SECOND QUARTER

• Tsunamis are giant sea waves generated by earthquakes and volcanic eruptions under the sea bed
• Tsunamis occur only at 7 and above magnitude
• Tsunamis are caused by vertical displacement of the seafloor
• Tsunami waves travel as fast as 500-950 km
• Earthquakes are capable of toppling electric posts and can bring significant damage to gas pipelines resulting to fire
• Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking
• Liquefaction happens when unconsolidated materials saturated with water are moved by seismic vibrations
• Subsidence is the motion of a surface as it shifts downward relative to sea level
• Landslides are a geological phenomenon that includes a wide range of ground movements such as rockfalls, deep failure of slopes and shallow debris flow
• Magma is composed of

  • Silicate Minerals
  • Dissolved Gases
  • Molten Silicates
• Silicates are the most common type of mineral and are the most abundant in rocks and magma
• • THE BASIC UNIT OF SILICATES IS CALLED THE SILICA TETRAHEDRON
• • SILICA
  • A TYPE OF SILICATE, IS USED AS A BASIS FOR CLASSIFYING MAGMAS
• MAGMATIC INTRUSIONS PRODUCE INTRUSIVE

  IGNEOUS ROCK BODIES CALLED PLUTONS,
• Dikes are Tabular intrusive structure that cuts across any layering in country rock
• Sill is a Tabular intrusive structure that parallels layering in country rock
• ULTRAMAFIC - Lower silica content; higher metallic content.

  • Lower viscosity, higher temperature.
• FELSIC - Higher silica content; lower metallic content. 

  • High viscosity, lower temperature.
• TEMPERATURE - Silica-poor magma has minerals with higher melting points than silica-rich magma.

  • 1300°C (ULTRAMAFIC) down to 750°C (FELSIC).
• VISCOSITY - The property to resist flow; silica tends to form complex molecular chains, which translates to less mobility, and therefore higher viscosity.

  • Silica-rich magma is more viscous than silica-poor magma.
• MOST COMMON GASES DISPERSED IN MAGMA

  Water vapor, carbon dioxide, sulfur dioxide
• MAGMA EXTRUSION

  Magma is fluid enough to eventually reach the earth’s surface. This process is best represented by volcanic eruptions. We now call the molten material, lava.
• VOLCANOES - The most distinct product of magma extrusion.
• SHIELD VOLCANOES - Broad, gently sloping (2-10 degrees). Large (up to several kilometers wide; 200 kilometers wide). Mostly lava.
• 1. LAVA DOME - Inverted bowl (gentle slopes close to the center, steep slopes farther from the center). Small (up to a kilometer high, up to few kilometers wide). Mostly lava.
• 1. PYROCLASTIC CONE - Steep slopes (>20 degrees). Small (10s to 100s of meters high). Mostly pyroclasts.
• 1. STRATO-VOLCANO - Intermediate slopes (10-30 degrees). Intermediate (several kilometers high, up to 20 kilometers wide). Alternating lavas and pyroclasts.
• 1. EXPLOSIVE - Due to the build-up of pressure in gas bubbles within the rising magma. Two factors come into play: viscosity and amount of dissolved gases.

  • Magma must contain sufficient volumes of gases to potentially generate the large gas pressures. At the same, time it must be viscous enough to prevent the escape of gas bubbles, and cause these to build up pressure.
• 1. EFFUSIVE - Magma must have minimal volumes of gases to generate low gas pressure, or at least should have low viscosity to allow gas bubbles to escape easily, and thus avoid the build up of pressure.
• Volcanic necks are shallow intrusions formed when magma solidifies in throat of volcano
• A volcanic hazard can be described in terms of the volcanic materials, behavior of the hazard and how it poses risks to life and property.
• A lava flow has molten rock, hot, flows downslope, low velocity and burns and buries
• volcanic gases has co2, so2, dense gases accumulate in depressions or low areas, and can cause asphyxiation, irritation etc.
• eruption cloud has volcanic gases and pyroclasts and rises into the atmosphere, controlled by buoyancy and wind direction. it causes aircraft malfunction.
• pyrcoclastic falls contain pyroclasts and its spread is influenced by prevailing winds. it poses roof collapse, driving obstruction, destroyed vegetation and respiratory irritation
• pyroclastic density currents involve volcanic gases and pyroclasts. it's hot, flows downslope and has high velocities. it can cause burn and buries
• lahars have water and volcanic debris. transport is controlled by water. it causes erodes and buries
• volcanic landslide has volcanic debris, transport is controlled by mainly gravity and causes erodes and buries.
• volcanic tsunami has water, caused by volcano related activities which displaces a significant volume of water, and causes wide and massive flooding of coastal areas.