Page 1 Activity Take a small coloured paper pellet and put it in a beaker half filled with water. Place the beaker on a tripod stand and heat it. As the water warms up, you will observe that the paper pellet is moving upward along with the warm layers of water and then sinks back along with the cooler layers of water. The molten magma inside the earth moves in a similar manner. The lithosphere is broken into a number of plates known as the Lithospheric plates. You will be surprised to know that these plates move around very slowly – just a few millimetres each year. This is because of the movement of the molten magma inside the earth. The molten magma inside the earth moves in a circular manner as shown in the activity. The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces (Fig. 3.1). 3 Our Changing Earth Glossary Lithospheric plates: The earth’s crust consists of several large and some small, rigid, irregularly- shaped plates (slabs) which carry continents and the ocean floor. Fig. 3.1: Evolution of Landforms Earth movements Endogenic forces Exogenic forces Sudden forces Diastrophic forces Erosional and Depositional Building mountains Earthquake Volcano Landslides River Wind Sea-waves Glaciers Endogenic forces sometimes produce sudden movements and at the other times produce slow movements. Sudden movements like earthquakes and volcanoes cause mass destruction over the surface of the earth. 2020-21 Page 2 Activity Take a small coloured paper pellet and put it in a beaker half filled with water. Place the beaker on a tripod stand and heat it. As the water warms up, you will observe that the paper pellet is moving upward along with the warm layers of water and then sinks back along with the cooler layers of water. The molten magma inside the earth moves in a similar manner. The lithosphere is broken into a number of plates known as the Lithospheric plates. You will be surprised to know that these plates move around very slowly – just a few millimetres each year. This is because of the movement of the molten magma inside the earth. The molten magma inside the earth moves in a circular manner as shown in the activity. The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces (Fig. 3.1). 3 Our Changing Earth Glossary Lithospheric plates: The earth’s crust consists of several large and some small, rigid, irregularly- shaped plates (slabs) which carry continents and the ocean floor. Fig. 3.1: Evolution of Landforms Earth movements Endogenic forces Exogenic forces Sudden forces Diastrophic forces Erosional and Depositional Building mountains Earthquake Volcano Landslides River Wind Sea-waves Glaciers Endogenic forces sometimes produce sudden movements and at the other times produce slow movements. Sudden movements like earthquakes and volcanoes cause mass destruction over the surface of the earth. 2020-21 Crater Lava tube Vent Lava Gases and ash Crust Mantle Magma Chamber Word Origin Fig. 3.2: A Volcano Epicentre Seismic waves radiate out in all directions Plate boundary Focus – this is where the earthquake occurs. It is the origin of the seismic energy A volcano is a vent (opening) in the earth’s crust through which molten material erupts suddenly (Fig. 3.2). Fig. 3.3: Origin of an Earthquake Activity Take a container, fill it with water and close it with a lid. Put the water to boil. Now put some peas, spoon and beads on top on the lid. What do you notice? As the water boils the lid begins to shake. The things which you have put on the lid also vibrate. The beads roll down and the spoon vibrates to make a sound. In the same manner, the earth vibrates when an earthquake occurs. Do you know? There are three types of earthquake waves: 1. P waves or longitudinal waves 2. S waves or transverse waves 3. L waves or surface waves Try to find out the properties of these waves from an encyclopedia. Similarly, when the Lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all round the earth. These vibrations are called earthquakes (Fig. 3.3). The place in the crust where the movement starts is called the focus. The place on the surface above the focus is called the epicentre. Vibrations travel outwards from the epicentre as waves. Greatest damage is usually closest to the epicentre and the strength of the earthquake decreases away from the centre. Endo (inside) Exo (outside) Endogenic Exogenic + genic (origin) 13 OUR CHANGING EARTH . 2020-21 Page 3 Activity Take a small coloured paper pellet and put it in a beaker half filled with water. Place the beaker on a tripod stand and heat it. As the water warms up, you will observe that the paper pellet is moving upward along with the warm layers of water and then sinks back along with the cooler layers of water. The molten magma inside the earth moves in a similar manner. The lithosphere is broken into a number of plates known as the Lithospheric plates. You will be surprised to know that these plates move around very slowly – just a few millimetres each year. This is because of the movement of the molten magma inside the earth. The molten magma inside the earth moves in a circular manner as shown in the activity. The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces (Fig. 3.1). 