Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement forms earthquakes.
earthquakes

Sentence1: measuring the hardness of minerals requires scratching those materials. 
Sentence2: To figure out the hardness of a mineral, the Moh's scale of hardness is used.
minerals

Sentence1: shelter is used for protection by animals against weather. 
Sentence2: sponges are used for protection by animals.

animals