Holly老師的英語新天地

雅思閱讀想拿高分(甚至滿分!!) 的不二法門，除了學會課堂中有教授的重要技巧外，就是練習、練習、再練習！All in all, Practice makes Perfect.  ~  Let’s Roll!

Exercise: You should spend about 20 minutes on Question 1—13 which are based on the Reading Passage below.

I Don’t Know Where I’m Gonna Go When the Volcano Blows

A. These words, suggested in a song by Jimmy Buffet in his 1979 Volcano album, probably reflect the concerns of many people living near active volcanoes. Volcanoes are beneficial to humans living on or near them. They produce fertile soil, and provide valuable minerals, water reservoirs, geothermal resources, and scenic beauty. But volcanoes can be very dangerous. Where can a person go to be safe from an erupting volcano? What types of volcanic hazards might they face? These questions are difficult to answer because there are many types of volcanic eruptions which produce different types of volcanic hazards.

B.   When Mount St. Helens erupted on May 18, 1980, red hot lava did not spew out of the volcano and pour down its flanks. This perception of a volcanic eruption is a common one and is probably due in part to pictures seen on television or in books of the beautiful lava flows and lava fountains in Hawaii. The type of eruptions in Hawaii is known as Hawaiian volcanism and is far less dangerous than the eruptions produced by Mount St. Helens. It is important to know what type of an eruption a volcano is most likely to produce so that the types of hazards produced by such an eruption can be identified. Knowledge of these types of hazards will help determine where a person would need to go to be safe during a volcanic eruption.

C.   Volcanic eruptions can be placed into two general categories: those that are explosive, such as at Mount St. Helens, and those that are effusive, such as in Hawaii. The most active volcano in the world, Kilauea Volcano on the big island of Hawaii, is generally a non-explosive volcano (though there have been occasions when it erupted explosively). Eruptions from it normally result in gently flowing lava flows, spatter cones, and lava fountains. Another type of non-explosive volcanism is flood basalts. Lava flows from this type of eruption arc extruded from fissures and cover vast areas. These non-explosive eruptions are the least dangerous type of volcanic eruption since people rarely get killed by them (Francis, 1993). However, they are devastating and may have global consequences.

D.   Many eruptions are explosive in nature. They produce fragmental rocks from erupting lava and surrounding country rock. Some eruptions are highly explosive and produce fine volcanic ash that rises many kilometers into the atmosphere in enormous eruption columns. Explosive activity also causes widespread ash fall, pyroclastic flows, debris avalanches, landslides, pyroclastic surges, and lahars. Explosivity is usually the result of gases expanding within a viscous lava. Another mechanism for explosions at volcanoes occurs when surface water or ground water enters a magma chamber. These eruptions are likely when a volcano occurs in a wet area or in the sea.

E.   Earthquakes related to volcanic activity may produce hazards which include ground cracks, ground deformation, and damage to manmade structures. There are two general categories of earthquakes that can occur at a volcano: volcano-tectonic earthquakes and long period earthquakes.

F.   Earthquakes produced by stress changes in solid rock due to the injection or withdrawal of magma (molten rock) are called volcano-tectonic earthquakes (Chouet, 1993). These earthquakes can cause land to subside and can produce large ground cracks. These earthquakes can occur as rock is moving to fill in spaces where magma is no longer present. Volcano-tectonic earthquakes don’t indicate that the volcano will be erupting but can occur at anytime.

G.   The second category of volcanic earthquakes are long period earthquakes which are produced by the injection of magma into surrounding rock. These earthquakes are a result of pressure changes during the unsteady transport of the magma. When magma injection is sustained a lot of earthquakes are produced (Chouet, 1993). This type of activity indicates that a volcano is about to erupt. Scientists use seismographs to record the signal from these earthquakes. This signal is known as volcanic tremor.

H.   People living near an erupting volcano are very aware of volcanic earthquakes. Their houses will shake and windows rattle from the numerous earthquakes that occur each day before and during a volcanic eruption. Residents in Pompeii felt earthquakes daily before Vesuvius erupted in A.D. 79 but continued to go about their daily routines (Francis, 1993). When Mount Pinatubo in the Philippines erupted in 1991, nerves were rattled as much as windows by volcanic earthquakes.

I.    Earthquakes exhibiting volcanic tremor warn of an impending eruption so that people can be evacuated to areas of safety. The volcanic tremor signal has been used successfully to predict the 1980 eruptions of Mount St. Helens and the 1991 eruption of Pinatubo. Volcano-tectonic earthquakes can cause damage to manmade structures and land sliding. To prevent damage from being done, structures should be built according to earthquake standards, building foundations should be constructed on firm ground and not unconsolidated material which may amplify earthquake intensity, and buildings should be constructed on stable slopes in areas of low hazard potential.

Adapted from www.geo.mtu.edu/volcanoes/hazards/primer

Question 1—5

Choose the most suitable headings for the paragraphs from the list of headings below. Paragraph A has been done for you as an example.

NB   There are more headings than paragraphs, so you will not use all of them.

Example                                         Answer

      Paragraph A                                      VI

1.   Paragraph C:

2.   Paragraph D:

3.   Paragraph F:

4.   Paragraph H:

5.   Paragraph I:

Question 6—8

Write NO MORE THAN THREE WORDS for each answer.

6.   What type of volcanic eruption is least devastating?

7.   What two materials mainly account for the explosive volcanic eruption?

8.   Which type of earthquake can indicate a possible occurrence of a volcano eruption?

Question 9—13

Complete the summary below. Choose NO MORE THAN TWO WORDS from the passage for each answer.

Among the hazards caused by volcanic eruption, volcanic earthquakes may produce damage to __9__ and manmade structures. Two types of earthquakes can occur at a volcano. Volcano-tectonic earthquakes are produced by the movement of __10__, which in turn results in the changes of stress. They can cause land-sliding and huge __11__ in ground. The other type called long period earthquakes are caused by the __12__ of the magma and people can predict a volcanic eruption by sensing their __13__.

Answer key: 1.V  2.I  3.VIII  4.III  5.IX  6. flood basalts  7. gases, water  8.long period earthquakes  9.ground  10.magma  11.cracks  12.transport  13.volcanic tremor