Weathering and Denudation - Video Notes (Chapter 9) - Flashcards

Flashcards covering definitions, processes, agents, and climatic variations of weathering as described in the notes.

What is Weathering?

The breakdown of rocks at or near the Earth’s surface without removal, through disintegration or decomposition by natural agents; weathering cannot occur on the Moon due to lack of suitable surface conditions.

What are the three main types of weathering?

Physical (mechanical) weathering, chemical weathering, and biological (organic) weathering.

What are Constructive Forces?

Internal forces within the Earth that form landforms.

What are Exogenic Forces?

External forces acting on the Earth’s surface (e.g., weathering, erosion, transport, deposition, soil formation) that derive energy from the Sun; climate acts as the driving agent.

What is Denudation?

The overall process that includes weathering, mass wasting, erosion, transportation, deposition, and soil formation; weathering is the essential initial phase.

What are the chief characteristics of weathering?

Disintegration or decay of rocks; depends on climate and rock properties; affects the Earth’s surface; forms soil; involves several processes; converts rocks into finer materials; prepares materials for transport by agents of gradation.

What are the main factors responsible for Physical (Mechanical) Weathering?

Temperature changes, moisture, frost action, and wind.

What is Block Disintegration?

Rapid rise and fall of temperature causing expansion and contraction, leading to cracking and splitting the rock into blocks.

What is Granular Disintegration?

Weathering into smaller mineral pieces due to different minerals having different hardness; common in cold or high-altitude areas.

What is Exfoliation in physical weathering?

Sudden temperature changes cause outer rock layers to peel off; water penetration can create fissures that enhance weathering.

What is Hydration in chemical weathering?

Expansion of minerals when they come into contact with rainwater, leading to disintegration.

What are the four main processes of Chemical Weathering?

Oxidation, carbonation, hydration, and solution.

What is Oxidation?

Reaction of minerals with atmospheric oxygen; iron-containing minerals rust and color changes occur (red, yellow, brown).

What is Carbonation?

Carbon dioxide in rainwater forms carbonic acid, dissolving calcareous rocks (gypsum, marble, limestone) and turning CaCO3 into soluble Ca(HCO3)2, removed by groundwater.

What is Solution in chemical weathering?

Dissolution of minerals in water; rate depends on mineral composition and rock structure; rocks with pore spaces (e.g., sedimentary rocks) are more vulnerable; salts like rock-salt and gypsum dissolve in rainwater.

What is Biological Weathering?

Also known as Organic Weathering; main agents are animals, insects, plants and humans; involves both physical disintegration and chemical decomposition.

How do humans contribute to weathering?

Mining, excavations, road/building construction, agriculture, and dumping of chemicals promote both physical and chemical weathering.

How do plants contribute to weathering?

Root systems press into rocks causing physical disintegration; vegetation can bind surfaces and reduce exposure to weathering.

How do animals and insects contribute to weathering?

Burrowing animals bring fine material to the surface; decaying animals release chemicals and acids that promote weathering.

What is the role of climate in weathering patterns?

Climate is the most important factor; different climates favor different weathering processes.

Weathering in Equatorial climates?

High humidity and high temperatures; chemical weathering is more active.

Weathering in Tropical climates?

Distinct dry and wet seasons; high evaporation; during wet season, oxides of iron and aluminium precipitate, promoting laterite soil formation.

Weathering in Desert (dry) climates?

Mechanical weathering dominates due to large diurnal temperature ranges.

Weathering in Mid-latitude/Temperate climates?

Frost action is the most powerful agent; in limestone regions, solution (chemical weathering) operates on a large scale.

Weathering in Polar climates?

Frost action is prevalent; chemical and biological weathering are negligible; melting water may contain more carbonic acid due to higher CO2 solubility at low temperatures, potentially increasing chemical weathering in polar regions.

What is the key takeaway about weathering and climate?

Climate largely governs the rate and type of weathering across regions; weathering is a crucial initiating stage of denudation.

Is weathering possible on the Moon?

No; the Moon lacks the climatic conditions necessary for weathering, so such processes do not occur there.