At 282 feet (86 m) below sea level， Badwater on Death Valley，s floor is the lowest point in the Western Hemisphere， while Mount Whitney only 85 miles (140 km) to the west rises to 14，490 feet (4，263 m). This is the greatest dryland topographic relief in the contiguous United States and is the terminus point of the Great Basin，s southwestern drainage. Although the extreme lack of water in the Great Basin makes this distinction of little current practical use， it does mean that in wetter times the lake that once filled Death Valley (Lake Manly) was the last stop for water flowing in the region， meaning the water there was relatively saturatedsaturated adj.渗透的， 饱和的， 深颜色的 in dissolved materials. Thus salt pans in Death Valley are among the largest in the world and are rich in minerals， such as borax and various salts and hydrates. The largest salt pan in the park extends 40 miles (65 km) from the Ashford Mill Site to the Salt Creek Hills， covering some 200 square miles (500 km2) of the Valley floor (Badwater， the Devils Golf Course and Salt Creek are all part of this feature). The second most wellknown playa in the park is the Racetrack， famous for its mysteriousmysterious adj.神秘的 moving rocks.
Death Valley is one of the hottest and driest places in North America due to its lack of surface water and its low relief. On July 10， 1913 a record 134 °F (~57 °C) was measured at Badwater which is (as of 2005) the highest temperature ever recorded on that continent. Daily summer temperatures of 120 °F (50 °C) or greater are common as well as below freezing nightly temperatures in the winter. Several of the larger Death Valley springs derive their water from a regional aquifer which extends as far east as southern Nevada and Utah. Much of the water in this aquifer was placed there many thousands of years ago， during the Pleistocene ice ages， when climate was cooler and wetter. Today，s drier climate does not provide enough precipitation to recharge the aquifer at the rate at which water is being withdrawn.
The hot， dry climate makes it difficult for soils to form. Mass wasting， the down slope movement of loose rock， is therefore the dominant erosive force in mountainous area， resulting in “skeletonized” ranges (literally， mountains with very little soil on them). Sand dunes in the park， while famous， are not nearly as numerous as their fame or dryness of the area may suggest. One of the main dune fields is near Stovepipe Wells in the northcentral part of the Valley and is primarily made of quartz sand. Another dune field is just 10 miles (16 km) to the north but is instead mostly composed of travertine sand. Yet another dune field is near the seldomvisited Ibex Hill in the southernmost part of the park， just south of Saratoga Springs (a marshlandmarshland n. 沼泽地）. Prevailing winds in the winter come from the north and prevailing winds in the summer， from the south. Thus the overall position of the dune fields remain moreorless fixed.
Yosemite National Park约塞米蒂国家公园
约塞米蒂国家公园位于中加州内华达山脉的西麓，离旧金山数小时车程，占地面积达1100平方英里，是美国景色最优美的国家公园之一。即使你有一周的时间，也只能领略一小部分美景。事实上，绝大部分游客目前游览的，只是其中约1英里宽、7英里长的约塞米蒂山谷。1984年联合国教科文组织将约塞米蒂国家公园作为自然遗产，列入《世界遗产名录》。
“约塞米蒂”源自印第安语，意即灰熊，是当地印第安土着的图腾。他们是约塞米蒂国家公园内最早的居民。相传一千多年以前，北美的印第安人就已经在这片广袤的谷地里生息繁衍，但直到1857年，随着加州黄金潮引来的滚滚人流，她的神秘面纱才被首次揭开。据说，爱好风景的林肯总统始终不能忘怀她的壮美，于1864年将山谷内的美洲杉丛林设为美国的第一个州立公园。1890年，约塞米蒂又成了国家公园，1984年终于跻身“世界文化遗产”。现在每年吸引的游客高达300万人次。
1864年，美国总统林肯将约塞米蒂谷划为予以保护的地区，因而约塞米蒂谷也被视为现代自然保护运动的发祥地。峡谷内有默塞德河流过，以及一些瀑布，包括高739米的约塞米蒂瀑布，它是北美落差最大的瀑布，在世界范围内排名第三。景观中还有许多美丽的山峰，其中最令人难忘的是船长峰，这是一个由谷底垂直向上高达1099米的花岗岩壁，是世界上最高的不间断陡崖之一。
约塞米蒂国家公园的设立，主要是由苏格兰自然学家缪尔促成的。缪尔被约塞米蒂谷壮观美丽的景色所折服，他献出了毕生的精力为保护约塞米蒂的环境而努力。他写道：“没有任何人工染成的楼台庙宇可以同约塞米蒂相媲美。其岩壁上每一块石头都焕发着生命的光芒……大自然仿佛在此荟萃精华。”
园内的地势落差极大，不断映入眼帘的山峰、峡谷、河流、瀑布，构成了山谷内鬼斧神工的雄伟景色。难怪19世纪着名旅行家约翰·穆尔要说：“内华达的宝藏不是黄金，而是约塞米蒂的天然风景。”记者来到美国两年多，看惯了一如高尔夫球场般精致美丽的风景区，乍一来到没有任何人工雕琢的约塞米蒂，油然产生一种心灵的震撼。约塞米蒂的湖泊是山脉的镜子，而山脉则是远古时代冰河和火山的杰作。当大地震让内华达山脉倾斜时，起源于白雪笼罩的山顶的马赛河却“暗渡陈仓”，悄悄地在山峦间切割出一条V形山谷，约塞米蒂由此诞生。内华达山脉顶峰的冰雪融化后，便形成“飞流直下三千尺”的瀑布，山谷内的湖泊因此水量丰沛，湖泊旁的草木也因此枝繁叶茂。
Yosemite National Park is without question one of America，s most beautiful national parks. Along with Yellowstone and Grand Canyongrand canyon n.(美)大峡谷， it is one of the three best known parks in the national park system， and one of the most famous parks on earth. It is also one of the most popular； in 1993 it was the third most visited park， behind only Great Smoky Mountain in Tennessee and Grand Canyon in Arizona， and in 1994 was visited by over 4 million people.
Yosemite is known for its spectacular and diverse attractions. It includes high Sierra Peaks (such as Mt. Lyell at 13，114 feet)， the highest highway pass in California (Tioga Pass)， the Yosemite Valley， Merced River， many acres of high altitudealtitude n.(尤指海拔)高度， 高处(海拔甚高的地方)， (等级， 地位等)高等 backcountry， some of the highest waterfalls in the word， and some of of the largest living things on earth in the sequoia groves. Park lands range in altitude from 2，000 feet to the peak of Mt. Lyell， supporting a variety of ecosystems. 94.5% of the park，s 747，956 acres is officially classified as wilderness.
The most famous section of the park is undoubtedly Yosemite Valley， where El Capitan， Half Dome， Yosemite Falls， and other wellknown features are located. The first view of the valley for many people is the beautiful “tunnel view”， shown below.
But the park contains a great deal more than just Yosemite Valley. It includes the Mariposa Grove， where the ancient and enormous sequoiassequoia n.［植］ 美洲杉 can be be seen， and Tuolumne Meadows and the back country of the High Sierra which can be accessed via the Tioga Road.
Yosemite is also known for some individuals who have contributed greatly to its preservation and fame. These folks include John Muir， whose lifelong efforts were in large part responsible for its establishment as one of the first national parks， and Ansel Adams， who lived for a while in the park and whose striking photographicphotographic adj.照相的 images brought the beauty of the park to many around the world.
Yosemite Valley