Short & Long Questions: The Changing Face of Earth | Window on the Word Class 7: Solutions, Notes & Worksheets PDF Download

Short Answer Questions

Q1: What are endogenic forces?
Ans: Endogenic forces originate from deep within the Earth and lead to the creation of significant landforms like mountains, volcanoes, and earthquakes.

Q2: Explain how tectonic plates move.
Ans: Tectonic plates move due to convection currents in the semi-liquid lower mantle, powered by heat from the Earth's core. They can move towards, away, or past each other.

Q3: What is the focus of an earthquake?
Ans: The focus is the point inside the Earth where an earthquake originates.

Q4: How are fold mountains formed?
Ans: Fold mountains are formed when two tectonic plates push towards each other, resulting in the land between them being folded upward.

Q5: What is the Ring of Fire?
Ans: The Ring of Fire is a region around the edges of the Pacific Ocean known for its high volcanic and seismic activity.

Q6: Define weathering.
Ans: Weathering is the process by which rocks break down and disintegrate due to factors like rain, temperature changes, and biological activity.

Q7: What are ox-bow lakes?
Ans: Ox-bow lakes are formed when a river's meander narrows and the river cuts through, leaving behind a U-shaped lake.

Q8: What causes tsunamis?
Ans: Tsunamis are often triggered by undersea earthquakes, causing massive waves when they reach land.

Q9: Explain how glaciers shape landscapes.
Ans: Glaciers, slow-moving rivers of ice, erode valleys and create features like U-shaped valleys and glacial lakes.

Q10: What are sand dunes and where are they found?
Ans: Sand dunes are mounds of sand formed by wind in deserts.

Long Answer Questions

Q11: Differentiate between endogenic and exogenic forces.
Ans: Endogenic forces are processes that originate from within the Earth and result from the movements and activities deep inside the Earth. They lead to the creation of significant landforms like mountains, volcanoes, and earthquakes. Exogenic forces, on the other hand, are processes that act on the Earth's surface, leading to the erosion, transportation, and deposition of material. These forces are powered by external factors like wind, water, and ice, and they work to modify the Earth's surface.

Q12: Explain the Theory of Plate Tectonics and how it relates to plate movements.
Ans: The Theory of Plate Tectonics is a scientific model that explains the movement of the Earth's lithospheric plates. According to this theory, the Earth's lithosphere is divided into several large and small plates. These plates are in constant motion, driven by convection currents in the Earth's mantle. These currents are powered by heat from the Earth's core. As a result, the tectonic plates move, leading to various geological activities like earthquakes, volcanic eruptions, and the formation of mountains.

Q13: Describe the formation of block mountains and rift valleys.
Ans: Block mountains and rift valleys are both geological features that result from the movements of tectonic plates. Block mountains form when two tectonic plates pull away from each other. This creates a series of faults or fractures in the Earth's crust. These faults can cause one section of land to be pushed upward while the adjacent land sinks, resulting in the formation of a block mountain. Rift valleys, on the other hand, form when two plates move away from each other, creating a large crack or fissure in the Earth's surface. As the land between these parallel faults subsides, a rift valley is formed.

Q14: Compare the Richter Scale and the Moment Magnitude Scale for measuring earthquakes.
Ans: The Richter Scale and the Moment Magnitude Scale (Mw) are both methods used to measure the magnitude of an earthquake. The Richter Scale measures the amplitude of seismic waves produced by an earthquake. It provides a numerical value that indicates the earthquake's size. However, it can underestimate the magnitude of larger, distant earthquakes. On the other hand, the Moment Magnitude Scale is a more modern and widely accepted scale. It takes into account various factors such as the fault length, amount of slip, and material properties of the rocks involved. This provides a more accurate assessment of an earthquake's impact, especially for extremely powerful earthquakes.

Q15: Explain the stages of a river and the features formed in each stage.
Ans: A river goes through three main stages: the upper course, middle course, and lower course. In the upper course, the river flows through mountainous terrain with steep gradients. The water is fast-moving and has significant erosive power. As the river flows, it erodes the land beneath it, creating features like V-shaped valleys and waterfalls. The eroded material is carried downstream. In the middle course, the river enters flatter terrain, such as plains. Here, the flow is slower, and the river starts to meander, forming large bends. Over time, the neck of these meanders may narrow, leading to the formation of ox-bow lakes. Additionally, periodic flooding occurs, depositing fertile silt along the floodplain. In the lower course, the river nears its mouth and the terrain is even flatter. The flow is slow, and the river carries a large amount of sediment. As the river approaches its mouth, it loses its power to carry sediment, leading to deposition. This restricts its flow, and the river may break up into a number of small, narrow channels called distributaries.