1、大学英语六级改革适用（阅读）模拟试卷 191及答案与解析 Section B 0 Tsunamis AUp until December of 2004, the phenomenon of tsunami was not on the minds of most of the worlds population. That changed on the morning of December 24, 2004 when an earthquake of moment magnitude 9.1 occurred along the oceanic trench off the coast o
2、f Sumatra in Indonesia This large earthquake resulted in vertical displacement of the sea floor and generated a tsunami that eventually killed 280,000 people and affected the lives of several million people. BAlthough people living on the coastline near the epicenter of the earthquake had little tim
3、e or warning of the approaching tsunami, those living farther away along the coasts of Thailand, Sri Lanka, India, and East Africa had plenty of time to move to higher ground to escape. CBut, there was no tsunami warning system in place in the Indian Ocean, and although other tsunami warning centers
4、 attempted to provide a warning, there was no effective communication system in place. Unfortunately, it has taken a disaster of great magnitude to point out the failings of the worlds scientific community and to educate almost every person on the planet about tsunami. How Tsunamis Are Generated DTh
5、ere is an average of two destructive tsunamis per year in the Pacific basin. Pacific wide tsunamis are a rare phenomenon, occurring every 10-12 years on the average. Most of these tsunamis are generated by earthquakes that cause displacement of the seafloor. EEarthquakes cause tsunami by causing a d
6、isturbance of the seafloor. Thus, earthquakes that occur along coastlines or anywhere beneath the oceans can generate tsunami. The size of the tsunami is usually related to the size of the earthquake, with larger tsunami generated by larger earthquakes. FBut the sense of displacement is also importa
7、nt. Tsunamis are generally only formed when an earthquake causes vertical displacement of the seafloor. The 1906 earthquake near San Francisco California had a Richter Magnitude of about 7.1, yet no tsunami was generated because the motion on the fault(断层 )was strike-slip motion with no vertical dis
8、placement. Thus, tsunamis only occur if the fault generating the earthquake has normal or reverse displacement. GBecause of this, most tsunamis are generated by earthquakes that occur along the subduction boundaries of plates, along the oceanic trenches. Since the Pacific Ocean is surrounded by plat
9、e boundaries of this type, tsunamis are frequently generated by earthquakes around the margins of the Pacific Ocean. Examples of Tsunamis Generated by Earthquakes HMay 22, 1960 A moment magnitude 9.5 earthquake occurred along the subduction zone off South America. Because the population of Chile is
10、familiar with earthquakes and potential tsunamis, most people along the coast moved to higher ground. 15 minutes after the earthquake, a tsunami with a run-up of 4.5m hit the coast. The first wave then retreated, dragging broken houses and boats back into the ocean. Many people saw this smooth retre
11、at of the sea as a sign they could ride their boats out to sea and recover some of the property swept away by the first wave. But, about 1 hour later, the second wave traveling at a velocity of 166 km/hr crashed in with a run-up of 8 m. This wave crushed boats along the coast and destroyed coastal b
12、uildings. This was followed by a third wave traveling at only 83 km/hr that crashed in later with a run-up of 11 m, destroying all that was left of coastal villages. The resulting causalities listed 909 dead with 834 missing. IHowever, the situation was quite different in Hawaii. A tsunami warning s
13、ystem had been in place and the tsunami was expected to arrive at 9:57 AM. It hit at 9:58 AM and 61 people died, mostly sightseers that wanted to watch the wave roll in at close range(obviously they were too close). The tsunami continued across the Pacific Ocean, eventually reaching Japan where it k
14、illed an additional 185 people. JAnother example. On March 11, 2011 a moment magnitude 9.0 earthquake struck off the northern coast of Japan. The earthquake generated a tsunami that rose up to 135 feet above sea level and killed over 20,000 people. Besides that high death toll, the tsunami caused on
15、e of the worst nuclear disasters in history. The Fukushima nuclear power plant, located on the coast was hit by a 49 feet tsunami wave that overtopped the tsunami protection walls that were only 19 feet high, and flooded the backup generators for the plant that were somehow placed on the first floor
16、 in a known tsunami zone! Prediction and Early Warning KFor areas located at great distances from earthquakes that could potentially generate a tsunami there is usually plenty of time for warnings to be sent and coastal areas evacuated, even though tsunami travels at high velocities across the ocean
17、s. Hawaii is a good example of an area located far from most of the sources of tsunami, where early warning is possible and has saved lives. For earthquakes occurring anywhere on the subduction margins of the Pacific Ocean there is a minimum of 4 hours of warning before a tsunami would strike any of
18、 the Hawaiian Islands. LThe National Oceanic and Atmospheric Administration(NOAA)has set up a Pacific warning system for areas in the Pacific Ocean, called the Pacific Tsunami Warning Center. It consists of an international network of seismographic stations, and tidal stations around the Pacific bas
