38447
This appeared to be confirmed by the exploration of the deep sea beds conducted by the Challenger expedition , 1872 – 1876 , which showed that contrary to expectation , land debris brought down by rivers to the ocean is deposited comparatively close to the shore on what is now known as the continental shelf .
 Challenger
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Challenger