Drrr

• Lava is a molten rock or magma that has reached the surface of the earth.
• Lava flows can be fluid or viscous depending on its composition, temperature, and gas content.
• Lava with low silica content, high temperature, and low gas content is considered more fluid.
• Lava with high silica content, low temperature, and has a high gas content is more viscous.
• Pahoehoe is lava flow that has high fluidity creating a smooth and ropy texture when they harden.
• As this type of lava cools, Pahoehoe transitions into an Aa.
• flammable resources such as wood, plants, and houses can get caught on fire as lava flows along their path.
• Kilauea Volcano: Mount Kilauea in Hawaii is one of the most recognizable volcanoes in the world that produces lava flow.
• . Hawaii is one of the known areas where lava flows constantly occur. Because the island of Hawaii is made out of active volcanoes, volcanic hazards have become part of their lives.
• Volcanic gases are composed of different materials depending on its location. Water vapor (H2O) and carbon dioxide (CO2 ) typically make up the bulk composition of volcanic gases, followed by sulfur dioxide (SO2 ). Other common volcanic gases include hydrogen chloride (HCl), and hydrogen fluoride (HF).
• Most volcanic gases are hazardous to people except for water vapor.
• Sulfur dioxide, when injected into the atmosphere, can form into sulfuric acid which is a component of acid rain.
• Acid rain does not only harm people but the environment as well. Acid rain can lessen water intake by plants making them difficult to thrive
• Carbon dioxide is also dangerous, especially in high concentrations. It can cause asphyxiation without warning because of the gas’ odorless and colorless nature
• Carbon dioxide is heavier than air, and it moves toward low-lying areas from its initial source which can create a high concentration of the gas within populated areas.
• The Disaster in Lake Nyos: One of the most notable disasters that occurred because of volcanic gases was in 1986 in Lake Nyos, Central Africa.
• Lake Nyos is a crater lake formed on the top of an old volcano
• Pyroclastic Flows are hot, dry, turbulent mass mixtures of different pyroclastic materials and gases that move downwards along the slope of a volcano at speed that can go up to several hundred meters per second.
•  Pyroclastic materials, also known as tephra, are a collective term for volcanic fragments that have been ejected out of a volcano which vary in sizes from ash to boulders.
• Pyroclastic flows are composed of two parts: a basal flow of coarse pyroclastic materials, and a turbulent ash cloud riding over the basal flow.
• When the turbulent ash cloud separates from the main pyroclastic flow, they are separately called the pyroclastic surge
• Pyroclastic surges have lower density and are more mobile than pyroclastic flows because of their higher ratio of gas to tephr
• Types of pyroclastic Flow

  • soufriere type
  • pelee type
  • merapi type
• The most notable type is called the Soufrière type. This forms from the collapse of a high vertical column coming from a highly explosive eruption. When the force of gravity overcomes the momentum of the upward thrust of the eruption, the pyroclastic materials begin to fall creating a pyroclastic flow along the sides of the volcano.
• The Pelée type occurs when a highly viscous lava dome blocks the opening of a volcano, building pressure until it can no longer be contained and explodes to one side of the volcano without forming a high eruption column
• The Merapi type, on the other hand, occurs when a lava dome grows too steep over a volcanic crater which then falls due to gravitational force.
• Pyroclastic flows and surges are also precursors to one of the many volcano hazards, like lahar, which is formed when pyroclastic materials mix with water or ice creating a muddy mixture that can affect areas further downslope.
• Tephras are fragments of volcanic material that are ejected into the atmosphere from the eruption of a volcano.
• They are differentiated based on the size of the ejected fragment. They can be classified as ash, if it is less than 2mm, lapilli if it is 2-64mm, or blocks and bombs if they are greater than 64 mm in size.
• Large tephras that leave the volcanic vent with force and trajectory are called ballistic projectiles. These can have speeds of up to hundreds of meters per second and affect areas that are usually within the fivekilometer radius of the volcanic vent.
• Tephra falls occur as a result of tephra being spewed out by a volcano initially hovering and riding over the prevailing wind direction before eventually falling into the earth’s surface. They can hang in the atmosphere for long periods of time before falling, especially the ash particles that can be carried even up to thousands of kilometers.
• Tephra fall deposits typically become thinner and finer as tephra goes farther from the volcanic eruption source. Tephra falls are also interchanged with ash falls
• Tephra falls have the widest range of effects amongst all other volcano hazards.
• Ballistic projectiles, on the other hand, have effects that are in relative proximity to the volcanic source
• Lahar is an Indonesian term for mudflow that has been globally used as a term for a specific type of mudflow.
• Lahar is created when tephras mix with water and form a slurry. It flows along the slopes of a topography.
• Lahar can form during the eruption event, called the primary lahar, or years after deposition of tephra called the secondary lahar.
• Primary lahar can form when pyroclastic flows occur along areas where bodies of water such as streams and rivers are present.
• Secondary lahar can form after an eruption event. Secondary lahar flows are generated when rain falls on unconsolidated tephra and mobilizes them downslope collecting more tephra as it progresses downward.
• Hyperconcentrated lahar destroys structures and agriculture through erosion.