Q l. Answer in brief.
(a) What is mechanical weathering ?
Ans.
Mechanical weathering is the physical process of breaking big rocks into small ones. The exposed part of the rock heats more while the inner part is comparatively cooler. As a result, the outer layers of the rocks fall apart from the main rock. Mechanical weathering mainly occurs because of the following reasons:
(1) Temperature (2) Frost (3) Crystal growth (4) Release of pressure (5) Water.
(b) What are the main types of chemical weathering?
Ans.
The main types of chemical weathering are:
(1) Carbonation (2) Solution (3) Oxidation
(1) Carbonation: The rainwater travels through the atmosphere before reaching the ground. Carbon dioxide in the air gets mixed in the water in this process. Dilute carbonic acid gets formed. Materials like limestone get easily dissolved in such acids.
(2) Solution : Some minerals in the rock get dissolved in water. Limestone is formed due to chemical precipitation between water and alkalis. Because of solution, alkalis in the rock dissolve and make them brittle.
(3) Oxidation : This process occurs in rocks which have iron present in them. The iron in the rock comes in contact with water and chemical reaction takes place between iron and oxygen. Hence, a reddish coloured layer forms on the rocks. This is called rust.
(c) How does biological weathering occur?
Ans.
(1) Besides mechanical and chemical weathering, biological factors are also responsible for weathering of rocks. (2) Pieces of rocks gets separated because of the roots of the trees. As the roots grow bigger, they create tension in the rocks and start breaking them. (3) Ants make large anthills. Rats, mice, rabbits and other worms and insects make burrows in the ground. Because of their activity, weathering of rock occurs. (4) Besides these, algae, moss, lichen, other flora etc. grow in the rocks. They also help in weathering.
(d) Distinguish between weathering and mass wasting.
Ans.
Q 2. Write whether the statements are true or false. Correct the incorrect ones.
(a) Climate affects earthquakes.
Ans. False – Internal movements affects earthquakes.
(b) Mechanical weathering is less effective in humid climates.
Ans. True.
(c) Mechanical weathering happens on a large scale in dry climates.
Ans. True.
(d) The breaking down of rocks into smaller particles is called weathering.
Ans. True.
(e) Lateritic rocks are formed through exfoliation.
Ans. False – Lateritic rocks are formed due to oxidation.
Q 3. Complete the flowchart below.
Ans.
Q 4. Identify the type of weathering from the given description.
(a) Some animals live inside the grounds by making burrows.
Ans. Biological weathering
(b) The rock rusts.
Ans. Chemical weathering
(c) Water which has accumulated in the crevices of the rocks freezes. Consequently, the rock breaks
Ans. Mechanical weathering
(d) The pipes supplying water in colder regions break.
Ans. Mechanical weathering
(e) Sand formation occurs in deserts
Ans. Mechanical weathering
Q 5. Using internet, look for incidences of a few landslides that have occurred in India and write about them briefly.
Ans.
(1) On 30 July 2014, a landslide occurred in the village of Malin in the Ambegaon taluka of the Pune district in Maharashtra, India. The landslide, which hit early in the morning while residents were asleep, was believed to have been caused by a burst of heavy rainfall, and killed at least 151 people. (2) Malpa landslide, Uttarkhand:- Consecutive landslides occurred in August 1998 in village of Mapla due to which 380 people died as an entire village was destroyed in the landslide. (3) Kedarnath landslide, Uttarakhand:- This landslide took place on June 16,2013 & was the result of Uttarkhand floods. Over 5700 people were reported dead and over 4200 villages were affected by floods and post flood landslide.