Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the world's volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth's surface. On the contrary, many of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates.
That the plates are moving is not beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth's interior. It is not possible to determine whether both continents are moving in opposite directions or whether one continent is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layers of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot spot population it appears that the African plate is stationary and that it has not moved during the past 30 million years.
The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate come to rest over a hot spot, the material rising from deeper layer creates a broad dome. As the dome grows, it develops seed fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain their mutability (inconstancy).
1.The author believes that_______.
A.the motion of the plates corresponds to that of the earth's interior
B.the geological theory about drifting plates has been proved to be true
C.the hot spots and the plates move slowly in opposite directions
D.the movement of hot spots proves the continents are moving apart
2.That Africa and South America were once joined can be deduced from the fact that_______.
A.the two continents are still moving in opposite directions
B.they have been found to share certain geological features
C.the African plates has been stable for 30 million years
D.over 100 hot spots are scattered all around the globe
3.The hot spot theory may prove useful in explaining_______.
A.the structure of the African plates B.the revival of dead volcanoes
C.the mobility of the continents D.the formation of new oceans
4.The passage is mainly about_______.
A.the features of volcanic activities
B.the importance of the theory about drifting plates
C.the significance of hot spots in geophysical studies
D.the process of the formation of volcanoes
5.Which movement of the two continents is NOT mentioned in the article?
A.Two continents were joined.
B.One continent is stationary while other drifting.
C.Two continents move in reverse direction.
D.Two continents move in the same direction.
長難例句分析
［長難例句］Unlike most of the world's volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth's surface; on the contrary, many of them lie deep in the interior of a plate.
［結(jié)構(gòu)分析］本句話中，主干是they are not found... on the contrary... many of them lie。unlike引導的是狀語，由that引導的主語從句修飾the great drifting plates。on the contrary為連接詞，把兩個句子連接在一起。
