Mountain Formation Summary

Mountain Trivia

• Tallest: Mount Everest
• Most climbed: Mount Fuji
• Smallest: Mount Wycheproof
• Longest S. American range: Andes
• Boundary between Europe & Asia: Ural Mountains

Definition & Key Ideas

• Mountains = landforms rising > 600\,\text{m}; steep slopes, confined summits.
• Volcanoes are one mountain type only; other formation processes: folding, faulting, uplift + erosion, volcanic construction.

Isostasy

• Crust “floats” on denser mantle; continents = lighter, oceans = heavier.
• Mountain roots = low-density rocks; basins = high-density.
• Isostatic rebound: crust rises after ice or overburden removal.

Orogenesis (Mountain Building)

• Three stages:
  1. Accumulation: marine sediments/volcanics \approx2000{-}3000\,\text{m} thick.
  2. Orogenic stage: compression → folding, thrust faults, metamorphism, intrusions.
  3. Rebound: uplift via isostasy.
• Plate-boundary settings:
  • Divergent – new crust, fissures, mid-ocean ridges.
  • Convergent – subduction, trenches, arcs, mountains.
  • Transform – faults, earthquakes, linear valleys.

Types of Mountains (by Origin)

• Folded: compressed sedimentary layers; narrow but very high (Himalayas, Alps, Andes, Rockies, Urals).
• Fault-Block: crust fractures → horsts (up) & graben (down) (Sierra Nevada, Harz).
• Dome (Upwarped): magma uplifts layers without eruption; steep sides, rounded top (Black Hills, Half Dome).
• Volcanic: erupted lava/ash piles up (Mt. Pinatubo, Mauna Kea).

Fold Varieties in Folded Mountains

• Anticline: upward arch.
• Syncline: downward trough.
• Monocline: step-like bend.
• Symmetrical: vertical axial plane.
• Asymmetrical: inclined axial plane.
• Recumbent: limbs & axial plane almost horizontal.
• Nappe: detached recumbent fold thrust forward.
• Dome & basin (upward/downward bulges); hogback (steep strata ridge).

Importance of Mountains

• Freshwater “towers”: supply 60{-}80\% of global fresh water.
• Agriculture, biodiversity, mineral & timber resources.
• Tourism & recreation hubs.
• Climate regulation; buffers against floods & landslides.
• Hydroelectric power potential.
• Health benefits: stress reduction, cardiovascular fitness.