Internationale des Associations d'Alpinisme (UIAA) has defined a list of 82 "official" Alpine summits that reach at least . The list includes not only mountains, but also subpeaks with little prominence that are considered important mountaineering objectives. Below are listed the 29 "four-thousanders" with at least of prominence. While Mont Blanc was first climbed in 1786 and the Jungfrau in 1811, most of the Alpine four-thousanders were climbed during the second half of the 19th century, notably Piz Bernina (1850), the Dom (1858), the Grand Combin (1859), the Weisshorn (1861) and the Barre des Écrins (1864); the ascent of the Matterhorn in 1865 marked the end of the golden age of alpinism. Karl Blodig (1859–1956) was among the first to successfully climb all the major 4,000 m peaks. He completed his series of ascents in 1911. Many of the big Alpine three-thousanders were climbed in the early 19th century, notably the Grossglockner (1800) and the Ortler (1804), although some of them were climbed only much later, such at Mont Pelvoux (1848), Monte Viso (1861) and La Meije (1877). The first British Mont Blanc ascent by a man was in 1788; the first ascent by a woman was in 1808. By the mid-1850s Swiss mountaineers had ascended most of the peaks and were eagerly sought as mountain guides. Edward Whymper reached the top of the Matterhorn in 1865 (after seven attempts), and in 1938 the last of the six great north faces of the Alps was climbed with the first ascent of the Eiger Nordwand (north face of the Eiger). Geology and orogeny Important geological concepts were established as naturalists began studying the rock formations of the Alps in the 18th century. In the mid-19th century, the now-defunct theory of geosynclines was used to explain the presence of "folded" mountain chains but by the mid-20th century the theory of plate tectonics became widely accepted. The formation of the Alps (the Alpine orogeny) was an episodic process that began about 300 million years ago. In the Paleozoic Era the Pangaean supercontinent consisted of a single tectonic plate; it broke into separate plates during the Mesozoic Era and the Tethys sea developed between Laurasia and Gondwana during the Jurassic Period. The Tethys was later squeezed between colliding plates causing the formation of mountain ranges called the Alpide belt, from Gibraltar through the Himalayas to Indonesia—a process that began at the end of the
{
        'QUESTION: What organization defines the official Alpine summits?': 'ANSWER: Internationales der Association von Alpinismus (UIAA)',
        'QUESTION: How many "official" Alpine summits are there on UIAA list?' : 'ANSWER: There are 82 "official" Alpine summits.',
        'QUESTION: Which peak was first climbed in 1786?' : 'ANSWER: Mont Blanc',
        'QUESTION: Who was one of the first climbers to successfully climb all the major 4,000 m peaks?' : 'ANSWER: Karl Blodig',
        'QUESTION: When did he complete these climbs?' : 'ANSWER: He completed his series of ascents in 1911.',
        'QUESTION: Which peak was first climbed by a female in 1808?' : 'ANSWER: Mont Blanc',
        'QUESTION: When was the last of the six great north faces of the Alps climbed?' : 'ANSWER: In 1938.',
        'QUESTION: What geological concept was established in the 18th century?' : 'ANSWER: Naturalists studied the rock formations of the Alps.',
        'QUESTION: What replaced the theory of geosynclines by mid-20th century?' : 'ANSWER: Plate tectonics theory.',
        'QUESTION: When did the formation of the Alps begin?' : 'ANSWER: About 300 million years ago.'
    }