Definition: You will be given three sentences. Read them, then identify a noun phrase (person, place, or thing) or event that is shared between all three sentences. As the output, write the span of the text corresponding to that phrase in each sentence. Keep the order of the sentences, that is, your answer should look like: 1: *a phras from sentence 1e* 2: *a phras from sentence 2* 3: *a phrase from sentence 3*
Input: 1: It may help scientists better understand why Yellowstone 's previous eruptions , in prehistoric times , were some of Earth 's largest explosions in the last few million years . 2: Volcanic activity triggers 2,000 to 3,000 small earthquakes per year , and the shake and shock waves travel at different speeds through molten , hot and other rock . 3: Scientist measured the thousands of small earthquakes in Yellowstone to scan the earth underneath it .

1: Yellowstone 's previous eruptions 2: 2,000 to 3,000 small earthquakes per year 3: small earthquakes in Yellowstone