Landslides and Volcanoes

• Study notes on types of landslides and volcanoes

Types of Landslides

• Debris flows: Fast-moving landslides of water-soaked rock and soil that are dangerous because they move quickly and strike without warning; triggered when slopes become saturated with water.
• Slumping landslides: Landslides where a mass of material moves downslope as a unit along a curved plane, leaving a scarp (drop-off) at the top; can result in terracing.
• Soil Creep landslides: Very slow landslides where soil moves downhill gradually, hardly noticeable.
• Rock fall landslides: Freefall of rock from a cliff, often due to physical weathering such as ice wedging; rock accumulates as talus at the cliff's base; earthquakes are often triggers.

Types of Volcanoes

• Volcanoes are distinguished by size, lava composition, and eruptive style.
• Main types: cinder cones, shield volcanoes, composite volcanoes (stratovolcanoes), and lava domes.

Cinder Cones

• The most common type of volcano.
• Small, steep-sided cones that forms quickly from a single eruption
• The eruption is gas-rich magma that erupts violently and solidifies into cinders

Shield Volcanoes

• Form by low-viscosity lava flows far from the source, creating gentle slopes.
• The Hawaiian Islands are home to some of the most famous shield volcanoes.

Composite Volcanoes

• Also known as stratovolcanoes.
• These are the largest volcanoes and form symmetrical cones.
• Built from layers of lava, ash, pumice, and tephra.
• The most explosive volcanoes and responsible for many famous eruptions.

Lava Domes

• Formed by small masses of thick lava that pile up around a vent instead of flowing.
• Tend to be the least explosive volcanoes

Caldera Volcanoes

• Form when the summit of a volcano collapses after a massive eruption
• Often associated with explosive eruptions that produce widespread ash deposits

Types of Volcanic Eruption

• Plinian: Powerful eruption producing an ash column that extends into the stratosphere, resulting in widespread ashfall, extremely explosive with ash columns extending for miles.
• Icelandic: Effusions of molten basaltic lava from long, parallel fissures.
• Strambolian: Moderately explosive eruptions of basaltic magma with moderate gas content; intermittent, discrete bursts eject pyroclasts high into the air.
• Vulcanian: Moderately explosive but intermittent, producing moderate ash columns; more explosive than Strombolian, can destroy the volcanic edifice; eruptions propelled by exsolution of volatiles in magmas beneath solidified lava plug.
• Hawaiian: Non-explosive eruptions of gusher-like lava fountains ("fire fountains"); generate red-hot lava rivers of fluid basaltic lavas; typical for shield volcanoes eruptions at summit and fissure vents.
• Pelean: Involves the explosive release of hot ash, lava, and gas; associated with explosive outbursts that generate pyroclastic flows (dense mixtures of hot volcanic fragments and gas).