It is the viscosity of magma that largely determines the nature and power of an eruption and the resultant severity of the hazard. Basic magma has a high proportion of dissolved gases and low silica content, making it very fluid. On the other hand, acidic magma is very rich in silica and has a relatively lower temperature, making it very thick and slow moving. The more viscous the magma, the greater the potential for explosive eruptions and these represent the greatest potential hazards. Non-explosive eruptions tend to produce mostly lava flows, which do not represent a particularly serious hazard to people, however they will destroy farmland and buildings.
The water builds up along the junction between the rock layers and seeps out of the cliffs as a series of springs. After periods of prolonged rainfall, the build up of water increases the weight of the cliff top. Increased pore pressure reduces the friction and allows large sections of the cliff top to break away. As the cliff top block subsides, it rotates along the slip plane within the cliff, resulting in the flat surface tipping back towards the cliff. The displacement shunts thousands of tonnes of material into the undercliffs, the area between the cliff top and the beach, generating mudslides within the softer Jurassic clays that in turn slide towards and across the beach.
Secondary Vents are extra vents that the lava seeped through Secondary Cones are built by lava and are on the volcano. The risks to people and property from volcanic eruptions are being destroyed by lava. Some risks to people are suffocation to the gas cloud. You can predict volcanic ruptures because there will be ground shaking, increase in temperature and the Earth’s surface will began to bulge. What role have volcanoes played in the evolution of life on the planet?
To what extent to you agree with the view that the hazards resulting from earthquakes and volcanic activity cannot be managed but merely adapted to. Earthquakes and volcanic activity are both nature disasters that human can’t control when or where it will happen and it may cause lots of death and economic loss. There is no way that we can stop it from being happened but we can definitely try to adapt it by many different ways. Firstly, volcanoes are found at destructive and constructive plate margins. At destructive plate margins, the oceanic plate goes under the continental plate due to it’s more dense, which is a process known as subduction.
The last is dam failure floods, which is when a dam gives way. Artificial levees built by man cannot always withstand periods of extreme flooding and can cause flash floods when they give way. Man made dams can do the same thing when they give way and create large amounts of damage. Altering of a stream channel in order to control the speed of the flow of water can cause bank erosion and damage to bridges and surrounding areas. Land use and other human activities also influence the peak discharge of floods by modifying how rainfall and snowmelt are stored on and run off the land surface into streams.
An inward tilt during eruption is much steeper than that of re-inflation. 6. What are "vesicles"? (page 99, para 1) Tiny bubbles that have gas trapped in them after the solidifying of the magma after eruption. 7.
Boscastle stands on the confluence of the River Jordan and the River Valency so there was an exceptional amount of water passing through the village. The steepness of the valley’s structure is a major physical factor as the rainwater falling on the hills travelled extremely quickly into the valley because of it. The shape of the valley also meant the rainwater was concentrated into a narrow space from the surrounding areas. Due to this there was an increase in run-off speed and discharge. This lead to the river channel in the village itself not being able to hold enough water and ascending from this, the flood later occurred.
The magma that reached the sea bed due to weakness in the crust cooled quickly and formed a layer of basalt above the sediments (see diagram 1). Other magma intrusions
They grow by piling up lava and ash into cones with steep-sided slopes, which are prone to collapse as massive landslides known as debris avalanches. The 1980 debris avalanche at Mount St. Helens literally opened a new chapter in the study of volcanic hazards. Debris avalanches were an under-appreciated hazard prior to 1980. More than 200 prehistoric debris avalanche deposits around the world were recognized because of observations of processes and resulting geologic features at Mount St. Helens. For example, the origin of puzzling, hilly volcanic deposits near Mount Shasta and Mount Rainier became clear.
c. hot fragments thrown a short distance from the volcano Which of the following volcanoes is generally the largest? c. shield volcano At what depth do gas bubbles have the most effect on magma? c. at very shallow levels, such as within the volcano A lava solidifies into nonvesicular basalt instead of vesicular basalt because: b. the magma has a low content of gas Shield volcanoes commonly have a. fire fountains b. all of the choices c. lava flows d. fissure eruptions Composite volcanoes are so called because they: c. ) are composed of lava flows, pyroclastic material, and mudflows What types of rocks would be most common in a composite volcano? a. felsic and intermediate lava flows and