Geography can help us understand the planet's movement, changes, and systems. Topics that are relevant to today such as climate change, water availability, natural resources, and more are much easier understood by those who know geography well. Geography is the study of the interaction between people and their environments, both natural and human. Geography (Geo means earth, graphia = write about, geography literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets.
Geography is often defined in terms of two branches:
human geography and
physical geography.
Human geography is concerned with the study of people and their communities, cultures, economies, and interactions with the environment by studying their relations with and across space and place.
Physical geography is concerned with the study of processes and patterns in the natural environment like the atmosphere, hydrosphere, biosphere, and geosphere.
The four historical traditions in geographical research are spatial analyses of the natural and human phenomena, area studies of places and regions, studies of human-land relationships, and the Earth sciences.
Unit-2
The Weather Machine
1. What is insolation?
Ans: The sun is the prime source of energy for all living things on Earth. The solar energy that the Earth receives travels through space to reach to the Earth in the form of solar radiation or insolation.
2. What is terrestrial radiation?
Ans: The incoming solar radiation is converted into heat energy when it reaches the Earth's surface. As the Earth's surface warms, it also radiates back the energy in the form of terrestrial radiation. As the outgoing terrestrial radiation passes through the atmosphere, a portion of it is also absorbed by the atmosphere.
3. What causes different weather conditions?
Ans: Incoming solar radiation and outgoing terrestrial radiation absorbed by the atmosphere provide the energy that keeps the atmosphere, the huge weather machine, in constant motion. This constant motion of the atmosphere brings about different weather conditions such as the formation of clouds and storms.
4. What is the difference between weather and climate?
Ans:
Weather: The condition of the atmosphere at a specific place over a short period of time.
Climate:The average weather conditions at a specific place over a considerable period of time of at least 30 years.
5. Why is there a decrease in temperature as one moves towards the North and South poles?
Ans: Temperatures are higher at or near the Equator. As you move away from the Equator and towards the North or South Poles, the temperature gradually decreases. This gradual decrease in temperature occurs because the surface of the Earth is curved. As a result, the sun's vertical rays strike different parts of the Earth's surface at different angles.
At the Equator, the vertical rays hit the Earth's surface at an angle of 90 degrees; towards the poles, the angle is much lower. The angle at which the sun's rays strike the Earth is called the angle of incidence.
6. Why does the atmosphere absorb less heat at higher altitudes?
Ans: At higher altitudes, the amount of atmosphere decreases and as a result, there is less water vapour in the air. The atmosphere here absorbs less heat and therefore the temperature at higher altitudes drops.
7. How does the sea influence the temperature of coastal areas?
Ans: The distance of a place from the sea has an effect on its temperature because water heats and cools more slowly than land. This difference in heating of land and water affects the temperatures of places located near the coast differently from those located inland.
For instance, San Diego, which has a coastal location, has a lower summer temperature and higher winter temperature than Dallas, which has an inland location, although both cities lie approximately at the same latitude.
8. What is maritime influence?
Ans: As the sea is cooler than the land in summer, it lowers the temperature of coastal places. However, during winter the sea is warmer than the land and keeps coastal places warmer by moderating the winter temperature. When the temperature of coastal places such as San Diego is influenced by the sea in this manner, it is called maritime influence. Such a climate is known as a maritime climate.
9. What is continental influence?
Ans: The effect of large land masses which result in extremes in temperature. Places such as Dallas, located in the interior of large continents or land masses, are under continental influence; that is, the sea does not have an effect on them as they are too far away from it.
10. What are the ocean currents?
Ans: Ocean currents are large streams of water flowing in the oceans. These are generated when winds blow over the water surface.
11. What are the two types of ocean currents?
Ans: There are two types of ocean currents. Those that bring water from the polar regions are called the cold ocean currents and those that bring warmer water to the polar regions are called the warm ocean currents.
