* Astronomy

At over over 30000 feet deep, the Marianas Trench in the Pacific Ocean is the deepest canyon...

Cotahuasi canyon
270 kilometres from Arequipa, we arrive at Cotahuasi canyon. Carved out of the earth by the Cotahuasi river, the canyon is one of the most spectacular spots in the Andes. Here, the mountains have been levelled, and a canyon excavated, by the force of the rivers flow, making it one of the deepest on the planet.
In the heart of the canyon, humans conquered the rock and constructed immense terrace systems, levelling the land and building containing walls irrigated by canals originating in the mountain peaks Coropuna and Solimana.

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Cotahuasi Canyon is considered deepest of the Americas. Its maximum depth is 3535 metres in the sector of Ninancocha, 335 metres more than the Colca Canyon, but less deep than several canyons in the Himalayas.

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Yarlung Tsangpo
For many years, the Yarlung Tsangpo in eastern Tibet was known to be among the deepest valleys in the world. Its inaccessibility meant that its depth could not be directly measured-until 1993, when, after 10 years of trying, explorer Richard Fisher obtained the permits he needed to visit the area. British botanist Francis Kingdon Ward explored (the west end of) the Yarlung Tsangpo at the beginning of the century, but no other Westerners were able to do so until Fisher led his expedition there.
With a group of fellow Americans, plus Chinese and Tibetan colleagues and Minba and Loba tribal co-explorers, Fisher set off into the unknown. The result was clear-cut: the discovery of the deepest valley on earth.
With soaring peaks on either side of the Yarlung Tsangpo, measurements were extremely difficult to take, but the conclusion was that the valley is 5075 metres deep near the Tibet-India border. The peaks of Namche Barwa (7753 metres) and Jala Peri (7282 metres) are 21 kilometres apart, and the Yarlung Tsangpo River flows between them at an elevation of 2,438 metres.

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