Here are 20 long-answer questions with 5–6 points each from Chapter 2: Inside Our Earth of CBSE Class 7 Geography:
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1. Describe the structure of the Earth.
Answer:
The Earth is made up of three main layers:
1. Crust – The outermost layer, made of solid rocks and minerals, with an average thickness of 35 km.
2. Mantle – Lies below the crust, extends up to 2900 km, and consists of semi-molten rock called magma.
3. Core – The innermost layer, divided into an outer liquid core and a solid inner core, primarily composed of iron and nickel.
4. Lithosphere – The rigid outer part of the Earth, including the crust and upper mantle.
5. Asthenosphere – A semi-fluid layer of the mantle that allows tectonic plates to move.
6. Temperature and Pressure Increase – As we go deeper into the Earth, temperature and pressure rise significantly.
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2. Explain the different types of rocks found inside the Earth.
Answer:
There are three main types of rocks:
1. Igneous Rocks – Formed by the cooling of molten magma, e.g., granite and basalt.
2. Sedimentary Rocks – Created from compressed layers of sediments over time, e.g., sandstone and limestone.
3. Metamorphic Rocks – Formed when existing rocks undergo heat and pressure, e.g., marble (from limestone) and slate (from shale).
4. Intrusive Igneous Rocks – Form deep inside the Earth, cool slowly, and have large crystals, e.g., granite.
5. Extrusive Igneous Rocks – Form on the surface due to lava cooling quickly, e.g., basalt.
6. Rock Cycle – The transformation of rocks from one type to another over time due to natural processes.
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3. What is the rock cycle? Explain its importance.
Answer:
The rock cycle is the continuous process of transformation of rocks:
1. Igneous Rocks Formation – Molten magma cools and solidifies into igneous rocks.
2. Formation of Sediments – Igneous rocks break down into sediments due to weathering and erosion.
3. Sedimentary Rocks Formation – Sediments get compressed and harden into sedimentary rocks.
4. Metamorphism – Sedimentary or igneous rocks undergo heat and pressure to form metamorphic rocks.
5. Melting and Magma Formation – Metamorphic rocks melt to form magma, restarting the cycle.
6. Importance – It helps in soil formation, maintains Earth’s natural balance, and provides minerals.
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4. What are igneous rocks? How are they classified?
Answer:
Igneous rocks are formed by the cooling of molten magma. They are classified as:
1. Intrusive Igneous Rocks – Formed deep inside the Earth, cool slowly, have large crystals, e.g., granite.
2. Extrusive Igneous Rocks – Formed on the Earth's surface, cool quickly, have small crystals, e.g., basalt.
3. Characteristics – Hard, durable, and rich in minerals like silica and iron.
4. Uses – Used in construction (granite), making roads, and decorative stones.
5. Examples – Granite, basalt, pumice, and obsidian.
6. Formation Process – Magma rises through cracks in the Earth's crust and solidifies into igneous rocks.
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5. What are sedimentary rocks? How do they form?
Answer:
Sedimentary rocks form from sediments deposited in layers over time:
1. Weathering and Erosion – Rocks break down into small pieces due to wind, water, and temperature changes.
2. Transportation – Sediments are carried by rivers, wind, and glaciers.
3. Deposition – Sediments settle in layers at the bottom of rivers, lakes, and seas.
4. Compaction and Cementation – Over time, pressure compresses the layers, and minerals bind them together.
5. Examples – Sandstone, limestone, shale, and conglomerate.
6. Uses – Building materials, fossil preservation, and oil/gas reservoirs.
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6. What are metamorphic rocks? How are they formed?
Answer:
Metamorphic rocks are formed when existing rocks undergo heat and pressure.
1. Formation Process – Igneous or sedimentary rocks undergo transformation due to high temperature and pressure.
2. Changes in Composition – The original rock changes in texture, mineral composition, and structure.
3. Examples – Marble (from limestone), slate (from shale), and quartzite (from sandstone).
4. Characteristics – Harder and more resistant than the original rock.
5. Uses – Used in construction (marble in flooring), sculptures, and roofing (slate).
6. Importance – Provides valuable minerals like graphite and gemstones.
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7. Explain the difference between intrusive and extrusive igneous rocks.
Answer:
The two types of igneous rocks differ based on their formation process.
1. Intrusive Igneous Rocks – Form deep inside the Earth's crust when magma cools slowly.
2. Extrusive Igneous Rocks – Form on the Earth's surface when lava cools quickly.
3. Crystal Size – Intrusive rocks have large crystals due to slow cooling (e.g., granite), while extrusive rocks have small crystals due to rapid cooling (e.g., basalt).
