Question: Adriana Ocampo has led six research expeditions to study what geological formation that is more than 180 km in diameter and 20 km in depth
Context: The Chicxulub crater ( ; ] ) is an impact crater buried underneath the Yucatán Peninsula in Mexico.  Its center is located near the town of Chicxulub, after which the crater is named.  It was formed by a large asteroid or comet about 10 to 15 kilometres (6 to 9 miles) in diameter, the Chicxulub impactor, striking the Earth.  The date of the impact coincides precisely with the Cretaceous–Paleogene boundary (K–Pg boundary), slightly less than 66 million years ago, and a widely accepted theory is that worldwide climate disruption from the event was the cause of the Cretaceous–Paleogene extinction event, a mass extinction in which 75% of plant and animal species on Earth suddenly became extinct, including all non-avian dinosaurs.  The crater is more than 180 km in diameter and 20 km in depth, well into the continental crust of the region of about 10–30 km depth.  It makes the feature the third of the largest confirmed impact structures on Earth. Wong How Man (born 1949) is an explorer and photojournalist from Hong Kong, and founder and president of the China Exploration & Research Society (CERS), a preeminent nonprofit organization specializing in exploration, research, conservation and education in remote China.  Between 1974, when he began exploring China as a journalist, and 1986, when he founded CERS, Wong led six major expeditions for the "National Geographic" magazine.  His writing for the "National Geographic" was nominated for the Overseas Press Club Award of America.  In his 1985 "National Geographic" expedition, Wong led a team that found a new source of the Yangtze River that is internationally recognized as the true geographic source of the river.  During this expedition he came across the hanging coffins, Wong developped a long life obsession with this peculiar coffins.  Wong documented this expedition in his 1989 book, "Exploring the Yangtze: China's Longest River".  Twenty years later, Wong led a team to discover a new source, four miles west of the source that he had previously discovered.  Subsequently, Wong led CERS expeditions that pinpointed the source of the Mekong in 2007 and discovered a new source for the Yellow River in 2008.  In 2011, he and his team defined the source of the Salween River. The Scotian Shelf is a geological formation, part of the Continental shelf, located southwest of Nova Scotia, Canada.  It covers an area of 120,000 km², is 700 km long and ranges in width from 120 to 240 km.  It has an average depth of 90 metres.  The Scotian Shelf contains the ecologically important Scotian Shelf Large Marine Ecosystem (LME) and the Scotian Shelf Waters (SSW). The Aluchin Horst (Aluchinskii Massif) is a mountainous geological formation in the Siberian Far East.  It is located right below the Arctic Circle, close to the Baimka River, a left tributary of the Bolshoy Anyui River, about 180 km southwest of Bilibino. Mount Dummett ( ) is an elongated mountain 11 nautical miles (20 km) east of Mount McCauley in the southern Prince Charles Mountains.  It was plotted from air photos taken by Australian National Antarctic Research Expeditions (ANARE) in 1956, and was named by the Antarctic Names Committee of Australia for R.B. Dummett, formerly Managing Director of BP Australia, in recognition of the valuable assistance given to ANARE by the company. Adriana Ocampo is a Colombian planetary geologist and the Science Program Manager at NASA Headquarters.  Her research contributed to the understanding of the Chicxulub impact crater.  She has led six research expeditions to the Chicxulub impact site.  Ocampo and her colleagues also discovered the Aorounga Crater Chain in Chad in 1996. The East Warburton Basin in South Australia is the site of a large impact crater of the Carboniferous period (around 360-300 million years ago).  The subterranean structure lies buried at a depth of ~4 km, and measures a minimum of 200 km in diameter.  For comparison, Chicxulub crater is about 180 km in diameter. Watson Escarpment ( ) is a major escarpment in the Queen Maud Mountains, trending northward along the east margin of Scott Glacier, then eastward to Reedy Glacier where it turns southward along the glacier's west side.  Somewhat arcuate, the escarpment is nearly 100 nautical miles (180 km) long, rises 3,550 m above sea level, and 1,000 to 1,500 m above the adjacent terrain.  The north-central part of the escarpment was observed from a vantage point on Supporting Party Mountain and was partially mapped in December 1929 by the Byrd Antarctic Expedition geological party under Laurence Gould.  The escarpment was more closely observed in December 1934 by the Byrd Antarctic Expedition geological party under Quin Blackburn, and was named by Byrd for Thomas J. Watson, American business executive, a patron of this expedition.  The escarpment was mapped in detail by United States Geological Survey (USGS) from surveys and U.S. Navy air photos, 1960-64. Hannan Ice Shelf ( ), is an 18-mile-wide ice shelf on the coast of Enderby Land, Antarctica.  The ice shelf is nourished by Molle and Kichenside Glaciers and borders McKinnon Island on all but its north side.  Photographed from Australian National Antarctic Research Expeditions (ANARE) aircraft in 1956.  First visited in October 1957 by an Australian National Antarctic Research Expeditions (ANARE) party led by B.H. Stinear.  Named by ANCA for F.T. Hannan, meteorologist at Mawson Station in 1957. The Witwatersrand Basin is a largely underground geological formation which surfaces in the Witwatersrand, South Africa.  It holds the world's largest known gold reserves and has produced over 1.5 billion ounces (over 40,000 metric tons), which represents about 50% of all the gold ever mined on earth.  The basin straddles the old provinces of Transvaal and the Orange Free State, and consists of a 5000–7000 m thick layer of Archean, mainly sedimentary rocks laid down over a period of about 260 million years, starting about 3000 million years ago.  The entire series of rocks, known as the “Witwatersrand Supergroup’’ consists of quartzites, banded ironstones, mudstones, tillites, conglomerates and some marine lava deposits.  Most of the basin is deeply buried under younger rocks, but outcrops occur in Gauteng, the Free State, as well as in some of the surrounding Provinces.  The outcrop in Gauteng forms the Witwatersrand ridge, from which the basin and its rocks derive their name.  It was on the southern portion of this ridge that gold was first discovered on the farm Langlaagte in 1886, 5 km west of Johannesburg.  Since this gold was embedded in a conglomerate, it was first assumed that this was alluvial gold in an old riverbed, that had been tilted as a result of earth movements.  However, when it was found that, traced downdip, the conglomerate was not merely developed for the narrow width of a river, but continued in depth, there came the realisation that this conglomeratic zone was part of a sedimentary succession.  The conglomerate was quickly traced east and westward for a total continuous distance of 50 km to define what became known as the “Central Rand Gold Field”.
Answer: The Chicxulub crater