12. How do ocean currents influence the temperatures of coastal areas?
Ans: Ocean currents can raise or lower the temperatures of nearby coastal areas. Coastal areas which are affected by warm currents will be kept warm during winter. For instance, the Warm Gulf Stream and the North Atlantic Drift keep.
the coastal areas of north-east America and north-west Europe warm. If cold ocean currents move along the coast they will lower the temperatures of these areas. The cold Oyashio current, for instance, lowers the temperature of the east coast of Japan throughout the year.
13. How does cloud cover affect the temperatures near the Equator?
Ans: Humidity is the amount of water vapour in the atmosphere and it influences the amount of cloud cover in the sky. When air cools,
water vapour condenses to form water droplets and clouds may form. The higher the humidity, the greater the amount of cloud cover.
In high humidity areas such as areas near the Equator, there is a greater amount of cloud cover, while in low humidity areas such as the desert areas there is a smaller amount of cloud cover.
14. What is aspect?
Ans: Aspect is the direction in which a slope faces in relation to the sun.
15. How does cloud cover affect the temperatures in the hot deserts?
Ans: In the hot desert, there is a lack of cloud cover. As a result, a greater amount of the incoming solar radiation reaches the Earth's surface causing day temperatures that reach 40 degrees C.
Unit - 3 An Eye On The Weather
1. What are the two characteristics of tropical storms?
Ans: Every year some coastal areas in the tropics are affected by violent tropical storms. These storms bring heavy rain and strong winds that reach a speed of about 200 km per hour. Such storms are sometimes accompanied by thunder and lightning.
2. How are tropical storms formed?
Ans: When air over the sea gets heated, it expands and rises very rapidly. This creates an area of intense low pressure. Warm moist air rises to great heights, condensing to form clouds and rain. Air from the surrounding higher pressure area rushes inward in a spiralling manner to replace the rising warm air. This air may spin in at a speed of about 200 km per hour, absorbing large amounts of moisture and forming cumulonimbus clouds and heavy rain. The cold air then sinks. The centre of the storm called the eye is an area of calm weather marked by clear skies.
Tropical Storms
3. What are some effects of tropical storms?
Ans: The effects of tropical storms can be very severe, especially if they hit a densely populated area. They can destroy lives and property. Storms with wind speeds of more than 200 km per hour can uproot trees, destroy crops and houses, overturn cars and damage ships.
4. What is a storm surge?
Ans: Tropical storms may cause storm surges. A storm surge occurs when strong winds raise the ocean surface into a giant wave. A storm surge can destroy coastal settlements and flood large areas.
5. What are floods?
Ans: A flood is a covering of water over land which is normally dry.We have seen how tropical storms can cause the formation of storm surges which cause the flooding of coastal settlements.
6. How does continuous rain cause flooding?
Ans: When it rains continuously for a much longer period than usual, there is a tendency for a river to flood. When rain falls, the water can seep into the ground or it can flow as surface runoff. If the continuous rain produces more water than the ground can absorb, the water starts to flow over the land. This increases the amount of surface runoff which flows into the rivers. If a river is unable to hold the amount of water, it then overflows its banks and a flood occurs.
7. How does snow melt cause flooding?
Ans: In temperate areas, floods may be caused by the melting of snow. During early spring, when the temperature rises, snow melts and this increases the amount of surface runoff. For instance, the melting of accumulated snow in the Himalayas may contribute to the Ganges River overflowing its banks.
8. What are droughts?
Ans: Droughts are unusually long periods during which little or no rain falls. When the expected rainfall fails to come or does not long, a drought sets in.
Unit-3.2
Forecasting The Weather
1. What is weather forecasting?
Ans: The science of predicting the weather is called weather forecasting. Today, weather forecasting involves the use of sophisticated equipment and instruments which are found at a meteorological station.
2. How is maximum temperature measured using a Six's thermometer?
Ans: The most common instrument used to measure air temperature is a maximum and minimum thermometer. It is either in the form of separate thermometers or joined in a U-shaped glass tube like the Six's thermometer. The maximum thermometer records the highest temperature and the minimum thermometer the lowest for the day.
