BBC行星地球第二集解说词

2. Mountains

Human beings venture into the highest parts of our planet at their peril. Some might think that by climbing a great mountain they have somehow conquered it, but we can only be visitors here. This is a frozen alien world. This is the other extreme - one of the lowest hottest places on Earth. It's over a hundred metres below the level of the sea. But here a mountain is in gestation. Pools of sulphuric acid are indications that deep underground there are titanic stirrings. This is the Danakil Depression in Ethiopia, lying within a colossal rent of the earth's surface where giant land masses are pulling away from one another. Lava rises to the surface through this crack in the crust creating a chain of young volcanoes. This one, Erta Ale, is today the longest continually erupting volcano on the planet, a lake of lava that has been molten for over a hundred years. These same volcanic forces also created Ethiopia's highlands. 70 million years ago this land was just as flat and as deep as the Danakil Depression. Molten lava rising from the earth's core forced up a huge dome of rock 500 miles wide, the roof of Africa. Over millennia, rain and ice carved the rock into a landscape of spires and canyons. These summits, nearly 3 miles up, are home to some very

remarkable mountaineers Gelada baboons. They are unique to the highlands of Ethiopia. The cliffs where they sleep are for expert climbers only, and Gelado certainly have the right equipment. the strongest fingers of any primate and an utterly fearless disposition. But you need more than a head for heights to survive up here. A day in a Gelado's life reveals how they've risen to the challenge. For all monkeys morning is grooming time, a chance to catch up with friends. But, unlike other monkeys, Gelados chatter constantly while they do it. It's a great way to network while your hands are busy. But these socials can't go on for too long. Gelados have a busy daily schedule and there's work to be done. Most monkeys

couldn't live up here. There's no food and few insects to feed on. But Gelados are unique they're the only monkeys in the world that live almost entirely on grass. They live in the largest assemblies formed by any monkeys. Some groups are 800 strong and they crop the high meadows like herds of wildebeest. The Gelados graze alongside Walia ibex, which are also unique to these highlands. These rare creatures are usually very shy but they drop their guard when the Gelados are around. You might expect that grazers would avoid each other's patch but this is a special alliance from which both partners benefit. It's not so risky to put your head down if others are on the lookout. Ethiopian wolves - they won't attempt an attack in broad daylight. But at dusk the plateau becomes a more dangerous place. With the grazing largely over there's a last chance to socialise before returning to the sleeping cliffs. An early warning system puts everyone on the alert. Their day ends as it began, safe on the steep cliffs. The Ethiopian volcanoes are dormant, but elsewhere others still rage. Volcanoes form the backbone of the longest mountain chain on our planet - the Andes of South America. This vast range stretches 5,000 miles from the Equator down to the Antarctic. It formed as the floor of the Pacific Ocean slid beneath the South American continent, buckling its edge. At the southern end stand the mountains of Patagonia. It's high summer, but the Andes have the most unstable mountain weather on the planet and storms can erupt without warning. Temperatures plummet and guanacos and their newborn young must suddenly endure a blizzard. Truly, all seasons in one day... A puma - the lion of the Andes. Pumas are usually solitary and secretive. To see a group walking boldly in the open is extremely rare. It's a family - a mother with four cubs. She has just one brief summer in which to teach them their mountain survival techniques. Rearing four cubs to this age is an exceptional feat, but she does have an excellent territory, rich in food and water. Although the cubs are now as large as their mother, they still

rely on her for their food. It will be another year before the cubs can hunt for themselves. Without their mother's skill and experience they would never survive their first winter. Battered by hurricane force winds, these slopes are now lifeless. Further north, they hold other dangers. Moving at 250 miles an hour, an avalanche destroys everything in its path. In the American Rockies a 100,000 avalanches devastate the slopes every winter. This huge mountain chain continues the great spine that runs from Patagonia to Alaska. The slopes of the Rockies, bleak though they are, provide a winter refuge for some animals. A mother grizzly emerges from her den after six months' dozing underground. Her two cubs follow her and take their first steps in the outside world. These steep slopes provide a sanctuary for the cubs. A male bear would kill and eat them given the chance. But big animals find it difficult to get about here. Males may be twice the size of a female and even she can have problems. Her cubs, however, make light of the snow and of life in general. But the mother faces a dilemma: it's six months since she last fed and her milk is starting to run dry. She must soon leave the safety of these nursery slopes and lead her cubs away from the mountain. If she delays, the whole family will risk starvation. Summer reveals the true nature of the Rockies. Stripped of snow, the peaks bear their sculpted forms. Only now can mountaineers reclaim the upper reaches. Two miles up the crumbling precipices seem devoid of life. But there are animals here - a grizzly bear. It seems to be an odd creature to find on these high rocky slopes. It's hard to imagine what could have attracted it here. At this time of the year bears should be fattening up for the winter. Yet they gather in some numbers on these apparently barren slopes. They're searching for a rather unusual food - moths. Millions have flown up here to escape the heat of the lowlands and they're now roosting among the rocks. Moths may seem a meager meal for a bear, but their bodies are rich in fat and can make all the difference in a bear's annual struggle for