How did President Polk's placement of soldiers along the Rio Grande contribute to the outbreak of war with Mexico?

He gave a reason for the expansion of the U.S. from the Atlantic to the Pacific.

Explanation:

radioactive dating, also known as  radioisotope dating  is a process that in  estimating the approximate  age  of  rocks. these data can be analyzed from  the studies dealing with the  decay of the radioactive elements that are present in these rocks. in nature, there are a few types of materials or atoms which are quite unstable and they spontaneously decay or breakdown to form other kinds of atoms.