在托福聽力自然科學(xué)類講座中，時(shí)常會(huì)出現(xiàn)一個(gè)名詞：Plate Tectonics板塊運(yùn)動(dòng)/地殼構(gòu)造論。很多同學(xué)都對(duì)這個(gè)學(xué)說(shuō)感到熟悉又陌生，今天我們就來(lái)聊聊我們腳下的土地到底是怎么運(yùn)動(dòng)的。

　　Plate tectonics is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large of tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of continental drift. Earth's lithosphere is broken into seven or eight major plates and many minor plates. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. Tectonic plates are composed of the continental plate and the denser oceanic plate. If two plates collide, the denser one will subduct beneath the less dense one. The three different types of plate boundaries are divergent boundaries, convergent boundaries, and transform boundaries.

　　板塊構(gòu)造學(xué)是一個(gè)已經(jīng)被普遍接受的科學(xué)理論，它認(rèn)為地球的巖石圈lithosphere是由許多自大約 34 億年前以來(lái)一直在緩慢移動(dòng)的大型構(gòu)造板塊組成。該模型建立在大陸漂移continental drift的概念基礎(chǔ)上。地球的巖石圈共被分成7至8個(gè)主要板塊和許多小板塊，在這些板塊相遇的地方，我們經(jīng)常能夠見到地震、火山、造山和海溝形成等活動(dòng)。構(gòu)造板塊由大陸板塊和密度更大的海洋板塊組成。當(dāng)兩個(gè)板塊碰撞時(shí)，密度較大的板塊將俯沖到密度較小的板塊下面。地球上一共存在三種主要的板塊邊界類型，分別為擴(kuò)張邊界、聚合邊界和轉(zhuǎn)換邊界。

　　分離型邊界 Divergent Boundary

　　Divergent boundaries occur where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin. As the ocean plate splits, the ridge forms at the spreading center, the ocean basin expands. At zones of continent-to-continent rifting, divergent boundaries may cause new ocean basin to form as the continent splits, spreads, the central rift collapses, and ocean fills the basin.

　　The most significant example of divergent boundaries is the East African Rift.

　　擴(kuò)張邊界出現(xiàn)在兩個(gè)板塊往相反方向移動(dòng)的地方。在海洋間的裂谷帶，海底擴(kuò)張形成了不同的邊界。隨著海洋板塊的分裂，一道洋脊在擴(kuò)張中心形成，海洋盆地也逐漸擴(kuò)大。在大陸間的裂谷帶，隨著大陸分裂、擴(kuò)張，中央裂谷漸漸塌陷，逐漸形成新的海洋。擴(kuò)張邊界最顯著的例子便是東非大裂谷。

　　聚合型邊界 Convergent Boundary

　　Convergent boundaries occur where two plates slide toward each other to form either a subduction zone or a continental collision. At zones of ocean-to-continent subduction, the dense oceanic lithosphere plunges beneath the less dense continent. At zones of ocean-to-ocean subduction, older, cooler, denser crust slips beneath less dense crust. This motion causes earthquakes and a deep trench to form in an arc shape. At zones of continent-to-continent subduction, plate edges are compressed, folded, and uplifted. The most obvious example is the Himalayas.

　　聚合邊界出現(xiàn)在兩個(gè)板塊相互擠壓碰撞的地方。在海洋和大陸板塊相互擠壓的地方，密度更高的海洋板塊將跌入到密度較小的大陸板塊之下，并形成海溝。在海洋和海洋板塊相互擠壓的地方，火山爆發(fā)和地震頻發(fā)。在大陸和大陸板塊相互擠壓的地方，板塊邊緣被壓縮、折疊、隆起。喜馬拉雅山脈就是大陸板塊和大陸板塊擠壓后的結(jié)果。

　　轉(zhuǎn)換型邊界Transform Boundary

　　Transform boundaries occur where two plates slide, or perhaps more accurately, grind past each other along transform faults, where plates are neither created nor destroyed. Transform faults occur across a spreading center. Strong earthquakes can occur along a fault. The San Andreas Fault in California is an example of a transform boundary.

　　轉(zhuǎn)換邊界出現(xiàn)在兩個(gè)板塊相互滑動(dòng)的地方，或者更準(zhǔn)確地說(shuō)，沿著斷層相互摩擦的地方。這個(gè)過(guò)程中既沒(méi)有新的板塊產(chǎn)生，也沒(méi)有板塊被破壞。而當(dāng)摩擦達(dá)到一定強(qiáng)度后，就有可能發(fā)生非常劇烈的地震。美國(guó)的圣安德烈亞斯斷層便是轉(zhuǎn)換邊界最經(jīng)典的一個(gè)例子。

　　現(xiàn)在大家是不是對(duì)Plate Tectonics有了更清晰的認(rèn)識(shí)了呢，希望這些內(nèi)容可以幫助到大家。下次再聽到相關(guān)內(nèi)容，可不要一頭小問(wèn)號(hào)了喲～