Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Fact 1: most canyons are formed by flowing rivers through erosion over long periods of time. 
Fact 2: Canyon Lake Canyon lake was formed by dams on the Salt River.
dams can form canyons.

Fact 1: a car engine usually converts gasoline into motion and heat through combustion. 
Fact 2: Combustion is never complete in gasoline and diesel engines.
Cars never completely convert gasoline into motion.

Fact 1: propulsion is used for flying by a spacecraft. 
Fact 2: Jet Propulsion Laboratory forerunner established.

Jets are used for flying by spacecraft.