19、in that can all send information via satellite to the Center located in Hawaii. MWhen an earthquake occurs somewhere in the region, the Center immediately begins to analyze the data looking for signs that the earthquake could have generated a tsunami. The tidal stations are also monitored, and if a
20、tsunami is detected, a warning is sent out to all areas on the Pacific coast. It takes at least 1 hour to assimilate all of the information and issue a warning. Thus for an average velocity of a tsunami of 750 km/hr, the regional system can provide a warning sufficient for adequate evacuation of coa
21、stal areas within 750 km of the earthquake. NIn order to be able to issue warnings about tsunami generated within 100 to 750 km of an earthquake, several regional warning centers have been set up in areas prone to tsunami generating earthquakes. These include centers in Japan, Kamchatka, Alaska, Haw
22、aii, French Polynesia, and Chile. These systems have been very successful at saving lives. For example, before the Japanese warning system was established, 14 tsunamis killed over 6000 people in Japan. Since the establishment of the warning system 20 tsunamis have killed 215 people in Japan. OLike a
23、ll warning systems, the effectiveness of tsunami early warning depends strongly on local authoritys ability to determine that there is a danger, their ability to spread the information to those potentially affected, and on the education of the public to heed the warnings and remove themselves from t
24、he area. 1 Pacific wide tsunamis occur once every 10-12 years averagely. 2 Compared with Japan, fewer people were killed in Hawaii by the 1960 tsunami. 3 Tsunami warning systems havent been set up when the tsunami in the Indian Ocean occurred. 4 The tsunami in 2011 not only killed many people but al
25、so caused a terrible nuclear disaster. 5 Some people mistakenly thought that the tsunami had retreated and went out to sea in hope of retrieving property. 6 It takes at least one hour for the tsunami warning center to analyze all of the information and issue a warning. 7 The scale of the tsunami is
26、usually determined by the size of the earthquake that causes it. 8 The Pacific Ocean is surrounded by subduction boundaries of plates, so tsunamis are often caused by earthquakes there. 9 To a great extent, the local government also plays an important role in the early warning of a tsunami. 10 Tsuna
27、mi warning centers have been established in several countries where earthquakes tend to generate tsunamis. 10 South Africa Safari Top Five National Parks and Game Reserves AA South Africa safari(游猎 )is the ideal wildlife trip to go on because the infrastructure and accommodation is superb in all the
28、 wildlife parks there and it is still highly affordable in comparison to other African countries. But given a choice some of the national parks and game reserves are better than others. Here is a top five list ranking them according to travel reports received at the African Safari Journals website,
29、my safari experience of twenty plus years, industry forums, magazines and the general consensus of the experts. Kruger National Park BThe Kruger National Park has to rank as one of the best South Africa safari destinations, only slightly behind the Masai Mara and Serengeti when it comes to wildlife
30、viewing because the vegetation in Kruger can be dense and sometimes impair the ability to see longer distances. But the variety of animals, birds and ecosystems that you can experience here are unparalleled anywhere else in Africa and the accommodation, roads and facilities are top notch and all at
31、a very affordable price. CIts not unusual to see lion, leopard, cheetah, a pack of wild dog, rhino, elephant, buffalo and a whole host of antelope, crocodile and hippo in the course of a single trip including a variety of insects and reptiles. On the bird front you will be spoiled with a seemingly n
32、ever-ending supply of eagles, hawks, water birds and a host of migratory and indigenous species to the tune of about 510 different varieties. DYou can easily do a self drive safari here and still see a decent amount of wildlife especially if you stick to the central and southern portions of this mas
33、sive park(larger than Ireland). The north has fewer animals due to dryer conditions but also fewer tourists which makes for a more isolated and intimate wildlife experience. If variety is the spice of life then a South Africa safari in the Kruger National Park is a rich dish indeed. Sabi Sands Game
34、Reserve ESharing a fenceless border on the western side of the Kruger National Park is the Sabi Sands game(猎物 )reserve which has a number of world famous private concessions like Mala Mala, Sabi Sabi and Londelozi. FThe removal of the fence between the two parks allows the animals to move around fre
35、ely and the game viewing experience is just as in the Kruger National with one important difference. Because this reserve is privately held, off road game tracking is allowed which improves your chances of finding the elusive(难以找到的 )big cats, elephant, rhino, buffalo and wild dog to a large degree.
