The eruption of Mount Pinatubo in the Philippines in 1991 released large amount of ash which combined with rain water to produce a thick mudflow. The mud killed nearly 900 people and buried thousands of buildings and over 40, 000 ha of farmland in the surrounding area.
Volcanic eruption can also produce huge waves in the ocean called Tsunami. These waves can be destructive.
Case Study 2
In 26th Dec, 2006, the earthquake was caused by subduction and triggered a series of devastation tsunamis along the coast of most landmasses bordering the Indian ocean, killing nearly 230, 000 people in fourteen countries and inundating coastal communities with waves up to 30 meters high. It was one of the deadliest natural disaster in recorded history. Indonesia, Sri Lanka, India and Thailand were the hardest hit.
THE FORMATION OF TSUNAMI
Seismic disturbances, volcanic activities, submarine faulting are the main reasons for occurrence of Tsunami. A seismic disturbance can move the seawater causing a rise or fall in the level of the ocean. The seismic disturbance occurs due to displacement of tectonic plate. This rise or fall in sea water level is the early formation of a tsunami wave. This wall of water sometime turns out to be more than 100 feet height. The earthquakes that take place on the seafloor or in coastal areas usually cause tsunamis. The energy produced by the earthquake is transmitted through the water causing violent movement of sea waves.
VOLCANIC PLUG– when the igneous rocks/magma in the vent solidifies in the extinct volcano and the sedimentary rock( mass resistant rocks) are weathered and exposed the igneous rock/volcanic plug will appear on the surface.