3 Our Changing Earth Glossary Lithospheric plates: The earth’s crust consists of several large and some small, rigid, irregularly- shaped plates (slabs) which carry continents and the ocean floor. Fig. 3.1: Evolution of Landforms Earth movements Endogenic forces Exogenic forces Sudden forces Diastrophic forces Erosional and Depositional Building mountains Earthquake Volcano Landslides River Wind Sea-waves Glaciers Endogenic forces sometimes produce sudden movements and at the other times produce slow movements. Sudden movements like earthquakes and volcanoes cause mass destruction over the surface of the earth. 2020-21 Crater Lava tube Vent Lava Gases and ash Crust Mantle Magma Chamber Word Origin Fig. 3.2: A Volcano Epicentre Seismic waves radiate out in all directions Plate boundary Focus – this is where the earthquake occurs. It is the origin of the seismic energy A volcano is a vent (opening) in the earth’s crust through which molten material erupts suddenly (Fig. 3.2). Fig. 3.3: Origin of an Earthquake Activity Take a container, fill it with water and close it with a lid. Put the water to boil. Now put some peas, spoon and beads on top on the lid. What do you notice? As the water boils the lid begins to shake. The things which you have put on the lid also vibrate. The beads roll down and the spoon vibrates to make a sound. In the same manner, the earth vibrates when an earthquake occurs. Do you know? There are three types of earthquake waves: 1. P waves or longitudinal waves 2. S waves or transverse waves 3. L waves or surface waves Try to find out the properties of these waves from an encyclopedia. Similarly, when the Lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all round the earth. These vibrations are called earthquakes (Fig. 3.3). The place in the crust where the movement starts is called the focus. The place on the surface above the focus is called the epicentre. Vibrations travel outwards from the epicentre as waves. Greatest damage is usually closest to the epicentre and the strength of the earthquake decreases away from the centre. Endo (inside) Exo (outside) Endogenic Exogenic + genic (origin) 13 OUR CHANGING EARTH . 2020-21 14 OUR ENVIRONMENT Activity Do you know? An earthquake is measured with a machine called a seismograph. The magnitude of the earthquake is measured on the Richter scale. An earthquake of 2.0 or less can be felt only a little. An earthquake over 5.0 can cause damage from things falling. A 6.0 or higher magnitude is considered very strong and 7.0 is classified as a major earthquake. A Seismograph EARTHQUAKE PREPAREDNESS Where to take shelter during an earthquake — Safe Spot – Under a kitchen counter, table or desk, against an inside corner or wall. Stay Away from – Fire places, areas around chimneys, windows that shatter including mirrors and picture frames. Be Prepared – Spread awareness amongst your friends and family members and face any disaster confidently. Fig. 3.3a: Destruction caused by an Earthquake in Gujarat 1. Read the ‘Earthquake – A case study’ given in the form of headlines that appeared in the newspapers after the quake. Arrange the events in the right sequence of their happening. 2. Imagine if a quake suddenly shook in the middle of the school day, where would you go for safety? Although earthquakes cannot be predicted, the impact can certainly be minimised if we are prepared before-hand. Some common earthquake prediction methods adopted locally by people include studying animal behaviour; fish in the ponds get agitated, snakes come to the surface. EARTHQUAKE HITS BHUJ A massive earthquake measuring 6.9 on Richter scale hit Bhuj Town on 26th January 2001. Fire in the city Hundreds of fires started as charcoal, cookers overturned. Emergency declared in quake zone The President declares a state of emergency. Atleast 971 students and 31 teachers are feared to have lost their lives following the collapse of school buildings. School worst affected CM’S APPEAL TO THE CENTRE Gujarat appeals for financial help. The Chief Minister of Gujarat has launched an appeal for the Centre to deal with the disaster. Destruction of Bhuj Phone lines, water pipelines and power stations transmission lines were knocked out. 1 2 3 4 5 6 7 BHUJ RELIEF EFFORT BLIGHTED.. Three days after the quake, concern rose about food, blankets and medical supplies not reaching everyone. Earthquake – A Case Study 2020-21 Page 4 Activity Take a small coloured paper pellet and put it in a beaker half filled with water. Place the beaker on a tripod stand and heat it. As the water warms up, you will observe that the paper pellet is moving upward along with the warm layers of water and then sinks back along with the cooler layers of water. The molten magma inside the earth moves in a similar manner. The lithosphere is broken into a number of plates known as the Lithospheric plates. You will be surprised to know that these plates move around very slowly – just a few millimetres each year. This is because of the movement of the molten magma inside the earth. The molten magma inside the earth moves in a circular manner as shown in the activity. The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces (Fig. 3.1). 