

1. Physical weathering and chemical weathering.

v Physical weathering is the process that causes the disintegration of rocks into small fragments without any chemical changes.

v The primary process in change physical weathering are abrasion.

v Chemical weather in refers to decomposition of rocks or many be defined as the breaking of rocks due to the alterations and hydrolysis are the most common occurrences.

2.Mountain and plain course of rivers.

v This course starts from a mountain range. Due to steep slope and high velocity of the river the vertical corrosion action is predominant.

v The work of a river is mainly deposition, building up of beds and forming extensive flood plains. The volume of water is greatly swelled by additional tributaries that join the main stream.

3.Valley and continental glacier.

v These Glaciers are formed on the mountains.

v They are also called as valley or alpine lacier.

v The Polar Regions are vastly covers of with ice.

v This extensive type of ice mass is called as continental glaciers.

4.Moraines and barchans.

v Moraines are made up of pieces of rocks, debris, boulders and day at the glacial valleys.

v Further they may be divided into Terminal moraines lateral moraines and medial moraines.

v These are crescent moon shaped dunes. They are morning dunes since they move steadily towards the prevailing wind directions.

5. Delta and loess.

v When the rivers reaches the sea the fine materials it has not yet dropped are deposited at its mouth, forming a fan chapped alluvial features called delta different types are bird foot delta arcuate delta, cuspate delta.

VI. Briefly.

1.Name the different types of weathering and explain any one is detail.

v Weathering can be defined as the decomposition of rocks. Weathering is a complex reaction

v of physical, chemical and biological process the alter the crust of earth.

v Weathering is classified into physical; chemical and biological weathering.

v Physical weathering is the process of causing disintegration of rocks into small fragments without chemical change.

v The physical weathering is done by the following process.

v Thermal stress

v Rocks are made up a combination of several minerals. The expansion and shrinking of temperature various from one another.

Frost weathering:-

v The mountainous areas experience frost condition and they have these types of weathering. Sometimes the cracks found on the rocks are called with water due to rain. It may freeze into ice during night due to very low temperature and melts during day time.

v The continuous freezing and melting of water cause the rocks to break into pieces. This type of weathering is said to be frost weathering.

Salt crystal growth.

v Salt crystallization, otherwise known as haloclassty, causes disintegration of rocks when saline in rock and evaporate, leaving salt crystals behind.

2. Name the different types of land forms associated with the three course of a river.

v This course starts from a mountain range. Due to steep slope and high velocity of the river, the vertical corrosionation is predominant. The gorges, canyons and V shaped valleys are formed.

v Due to unequal resistance of hard and soft rocks traversed by the rivers the out crop of band of hard rock may cause a jump or fall downstream leading to the formation of rapids. Similar falls of great dimension are also referred to as cataracts. When rivers plugs down in a sudden fall of some down in a sudden of some height, they are called waterfalls.

3. Write an essay on the Erosional process of waves.

v The most powerful agents of marine are coastal erosion are the waves. Along the coast waves are agents of erosion, transport and deposition.

v Generally a very steep rock face adjoining the coast forms a cliff.

v Prolonged wave attract on the base of a cliff excavated hole called caves.

v When 2 caves approach one another, arch formed further erosion by wave will ultimately to the total. Collapse will remain as a pillar of rock known as stack.

v It is further erosion, it then forms stumps which are only just visible above the sea level.

4. Write an essay on depositional landform of glaciers.

v Moraines are made up of pieces of rocks, debris, bounders and clay at the glacier valleys. Further they may be divided into terminal, lateral, medial moraines.

v They are deposits of day and debris and resembles like a half buried.

v Eg. The other depositional features are outwash plain and Eskers.

5. Describe about wind erosional features.

v Wind is a predominant agent of denudation in arid and semi-arid regions, because of scarce rainfall and sparse.

v The sand particles carried by the sand strike rocks pillar made up of hard and soft rock found at bottom, they are eroded faster than the hard rock found at the top.

v These are isolated residual hills rising abruptly from ground level. They are characterized by their very steep slopes and rounded tops.