［參考譯文］和大多數(shù)火山不同，它們都不位于形成地球表面的巨大漂移板塊的連接點，反而有很多藏于板塊的深處。
全文參考譯文
地球上零碎分布著一百多個相互獨立并且面積不大的火山活動區(qū)，地質(zhì)學家稱之為“熱點區(qū)”。和大多數(shù)火山不同，它們都不位于形成地球表面的巨大漂移板塊的連接點，反而有很多藏于板塊的深處。大部分熱點區(qū)移動極其緩慢，有時候，板塊滑過這些熱點區(qū)，便留下死火山的痕跡。熱點區(qū)加上其火山痕跡是板塊移動的象征。
板塊漂移學說如今已是無需質(zhì)疑的了。例如非洲和南美洲，因為有新物質(zhì)深入洋底，兩個大陸距離愈來愈遠。即使遠隔大洋，可相互吻合的海岸線和似乎好像跨越過海的地質(zhì)特征，均會讓人想到這兩個大陸曾是相連的。帶著兩個大陸漂移的板塊做相對運動，這已得到具體解釋，但不能把一個板塊相對于另一板塊的運動簡單地解釋為板塊與地球內(nèi)部之間的運動。由于人們還沒法肯定兩個大陸是否在朝相反的方向運動，也沒法肯定是否是一個大陸原地不動，而另一個大陸正在遠離它而去。因而位于地殼深處的熱點區(qū)提供了解決這一問題的測量儀。從熱點區(qū)的人口情況分析顯示，好像非洲板塊是不動的，3000萬年過去了也沒見移動。
熱點區(qū)的重要意義并不僅僅只是它們所起到的參照物的作用。如今它們還對推動板塊在地球表面漂移這一地球物理進程有重要作用。當大陸板塊漂移到熱點區(qū)上方時，由地殼深處涌出的物質(zhì)便會使板塊凸起，形成巨大圓蓋。圓蓋不斷裂大，板塊出現(xiàn)深深的裂痕。至少有幾次，大陸差點順著這些裂痕完全分開。因而，熱點區(qū)理論解釋了新海洋的起因。這樣一來，就像早些時候的一些理論已經(jīng)解釋了大陸的流動性一樣，熱點區(qū)理論或許能對大陸板塊的不穩(wěn)定性加以說明。
題目答案與解析
1.作者相信，________。
A.板塊的運動與地球內(nèi)部的運動相似
B.有關(guān)板塊漂移的地質(zhì)理論已經(jīng)被證實是正確的
C.熱點與板塊向相反的方向緩慢移動
D.熱點的運動證明大陸正在逐漸分離
【答案】B
【解析】從文章第一段的內(nèi)容可知，地球上散布著一百多個熱點；大多數(shù)的熱點獨自緩慢運動，某些情況下，經(jīng)過這些熱點的板塊運動留下死火山的痕跡；熱點及其火山痕跡是標志板塊遷移的符號；從文章第二段的內(nèi)容可知，如今，有關(guān)板塊在運動的理論已經(jīng)無可爭辯；然后舉例進一步說明；從文章最后一段的內(nèi)容可知，熱點的重要性并不僅限于作為參照體系這一作用上；現(xiàn)在看來，它們對推動板塊在地球上移動的地球物理學的過程也產(chǎn)生了重大影響；因此，正如早期的理論解釋了大陸的移動那樣，熱點或許可以解釋大陸的不穩(wěn)定性。據(jù)此可知，作者認為有關(guān)大陸移動的理論是正確的。B項文中的意思相符，因此為正確答案。
2.推論出非洲和南美洲曾經(jīng)連在一起，可以依據(jù)________。
A.這兩個洲仍然在向相反的方向移動 B.人們發(fā)現(xiàn)，這兩個洲具有引人注目的地質(zhì)特征
C.非洲板塊已經(jīng)穩(wěn)定了3000萬年 D.地球各地散布著一百多個熱點
【答案】B
【解析】本題可參照文章的第二段。從中可知，由于新物質(zhì)被增添進非洲和南美洲之間的海底，因此這兩個洲正在逐漸分離；相吻合的海岸線以及似乎橫跨海洋的地質(zhì)特征提示人們——這兩塊大陸曾經(jīng)連接在一起。據(jù)此可知，人們之所以認為非洲和南美洲曾經(jīng)連在一起，是因為它們的某些地質(zhì)特征相似。B項與文中的意思相符，因此為正確答案。
3.熱點理論在解釋_______時可能被證實有用。
A.非洲板塊的結(jié)構(gòu) B.死火山的復活
C.大陸的漂移 D.新海洋的形成
【答案】D
【解析】本題可參照文章的第三段。從中可知，熱點的重要性并不僅限于作為參照體系這一作用上；現(xiàn)在看來，它們對推動板塊在地球上移動的地球物理學的過程也產(chǎn)生了重大影響；當一個大陸性板塊在一個熱點上停止移動時，從地球更深層涌出的物質(zhì)會形成一個巨大的圓丘；隨著圓丘不斷增長，它會出現(xiàn)深深的裂溝；在某些情況下，大陸至少可能會沿著這樣的一些裂縫完全分裂，于是，該熱點便開始形成一個新海洋；因此，正如早期的理論解釋了大陸的移動那樣，熱點或許可以解釋大陸的不穩(wěn)定性。據(jù)此可知，熱點理論可以用于解釋大陸的不穩(wěn)定性，即熱點可以促使形成新海洋。D項與文章的意思相符，因此為正確答案。
4.本篇文章主要是關(guān)于________。
A.火山運動的特點 B.有關(guān)板塊漂移理論的重要性
C.地質(zhì)物理研究中熱點的重要性 D.火山形成的過程
【答案】C
【解析】從文章第一段的內(nèi)容可知，地球上散布著一百多個與外部隔絕的火山活動小區(qū)域，地質(zhì)學家稱之為熱點；隨后說明了熱點的特點；文章第二段說明了板塊漂移理論，最后一句話指出：根據(jù)熱點密度的分析可以看出——非洲板塊靜止不動了3000萬年；從文章第三段的內(nèi)容可知，熱點的重要性并不僅限于作為參照體系這一作用上，它們對推動板塊地球上移動的地質(zhì)物理過程也產(chǎn)生了重大影響；然后具體說明了熱點如何促使形成了新海洋；從文章的最后一句話可知，正如早期的理論解釋了大陸的移動那樣，熱點理論或許可以解釋大陸的易變性。據(jù)此可知，本文主要講的是熱點理論在地質(zhì)物理研究中的重要作用。C項與文章的意思相符，因此為正確答案。
5.對于兩個大陸之間的運動關(guān)系，文中沒有提及是哪一個？
A.兩個大陸連接起來。 B.一個大陸固定不動，另一個大陸在漂移。
C.兩個大陸背向漂移?！.兩個大陸相向漂移。
【答案】D
【解析】本題考查對細節(jié)的理解。全文中沒有提到大陸板塊相撞的話題。
