When Mount Pinatubo suddenly erupted on 9 June 1991, the power of volcanoes past and present again hit the headlines
But the classic eruption – cone-shaped mountain, big bang, mushroom cloud and surges of molten lava – is only a tiny part of a global story. Volcanism, the name given to volcanic processes, really has shaped the world. Eruptions have rifted continents, raised mountain chains, constructed islands and shaped the topography of the earth. The entire ocean floor has a basement of volcanic basalt.
What comes out of volcanic craters is mostly gas. More than 90% of this gas is water vapour from the deep earth: enough to explain, over 3,500 million years, the water in the oceans. The rest of the gas is nitrogen, carbon dioxide, sulphur dioxide, methane, ammonia and hydrogen. The quantity of these gases, again multiplied over 3,500 million years, is enough to explain the mass of the world’s atmosphere. We are alive because volcanoes provided the soil, air and water we need.
C These zones are lines of weakness, or hot spots. Every eruption is different, but put at its simplest, where there are weaknesses, rocks deep in the mantle, heated to 1,350oC, will start to expand and rise. As they do so, the pressure drops, and they expand and become liquid and rise more swiftly.
The biggest eruptions are deep on the mid-ocean floor, where new lava is forcing the continents apart and widening the Atlantic by perhaps five centimetres a year. Look at maps of volcanoes, earthquakes and island chains like the Philippines and Japan, and you can see the rough outlines of what are called tectonic plates – the plates which make up the earth’s crust and mantle. The most dramatic of these is the Pacific ‘ring of fire’ where there have the most violent explosions – Mount Pinatubo near Manila, Mount St Helen’s in the Rockies and El Chichón in Mexico about a decade ago, not to mention world-shaking blasts like Krakatoa in the Sunda Straits in 1883.
Reading Passage 162 has four sections A-D
Choose the correct heading for the each section from the list of headings below.
Write the correct number i-vi in boxes 14-17 on your answer sheet.
List of Headings
ii Efforts to predict volcanic eruption
iii Volcanoes and the features of our planet
iv Different types of volcanic eruption
v International relief efforts
vi The unpredictability of volcanic eruption
14 Section A
15 Section B
16 Section C
17 Section D
Answer the questions below using NO MORE THAN THREE WORDS AND/ OR A NUMBER from the passage for each answer.
Write your answers in boxes 18-21 on your answer sheet.
19. What is the name given to molten rock from the mantle?
20. What is the earthquake zone on the Pacific Ocean called?
21. For how many years did Mount Pinatubo remain inactive?
Complete the summary below. Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 22-26 on your answer sheets.