The interaction of the Cretaceous/Tertiary Extinction Bolide with the atmosphere, ocean, and solid Earth
The interaction of the Cretaceous/Tertiary Extinction Bolide with the atmosphere, ocean, and solid Earth
复制标题
白垩纪/第三次灭绝火流星与大气、海洋和固体地球的相互作用
DOI：
10.1130/spe190-p103
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发表时间：
1981
影响因子：
2.2
通讯作者：
T. Ahrens
中科院分区：
文献类型：
--
作者：
J. D. O'keefe;T. Ahrens
大规模（~10公里直径）的小行星、彗星和流星体群撞击被水和气体层（大气层）覆盖的硅酸盐地球的力学表明，速度为15至45公里/秒的火流星在通过海洋和大气层时，只有~ 15%至~ 5%的能量被直接吸收。在撞击地球时，约10至10^2倍的水或岩石可以喷射到平流层：然而，只有约0.1倍的火流星质量是小于1微米的颗粒。蒸发、熔化和（< 1 mm）固体喷出物将其能量的约40%转移到大气层和可能的海洋表面水，产生短暂的，可能致命的（对大型动物）加热脉冲。最初的高速喷出物，在陨石坑流早期上升到平流层以上，富含火流星物质，并具有在白垩纪/第三纪（C/T）边界层中测量的（0.01至0.2）范围内的外星物质浓度。我们认为，C/T边界层的起源是这个喷出物，这是严重的冲击和在<1-μm的范围，因此，一旦夹带在平流层可能会蔓延到世界各地。火流星穿透大气层时会在大气层中产生一个暂时的空洞，周围是强烈冲击的空气。由此产生的向内和向上流动的冲击大气向后沿着火流星的轨迹阁楼的蒸汽，细熔化和固体喷出物的高度大于10公里。较大的，毫米到厘米大小的，通过这种机制被抬升的熔融液滴重新进入大气，可能代表微玻璃陨石和玻璃陨石。足够的撞击引起的蒸汽，熔化和粉碎的硅酸盐被喷射到平流层高度，以显着降低地球表面的光照水平。加热的短期效应，随后是灰尘和可能的水-云甲板引起的全球性冷却，提供了几种机制，造成严重的环境压力的生物群，并可能引起发生在C/T边界的各种和大规模的降水。
The mechanics of large-scale (~10-km diameter) asteroidal, cometary, and meteoroid swarm impact onto a silicate Earth covered by water and a gas layer (atmosphere) demonstrate that only ~ 15% to ~ 5% of the energy of 15 to 45 km/s bolides is taken up directly during the passage through the ocean and atmosphere, respectively. Upon impact with the Earth, ~ 10 to 10^2 times the bolide mass of water or rock can be ejected to the stratosphere: however, only ~0.1 bolide masses is in < 1 μm particles. The vaporized, melted, and (< 1 mm) solid ejecta transfer up to ~40% of their energy to the atmosphere and possibly oceanic surface water, giving rise to a short, possibly lethal (to large animals) heating pulse. The initial high-speed ejecta that lofted to and above the stratosphere early in the cratering flow is enriched in bolide material and has concentrations of extraterrestrial material in the range of those measured (0.01 to 0.2) in the Cretaceous/Tertiary (C/T) boundary layer. We suggest that the origin of the C/T boundary layer is this ejecta, which is heavily shocked and in the < l-μm range and, hence, once entrained in the stratosphere may be spread worldwide. Penetration of the atmosphere by the bolide creates a temporary hole in the atmosphere surrounded by strongly shocked air. The resultant inward and upward flow of the shocked atmosphere backward along the bolide trajectory lofts the vapor, fine-melted and solid ejecta to heights greater than 10 km. The larger, millimeter- to centimetersize, melt droplets that are lofted by this mechanism reenter the atmosphere and may represent microtektites and tektites. Sufficient impact-induced vapor, melted and comminuted silicate is ejected to stratospheric heights to markedly reduce the light levels at the Earth’s surface. The short-term effects of heating, followed by dust and possibly water-cloud deck induced worldwide cooling, provide several mechanisms to cause severe environmental stress to biota and possibly give rise to the varied and massive extinctions that occurred at the C/T boundary.