3 Our Changing Earth Glossary Lithospheric plates: The earth’s crust consists of several large and some small, rigid, irregularly- shaped plates (slabs) which carry continents and the ocean floor. Fig. 3.1: Evolution of Landforms Earth movements Endogenic forces Exogenic forces Sudden forces Diastrophic forces Erosional and Depositional Building mountains Earthquake Volcano Landslides River Wind Sea-waves Glaciers Endogenic forces sometimes produce sudden movements and at the other times produce slow movements. Sudden movements like earthquakes and volcanoes cause mass destruction over the surface of the earth. 2020-21 Crater Lava tube Vent Lava Gases and ash Crust Mantle Magma Chamber Word Origin Fig. 3.2: A Volcano Epicentre Seismic waves radiate out in all directions Plate boundary Focus – this is where the earthquake occurs. It is the origin of the seismic energy A volcano is a vent (opening) in the earth’s crust through which molten material erupts suddenly (Fig. 3.2). Fig. 3.3: Origin of an Earthquake Activity Take a container, fill it with water and close it with a lid. Put the water to boil. Now put some peas, spoon and beads on top on the lid. What do you notice? As the water boils the lid begins to shake. The things which you have put on the lid also vibrate. The beads roll down and the spoon vibrates to make a sound. In the same manner, the earth vibrates when an earthquake occurs. Do you know? There are three types of earthquake waves: 1. P waves or longitudinal waves 2. S waves or transverse waves 3. L waves or surface waves Try to find out the properties of these waves from an encyclopedia. Similarly, when the Lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all round the earth. These vibrations are called earthquakes (Fig. 3.3). The place in the crust where the movement starts is called the focus. The place on the surface above the focus is called the epicentre. Vibrations travel outwards from the epicentre as waves. Greatest damage is usually closest to the epicentre and the strength of the earthquake decreases away from the centre. Endo (inside) Exo (outside) Endogenic Exogenic + genic (origin) 13 OUR CHANGING EARTH . 2020-21 14 OUR ENVIRONMENT Activity Do you know? An earthquake is measured with a machine called a seismograph. The magnitude of the earthquake is measured on the Richter scale. An earthquake of 2.0 or less can be felt only a little. An earthquake over 5.0 can cause damage from things falling. A 6.0 or higher magnitude is considered very strong and 7.0 is classified as a major earthquake. A Seismograph EARTHQUAKE PREPAREDNESS Where to take shelter during an earthquake — Safe Spot – Under a kitchen counter, table or desk, against an inside corner or wall. Stay Away from – Fire places, areas around chimneys, windows that shatter including mirrors and picture frames. Be Prepared – Spread awareness amongst your friends and family members and face any disaster confidently. Fig. 3.3a: Destruction caused by an Earthquake in Gujarat 1. Read the ‘Earthquake – A case study’ given in the form of headlines that appeared in the newspapers after the quake. Arrange the events in the right sequence of their happening. 2. Imagine if a quake suddenly shook in the middle of the school day, where would you go for safety? Although earthquakes cannot be predicted, the impact can certainly be minimised if we are prepared before-hand. Some common earthquake prediction methods adopted locally by people include studying animal behaviour; fish in the ponds get agitated, snakes come to the surface. EARTHQUAKE HITS BHUJ A massive earthquake measuring 6.9 on Richter scale hit Bhuj Town on 26th January 2001. Fire in the city Hundreds of fires started as charcoal, cookers overturned. Emergency declared in quake zone The President declares a state of emergency. Atleast 971 students and 31 teachers are feared to have lost their lives following the collapse of school buildings. School worst affected CM’S APPEAL TO THE CENTRE Gujarat appeals for financial help. The Chief Minister of Gujarat has launched an appeal for the Centre to deal with the disaster. Destruction of Bhuj Phone lines, water pipelines and power stations transmission lines were knocked out. 1 2 3 4 5 6 7 BHUJ RELIEF EFFORT BLIGHTED.. Three days after the quake, concern rose about food, blankets and medical supplies not reaching everyone. Earthquake – A Case Study 2020-21 15 OUR CHANGING EARTH Fig. 3.5: Features made by a river in a flood plain Do you know? MAJOR LAND FORMS The landscape is being continuously worn away by two processes – weathering and erosion. Weathering is the