lesson 15/16: erosion and weathering

Question 1

erosion and weathering

Answer 1

Mechanical, chemical, and biological weathering, along with erosion, collaborate to shape landforms. Mechanical weathering physically breaks down rocks, while chemical weathering alters their composition. Biological weathering involves roots and organisms weakening rocks. Finally, erosion transports weathered material away, reshaping the landscape over time.

Question 2

mechanical

Answer 2

• Wind-driven sand and other particles erode the surfaces of buildings and statues, gradually wearing them down or smoothing their features.
• Mechanical weathering is the process through which large rocks are broken into increasingly smaller pieces
• It occurs near the Earth’s surface and disintegrates rocks without changing their chemical composition
• Mechanical weathering is caused by thermal expansion and contraction, ice wedging, abrasion, and human actions
• It is a set of weathering processes that break apart rocks into particles (sediment) through physical processes

Question 3

chemical

Answer 3

• Chemical weathering involves the chemical alteration of minerals within rocks, forming new minerals and soluble salts. This type of weathering contributes to soil formation.
• The types of chemical weathering include dissolution, hydrolysis, carbonation, oxidation, and hydration
• Dissolution is the process where minerals dissolve in water. Carbonate rocks like limestone are particularly susceptible, leading to karst landscapes with features like sinkholes and caves.
• Hydrolysis is the reaction of minerals with water, forming new minerals and releasing ions. This process is essential in breaking feldspar minerals into clay.
• Carbonation occurs when carbon dioxide dissolves in water and forms weak carbonic acid. The acid reacts with minerals like calcium carbonate in rocks and breaks them up.
• Oxidation involves the reaction between minerals and oxygen. It commonly occurs as rusting in iron-rich rocks. This process weakens rocks and changes their composition.
• Hydration is the absorption of water into the crystal structure of minerals. This makes them expand and weaken. This is distinct from simple wetting.

Question 4

biological

Answer 4

• Animals burrow, tramp, and bring material to the surface for more weathering, and they help transmit gases and water to depths
• Plant’s roots wedge the rocks apart
• Algae, lichen, bacteria and mosses often grow on rock surfaces, especially in humid regions. They produce weak acids, which convert some of the minerals to clay
• Biological weathering is the disintegration of rock due to the actions of organisms such as bacteria, plants, and animals
• Plants and animals also contribute to physical weathering. Roots growing into rock crevices exert pressure and cause mechanical fracturing. Burrowing animals move rocks and aid in their breakdown.
• Plants, funghi, and bacteria contribute to chemical weathering through the production of organic acids which enhance mineral breakdown. Bird droppings and bat guano and the chemicals released by lichens also cause chemical weathering.
• Roots from nearby vegetation grow into cracks and crevices. This causes physical disruption and sometimes introduces moisture and organic acids.
• Microorganisms and algae grow on surfaces, especially in damp conditions. This causes discoloration and potential physical damage. Chemical damage also occurs when organisms produce acidic compounds.