The thermometer contains two liquids, alcohol and mercury. When the temperature rises, both the liquids expand but the alcohol vapourises when it expands. The alcohol in the left arm then pushes the mercury down the left arm and up the right arm. The alcohol in the right arm expands and vapourises to occupy the vacuum space in the conical bulb. The expanded mercury also pushes up the index. The bottom of the index in the right arm marks the highest temperature.
3. How is the minimum temperature measured using a Six's thermometer?
Ans: When the temperature drops, both the liquids contract. The vapour in the conical bulb condenses to liquid which forces the mercury down the right arm and up the left arm. In this way, the index on the left arm is pushed up and the bottom marks the lowest temperature.
To take the readings, look at the lower end of the index in the maximum and minimum thermometers. Once both the readings have been taken for the day, either use a magnet or swing the thermometer hard to reset the index for the next day's reading.
Diurnal (Daily) temperature range
= maximum temperature - minimum temperature
= ( 31.3 - 25.8) ૦ C
= 5.5 ૦ C
Average (mean) daily temperature
= (maximum temperature + minimum temperature) 2
= (31.3 + 25.8) 2
= 28.6 ૦ C
Average (mean) daily temperature
= sum of temperature for 24 hours / 24
= 680.5 / 24
= 28.4 ૦ C
Mean monthly temperature
= sum of the mean daily temperatures for the month/ total number of days in the month
= 848.6 /30
= 28.3૦ C
Annual temperature range
= highest mean monthly temperature - lowest mean monthly temperature
= (28.8 - 26.3 )૦ C
= 2.5 ૦ C
Mean annual temperature
= sum of the mean monthly temperatures for twelve months/ total number of months
= 330.9/12
= 27.6 ૦ C
4. What is the instrument that is used to measure air pressure?
Ans: Air pressure can be measured by using an instrument known as a barometer.
5. How is pressure measured by using a mercury barometer?
Ans: The mercury barometer consists of a glass tube sealed at the upper end. The lower end is submerged in an open container of mercury, whose surface is exposed to air. When the pressure is high, the air exerts a greater force on the mercury in the container which then pushes up the mercury in the column. The mercury in the column drops when the pressure is low. It is the height of this column of mercury which gives the measurement of the air pressure. The unit of measurement for pressure in millibars (Mb). A column containing 760 mm of mercury corresponds to a pressure of 1013 millibars which is the pressure at sea level.
6. When will the barograph drum contract and expand?
Ans: Aneroid barograph is an instrument which has two drums. The smaller drum has had most of the air removed from it. This drum contracts and expands according to changes in air pressure. When the outside air pressure is high, it exerts a force on the drum. The drum then contracts. When the outside air pressure is low, the drum expands as the air does not exert much force on it.
7. What are isobars?
Ans: After the pressure readings are taken, they can be represented on a map in a series of lines. Each line joins places that have recorded the same pressure readings. These lines joining places with equal pressure are called isobars.
8. What is the instrument used for measuring wind direction?
Ans: The wind vane consists of a freely-rotating pointer arm which moves with the wind. The pointers are arms bearing the four main directions: north, south, east and west. The arrow points to the direction from which the wind is blowing. If, for instance, the arrow is pointing to the north-east, it means that a north-easterly wind is blowing.
9. What happens to the cups of the anemometer when there is wind?
Ans: An anemometer is an instrument which is used to measure the speed of the wind.
It consists of three or four cups attached to the ends of horizontal spokes that are mounted on a high vertical spindle. When there is wind, the cups rotate and this rotation is recorded on a central rod which transmits the speed of the wind to an electrically operated dial. Wind speed is expressed in knots or on a scale of 0 to 12 on the Beaufort scale.
10. What is the instrument used to measure relative humidity?
Ans: The instrument for measuring relative humidity is known as a hygrometer. One common type of hygrometer is the wet and dry bulb hygrometer which consists of two thermometers. The dry bulb thermometer measures the air temperature. A wick is attached to the bottom of the wet bulb and is dipped in a bottle of water. The wet bulb thermometer usually gives a lower reading because when the water from the wick wrapped around its bulb evaporates, it cools the thermometer. The difference in the readings from the two thermometers is called the wet bulb depression.
