Environmental Hazards Flashcards
What happens at conservative plate boundaries and where are they found
Found between the Pacific and North America plate. Plates slide past each other. Movement isn’t smooth and pressure build up until plates jerks past each other. Cause earthquakes
What happens at collision plate boundaries and where are they found
Found between Indian and Eurasian plate boundaries
Two continental plates move together. Crust is too light to sink so it’s forced upwards as plates move together. Causes mountain ranges and earthquakes
What happens at destructive plate boundaries and where are they found
Found at Eurasian and Pacific plate. 2 plates moving together. Involves the oceanic plate and continental plate. Oceanic plate is heavier so is pushed down to the mantle where it melts. This forces magma into the earth. Can form fold mountains and cause earthquakes
What happens at constructive plate boundaries and where are they found
Found between the Pacific and Naza plate. When two plates move apart. The crust cracks and splits moving apart allowing magma to reach the surface. Cause volcanic eruptions and sometimes earthquakes
What types of volcanoes are there
Still active
Dormant
Extinct
Where are volcanoes distributed around the world
Active volcanoes occur mainly along fault lines or plate boundaries at edges of tectonic plates. Can occur at destructive or constructive plate boundaries. Volcanoes are confined to specific belts or areas. Around the Pacific Ocean, active volcanoes form the ring of fire. In the centre of the Atlantic Ocean, a line of volcanoes form the Mio Atlantic Ridge
Describe the Mount St Helen Eruption
Erupted on 18th May 1980 at 08:32 in Washington State, West Coast of USA
What caused the Mount St Helen Eruption
It lies close to a destructive plate boundary where the smaller Juan de Fuca plate is being forced under the North American Plate
What impacts on the landscape did the Mount St Helen Eruption have
All plant and animal life living within 25km radius were killed, including full grown trees by blast and pyroclastic flow. The eruption left a horse shoe shaped crater 1-2 miles wide and 0.5 miles deep. Lahars poured down the valley below killing fish, choking rivers with rock debris and ripping trees from their roots
What impact on the people did the Mount St Helen Eruption have
61 people died and 198 people had to be rescued. Mudflows destroyed roads, bridges, houses and logging camps. The exposition flattened buildings and trees destroying power supplies. Ash clouds resulted in flights being cancelled. Ash caused £100 million damage to farming industry and crops. Ash clogged up car engines. Tourists no longer visited area causing reduction in economy
How could scientists have predicted the Mount St Helen Eruption
Measuring the frequency of earthquakes on the mountain ( greater the frequency, nearer the eruption ). Measuring the size of the volcanic cone to show the build up of magma in the vent. Increasing numbers of sulphur dioxide at the crater could indicate an eruption. Increase in water temperatures could indicate an eruption
How effective are prediction methods for volcanic eruptions
Scientists can’t give precise dates of any eruptions. Scientists didn’t predict that the Mt St Helen Eruption blast would occur on the north face which resulted in people being killed outside the exclusion zone
Describe short term aid of Mt St Helen Eruption
Parts of St Helens were closed off just before the eruption to reduce the loss of life however it wasn’t effective as the exclusion zone was inaccurate. Rescue centres were set up which helped shelter those who had lost their home. Ash was cleared up which took 10 weeks and cost £1 million. Electricity was restored to the area. 200,000 people were temporarily employed to clean up minor damage to clear roads to resume traffic.
Describe long term aid of Mt St Helen Eruption
US Government gave $145 million to rebuild houses, repair roads and construct a new highway for locals. Millions of trees were replanted which restores the oxygen that the trees provide to area. Local rivers were dredged to remove logs and levees which reduced flooding. Farmers were compensated for loss of crops. $50 million of federal money was invested into Mt St Helen Visitor Centre to help attract visitors back to area. $1 million was spent to remove 1 million tonnes of ash from roads and airports.
Describe effectiveness of aid from Mt St Helen Eruption
The money given by the federal government allowed quick recovery. Tourism is more popular than ever. Environmentally, the area has taken longer to restore. Trees will not fully grow back until 2059 meaning normal levels of wildlife won’t be back to normal until then either.