4. Appearance – Intrusive rocks are coarse-grained, whereas extrusive rocks are fine-grained.
5. Examples – Granite (intrusive), basalt (extrusive), pumice (extrusive).
6. Uses – Intrusive rocks are used in construction, while extrusive rocks are used for road building and landscaping.
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8. How does the lithosphere differ from the mantle?
Answer:
The lithosphere and mantle are two different layers of the Earth.
1. Lithosphere – The outermost solid layer of the Earth, including the crust and uppermost mantle.
2. Mantle – The layer beneath the lithosphere, extending up to 2900 km.
3. Composition – The lithosphere is made of solid rock, while the mantle consists of semi-molten magma.
4. Thickness – The lithosphere is about 100 km thick, whereas the mantle is much thicker.
5. Role – The lithosphere forms the Earth's land and ocean floor, while the mantle drives plate tectonics.
6. Temperature – The mantle is much hotter than the lithosphere, leading to convection currents.
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9. What are minerals? How are they classified?
Answer:
Minerals are naturally occurring substances found in rocks.
1. Definition – Minerals are solid, naturally occurring substances with a definite chemical composition.
2. Types – Metallic (contain metals) and non-metallic (do not contain metals).
3. Metallic Minerals – Include iron, copper, gold, and aluminum; used in industries.
4. Non-Metallic Minerals – Include limestone, mica, and coal; used in construction and energy production.
5. Formation – Formed through geological processes like cooling of magma and sedimentation.
6. Uses – Essential for making metals, fuels, and industrial products.
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10. Explain the process of weathering and erosion.
Answer:
Weathering and erosion break down and transport rocks.
1. Weathering – The breakdown of rocks due to wind, water, temperature, and biological factors.
2. Types of Weathering – Physical (temperature changes), chemical (reaction with water and gases), and biological (plants and animals).
3. Erosion – The movement of weathered rock particles by wind, water, glaciers, and gravity.
4. Transportation – Eroded materials are carried to rivers, lakes, and oceans.
5. Deposition – Sediments settle down and form new landforms like deltas and sand dunes.
6. Impact – Leads to soil formation and landscape changes but also causes land degradation.
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11. How do plate tectonics affect the Earth’s surface?
Answer:
Plate tectonics cause significant geological changes.
1. Movement of Plates – The Earth's lithosphere is divided into plates that move over the asthenosphere.
2. Earthquakes – Occur when plates collide or slide past each other.
3. Volcanoes – Form at plate boundaries where magma escapes to the surface.
4. Mountain Formation – Happens when two continental plates collide, e.g., Himalayas.
5. Oceanic Changes – New ocean floors form due to seafloor spreading.
6. Continental Drift – Continents slowly move over time due to plate movements.
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12. What are the different layers of the Earth?
Answer:
The Earth has three main layers.
1. Crust – The outermost layer, made of solid rocks and minerals.
2. Mantle – Lies beneath the crust, made of semi-molten magma.
3. Core – The innermost layer, composed of iron and nickel.
4. Inner Core – Solid due to extreme pressure.
5. Outer Core – Liquid, responsible for Earth's magnetic field.
6. Thickness – Crust (5–70 km), Mantle (2900 km), Core (3500 km).
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13. What is the role of magma in the formation of rocks?
Answer:
Magma plays a key role in rock formation.
1. Igneous Rock Formation – Magma cools and solidifies to form igneous rocks.
2. Intrusive Rocks – Magma cools slowly inside the Earth, forming large crystals.
3. Extrusive Rocks – Lava cools quickly on the surface, forming fine-grained rocks.
4. Metamorphism – Magma’s heat changes existing rocks into metamorphic rocks.
5. Volcanic Activity – Magma erupts as lava, creating volcanic landforms.
6. Rock Cycle Contribution – Magma melts old rocks and recycles Earth's materials.
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14. How do earthquakes occur? What are their effects?
Answer:
Earthquakes occur due to the sudden movement of tectonic plates.
1. Causes – When stress builds up at plate boundaries, rocks break, releasing energy.
2. Focus and Epicenter – The focus is the underground point where the earthquake starts; the epicenter is directly above it on the surface.
3. Seismic Waves – Travel through the Earth, causing shaking.
4. Effects – Damage to buildings, loss of life, and changes in landforms.
5. Tsunamis – Underwater earthquakes can trigger giant waves.
6. Measurement – Recorded on a seismograph and measured using the Richter scale.
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15. How do human activities affect the Earth's surface?
Answer:
Human activities cause significant changes to the Earth's surface.
1. Deforestation – Clearing forests increases soil erosion.
2. Mining – Extracting minerals disturbs land and pollutes water.
3. Urbanization – Expanding cities leads to land degradation and loss of biodiversity.
4. Pollution – Industrial and agricultural activities contribute to air, water, and soil pollution.
5. Climate Change – Burning fossil fuels increases greenhouse gases.
6. Soil Erosion – Overgrazing and farming practices deplete soil quality.
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6. What are metamorphic rocks? How are they formed?
