John Wesley Powell (1834-1902) was perhaps the greatest in a long line of fearless and dynamic American explorers of the nineteenth century. To Powell, the pursuit of science and the expansion of human knowledge were of the utmost importance. Whether he sought to be anonymous or not, Powell's achievements brought him glory - and the fact that he achieved them with one arm (he lost the other at the Battle of Shiloh in 1862) made them all the more glorious.
What does dynamic most likely mean as it is used in the above paragraph?