排序方式： 共有4条查询结果，搜索用时 31 毫秒
1
1.
超级火山喷发可以在极短时间内剧烈改变区域地形地貌,引起全球性气候巨变,是人类赖以生存的地球宜居环境的严重威胁。因此,剖析地质历史上的超级火山喷发事件及其环境效应,将有助于我们预测和应对未来可能的超级火山喷发及其造成的自然灾难。本文从超级火山和超级喷发的定义入手,重点介绍超级火山喷发的固相和气相产物、如何鉴别地质历史上的超级火山喷发、以及超级火山喷发可能带来的环境和社会影响。由于最近一次超级火山喷发发生在2.6万年前的新西兰,人类文明并没有经历过超级火山喷发,科学家们主要通过二十世纪以来有记录的小型火山喷发、冰芯和年轮记录、火山-环境-气候模型等来推测、反演和模拟超级火山喷发对气候和环境的影响。已有的研究表明,超级火山喷发产生的碎屑熔岩流和岩浆房塌陷产生的破火山口给周边地区环境造成直接的摧毁;进入平流层的火山气体经过物理化学变化形成气溶胶,有效的反射和吸收太阳辐射,从而导致长达数年的区域甚至全球性的剧烈降温和降水减少。尽管科学家们已经做了很多数值模拟和推演,但超级火山喷发的影响仍然是难以估计的。特别是超级火山喷发发生的季节和地点会带来不同的火山-海洋-大气-植被耦合效应,导致不同规模的气候和环境变化,未来应当加强这方面的研究。 相似文献
2.
Ben?G.?MasonEmail author David?M.?Pyle Clive?Oppenheimer 《Bulletin of Volcanology》2004,66(8):735-748
A compilation and analysis of the size and frequency of the largest known explosive eruptions on Earth are presented. The largest explosive events are defined to be those eruptions yielding greater than 1015 kg of products (>150 times the mass of the 1991 eruption of Mt. Pinatubo). This includes all known eruptions with a volcanic explosivity index (VEI) of 8. A total of 47 such events, ranging in age from Ordovician to Pleistocene, are identified, of which 42 eruptions are known from the past 36 Ma. A logarithmic magnitude scale of eruption size is applied, based on erupted mass, to these events. On this scale, 46 eruptions >1015 kg are defined to be of magnitude M8. There is one M9 event known so far, the Fish Canyon Tuff, with an erupted mass of >1016 kg and a magnitude of 9.2. Analysis of this dataset indicates that eruptions of size M8 and larger have occurred with a minimum frequency of 1.4 events/Ma in two pulses over the past 36 Ma. On the basis of the activity during the past 13.5 Ma, there is at least a 75% probability of a M8 eruption (>1015 kg) occurring within the next 1 Ma. There is a 1% chance of an eruption of this scale in the next 460–7,200 years. While the effect of any individual M8 or larger eruption is considerable, the time-averaged impact (i.e., erupted mass×frequency) of the very largest eruptions is small, due to their rarity. The long-term, time-averaged erupted mass flux from magnitude 8 and 9 eruptions is ~10–100 times less than for M7 eruptions; the time-averaged mass eruption rate from M7 eruptions is 9,500 kg s–1, whereas for M8 and M9 eruptions it is ~70–1,000 kg s–1. Comparison of the energy release by volcanic eruptions with that due to asteroid impacts suggests that on timescales of <100,000 years, explosive volcanic eruptions are considerably more frequent than impacts of similar energy yield. This has important implications for understanding the risk of extreme events.Editorial responsibility: R. Cioni 相似文献
3.
The climatic impact of supervolcanic ash blankets 总被引：1，自引：0，他引：1
Supervolcanoes are large caldera systems that can expel vast quantities of ash, volcanic gases in a single eruption, far larger than any recorded in recent history. These super-eruptions have been suggested as possible catalysts for long-term climate change and may be responsible for bottlenecks in human and animal populations. Here, we consider the previously neglected climatic effects of a continent-sized ash deposit with a high albedo and show that a decadal climate forcing is expected. We use a coupled atmosphere-ocean General Circulation Model (GCM) to simulate the effect of an ash blanket from Yellowstone volcano, USA, covering much of North America. Reflectivity measurements of dry volcanic ash show albedo values as high as snow, implying that the effects of an ash blanket would be severe. The modeling results indicate major disturbances to the climate, particularly to oscillatory patterns such as the El Niño Southern Oscillation (ENSO). Atmospheric disruptions would continue for decades after the eruption due to extended ash blanket longevity. The climatic response to an ash blanket is not significant enough to instigate a change to stadial periods at present day boundary conditions, though this is one of several impacts associated with a super-eruption which may induce long-term climatic change. 相似文献
4.
《地学前缘(英文版)》2024,15(1):101694
The end–Permian mass extinction was one of the major global crises spanning the entire Early Triassic or longer. Eruptions of volcanos were one of the factors that delayed the biotic recovery after this event. Supervolcano eruptions can cause catastrophic effects on global environment, climate, and life. Here we investigate the tuff layers from Early–Middle Triassic boundary in the Yangtze Block and identify a supervolcano eruption event. The zircon U–Pb ages of the section–Langdai, section–Daijiagou and section–Longmendong tuff samples are 247.1 ± 1.9 Ma, 247.6 ± 2.0 Ma and 247.7 ± 1.7 Ma, respectively. These ages mark the Olenekian–Anisian boundary. The zircon grains from the tuff layers have negative εHf(t) (−15.3 to −0.8), two–stage Hf model (TDM2) ages (1.7 to 2.2 Ga) and display high–δ18O values (mostly > 10‰). Clay minerals and quartz dominate the rock composition. The whole rock compositions show that the tuff layers were derived from magma of intermediate to felsic composition, which formed by the remelting of Paleoproterozoic materials of continental crust. The volcanic eruption site is located in the Jinshajiang–Ailaoshan–Song Ma suture zone in the southwestern margin of the Yangtze Block. A combination of the closure of the Paleo–Tethys Ocean Basin and the collision of the Indochina Block and South China contributed to the eruption, which was a supervolcano eruption under the active continental margin arc settings. We speculate that this supervolcano eruption might have contributed to the delayed biotic recovery after the end–Permian mass extinction. 相似文献
1