breaking up of the rocks on the earth’s surface. Erosion is the wearing away of the landscape by different agents like water, wind and ice. The eroded material is carried away or transported by water, wind, etc. and eventually deposited. This process of erosion and deposition create different landforms on the surface of the earth. Work of a River The running water in the river erodes the landscape. When the river tumbles at steep angle over very hard rocks or down a steep valley side it forms a waterfall (Fig. 3.4). • There are thousands of small waterfalls in the world. The highest waterfall is Angel Falls of Venezuela in South America. The other waterfalls are Niagara falls located on the border between Canada and USA in North America and Victoria Falls on the borders of Zambia and Zimbabwe in Africa. The Niagra falls Hard rock Softer rock undercut by the power of the water Fig. 3.4: Waterfall As the river enters the plain it twists and turns forming large bends known as meanders. Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loop come closer and closer. In due course of time the meander loop cuts off from the river and forms a cut-off lake, also called an ox-bow lake. At times the river overflows its banks. This leads to the flooding of the neighbouring areas. As it floods, it deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile floodplain. The raised banks are called levees. As the river approaches the sea, the speed of the flowing water decreases and the 2020-21 Page 5 Activity Take a small coloured paper pellet and put it in a beaker half filled with water. Place the beaker on a tripod stand and heat it. As the water warms up, you will observe that the paper pellet is moving upward along with the warm layers of water and then sinks back along with the cooler layers of water. The molten magma inside the earth moves in a similar manner. The lithosphere is broken into a number of plates known as the Lithospheric plates. You will be surprised to know that these plates move around very slowly – just a few millimetres each year. This is because of the movement of the molten magma inside the earth. The molten magma inside the earth moves in a circular manner as shown in the activity. The movement of these plates causes changes on the surface of the earth. The earth movements are divided on the basis of the forces which cause them. The forces which act in the interior of the earth are called as Endogenic forces and the forces that work on the surface of the earth are called as Exogenic forces (Fig. 3.1). 3 Our Changing Earth Glossary Lithospheric plates: The earth’s crust consists of several large and some small, rigid, irregularly- shaped plates (slabs) which carry continents and the ocean floor. Fig. 3.1: Evolution of Landforms Earth movements Endogenic forces Exogenic forces Sudden forces Diastrophic forces Erosional and Depositional Building mountains Earthquake Volcano Landslides River Wind Sea-waves Glaciers Endogenic forces sometimes produce sudden movements and at the other times produce slow movements. Sudden movements like earthquakes and volcanoes cause mass destruction over the surface of the earth. 2020-21 Crater Lava tube Vent Lava Gases and ash Crust Mantle Magma Chamber Word Origin Fig. 3.2: A Volcano Epicentre Seismic waves radiate out in all directions Plate boundary Focus – this is where the earthquake occurs. It is the origin of the seismic energy A volcano is a vent (opening) in the earth’s crust through which molten material erupts suddenly (Fig. 3.2). Fig. 3.3: Origin of an Earthquake Activity Take a container, fill it with water and close it with a lid. Put the water to boil. Now put some peas, spoon and beads on top on the lid. What do you notice? As the water boils the lid begins to shake. The things which you have put on the lid also vibrate. The beads roll down and the spoon vibrates to make a sound. In the same manner, the earth vibrates when an earthquake occurs. Do you know? There are three types of earthquake waves: 1. P waves or longitudinal waves 2. S waves or transverse waves 3. L waves or surface waves Try to find out the properties of these waves from an encyclopedia. Similarly, when the Lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all round the earth. These vibrations are called earthquakes (Fig. 3.3). The place in the crust where the movement starts is called the focus. The place on the surface above the focus is called the epicentre. Vibrations travel outwards from the epicentre as waves. Greatest damage is usually closest to the epicentre and the strength of the earthquake decreases away from the centre. Endo (inside) Exo (outside) Endogenic Exogenic + genic (origin) 13 OUR CHANGING EARTH . 