Why volcanoes happen?

1. Why volcanoes happen? • Radioactivity within the earth is what's cause most volcanoes upon the surface. • Heat from the inner core melts rock in the upper mantle. This turns into molten rock known as magma. This is less dense than the surrounding rock and will float towards the earth's crust through weak areas within the earth's core. • Magma accumulates in a chamber 2-4 km below the Earth's surface. As the chamber fills, it pushes the earth's surface outward. When the pressure in the chamber is great enough. Cracks may appear on the surface due to pressure. Wherever these cracks lead to a opening, in the earth's surface, the magma will escape as a lava flow.

2. Where in the world? The image above shows where volcanoes are found around the earth active, inactive, and extinct volcanoes. From the image you can see the ring that circles the pacific ocean. Northern hemisphere has little numbers of volcanoes this is because there are few plates moving. The only notice able plate is the north American plate which affects Greenland and the Eurasian plate going to the east of Siberia.

3. Volcano in LEDCLocation: Luzor Island, PhilippinesInformation: Mt Pinatubo is located on the plate boundary of the Philippines plate and the Eurasian plate. The Philippine plate slides under the Eurasian one and melts. The increased magma causes the pressure to build up and lava escapes through a vent as a volcano. Effects:Steam and gas sent 30km into the sky50cm of ash covered farmland200,000 homes collapsed under the weight of the ash on topPower supplies were cut off6 people died in initial explosion15,000 people had to be evacuated form the nearby American Airforce base The years crop was destroyedOver 1 million animals diedFlooding occurred600 people died of disease

4. Mount St. Helens Build-Up - During 1980 scientists had warned that a large bulge which was developing on the snow-covered, slopes of Mt St Helens might trigger an avalanche or eruption. This began. early on 18 May with an earthquake5 on the Richter scale which loosened the whole northern slope of the mountain. An enormous avalanche followed. Eruption- Then, in an enormous blast, hot gases, earth and rocks rocketed out of the volcano’s side, flattening forests over 25km away. At the same time, furious blasts sent lava, steam, ash and rock skyward. The initial blasts ejected about 400 million tonnes of debris.

5. Damage- 62 people died in choking smoke and many more were injured. Rivers were flooded and silted for up to 24 kilometres, 400 square kilometres of forests were destroyed and disappeared, and roads and bridges were also destroyed. Economic losses were estimated at $1.2 billion. The northern slope is loosened by an earthquake The eruption causes debris to fly 25km away. The initial blast is over and columns of gases from and continue up into the sky blocking the sunlight and leaving a dark black haze.

6. Threats to Humans or Environment • In the immediate area, threats are: high-speed, toxic gases and debris (pyroclastic flows); blast effects; lava flows; volcanic earthquakes; landslides; collapses of the mountain or structures; and mudflows, while ash clouds or deposits can be hazards much further away. • Over 100,000 deaths have been caused by volcanoes world-wide. Compared to some hazards this figure is relatively low. • Varying with size, location and numbers of settlements using nearby rich agricultural land found near volcanoes. • Volcanoes can cause massive destruction to whole towns, crops, forests, roads, etc creating many evacuees who must be sheltered, fed costing the LEDC’s money. Lava flows may also block rivers, causing floods, mud flows and landslides.