In some places the rock floor beneath the ice is 8, 000 feet below sea level . 冰层覆盖下的岩层在有些地方为海面下八千英尺深。
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Technology of pre - stressed bolt support for rock floor gateway in deep mine complicated conditions 深井复杂条件下底板岩巷预应力锚杆支护技术
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In the heart of the continent it is almost as high as the summits of the alps , yet soundings show that in places that rock floor is below sea level 大陆的中心几乎与阿尔卑斯山等高，然而，超声探测显示，岩石底部的许多地点都低于海平面。
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