I. Choose the correct answer:-

1._________ is the only planet has organisms in it. Earth

2. The Pangea is broken into —— major plates.7

3. The ______________of the earth is not stable. Crust.

4. Large scale vertical movements of the earth crust are called ____________ movements. Endogenic.

5. The point of origin of the earthquake is called Focus.

II. Fill in the blanks:-

1. The continents crust is composed of granite layer.

2. The SIAL layer is floating on the SIMA layer.

3. Large scale horizontal movements of the earth crust arecalled Endrogenic movements.

4. Surface is also known as L waves.

5. A volcano is a vent or an opening in the earth crust.

III Match it:

1. Mauna loa – Hawai

2. Vesuvius – Italy

3. Kilimanjaro – Africa

4. Fujiyama – Japan

5. Norcondam – India.

IV Answer the following:

1. Name the types of layers of the earth.

v The crust

v The mantle

v The core

2. Pangea:

v A few million years ago all the present continents were clusterd together around South pole.

v This super continent was called Pangea.

Panthalassa:

v The Pangea was surrounded by a mega ocean called panthalassa. Panthalassa was otherwise known as Super Ocean.

3.Name the major plates of the world.

v Eurasia, Antarctica, North America, Pacific, South America, Africa and Indo Australian plates.

4. Name the forces which affect the Earth movements.

v Endogenic or Internal forces: Such internal forces are earthquake volcano and landslide.

v Exogenic or External forces: Such external forces are river wind, glacier and sea waves.

5.What is mean by anticline and syncline?

v Horizontal movements of the earth crust make folding and displacement of the layers of rocks.

v Simple folding consists of alternating upfolds called Anticlines and downfolds called synclines.

6.What are the types of volcanoes?

v Active volcano

v Dormant volcano

v Extinct volcano.

V Distinguish between:

1. SIAL

v The sontinental crust is composed of a layer.

v It is made up of of silica and aluminium.

v The average depth of sial is about 20 k.m.

SIMA

v The oceanic crust is composed of basaltic layer.

v It is made up of silica and magnesium.

v The average depth of sima is about 25 k.m..

2.Crust

v The upper most layer of the earths surface.

v It is also called as lithosphere.

v It is divided into sima and sial.

CORE

v The inner most layer of the earth surface.

v It is also called as Baryspere.

v This divide into inner core and outer core.

3. Dormant

v They are called sleeping volcanoes.

v These volcanoes have been active in the past stopped erecting lava now, but it can erupt at any time in the future. Eg. Vesuvius in Italy.

EXTINCT

v They are called dead volcanoes.

v These volcanoes erupted in the past but they did not do so recently and in future it is expected there will not be any eruptions. Eg. Kilimanjaro in Africa.

4. Endogenic forces and exogenic forces.

v It originates and acts from within the earths crust.

v It gives rise to deformation and irregularities on the crust of the earth.

v These movements which bring about vast changes on the crust of the earth.

v It originates and acts on the surface.

v It removes the irregularities to made a leveled on and below the crust.

5.Primary waves and secondary waves:-

v P-waves moves faster and are the first to be recorded by the seismograph.

v It can travels through gaseous liquid and solid materials.

v It travels at a speed of 8k.m./sec.

v S – Waves are slower than the P-waves.

v It can travel through solid materials.

v It travels at a speed of 5k.m./sec.

VI. Answer in briefly.

1. Name the layers of the earth and explain the crust in detail.

Layers of the earth

v Crust mantic core sial upper mantle upper core sima lower mantle lower core.

v The uppermost layer of the earths surface is called the crust.

v The continental crust is composed of a layer called the sial  which is made up of silica and Aluminum.

v The oceanic crust is composed of basaltic layer layer called the  sima which is made up of silica and magnesium.

v Crust is thicker on the continents and thinner in the ocean floor.

v The sial layer is floating on the sima layer.

v The average depth of sial is about 20 k.m.

v The average depth of sima is about 25 k.m.

v The average density of the crust is about 3gkm.

2. Describe the types of earthquakes waves.

Earth quake waves are divided into body waves and surface waves.

Body waves:-

Body waves are produced by the release of energy at the focus and move in all directions.

These are two types of body waves.

1.Primary waves or p-waves

2.Secondary waves or s-waves.

Primary waves:-

v P-waves move faster and are the first to be recorded by the seismograph.

v It can pass through gases, liquids and solids.

v It travels at a speed of 8k.m./sec.

Secondary waves:-

v S-waves are slower than the p-waves. It can travel through solid materials.

v During the occurrences of secondary waves, particles oscillate in the directions of wave travel.

v It travels at a speed of 5k.m./sec.

Surface waves.

v These waves are the last to be recorded on the seismograph.

v These Waves cause most of the damages on the surface.

v They are called as L-waves.

v They travel at a speed of 4km/sec.