You don't truly know the power of nature until you have 400 pounds of it charging at you, ready to pounce ... as one woman in Canada found out when she came across a grizzly. Take a look at this wild video ... a woman hiking with her dog has a surreal grizzly bear encounter that -- by some miracle -- doesn't end in absolute tragedy. For an agonizing couple minutes, the bear chases down the hiker and her dog ... getting as close as about a couple feet away ... all while the woman frantically