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)。

　　譯文

　　地球上散落分布著100多個(gè)互不相連的小火山活躍區(qū)，地質(zhì)學(xué)家稱之為熱點(diǎn)。與地球上大多數(shù)火山不同的是，它們并不總是在構(gòu)成地球表面的巨大漂流板塊之間的連接處上出現(xiàn)；相反，許多熱點(diǎn)處于板塊較深的內(nèi)部。大多數(shù)熱點(diǎn)移動(dòng)極為緩慢，有些時(shí)候，板塊滑過(guò)這些熱點(diǎn)便留下了死火山的痕跡。熱點(diǎn)及其火山痕跡是板塊漂移的標(biāo)志�！　‖F(xiàn)在對(duì)于板塊漂移這一理論是毋庸置疑的。例如，由于有新的物質(zhì)注入二者之間的海底，非洲和南美洲距離越來(lái)越遠(yuǎn)。即使跨越海洋，但是由于相互吻合的海岸線和某些可樂(lè)了海洋類似的地質(zhì)特征都能使人會(huì)想到整個(gè)兩個(gè)大陸曾經(jīng)是連在一起的。對(duì)于這些大陸的板塊的相對(duì)運(yùn)動(dòng)已經(jīng)能夠被詳細(xì)地解釋出來(lái)，但是以地球內(nèi)部為參照物，不能很好地說(shuō)明一個(gè)板塊相對(duì)于另一個(gè)板塊的相對(duì)運(yùn)動(dòng)之間的關(guān)系。人們不能確定是兩個(gè)大陸都朝相反的方向運(yùn)動(dòng)漂移而去，還是一個(gè)大陸靜止不動(dòng)另一個(gè)大陸從他身邊漂移而走。處于地球更深層的熱點(diǎn)提供了解決該問(wèn)題的測(cè)量?jī)x器。通過(guò)對(duì)熱點(diǎn)區(qū)域的研究情況發(fā)現(xiàn)，非洲板塊似乎是靜止不動(dòng)的，至少在過(guò)去的3000萬(wàn)年里沒(méi)有移動(dòng)過(guò)。

　　熱點(diǎn)的重要性不僅只是局限于其作為參照系統(tǒng)所表現(xiàn)的作用�，F(xiàn)在看來(lái)，熱點(diǎn)還對(duì)推動(dòng)板塊在地球表面漂移這一地球物理過(guò)程有重大影響。當(dāng)大陸板塊漂移到熱點(diǎn)上方時(shí)，來(lái)自地球深層的物質(zhì)便形成了巨大的拱形隆起物。隨著該拱形的增長(zhǎng)，板塊出現(xiàn)深深的裂縫。至少有些情況下，大陸可能會(huì)沿著其中的某些裂縫完全裂開(kāi)，該熱點(diǎn)就引發(fā)了一個(gè)新的海洋的形成。因此，正如早期的理論解釋了大陸的漂移性一樣，熱點(diǎn)理論或許能夠解釋大陸板塊的易變性。

　　詞匯

　　Coastlinen  n. 海岸線

　　例句：Unrestricted hotel development have ruined the coastline. 無(wú)限制地發(fā)展飯店已經(jīng)使沿海地區(qū)遭到破壞。

　　Continent  n. 大陸， 洲a. 自制的

　　派生：continence, continency n. 克己；自制 continental a. 大陸的 continently ad. 自制地

　　例句：Africa is a very large continent. 非洲是一塊非常大的大陸。

　　詞組：the continent of Asia亞細(xì)亞大陸

　　反義詞：incontinent; island; isle

　　Drifting  adj. 漂流的， 飄動(dòng)的

　　例句：He is drifting through life. 他隨波逐流地過(guò)日子。

　　Determine  vt. 決定， 決心vi. 決定， 決心

　　派生：determined a. 堅(jiān)決地 determiner n. 限定詞

　　例句：A rather elaborate analysis was required to determine the cross-over values. 要求相當(dāng)精確地分析才能確定其交換值。

