23 第
章
景致各有千秋的美国国家公园
1
contains 83 separate caves, including the nation's deepest limestone cave－1,597 feet (486.8 m)－and third longest. Carlsbad Cavern, with one of the world's largest underground chambers and countless formations, is also highly accessible, with a variety of tours offered year round.
The story of the creation of Carlsbad Cavern begins 250 million years ago with the creation of a 400 mile long reef in an
inland sea that covered this region. This horseshoe shaped reef formed from the remains of sponges, algae and seashells and from calcite that precipitated directly from the water. Cracks developed in the reef as it grew seaward. Eventually the sea evaporated and the reef was buried under deposits of salts and gypsum.
Then, a few million years ago, uplift and erosion of the area began to uncover the buried rock reef. Rainwater, made slightly acidic from the air and soil, seeped down into the cracks in the reef, slowly dissolving the limestone and beginning the process that would form large underground chambers. At the same time, hydrogen sulfide gas was migrating upward from vast oil and gas deposits beneath the ancient reef. This gas dissolved in the percolating ground water to form sulfuric acid. The added power of this corrosive substance explains the size of the passageways.
The exposed reef became part of the Guadalupe Mountains and the underground chambers became the wonder of Carlsbad Cavern.
The decoration of Carlsbad Cavern with stalactites, stalagmites and an incredible variety of other formations began more than 500,000 years ago after much of the cavern had been carved out.
It happened slowly, drop by drop, at a time when a wetter, cooler climate prevailed. The creation of each formation depended on water that dripped or seeped down into the limestone bedrock and into the cave. As a raindrop fell to the ground and percolated downward, it absorbed carbon dioxide gas from the air and soil, and a weak acid was formed. As it continued to move downward the drop dissolved a little limestone, absorbing a bit of the basic ingredient needed to build most cave formations－the mineral calcite.
Once the drop finally emerged in the cave, the carbon dioxide escaped into the cave air. No longer able to hold the dissolved calcite, the drop deposited its tiny mineral load as a crystal of calcite.
Billions and billions of drops later, thousands of cave formations had taken shape. And, oh, the shapes they took! Where water dripped slowly from the ceiling, soda straws and larger stalactites appeared. Water falling on the floor created stalagmites. Sometimes a stalactite and stalagmite joined, forming a column.
Draperies were hung where water ran down a slanted ceiling. Water flowing over the surface of a wall or floor deposited layers of calcite called flowstone. Cave pearls, lily pads and rimstone dams appeared where pools of water or streams occurred in the cave. Like oyster pearls, cave pearls
24 were made as layer upon layer of calcite built up around a grain of sand or other tiny object. Lily pads formed on the surface of pools, while dams formed where water flowed slowly on the floor. Another type of cave formation that decorated cave walls and even other formations was popcorn, which may have formed when water evaporated and left behind calcite deposits.
Some of the more unusual formations to occur in Carlsbad Cavern are helictites, which grow seemingly without regard to gravity, their twisting shapes governed by crystal shapes, impurities and the force of water under pressure. Other rare formations are those composed not of calcite, but of aragonite, a mineral chemically identical to calcite but with a different crystal structure. These formations tend to be small, delicate and needle-like.
卡尔斯巴德洞穴国家公园位于美国西部的新墨西哥州佩科斯河西岸吉娃娃森林内 部，面积 189 平方千米。这是一个神奇的洞穴世界，以丰富多样而美丽的矿物质而著
称。《世界文化遗产目录》中收录卡尔斯巴德洞穴是遵循了如下标准：它是一种重要的
地质过程的实例，包含了特殊的自然美景。
洞穴形成于 2.8 亿～2.25 亿年前的二叠纪。现已发现 83 个洞穴，最深的位于地表下 305 米；最大的一个比 14 个足球场还要大。整个溶洞群长达近百千米。2.8 亿～2.5 亿年 前，雨水渗入瓜达卢佩山石灰岩山体的裂缝，溶解了松软的岩石，刻凿出隧洞和洞穴，
水从洞穴中流出，留下的矿物质形成了各种造型。溶洞分为三层，山体内地上 330 米 处一层，地上 250 米一层和地上 200 多米处一层。洞穴中的钟乳石千姿百态，令人目 不暇接，引发人无数的遐想。钟乳石都有形象的名字，如“恶魔之泉”、“国王宫殿”、
“太阳神殿”等。另外，洞穴中还有岩帷幕和洞穴珍珠，前者轻轻击打能发出悦耳的声 音，后者是小沙粒外层裹上了一层碳酸钙，形成了有光泽的石球，如珍珠般璀璨。最 吸引人的是巨室洞穴，1200 米长，188 米宽，85 米高。四壁的钟乳幔将其装点得犹如一 座豪华的宫殿。
◆designated：指定的
◆chamber：内庭
◆horseshoe：马蹄铁
◆reef：暗礁
◆hydrogen sulfide：硫化氢
◆stalagmites：石笋
◆dioxide：二氧化物
◆stalactites：钟乳石
◆calcite：方解石
★
Words Tips
25 第
章
景致各有千秋的美国国家公园