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 shouts to scare the animal off.

But rather than scaring the grizzly, the woman's shouts only makes it stand on its back legs to display its size -- and it's HUGE!!!

The grizzly circles, stalks and charges ... but the woman and her dog are able to fend it off before it leaves them alone.

A friend of the woman who had the encounter posted the video on Instagram ... and the caption warned hikers to carry bear spray when trekking through bear country.

Thankfully, no one was hurt ... but it looked like a bear-y close call.