36、They also make use of two way radios in each safari vehicle so that if one finds something noteworthy the others can be alerted. GThe sand and sabi rivers which bisect the reserve provide the focal point which attracts the wildlife to the area especially in the dry season. So viewing the big cats on
37、 a South Africa safari here is virtually guaranteed and the accommodation is some of the best in the world as illustrated by the Singita lodge which was the first and only accommodation in the history of the Conde Nast Gold List Reader Poll to get a perfect 100 score, an honour it has held for three
38、 years. There are about thirty different top class lodges situated in the reserve. HBut this all comes at a price and unless you have reasonably deep pockets, this fantastic reserve will be out of reach which is why it doesnt get the No. one ranking for South Africa safari national parks and reserve
39、s. Hluhluwe Umfolozi National Park IIf you want to see the endangered black and white rhinos in the wild then this is the park to head for because this is where the unstoppable tide to extinction for the white rhino in Southern Africa was stemmed(遏制 ). It now boasts the largest population of white r
40、hino in the world numbering over 1,600 and also a slowly increasing population of black rhino at just over 400. JOn a South Africa safari here you will also be able to see lion, leopard, buffalo, elephant and cheetah in this park and more than 400 bird species have been recorded. Due to the large nu
41、mber of resident elephants you might have some close encounters with them on the roads as they cross in front of you. You can go for a daily walk in the park in the company of an armed ranger or you can do a several day extended hike in the southern Umfolozi portion. Madikwe Game Reserve KThis is a
42、latter day Noahs ark story because most of the wildlife contained in this park was relocated here from other areas in 1991. Twenty seven different species amounting to over 10,000 head of game were re-introduced into this area where they once thrived but had disappeared because of hunting and habita
43、t destruction. A huge advantage of taking a South Africa safari in this park is that it is not situated in a malaria area so you dont have to bother about taking malaria tablets as you do in most other reserves. LAll of the big five are on view here as well as cheetah and the rare wild dog packs whi
44、ch are the stars of the show here being regularly sighted patrolling their huge territories. Your chances of seeing them seem to be better here than most other parks. Rare antelope like the eland, gemsbok and sable put in an appearance here too and you will be able to enjoy your wildlife viewing in
45、relative peace and isolation because not many tourists know about this excellent game reserve. Kgalagadi Transfrontier Park MThe locals know that this is an excellent game park and it falls into that “best kept secret“ category that each country seems to have where for some unknown reason a reserve
46、doesnt get the notice from tourists and safari companies that it deserves. Maybe its because this reserve is set in the Kalahari desert and people dont normally associate deserts with lots of wildlife but there are always exceptions to the rule and this South Africa safari park qualifies. NYou can s
47、ee some pretty specialised and very interesting game here such as the gemsbok antelope which can go for months without water, springbok, blue wildebeest, eland and red hartebeest. And wherever there is a good supply of antelope, the predators are never far away such as the black maned lions which th
48、is area has a disproportionate supply off, leopard and cheetah which can make full use of the wide open spaces to chase their prey at top speed. OThe meerkat(suricate)is also regularly seen here and bat eared foxes contribute to the scavenging duties. This South Africa park is famous for birds of pr
49、ey such as the pygmy falcon and the sociable weaver which builds nests which are the bird equivalent of apartment blocks that are sometimes so big they break the branches they rest on. PThere are hundreds of companies offering safari trips to South Africa. This Top Safari in South Africa operators list helps you choose effectively between them. South Africa safari trip reports give you a great idea of what to expect from a trip like this by learning from other peoples travel experiences. 11 When tourists want to ha