　　詞組：be determined to do sth. 決心做某事determine on/ determine upon  決定determine  sb. against sth./ determine sb. to do sth. 使某人決定不做某事

　　Entirely  ad. 完全， 全然， 一概

　　例句：I meant to mail the letter, but it entirely slipped my memory. 我本來(lái)準(zhǔn)備發(fā)這封信的，卻完全給忘掉了。

　　同義詞：altogether completely exclusively fully solely thoroughly totally wholly

　　Frame  n. 框， 結(jié)構(gòu)， 體格vt. 構(gòu)成， 設(shè)計(jì)， 制定， 使適合， 陷害

　　例句：He had a deep, resonant voice, fitted to his massive frame. 他的嗓音低沉，帶著回音，同他魁梧的體格非常相配。

　　詞組：picture frame 畫(huà)框， 相框 (=sheriffs picture frame)絞架be not framed for 不適于； 經(jīng)不起； 受不住out of frame 紛亂， 無(wú)秩序frame of mind 心情， 心境frame to oneself 想象frame up (美俚)誣陷frame well 有才能， 有希望

　　同義詞：arrange body border bound build construct design devise edge figure form make plan put together skeleton support trim

　　Geologist  n. 地質(zhì)學(xué)家；地質(zhì)學(xué)者

　　例句：One was blue, and a geologist; one was a horsewoman and smoked cigars. 她們中間一個(gè)是女才子，地質(zhì)學(xué)家；一個(gè)是女騎手，還會(huì)吸雪茄。

　　Geophysical   a. 地球物理學(xué)的

　　例句：The method has proved more and more to be of very great geophysical significance. 這個(gè)方法在地球物理學(xué)上的重要性越來(lái)越明顯。

　　Interior   n. 內(nèi)部， 內(nèi)政a. 內(nèi)部的， 心靈的， 內(nèi)地的， 內(nèi)政的

　　例句：He discussed the propagation of waves through the earth's interior. 他探討了地震波在地球內(nèi)部的傳播。

　　詞組：an interior city內(nèi)地城市

　　同義詞：core heart inner inside middle nucleus

　　反義詞：exterior; foreign

　　Milestone   n. 里程碑， 里程石， 里程標(biāo)

　　例句：This Games will be a milestone in Olympic history, and in the history of China. 北京的奧運(yùn)會(huì)將成為奧林匹克歷史和中國(guó)歷史中的一個(gè)里程碑。

　　Mobility   n. 可動(dòng)性， 流動(dòng)性， 機(jī)動(dòng)性

　　例句：There has been a tremendous increase in mobility. 人才流動(dòng)已經(jīng)有了大幅度增加。

　　Mutability   n. 易變性， 性情不定

　　詞組：mutability of human affairs人世滄桑

　　Reminder   n. 提醒的人， 暗示

　　例句：They need reminders to slow down to the pace of family life and show their care for loved ones. 人們需要經(jīng)常被提醒一下，以便停下來(lái)關(guān)照一下家庭生活，并向心上人表達(dá)關(guān)愛(ài)。

　　詞組：a reminder slip催詢單a reminder tray意見(jiàn)箱a gentle reminder暗示

　　Readily   ad. 迅速地， 輕易地， 樂(lè)意地

　　例句：He readily agreed to help us. 他欣然同意幫助我們。

　　Scattered  a. 分散的， 散亂的

　　例句：Factories should be scattered instead of being concentrated in a single area. 工廠應(yīng)分散布局而不應(yīng)集中在一個(gè)地區(qū)。

　　詞組：scattered set無(wú)核集scattered sheaf散射層

　　Significance   n. 重要性， 意義， 意味

　　例句：Most leaders'vanity causes them to exaggerate their own significance. 絕大多數(shù)領(lǐng)導(dǎo)人出于虛榮心往往喜歡夸大他們自己的重要地位。

　　詞組：of no (little) significance 無(wú)關(guān)緊要的

　　同義詞：connotation consequence drift effect gist implication importance meaning substance