When the air is not saturated, the two thermometers show different readings. When the air is saturated, there is no evaporation and hence no cooling. The two thermometers will then show the same reading. The wet bulb depression is 0⁰ and the relative humidity is 100%.
11. What are the different parts of a simple rain gauge?
Ans: Rainfall is measured by an instrument called a rain gauge. A simple rain gauge consists of an outer casing, a copper cylinder, a metal funnel which leads into a glass bottle and a measuring cylinder.
The metal funnel has a diameter of 20 cm. The hole in the funnel which leads into the glass bottle is very small to minimise evaporation. Rainwater that is collected in the glass bottle is then emptied into a measuring cylinder at the end of the day. The rainwater in the measuring cylinder is measured at eye level to obtain an accurate reading. these readings are recorded once every 24 hours.
12. how does a tipping bucket work?
Ans: A tipping bucket is another type of rain gauge. It has a funnel leading to two small free-swinging containers. Each of these containers can collect about 0.2 mm of rain. When the container beneath the funnel is filled with water, the weight of its water causes it to tip and empty itself. The second container immediately moves under the funnel to catch the water. When it is filled with water it also tips and empties itself. Each time a container tips the water, a recording is made on a chart or in a computer.
Earth's Natural Vegetation
1. What is natural vegetation?
Ans: We live on a beautiful Earth which is covered with many types of plants such as trees, shrubs grasses, mosses, lichens, and algae. Most of these grow naturally while others are planted by people. The plants which grow by themselves are called natural vegetation while those which are grown by people are called cultivated vegetation.
2. How do the climatic factors of precipitation and temperature influence the distribution of natural vegetation?
Ans: The distribution of natural vegetation is influenced by climate factors such as precipitation and temperature. Precipitation influences the distribution of the main types of natural vegetation.
Although the distribution of the main types of vegetation is influenced by the variation in precipitation, it is the temperature that influences the distribution of the sub-types. If you travel from the equator to the Poles. We would observe that as the temperature decreases towards the Poles, the vegetation sub-type changes.
3. Where can we find the tropical rainforest?
Ans: The tropical rainforest is found in areas with an equatorial climate, such as in parts of Central and South America, Africa, and Southeast Asia. The Amazon Basin and the Zaire Basin are the two largest areas of tropical rainforest. 4. What are the characteristics of the tropical rainforest? Ans: The characteristics of the tropical rainforest are - a) The trees in the tropical rainforest are tall and grow very close together. As a result, the forest is very dense. b) The trees in tropical forests have broad leaves with a waxy, leathery, or hairy texture. The texture of the leaves allows the rainwater to run off easily. In addition, it minimizes the loss of moisture through transpiration. c) The trees in the tropical rainforest have shallow roots because water and nutrients are found in the top layer of the soil. This is the result of the high precipitation and temperature of the equatorial climate.
5. Where can we find the mangrove forest?
Ans: Along tropical coastal areas where the ground is muddy and water-logged, we are able to find the mangrove forest. Generally, the mangrove forest is found along sheltered, low-lying tropical coasts such as those in West Africa, Southeast Asia, and Australia.
Unit-6.3 The Power of Volcanoes
Q.1. What is a volcano?
Ans: A volcano is an opening in the Earth's crust from which materials such as magma and gases are ejected. When materials are ejected from this opening, we say that a volcanic eruption occurs.
Q.2. What is the structure of a volcano?
Ans: When a volcano erupts, magma from the Earth's interior is ejected to the surface. The magma when it reaches the Earth's surface is called lava. In some instances, the lava is ejected high up into the air with explosive force. This lava cools and solidifies, forming small fragments such as cinders and volcanic ash. Gases such as stream, carbon dioxide and sulphur dioxide are also given off.
