[解析]
(1)C.推理判断题。根据第二段中的It took shape about twenty years after the violent eruption of Santa Maria in 1902它是在1902年圣玛丽亚火山猛烈喷发20年后形成的。可知,圣地亚古多火山大约形成于1922年左右。故选C.
(2)C.细节理解题。根据第四段中的What we know for sure is that magma and gas are steadily rising from deep within the system我们可以肯定的是,岩浆和气体正从星系深处稳步上升。可知,科学家目前只确定圣地亚古多火山内部岩浆和气体在持续上升。故选C.
(3)A.细节理解题。根据第五段末句The materials that were sent out cover the top,reclosing Santiaguito's vent and starting the process over again送出的材料覆盖了顶部,重新关闭了圣地亚哥的通风口,重新开始了这个过程。可知,圣地亚古多火山喷发完之后,火山口会再次闭合。故选A.
(4)B.词义猜测题。根据划线词所在的句子"Most often,they tend to small,producing mainly ash plumes(火山灰) that can reach a height of nearly 1,640 feet,lava flows that travel about two miles from the top.However,there are some eruptions they are very hazardous.最常见的情况是,它们往往很小,主要产生灰羽,可以达到近1640英尺的高度,熔岩流从顶部移动约两英里。然而,也有一些火山爆发,它们非常危险。"以及最后一段的内容" "At times,larger explosions happen,producing ash plumes that rise less than kilometers above the vent." Grocke ways.Such cases can result in hot fast moving flow made up of gas,ash,and rock,which can be deadly to local communities.Volcanic mudflow are also another serious risk."有时,更大的爆炸发生,产生的火山灰羽上升不到公里以上的通风口,"格罗克的方式。这种情况会导致由气体、火山灰和岩石组成的高速流动,这对当地社区是致命的。火山泥石流也是另一个严重的风险。"可以判断,有时大规模的火山喷发会很危险,会危及人们的性命。hazardous的含义是"危险的"。A.Weak虚弱的;B.Dangerous危险的;C.Brief简短的;D.Similar相似的。故选B.