Volcanism & Plutonic Landforms

Internal Processes / Volcanism & Plutonic Landforms - Volcanoes

Volcanism & Plutonism

Hot spots - plates slide over rising plumes of magma
- evidence - island size and plate movement
  - Hawaii, Yellowstone, Galapagos Island

Flows & Eruptions

Basalt flows - darker lavas (dense material lacking silica)
- associated with divergent plate boundaries and hot spots
  - calm flows with little trapped gas
    - Hawaii and Iceland - fluid layers cover the islands
- two major types- commonly found on Shield Volcanoes
  - pahoehoe (or ropy) type
  - aa (or blocky) type
- Flood basalts - magma wells up through fissures
  - cover great distances (like 200,000 sq mi)
  - usually produce flat landforms (plateaus)
    - Columbia Plateau
    - India’s Deccan Plateau
Violent eruptions - associated with convergent plate boundaries
- trapped gas as magma cools
  - builds up explosive pressure
    - composite volcanoes

hurls massive amounts of ash & pyroclastics (small rocks)
- Mt. Pinatubo in Philippines
- Mt. St. Helens, Washington (1980)
- Mt. Etna (Sicily) more recent (2002)