Answer:
Metamorphic rocks are formed when existing rocks undergo heat and pressure.
1. Formation Process – Igneous or sedimentary rocks undergo transformation due to high temperature and pressure.
2. Changes in Composition – The original rock changes in texture, mineral composition, and structure.
3. Examples – Marble (from limestone), slate (from shale), and quartzite (from sandstone).
4. Characteristics – Harder and more resistant than the original rock.
5. Uses – Used in construction (marble in flooring), sculptures, and roofing (slate).
6. Importance – Provides valuable minerals like graphite and gemstones.
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7. Explain the difference between intrusive and extrusive igneous rocks.
Answer:
The two types of igneous rocks differ based on their formation process.
1. Intrusive Igneous Rocks – Form deep inside the Earth's crust when magma cools slowly.
2. Extrusive Igneous Rocks – Form on the Earth's surface when lava cools quickly.
3. Crystal Size – Intrusive rocks have large crystals due to slow cooling (e.g., granite), while extrusive rocks have small crystals due to rapid cooling (e.g., basalt).
4. Appearance – Intrusive rocks are coarse-grained, whereas extrusive rocks are fine-grained.
5. Examples – Granite (intrusive), basalt (extrusive), pumice (extrusive).
6. Uses – Intrusive rocks are used in construction, while extrusive rocks are used for road building and landscaping.
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8. How does the lithosphere differ from the mantle?
Answer:
The lithosphere and mantle are two different layers of the Earth.
1. Lithosphere – The outermost solid layer of the Earth, including the crust and uppermost mantle.
2. Mantle – The layer beneath the lithosphere, extending up to 2900 km.
3. Composition – The lithosphere is made of solid rock, while the mantle consists of semi-molten magma.
4. Thickness – The lithosphere is about 100 km thick, whereas the mantle is much thicker.
5. Role – The lithosphere forms the Earth's land and ocean floor, while the mantle drives plate tectonics.
6. Temperature – The mantle is much hotter than the lithosphere, leading to convection currents.
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9. What are minerals? How are they classified?
Answer:
Minerals are naturally occurring substances found in rocks.
1. Definition – Minerals are solid, naturally occurring substances with a definite chemical composition.
2. Types – Metallic (contain metals) and non-metallic (do not contain metals).
3. Metallic Minerals – Include iron, copper, gold, and aluminum; used in industries.
4. Non-Metallic Minerals – Include limestone, mica, and coal; used in construction and energy production.
5. Formation – Formed through geological processes like cooling of magma and sedimentation.
6. Uses – Essential for making metals, fuels, and industrial products.
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10. Explain the process of weathering and erosion.
Answer:
Weathering and erosion break down and transport rocks.
1. Weathering – The breakdown of rocks due to wind, water, temperature, and biological factors.
2. Types of Weathering – Physical (temperature changes), chemical (reaction with water and gases), and biological (plants and animals).
3. Erosion – The movement of weathered rock particles by wind, water, glaciers, and gravity.
4. Transportation – Eroded materials are carried to rivers, lakes, and oceans.
5. Deposition – Sediments settle down and form new landforms like deltas and sand dunes.
6. Impact – Leads to soil formation and landscape changes but also causes land degradation.
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11. How do plate tectonics affect the Earth’s surface?
Answer:
Plate tectonics cause significant geological changes.
1. Movement of Plates – The Earth's lithosphere is divided into plates that move over the asthenosphere.
2. Earthquakes – Occur when plates collide or slide past each other.
3. Volcanoes – Form at plate boundaries where magma escapes to the surface.
4. Mountain Formation – Happens when two continental plates collide, e.g., Himalayas.
5. Oceanic Changes – New ocean floors form due to seafloor spreading.
6. Continental Drift – Continents slowly move over time due to plate movements.
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12. What are the different layers of the Earth?
Answer:
The Earth has three main layers.
1. Crust – The outermost layer, made of solid rocks and minerals.
2. Mantle – Lies beneath the crust, made of semi-molten magma.
3. Core – The innermost layer, composed of iron and nickel.
4. Inner Core – Solid due to extreme pressure.
5. Outer Core – Liquid, responsible for Earth's magnetic field.
6. Thickness – Crust (5–70 km), Mantle (2900 km), Core (3500 km).
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13. What is the role of magma in the formation of rocks?
Answer:
Magma plays a key role in rock formation.