2020-21 14 OUR ENVIRONMENT Activity Do you know? An earthquake is measured with a machine called a seismograph. The magnitude of the earthquake is measured on the Richter scale. An earthquake of 2.0 or less can be felt only a little. An earthquake over 5.0 can cause damage from things falling. A 6.0 or higher magnitude is considered very strong and 7.0 is classified as a major earthquake. A Seismograph EARTHQUAKE PREPAREDNESS Where to take shelter during an earthquake — Safe Spot – Under a kitchen counter, table or desk, against an inside corner or wall. Stay Away from – Fire places, areas around chimneys, windows that shatter including mirrors and picture frames. Be Prepared – Spread awareness amongst your friends and family members and face any disaster confidently. Fig. 3.3a: Destruction caused by an Earthquake in Gujarat 1. Read the ‘Earthquake – A case study’ given in the form of headlines that appeared in the newspapers after the quake. Arrange the events in the right sequence of their happening. 2. Imagine if a quake suddenly shook in the middle of the school day, where would you go for safety? Although earthquakes cannot be predicted, the impact can certainly be minimised if we are prepared before-hand. Some common earthquake prediction methods adopted locally by people include studying animal behaviour; fish in the ponds get agitated, snakes come to the surface. EARTHQUAKE HITS BHUJ A massive earthquake measuring 6.9 on Richter scale hit Bhuj Town on 26th January 2001. Fire in the city Hundreds of fires started as charcoal, cookers overturned. Emergency declared in quake zone The President declares a state of emergency. Atleast 971 students and 31 teachers are feared to have lost their lives following the collapse of school buildings. School worst affected CM’S APPEAL TO THE CENTRE Gujarat appeals for financial help. The Chief Minister of Gujarat has launched an appeal for the Centre to deal with the disaster. Destruction of Bhuj Phone lines, water pipelines and power stations transmission lines were knocked out. 1 2 3 4 5 6 7 BHUJ RELIEF EFFORT BLIGHTED.. Three days after the quake, concern rose about food, blankets and medical supplies not reaching everyone. Earthquake – A Case Study 2020-21 15 OUR CHANGING EARTH Fig. 3.5: Features made by a river in a flood plain Do you know? MAJOR LAND FORMS The landscape is being continuously worn away by two processes – weathering and erosion. Weathering is the breaking up of the rocks on the earth’s surface. Erosion is the wearing away of the landscape by different agents like water, wind and ice. The eroded material is carried away or transported by water, wind, etc. and eventually deposited. This process of erosion and deposition create different landforms on the surface of the earth. Work of a River The running water in the river erodes the landscape. When the river tumbles at steep angle over very hard rocks or down a steep valley side it forms a waterfall (Fig. 3.4). • There are thousands of small waterfalls in the world. The highest waterfall is Angel Falls of Venezuela in South America. The other waterfalls are Niagara falls located on the border between Canada and USA in North America and Victoria Falls on the borders of Zambia and Zimbabwe in Africa. The Niagra falls Hard rock Softer rock undercut by the power of the water Fig. 3.4: Waterfall As the river enters the plain it twists and turns forming large bends known as meanders. Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loop come closer and closer. In due course of time the meander loop cuts off from the river and forms a cut-off lake, also called an ox-bow lake. At times the river overflows its banks. This leads to the flooding of the neighbouring areas. As it floods, it deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of a flat fertile floodplain. The raised banks are called levees. As the river approaches the sea, the speed of the flowing water decreases and the 2020-21 16 OUR ENVIRONMENT river begins to break up into a number of streams called distributaries. The river becomes so slow that it begins to deposit its load. Each distributary forms its own mouth. The collection of sediments from all the mouths forms a delta. Work of Sea Waves The erosion and deposition of the sea waves gives rise to coastal landforms. Seawaves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called sea caves. As these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches. Further, erosion breaks the roof and only walls are left. These wall like features are called stacks. The steep rocky coast rising almost vertically above sea water is called sea cliff. The sea waves deposit sediments along the shores forming beaches. Work of Ice Glaciers are “rivers of ice” which too erode the landscape by bulldozing soil and stones to expose the solid rock below. Glaciers carve out deep hollows there. As the ice melts they get filled up with water and become beautiful lakes in the mountains. The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines. Let’s do Find out the names of a few rivers of the world that form a delta. Fig. 3.8: A Glacier Main river Distributary Fig. 3.6: A Delta Sea Cave Sea Arch Stack Fig. 3.7: Features made by sea waves 2020-21Read More
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