In an eruption, materials are ejected through an opening at the Earth's surface, called a vent, and rise through a passageway in the volcano called a pipe. These materials are released through the crater which is a bowl-shaped depression at the top of the volcano. Over time, ejected materials such as lava, ash and cinder build up the cone of the volcano.
Q.3. What are 'active', 'dormant' and extinct' volcanoes'?
Ans: Volcanoes may be described as 'active', 'dormant' or 'extinct'. A volcano which erupts is an active volcano. A volcano which has been inactive for a long period of time, such as a hundred years, is dormant. an extinct volcano is one that scientists believe will not erupt again. However, we cannot be absolutely certain. Some volcanoes which are dormant or thought to be extinct may erupt one day. For example, Mt St. Helens in the USA had been dormant for more than 100 years but became active in 1980.
Q.4. What is the classification of volcanoes?
Ans: Volcanoes can be classified into three types according to the types of material that form them. They are-
i) basic lava:This type of volcano is formed from fluid lava which flows quite rapidly, spreading over a wide area before solidifying. This results in a gentle-sided volcano which usually erupts gently. An example is Mauna Loa in Hawaii, USA.
ii) acid lava:Forms this volcano is thick or viscous. It is slow-flowing and solidifies quickly near the vent. This produces a cone with steep slopes. The volcano usually erupts violently. An example is Mt Stromboli in Italy.
iii) composite:Consists of alternate layers of viscous lava, ash and cinder. The slopes of the volcano are usually steep near the summit and gentler near the base. Lava often escapes through the sides of the cone and builds up to form secondary cones. The volcano usually erupts violently. An example is Mt Mayon in the Philippines.
Q.5. What is the Pacific Ring of Fire?
Ans: Volcanoes are found mainly along plate boundaries and are concentrated in a belt around the Pacific Ocean. This belt of volcanoes is called the Pacific Ring of Fire.
Q.6. What damage do volcanic eruptions cause?
Ans: Some volcanoes erupt frequently and people who live near them learn to cope with this. In Japan, for instance, annual drills are organised to help the people living near Sakurajima, an active volcano in Kagoshima to prepare for disasters. Students in Kagoshima are also required to wear helmets as a safety measure. A volcanic eruption can kill many people and destroy settlements, leading to a great loss of property. For instance, the eruption of Mt Pinatuba in the Philippines in 1991 released a large amount of ash which combined with rainwater to produce a thick mudflow. Volcanic eruptions can also produce huge waves in the ocean called tsunamis. These waves can be very destructive. For example, the 1883 eruption of Krakatoa in Indonesia resulted in tsunamis. Waves up to 35 m high swept along the coasts of Sumatra and Java, destroying hundreds of settlements and drowning over 30,000 people.
Unit- 6.4 Earthquakes
Q.1. What is an earthquake?
Ans: As plates move towards or away from each other or slide past each other, the movement is not smooth. The Earth's crust behaves in a way similar to the ruler described above. Friction between the moving plates causes stress to build up in the crust and eventually faulting occurs. The rocks break and move in sudden jerks along the fracture. The energy which has been stored up in the rocks is suddenly released as shock waves. This results in vibrations or tremors of the earth's surface called earthquakes.
Q.2. What are the main earthquake zones?
Ans: The greatest concentration of earthquakes is found around the Pacific Ocean. Another major zone of earthquakes stretches from the Mediterranean Sea to the Himalayas. The two major earthquake zones occur at boundaries where plates are moving towards each other.
Q.3. What damage do earthquakes cause?
Ans: Earthquakes can bring about the great loss of life and damage to property. For instance, the severe earthquake that shook the city of Kobe, Japan in 1995, killed more than 5,000 people and injured thousands more.
When earthquakes occur near the coast or under the sea, this can result in destructive tsunamis. For instance, the 1964 Alaskan earthquake caused tsunamis which led to the loss of life.
Q.4. How can damage caused by earthquakes be reduced?
Ans: Although it is not possible to prevent earthquakes, certain measures can be taken to reduce the damage that earthquake's strong vibrations on the ground.
