Originally Posted By: hikermor
Lots of things can mess with your compass. Rocks containing significant amounts of iron, like many volcanics. I have seen needles 45 degrees off from local lava flows.

I always like to check the compass against the North Star just to be sure everything is OK.


+1 on the above comments.

This past weekend, we were in an area that has literally millions of tons of boulders and rocks that played havoc on the compass (did not need it, but always have it on me). At times, the compass would be off more 30 degrees in many different directions and it is easy to imagine how less experienced people could wander off in the wrong direction and never realize it until they were really lost...
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Earth and sky, woods and fields, lakes and rivers, the mountain and the sea, are excellent schoolmasters, and teach some of us more than we can ever learn from books.

John Lubbock