By Becky and Nick

How are volcanic magnitudes measured? There is one special way to show the intensity of the explosion of a volcano. This is called the VEI (Volcanic Explosivity Index). It shows the intensity from; very large, large, moderate, small and non explosive.

VEIDescriptionPlume HeightVolumeClassificationHow oftenExample 0non-explosive< 100 m1000s m 3 HawaiiandailyKilauea 1gentle m10 000s m 3 Haw/Strombolia n dailyStromboli 2explosive1-5 km s m 3 Strom/VulcanianweeklyGaleras, severe3-15 km s m 3 VulcanianyearlyRuiz, cataclysmic10-25 km s m 3 Vulc/Plinian10s of years Galunggung, paroxysmal> 25 km1 km 3 Plinian100s of yearsSt. Helens, colossal> 25 km10s km 3 Plin/Ultra-Plinian100s of yearsKrakatau, super-colossal> 25 km100s km 3 Ultra-Plinian1000s of yearsTambora, mega-colossal> 25 km1 000s km 3 Ultra-Plinian s of years Yellowstone, 2 Ma

The VEI was introduced in 1982 by; Chris Newhall, Stefen Self and the U.S Geological Survey. The VEI goes from 0-8, 0 being non explosive and 8 being the highest magnitude, in other words very large. On the VEI there are examples of different volcanic eruptions, some are small and some are very large. The small and one of the larger eruptions passed 5, ,000 years ago, but the larger ones are more recent. E.g. Tambora 1815 (magnitude level 7) Pinatubo 1991 (magnitude level 6)

Mount Tambora is an active stratvolcano, it is located on an island called Sumbawa. This volcano was formed by a constructive plate boundary, it raised the mountain over 4.300m. On April 5, 1815 a moderate eruption occurred followed by tremendous thunder. Ash started to fall on the 6th. The first super-colossal eruption was at approximately 7 p.m. on the 10 of April 1815 where 20cm rocks started to drop from the sky as the volcano was lighting up with lava. The magma chamber filled and it eventually erupted violently, on the VEI it was approximately a 7.

All vegetation on the island was destroyed 10,000 were killed from pyroclastic flows Sumbawa island were 38,000 killed from starvation 10,000 were killed in Lombok island because of disease and hunger

How Are Earthquake Magnitudes Measured? There are two ratings in order to describe an earthquakes intensity, these two ratings describe the power of the earthquake from two different perspectives. Richter scale Mercalli scale

The Richter scale is a logarithmic scale to show the amount of energy that is released by an earthquake. From a value of 1 to 10, 10 being the strongest amount of energy released. With each increase of value it shows a 10 fold increase in energy.

The Mercalli scale was developed in 1931 by Harry Wood and Frank Neumann. The scale has 12 different levels of intensity, it ranges from slight shaking, to devastating destruction, and its measured in roman numerals. It does not have a mathematical basis; instead it is an arbitrary ranking based on observed effects.

The Valdivia earthquake otherwise known as the great Chilean earthquake took place on Sunday the 22 nd of May in It was one of the most powerful earthquakes ever recorded in the Earth’s history. It was rated a 9.5 on the Richter scale and on the Mercalli scale the earthquake was rated XI. And its resulting tsunami affected southern Chile, Hawaii, Japan, the Philippines, southeast Australia, eastern New Zealand and the Aleutian islands in Alaska. The after effects killed 5,000 people and left another 2 million homeless. Most of the damage and deaths were caused by a series of tsunamis that were generated by the earthquake.