When parts of the mantle or crust melt, magma is formed. Within these magma chambers, gases in the chambers are causing an increase in pressure. As the pressure gets higher, the magma moves up. It moves up into the “throat” or the volcano, and thus causing an eruption. During some eruptions, you can even see lightning due to ash particles that cause electric sparks.
A volcano is a surface landform resulting from the extrusion of magma from underground as lava, ash, rocks, and gasses are erupted in various proportions. A hazard is something that poses a threat to life, the environment or property. Volcanoes can compromise all these things through the many hazards volcanoes presents. These include lahars, flash flooding, landslides, pyroclastic flows, ash clouds and many others. Each year, around 60 major volcanoes erupt globally.
Thicker, more viscous magma has a greater potential for explosive eruptions and therefore represent the greatest potential hazards. The thickest type of magma is known as Acid Magma. Its relatively low temperature (600C-1000C), high silica content and low proportion of dissolved gases causes its toothpaste-like consistency that leads to blockages and powerful eruptions. This can mean that the eruptions caused by thick magma can be less frequent and more difficult to predict, meaning that when an eruption does occur, it is usually with little or no warning, which can lead to catastrophic consequences as any nearby settlement will be relatively unprepared for the effects of a violent volcanic eruption. Furthermore, acid magma is more likely to produce clouds of smoke and ash due to the explosive nature of the eruption it causes, than thinner, basic lava.
The difference in pace and movement of plates, triggers the up build friction. When this friction is released- Earthquakes are generated. An example of an event is the San Francisco earthquake in 1989 on October 17 measuring 6.9 on the Richter scale. Tsunamis are one result of earthquakes. A sudden shift in
It allows us to understand how sedimentary rocks, metamorphic rocks, and Igneous Rocks use one another to not only form the Rock Cycle, but also other processes that are important to our planet. The rock cycle beings with hot magma, deep below the earth’s surface. Once the magma dries, crystallization occurs, and results in igneous rocks. Over time weathering occurs to the igneous rocks. Over time weathering takes over the igneous rocks.
Volcanoes are found mainly in three locations, at constructive and destructive plate margins and at hotspots. The most dangerous volcanoes occur at destructive, convergent plate margins. Here one plate subducts beneath the other, and as it descends, friction, increasing pressure, and heat from the asthenosphere and mantle melt the plate to form an acidic magma chamber. The magma at these boundaries is andesitic and rhyolitic, meaning that they have a high viscosity. Because of this the lava is resistant to flow and often forms blockages in vents.
In which ways does volcanic activity vary in relation to the type of plate margin along which it occurs? (10 Marks) Volcanic activity can occur at constructive or destructive plate margins, but it can also occur at hotspots in which no plate margin is involved. At destructive margins two plates which are moving together can be either both oceanic plates or one continental and the other oceanic. In the case of one continental plate and one oceanic plate, volcanic eruptions are very violent and emit andesitic or rhyolitic lava. These types of lava are very viscous due to its high silica content.
This knowledge of plate margins and their movement against one another can help us to understand the distribution of seismic and volcanic events and this is because the majority of events are associated at these plate margins. Wegener’s theory of plate tectonics suggests that all the continents were once joined together in a super continent called Pangea and have since drifted apart due to plate tectonics. To add to this, Sea floor spreading was discovered showing that rock is being created and destroyed, leading us to believe in the existence of plates and plate boundaries. Wegener gained evidence from paleo magnetism and suggested that there were numerous reasons and pieces of evidence for the continents drifting apart. Biologically, there was evidence that proved his theory for example, the Mesosaurus reptile fossils were only found in Africa and South America, proving his ‘jig-saw’ fit idea.
The nature of an event is initially determined by how the cause was stimulated. Volcanic eruptions occur in many different forms determined by the plate margin they are on. The eruptions on Montserrat 1995 show a strong example of the nature of a volcano at a destructive plate margin. The Soufriere Hills volcano had lay dormant for a long period of time. When the eruption did occur it was seen as explosive as it produced large volumes of acidic lava, ash, pyroclastic flows and steam.
Gases dissolved in magma provide the motive force of volcanic eruptions, sulphurous volcanic gas and visible steam are usually the first things noticed on an active volcano as well as others that escape unseen for example through hot fumaroles, active vents, and porous ground surfaces. The limitations of taking these samples are remote location of these sites, intense and often hazardous fumes, frequent bad weather, and the potential for sudden eruptions can make regular sampling sometimes impossible and dangerous. Measuring gases remotely is possible but requires ideal weather and the availability of suitable aircraft or a network of roads around a