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N a rock formed by the fusing together on the ground of small rock fragments (less than 2 mm across) ejected from a volcano 凝灰岩
The volcaniclastic rocks can be seen as fused lumps, fused breccias and fused tuffs.
火山碎屑岩可见熔集块岩、熔角砾岩和熔结凝灰岩。
The dates of these tuffs proved indistinguishable-4.4 million years for both. This meant the volcanic eruptions had captured between them a focused lens of time-perhaps as little as a thousand years.
上下两层凝灰岩的生成年代无法区别，它们都诞生于440万年前，这意味着短时间内的两次火山喷发——也许只间隔了短短的一千年——将化石俘获在其间。
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