Assertion: natural gas | /r/HasProperty | formed over millions of years
Facets:
value: from decaying plant
type: LOCATION
value: largely
type: DEGREE
Source sentences:
text: Natural gas is an odourless, colourless gas, largely formed over millions of years underground.
text: Natural gas is a fossil fuel formed over millions of years from decaying plant and animal matter buried in sedimentary rock layers.