ERTH - Natural disasters class FEB 5th

Volcanic Fundamentals

• Dust Observation: Observing dust after a night with no apparent wind suggests volcanic activity, such as eruptions from nearby volcanoes like Mount Rainier.

Mount Rainier vs. Mount St. Helens

• Mount Rainier is characterized by steep slopes and is more explosive compared to Mount St. Helens.

Elements in Volcanoes

• Commonly present elements in volcanic activity:

  • Magnesium, Sodium, Phosphorus, Beryllium, Boron, Carbon, etc.

• Volcanoes can contain most elements on the periodic table, except for the heaviest.

• Earth's crust is low in density elements (potassium, sodium, aluminum), while the core contains denser elements (iron, nickel).

Elements in Magmas

• Critical elements in volcanic rocks include:

  • Sodium, Potassium, Magnesium, Calcium, Iron, Silicon, and Oxygen.

• Common compounds formed include oxides, such as:

  • Potassium Oxide (K2O), Sodium Oxide (Na2O), Iron Oxide (FeO), Silicon Oxide (SiO2).

• Quartz (SiO2): A prevalent and stable mineral at the surface, can have complex compositions in other minerals.

Rock Chemistry and Analysis

• Rocks can vary significantly in mineral composition:

  • Example: Complex minerals may contain 12 or more elements.

• Rock composition can be analyzed through:

  • X-ray refractometry or laser ablation mass spectrometry.

Types of Igneous Rocks

• Critical volcanic rock types to know:

  • Basalt: Typically black, forms rapidly, fine crystals, common in shield volcanoes (e.g., Hawaiian islands).

  • Andesite: Formed in subduction zones, associated with stratovolcanoes.

  • Dacite: Intermediate in composition, less commonly discussed.

  • Rhyolite: High silica content, extremely explosive, erupts in caldera events.

Volcanic Eruption Types

• The physical characteristics and eruption styles are based on:

  • Viscosity, gas content, and silica content.

• Types of eruptions:

  • Flood Eruptions: Minimal ash, lava flows to lower altitudes.

  • Hawaiian Eruptions: More gas and pressure than flood eruptions.

  • Strombolian Eruptions: More explosive, characterized by spatter and lava ejecta.

  • Subplinian and Plinian Eruptions: Very intense eruptions, characterized by significant ash and gas production.

Viscosity and Eruption Dynamics

• Viscosity: The resistance to flow; high silica content increases viscosity.

• Examples of relative viscosities:

  • Water < Molasses < Toothpaste.

Bowen's Reaction Series

• A model demonstrating how magma crystallizes as it ascends:

  • Initial melting: calcium and iron-rich minerals (olivine and plagioclase).

  • Higher up: increases in sodium-rich minerals in the magma composition.

• Stries from Basalt to Rhyolite along a spectrum of magma evolution.

Tectonic Activity and Location of Volcanoes

• Subduction Zones: Major areas for volcanic activity, producing intermediate and explosive volcanism.

• Locations to consider include: Aleutian Islands, Kamchatka, Japan, Philippines, and the Andes.

Modern Volcanic Awareness

• San Figueroa Volcano: An example of a stratovolcano currently erupting, produces significant ash that can impact air travel.

• Pyroclastic Flows: The most deadly aspect of eruptions, rapid and destructive flows of hot ash and gas that devastate valleys.

Summary of Key Points

• Volcanoes relate closely to tectonic plate movements and mantle plumes.

• Understanding the relationships between magma composition, eruption style, and fallout effects is crucial for grasping volcanic behavior and hazards.