单项选择题

The ocean bottom — a region nearly 2.5 times greater than the total land area of the Earth — is a great frontier that even today is largely unexplored and unknown. Until about a century ago, no one had access to the deep-ocean floor, which was hidden under waters over 3,600 meters deep. To humans, the deep-ocean bottom, totally without light but with intense pressures hundreds of times greater than at the Earth’s surface, is an unfriendly environment, in some ways as forbidding and remote as loneliness of outer space.
Although researchers have taken samples of deep-ocean rocks and deposits for over a century, the first detailed global investigation of the ocean bottom did not actually start until 1968, with the beginning of the National Science Foundation’s Deep Sea Drilling Project (DSDP). Using techniques first developed for the offshore oil and gas industry, the DSDP’s drill ship, the Glomar Challenger, was able to maintain a steady position on the ocean’s surface and drill in very deep waters, collecting samples of deposits and rocks from the ocean floor.
The Glomar Challenger completed 96 voyages in a 15-year research program that ended in November 1983. During this time, the drill ship covered 600,000 kilometers and took almost 20,000 samples of sea-bed rocks and deposits at 624 drilling sites around the world. The samples have allowed scientists to rethink what the planet looked like hundreds of millions of years ago and to calculate what it will probably look like millions of years in the future.
The samples have also produced information related to understanding the world’s past climates. Deep-ocean deposits provide a climatic record tracing back hundreds of millions of years, because they are largely isolated from the erosion (侵蚀) and the intense chemical and biological activity that rapidly destroy much land-based evidence of past climates. This record provided insights into the patterns and causes of past climatic change — information that may be used to predict future climates.
The samples provide better information about the world’s past climate because they ______.