To minimize damage caused by outbreaks of fire during earthquakes, systems can be installed to automatically cut off electricity and gas supplies during an earthquake. The use of non-flammable materials in the construction of buildings is another way to help lessen the damage caused by fires.
Unit-7.1 Rocks
Q.1. What are the three main types of rock?
Ans: There is a great variety of rocks. For instance, rocks are varied in their mineral composition. Rocks are also different in many other ways, such as in their colour, hardness as well as grain size.
However, all these rocks can be classified into three main types - igneous, sedimentary, and metamorphic rocks - depending on how they are formed.
Q.2. How are igneous rocks formed?
Ans: When the molten rock cools and solidifies, it becomes mineral crystals. The process of forming mineral crystals is called crystallization. As the mineral crystals form, they join together or interlock into masses of igneous rocks.
Q.3. What is the characteristic of igneous rocks?
Ans: Generally, igneous rocks have a crystalline appearance because they are made up of mineral crystals. Igneous rocks with large crystals which can be seen by the naked eye are described as coarse-grained.
Q.4. How are sedimentary rocks formed?
Ans: Sedimentary rocks are formed in two ways. Some are formed by pressing together or compacting loose particles which have been deposited on land or in water bodies such as seas or lakes. These loose particles are called sediments. Other sedimentary rocks are formed by the crystalization of dissolved minerals.
Q.5. How are metamorphic rocks formed?
Ans: The temperature and pressures inside the Earth are much higher than those on the Earth's surface. When rocks are subjected to greater heat and pressure inside the Earth, they are changed into rocks that are different from the original. This change occurs while the original rocks are still in a solid state. The new rocks that are formed by changing existing rocks under heat and pressure are called metamorphic rocks.
Unit - 7.2 Weathering The Earth's Materials
Q.1. What is the difference between weathering and erosion?
Ans: Weathering is the breaking down of rocks. In this process, the rocks which have been broken down are not transported away but remain at the original site. Weathering is brought about by agents such as temperature changes, water, and living things.
Erosion is the breaking down of rocks and removal of the broken rock from its original site. Erosion is brought about by moving agents such as rivers and waves.
Q.2 What is physical weathering?
Ans: Physical weathering is the breaking down or physical disintegration of rocks, without chemical change. It is also known as mechanical weathering.
Q.3. How does pressure release break down rocks?
Ans: Weathering by pressure release occurs in areas where large amounts of overlying rock are removed by erosion.
Q.4. How does freeze-thaw action break down rocks?
Ans: Freeze-thaw occurs in mountainous areas and some parts of the temperature region which experience temperatures that frequently fluctuate above and below freezing point. It is most effective in rocks that have many joints.
Q.5. How does alternate expansion and contraction break down a rock?
Ans: Alternate expansion and contraction of rocks take place in areas that experience high temperatures in the day and low temperatures at night. In hot deserts, for instance, the daytime temperature often rises above 40⁰С but at night it falls to below 10⁰С.
Q.6. What is chemical weathering?
Ans: The breaking down of rocks by means of chemical processes is called chemical weathering. It is also known as rock decomposition.
Q.7. What is biological weathering?
Ans: Biological weathering is the breaking down of rocks as a result of the activities of living things.
Q.8. How do the activities of living things break down rocks?
Ans: Biological weathering can also be a chemical process. For instance, when living things in the soil such as earthworms and insects respire, they give out carbon dioxide. Carbon dioxide dissolves in the water present in the soil, forming carbonic acid. Moreover, when plants and animals decay, CO2 and organic acids are produced. The carbonic acid and the organic acids react with minerals in the rocks, forming new substances which weaken the rocks and cause them to break down.
Q.9. What are the four main factors that influence weathering?
Ans: There are four main factors that influence the type and rate of weathering. They are the mineral composition of the rock, its grain size, the presence of lines of weakness in the rock, and climate conditions. It is important to note that in many instances, the type and rate of weathering depend not on any one factor alone, but on a combination of these factors.
