Skip to main content

Volcanism; chemical weathering

Short answer

Volcanism is the process where magma, gases, and rock fragments rise from Earth's interior, erupting on the surface or intruding into the crust. Chemical weathering alters rock minerals into stable clays and soluble salts via processes like solution, carbonation, hydrolysis, oxidation, and hydration, fastest in warm, wet climates.

What is volcanism? Describe chemical weathering.

Volcanism (vulcanicity) is the set of processes by which magma, gases and fragmented rock rise from the earth's interior and are erupted on the surface through a vent or fissure, or are intruded into the crust.

  • Volcanism produces lava, gases and pyroclasts, and builds cones, calderas and lava plateaus. Associated features are hot springs, geysers and fumaroles.

Chemical weathering

Chemical weathering changes the minerals of the rock into new, more stable minerals (mostly clay) and soluble salts. It is fastest in warm, wet climates. Main processes:

  • Solution: soluble minerals such as rock salt and gypsum dissolve in water.
  • Carbonation: CO2_2 in rain forms carbonic acid, which dissolves limestone: CaCO3+H2O+CO2→Ca(HCO3)2CaCO_3 + H_2O + CO_2 \rightarrow Ca(HCO_3)_2. This produces karst.
  • Hydrolysis: feldspar reacts with water to form clay: 2KAlSi3O8+2H++H2O→Al2Si2O5(OH)4+4SiO2+2K+2KAlSi_3O_8 + 2H^+ + H_2O \rightarrow Al_2Si_2O_5(OH)_4 + 4SiO_2 + 2K^+ (orthoclase to kaolinite).
  • Oxidation: iron minerals combine with oxygen and turn into rust-coloured oxides, e.g. 4FeO+O2→2Fe2O34FeO + O_2 \rightarrow 2Fe_2O_3.
  • Hydration: minerals take up water and swell, e.g. anhydrite to gypsum, hematite to limonite.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Engineering Geology I chapter 6 questions →