All volcanoes are formed by the accumulation of magma (molten rock that forms below the earth’s surface). Magma can erupt through one or more volcanic vents, which can be a single opening, a cluster of openings, or a long crack, called a fissure vent. It forms deep within the earth, generally within the upper part of the mantle, or less commonly, within the base of the earth’s crust. Some lava (molten rock that erupts at the earth’s surface) can be as thick and viscous as toothpaste, while other lava can be as thin and fluid as warm syrup and flow rapidly down the sides of a volcano. Once lava hardens it forms igneous rock. After many eruptions, the volcanic materials pile up around the vent or vents. These piles form a topographic feature, such as a hill, mountain, plateau, or crater, that we recognize as a volcano.
- volcano [vɔlˈkeinəu] n.火山
- accumulation [əkju:mjuˈleiʃ(ə)n] n.堆积物
- magma [ˈmæɡmə] n.岩浆
- molten [ˈməultən] adj.熔化的
- erupt [iˈrʌpt] v. 喷出
- volcanic vent [vɔlˈkænik - vent] n.火山口
- vent [vent] n. 孔，口，裂口
- cluster [ˈklʌstə] n. 串
- a cluster of [ə - ˈklʌstə - əv] adj. 成群的，成串的
- crack [kræk] n. 断裂处
- fissure vent [ˈfɪʃə - vent] n. 断裂口
- fissure [ˈfiʃə] n. 裂缝，裂隙
- mantle [ˈmæntl] n. 地幔
- crust [krʌst] n. 地壳
- lava [ˈlɑ:və] n. 熔岩
- thick [θik] adj. 厚的
- viscous [ˈviskəs] adj. 粘性的
- toothpaste [ˈtu:θpeist] n.牙膏
- thin [θin] adj. 薄的
- fluid [ˈflu:ɪd] adj. 易流动的
- syrup [ˈsirəp] n. 糖浆
- harden [ˈhɑ:dn] v. 变硬，凝固
- igneous rock [ˈiɡniəs - rɔk] n.火成岩
- pile up [pail - ʌp] v. 堆积
- pile [pail] n. 堆积，堆
- topographic [ˌtɔpəˈɡræfik] adj. 地形学上的
- plateau [ˈplætəu] n. 高地
- crater [ˈkreitə] n. 坑，火山[喷火]口；(月球上的)环形山
- recognize [ˈrekəɡnaiz] v. 识别
