‘The extent to which volcanic processes represent hazards depends on where and when they occur’. Discuss this statement…
Since lava is liquid, any argon-40 gas previously trapped in lava will be able to escape as gas is less dense than liquid. When there is no argon gas in the lava, it is known as the zero point (zero argon trapped in lava). As soon as the lava solidifies, there are no outlets for argon-40 gas to…
On December, 6th, 1917, an unexpected explosion at Halifax, Harbour front had left the citizens of the Nova Scotia capital and the rest of Canada devastated. Five minutes after 9:00 a.m on that day, hundreds of people were killed and thousands were severely injured by the impact.…
Volcanoes are formed on land near coastal areas when a continental plate and an oceanic plate converge. The oceanic plate submerges, due to its higher density, and is pushed deeper and deeper beneath the surface. The high temperature and pressures below melt the rock which creates hot, buoyant magma. Ultimately this magma rises towards the surface and accumulates in a reservoir, known as the magma chamber. The eruption occurs when the pressure within in the chamber surpasses the pressure of the upper rock, magma forces its way through the cracks in Earth’s crust. Magma that is low in gas and silicon dioxide produces thin quickly spreading lava which has a low viscosity, while a magma that is heavily composed of gas and silicon dioxide will yield a thick, viscose magma. The thicker magma builds up and because of this pressure, will cause a large…
Volcanologists have named four stages of volcanic activity, Ape Canyon, Cougar, Swift Creek, and Spirit Lake. These stages are separated by dormant intervals. Little is known about the Ape Canyon stage (300-35 thousand years ago) (ka). During this stage, lava domes in two distinct periods, one from 300 to 250 thousand years ago (ka) and a second from 125-35 ka. Geologists have found layers of ash and rocks that were changed hydrothermally,…
Beginning in the year 62 CE, violent earthquakes rocked the region, warning of volcanic activity. The eruption, beginning that fateful August morning, lasted over 24 hours. The eruption was the first one ever recorded in history. An explosion came from the mountain and fine ash fell on the…
The volcano had little mountains regrowing. Solid rock was being pushed up, growing around 16ft a day. The thing was that after it grew it suddenly collapsed. The process of that kept happening over time. But when the volcano erupted in 2004 after its rebuilding it wasn’t the same eruption that happened in 1980. The volcano poured out very little lava, but mostly dark ash and light steam. In the eruption of 1980 the volcano poured out fluid lava. It poured out fluid lava because the spines pushed up and created the lava to come out…
Mt St Helens was the most disastrous volcanic eruption in US history. 57 people died, more than 200 homes were lost and more than 200 miles of roads and railways were damaged. This Stratovolcano is rated a 5 on the explosivity index. Like The eruption of Mt St Helens, Mt Vesuvius was the biggest catastrophic eruption in European history. 13,000 people died and Two Cities were utterly destroyed (Pompeii and Herculaneum). Mt Vesuvius Is the only active volcano on the European mainland. Mt Vesuvius is one of the deadliest eruptions ever. Mt Vesuvius ejected about 12 miles of debris into the air, about double the size of Mount Everest. Then a searing combination of pumice and ash of up to 1300 degrees Fahrenheit hit the city at 70 miles an hour.…
Lava flows are commonly found in Iceland and Hawaii. They can be halted by spraying cold water on them (Heimaey, Iceland) but most of unstoppable. In 1990 a lava flow from Puu Oo crater in Hawaii buried the village of Kalapana. When they can’t be stopped they create millions of dollars in damage and severe loss of life. After the primary hazards can come more hazards that are triggered by the volcanic eruption.…
Analyse the factors that cause differences in the hazards caused by volcanoes around the world (40 marks)…
One time in Hawaii, in 1888, there was a small village just next to a little beach. Not far from the village, there was a huge “lava pit.” Scientists believed that it was just a volcano that had formed underground and only the opening at the top could be seen from the surface. The lava pit had always been filled with lava, and people wondered if it would ever erupt.…
The area also held an alter for rites associated with the imperial cults along with trees and a fountain.…
From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating large pyroclastic flows, which left extensive ignimbrite deposits. Ash from these eruptions has been found as far away as Rome, 800 km to the north.…
The Unzen eruption in 1792 started with a dacitic lava flow coming from the Fugen-Dake lava tube. Suddenly the Mayu-Yama dome collapsed unexpectedly following a post eruption earthquake which started a deadly landslide and mega-tsunami which reached over 300 feet tall. The lava that flowed from the Unzen eruption was very Basaltic which meant it was Mafic. The lava was very hot and had a low viscosity and silica content. This lava can flow rapidly and for long distances. Unzen contained several lava tubes which acted as a conduit for the Basaltic lava. A cooled crust formed on top of the flow which prevented cooling and allowed flow under the cooled crust. The Volcano showed signs of Pahoehoe after the eruption which is basalt with a glassy ropy texture. The Unzen eruption also created landslide debris and Lahars which acted as transports for water rich slurries. The 1792 eruption was Effusive compared to the 1990s eruption which was explosive.…
This is partly due to the fact that the volcano was covered in cloud at high elevation and helicopters were not in use; so, most of the information we have comes from what happened on Highway 11 during the eruption. In the months and years following the eruption, the vents and flows have been examined and mapped extensively, however. The eruption occurred along almost the entire length of the SW rift zone (from 8000 to 13,000 ft) and opened up almost simultaneously (like a zipper) from an essentially continuous vent system. Consequently, lava flows poured down at numerous places on both the west and east side of the rift. The eruption lasted only two weeks but the eruption of 1859 lasted almost a whole year. So, given that the flow volume is 4 to 5 times greater than the 1984 eruption (which lasted 3 weeks) it must have been a spectacular eruption. In places the flows were obviously very fluid and flowing rapidly, since they eroded the bases of prehistoric spatter cones during emplacement. It must have been coming downhill like gangbusters! The lava flow was compositionally very heterogeneous, with the upper part of the rift eruption evolved magmas (MgO 7 wt. %). Compositions became more primitive (MgO up to 10 wt. %) down rift. However, the lowest elevation flows were the somewhat more evolved (MgO 8 wt. %). The data are consistent with mixing of a relatively primitive magma with an evolved magma that may have been residing in the rift zone (this older magma has compositions very similar to the lava produced by the 1949 summit…