Icebergs
Icebergs are among nature's most spectacular creations, and yet most people
have never seen one. A vague air of mystery envelops them. They come into
being -- somewhere -- in faraway, frigid waters, amid thunderous noise and
splashing turbulence, which in most case no one hears or sees. They exist
only a short time and then slowly waste away just as unnoticed.
Objects of sheerest beauty they have been called. Appearing in an endless
variety of shapes, they may be dazzlingly white, or they may be glassy
blue, green or purple, tinted faintly or in darker hues. They are
graceful, stately, inspiring -- in calm, sunlight seas.
But they are also called frightening and dangerous, and that they are -- in
the night, in the fog, and in storms. Even in clear weather one is wise to
stay a safe distance away from them. Most of their bulk is hidden below the
water, so their underwater parts may extend out far beyond the visible top.
Also, they may roll over unexpectedly, churning the waters around them.
Icebergs are parts of glaciers that break off, drift into the water, float
about awhile, and finally melt. Icebergs afloat today are made of
snowflakes that have fallen over long ages of time. They embody snows that
drifted down hundreds, or many thousands, or in some cases maybe a
million years ago. The snows fell in polar regions and on cold mountains,
where they melted only a little or not at all, and so collected to great
depths over the years and centuries.
As each year's snow accumulation lay on the surface, evaporation and
melting caused the snowflakes slowly to lose their feathery points and
become tiny grains of ice. When new snow fell on top of the old, it too
turned to icy grains. So blankets of snow and ice grains mounted layer upon
layer and were of such great thickness that the weight of the upper layers
compressed the lower ones. With time and pressure from above, the many
small ice grains joined and changed to larger crystals, and eventually the
deeper crystals merged into a solid mass of ice.
冰山 冰山是大自然最壮观的创造之一，但大多数人却从未看到过冰山，一种朦胧神秘的气氛
笼罩着它们。 冰山形成于久远的、寒冷的水体中，而且伴随着雷声轰鸣般的嘈杂和水花汹
涌的风暴，但却无人耳闻目睹。冰山仅存在短短的一段时间就慢慢地悄无声息地融化掉。冰 山具有最纯粹的美，人们如是说。
冰山呈现出千姿百态，可能白得耀眼，或者是闪耀着蓝 色、绿色或紫色的玻璃般的光芒，或浓或淡。 它们在平静的阳光照耀的海水中显得优雅堂
皇，令人浮想联翩。 但是人们亦把冰山称为恐怖的和危险的。 它们的确如此--在夜间，雾 天和风暴肆虐时。
即便是在晴朗的天气里，与它们保持一段安全距离也是明智的。 冰山的 大部分体积稳藏于水下，因此其水下部分的伸展远远超过可见的顶部。 冰山也可能出人意
料地翻滚，剧烈地搅动周围的水体。 冰山是冰川的一部分，从冰川断裂漂流进水中，一段 时间后融化。 今天的冰山由多年前降落的雪花形成。
它们的体内是数百年，或数千年，有 时甚至是数百万年前的降雪。 这些雪花落在极地或寒冷的山上，仅有少量融化或根本不融
化，这样经过许多年或许多世纪后积累了巨大的深度。 由于每年的雪花积累在表面之上， 蒸发和融化使得雪花慢慢失去其羽状尖端而变成微小的冰粒。
当新的雪花降落到旧的表面 上，也变成了冰粒。 因而雪花覆盖层和冰粒层层堆积起来直到如此之大的厚度以致较上层 的重量压缩较下层。
在时间和压力的作用下，许多小冰粒结合到一起变成更大的晶体，最 终较底层的晶体合并成庞大而坚固的冰块。
浮游生物