are in.
The next hazard are pyroclastic flows these are where the volcano erupts and creates a huge dense gas cloud that follows the contours of the land this cloud of rock gas and ash can get up to high speeds and wipe out everything in there path. Pyroclastic flows are usually only linked with explosive volcanoes because of the large quantities of gas and ash.
Volcanoes they are usually created when the extreme heat of the erupting volcano melts a glacier can also create lahars. Which in turns flows down the volcano collecting mud, ash, rocks and other debris causing a huge destructive mud flow which tends to do large scale damage to everything in its path.
The final major hazard that was related to a volcano was avalanches, which would be caused by the vibrations caused by the erupting volcano. They can also be created by the build up of ash in an unstable area, which was then triggered of by heavy rain, which in turn set of the landslide. Landslides are also the main hazards that are linked to mass movement.
Mass movement has a few hazards that can cause large-scale damage. The hazards are mainly only linked too large-scale landslides that build up over large periods of time.
The first hazard is a mudflow or lahars these are can be created in very wet conditions where it has been raining for a long period of time. Then the water has built up under the layers, which has reduced the pore pressure, which in turn has made the land unstable. Now that the soil is so unstable it tends to slide and cause a mudflow which flows over slopes well and can cause large amounts of damage.
Landslides are caused by large amounts of debris, which has built up over a period of time, and then become unstable. The material then starts to slide down hill until it reaches a more stable angle to rest at. These can cause some damage depending on the size of the debris that has been resting there.
The next hazard is rockslides these are usually found in mountainous areas where there are large drops and cliffs. These are created when a layer of rock becomes unstable and can no longer support its own wait so the it breaks away and slides down to the ground until it finds a stable angle of rest.
Avalanches are usually caused either by the weight of the ice and the snow becoming to much which then causes the snow to flow down the mountain. Or it also tends to be when the snow becomes to warm and parts of it breaks away from the rest and slides down the mountain. Minor vibrations can also cause the avalanche when it becomes unstable and this can cause it to slide.
Generally the build causes mass movement up of water between the layers which makes the land unstable. Or it can be caused by minor movement which can cause the land to move quickly or just to creep until the land gives way and slides away causing damage to the land that was being supported by the land.
There are many similarities between the hazards that are associated with volcanoes and mass movement. The first one would be a landslide that can be triggered in many ways but the main way would have to be vibrations that are sent through the ground these vibrations do not have to big to start a landslide. This can be linked to volcanoes because when they have erupted there tends to be loose debris on the slopes that builds up and when the volcano has a final eruption it shakes the debris down its edges which then causes a landslide. This happened at Mt St. Helens when it erupted it caused many landslides and also within the main eruption most of one side of the volcano became a landslide. The next would have to be lahars, which are huge quantities of mud that have been mixed with water to create a river of fast moving mud these are usually created on volcanoes when they explode. This again happened when Mt St Helens erupted it melted the glaciers on its summit, which caused avalanches and also caused huge lahars, which wiped out a lot of the wildlife. The Lahars then flows down the volcano and picks up mud and debris as it goes. This then flows into populated area and causes serious damage to the buildings and wipes out crops as well as damaging water supplies in developing countries. Lahars can be linked to mass movement because when glaciers heat up they can flow down hill and cause lahars it can also be linked to mass movement in the form of a mud flows. Which is created when there has a lot of rain, which causes a lot of land to move quickly, and this causes a lot of damage to surrounding land.
There are also many differences between hazards linked with volcanoes and mass movement for example volcanoes are usually linked with large explosions where as mass movement does not need large movements to trigger it off. All it needs are slight movements in weight distribution and it can cause creep or a landslide mass movement can also be caused by water build up. As well as that volcanoes tend to be triggered from the inside where as mass movement can be triggered from the outside for example human activity, which can cause a lot of damage to the land like. Land that has been reformed so that houses can be built on it this happened in San Francisco where there was an earthquake which disrupted the land and caused the land under the house to move which destroyed many houses. Also the speed in which both volcanoes and mass movement happen, volcanoes happen very quickly due to explosion and violent activity which move the land where as mass movement can take longer periods of time because the soil creeps along at very low speeds. This can still cause a lot damage because it can leave more land higher up unstable which can cause larger landslides it can also leave buildings unstable because the soil under the building has slipped away from the foundations. Volcanoes are associated with heat and lava flows but mass movement does not need heat to trigger it off in most cases it has been heavy rain that has caused mass movement to happen. When there is a large build up of water under the layers the pore pressure is reduced and it causes the land to be unstable causing landslides and creep. Hazards linked to mass movement and volcanoes have been to link the two together for example mount St Helens that had many examples of mass movement.
When Mt St Helens erupted in May 18th it showed many examples of mass movement that were linked to its eruption. The first area of mass movement was the one sided of the volcano sliding down creating a huge landslide which caused large scale devastation to the surrounding land it also caused a pyroclastic flow which wiped out extensive amount of the surrounding area of land. The eruption also melted the glaciers on the summit of Mt St Helens and this caused huge lahars or mudflows, which carried large boulders, and this wiped out large areas of forest. There were also many landslides, which were not as bad as the first main slide, but they still caused some damage.