1. Igneous Rock Formation – Magma cools and solidifies to form igneous rocks.
2. Intrusive Rocks – Magma cools slowly inside the Earth, forming large crystals.
3. Extrusive Rocks – Lava cools quickly on the surface, forming fine-grained rocks.
4. Metamorphism – Magma’s heat changes existing rocks into metamorphic rocks.
5. Volcanic Activity – Magma erupts as lava, creating volcanic landforms.
6. Rock Cycle Contribution – Magma melts old rocks and recycles Earth's materials.
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14. How do earthquakes occur? What are their effects?
Answer:
Earthquakes occur due to the sudden movement of tectonic plates.
1. Causes – When stress builds up at plate boundaries, rocks break, releasing energy.
2. Focus and Epicenter – The focus is the underground point where the earthquake starts; the epicenter is directly above it on the surface.
3. Seismic Waves – Travel through the Earth, causing shaking.
4. Effects – Damage to buildings, loss of life, and changes in landforms.
5. Tsunamis – Underwater earthquakes can trigger giant waves.
6. Measurement – Recorded on a seismograph and measured using the Richter scale.
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15. How do human activities affect the Earth's surface?
Answer:
Human activities cause significant changes to the Earth's surface.
1. Deforestation – Clearing forests increases soil erosion.
2. Mining – Extracting minerals disturbs land and pollutes water.
3. Urbanization – Expanding cities leads to land degradation and loss of biodiversity.
4. Pollution – Industrial and agricultural activities contribute to air, water, and soil pollution.
5. Climate Change – Burning fossil fuels increases greenhouse gases.
6. Soil Erosion – Overgrazing and farming practices deplete soil quality.
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16. What is the importance of rocks in our daily life?
Answer:
Rocks play a vital role in various aspects of human life.
1. Building Materials – Rocks like granite and limestone are used in construction.
2. Industrial Use – Minerals from rocks are used in manufacturing metals, glass, and cement.
3. Energy Sources – Coal and petroleum, found in sedimentary rocks, are important fuels.
4. Jewelry and Ornaments – Precious stones like diamonds, rubies, and emeralds come from rocks.
5. Soil Formation – Weathering of rocks provides essential minerals for plant growth.
6. Scientific Study – Rocks help geologists understand Earth’s history and natural processes.
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17. How do volcanic eruptions occur? What are their effects?
Answer:
Volcanoes erupt when magma from the Earth's mantle reaches the surface.
1. Cause of Eruption – Magma rises through cracks in the Earth's crust due to pressure buildup.
2. Formation of Lava – Once magma reaches the surface, it is called lava and cools to form new land.
3. Volcanic Gases – Volcanoes release gases like carbon dioxide and sulfur dioxide.
4. Destruction – Lava flows can destroy cities, forests, and farmlands.
5. Climate Impact – Volcanic ash can block sunlight and lower global temperatures.
6. Creation of Landforms – Volcanic activity creates islands (e.g., Hawaii) and mountains.
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18. What are the differences between the inner core and outer core?
Answer:
The core of the Earth is divided into two parts:
1. Composition – Both the inner and outer core are made of iron and nickel.
2. State of Matter – The inner core is solid due to high pressure, while the outer core is liquid.
3. Temperature – The inner core is hotter (up to 6000°C) than the outer core.
4. Movement – The outer core’s liquid movement generates Earth’s magnetic field.
5. Thickness – The inner core is about 1,220 km thick, while the outer core is about 2,300 km thick.
6. Seismic Waves – The inner core reflects seismic waves differently than the outer core, helping scientists study Earth's interior.
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19. Explain how fossils are formed and their significance.
Answer:
Fossils are the preserved remains of ancient plants and animals.
1. Formation Process – Organisms get buried under layers of sediment and slowly turn into rock.
2. Sedimentary Rocks – Most fossils are found in sedimentary rocks.
3. Types of Fossils – Can include bones, shells, imprints, or preserved traces like footprints.
4. Historical Evidence – Fossils help scientists study ancient life and past climates.
5. Evolutionary Studies – Provide evidence for the theory of evolution.
6. Petroleum and Coal – Fossilized plants over millions of years form coal and petroleum.
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20. What are tectonic plates? How do they cause earthquakes and volcanoes?
Answer:
Tectonic plates are large pieces of the Earth’s lithosphere that move over the mantle.
1. Plate Movement – Plates move due to convection currents in the mantle.
2. Earthquakes – Occur when two plates collide, move apart, or slide past each other.
3. Volcanoes – Form when plates separate, allowing magma to rise to the surface.
4. Mountain Formation – Happens when two continental plates collide (e.g., Himalayas).
5. Seafloor Spreading – Occurs when oceanic plates move apart, creating new ocean floor.
6. Continental Drift – Slow movement of continents over millions of years due to plate motion.
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