n.火山喷发碎屑

A shower of tephra, stones and lapillus rained down and lasted 8 days and nights. 火山灰、浮石、火山砾构成的“阵雨”下了8天8夜。

Explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. 爆炸性喷发产生的混合火山灰和其他碎片所谓火山灰，而不是熔岩流。

It is capable of intrusion into adjacent rocks or of extrusion onto the surface as lava or ejected explosively as tephra to form pyroclastic rock. 它有能力入侵到邻近的石块或挤压到表面的熔岩或跳伞爆炸性作为火山灰形成火山碎屑岩。

New information on the response of vegetation to air-fall volcanic ash is provided by analysis of phytoliths from sediments containing major tephra beds. 含火山灰层沉积的植硅体分析为了解植被对从空中下降的火山灰的反应提供新的信息。

All evidences indicate that the lava flow, tephra, ash and toxic gases of the volcanic activities are the main factors that caused the biological hazard and the fossil preservation of "Jehol Biota" in Sihetun and the adjacent area. 种种迹象表明 ,四合屯及其周边地区的义县组火山活动所产生的熔岩流和有毒、有害气体以及频繁爆发的火山灰等是造成热河生物群灾难事件并使其得以保存的主要因素

Two layers of tephra deposits can be identified from the upper sediments in Core CSH1 and are characterized by coarser particle,higher SiO_2 and Na_2O contents and lower contents of clay minerals,volatiles,Fe_2O_3,MgO,CaO and Sr. 从岩芯最上部的沉积物中可识别出2层火山碎屑沉积,它们都具有沉积物粒径突然变粗、SiO2和Na2O等化合物的质量分数突然增加以及粘土矿物、挥发份、Fe2O3、MgO、CaO和Sr的质量分数迅速下降等特征。