What Am I Riddles

Question: I'm a measurement of time.
But you'll find me on a map, not a clock.

What am I?

Question: A trail, a union, together tied.
Come across me and you will find,
you cannot change the course I'm on,
without me you cannot travel on.

What am I?

Question: I have heard of a something-or-other, growing in its nook, swelling and rising, pushing up its covering. Upon that boneless thing a cocky-minded young woman took a grip with her hands; with her apron a lord's daughter covered the tumescent thing.

What is it?

Question: I'm round at the ends and high in the middle.What am I?

Question: I turn polar bears white
and I will make you cry.
I make guys have to pee
and girls comb their hair.
I make celebrities look stupid
and normal people look like celebrities.
I turn pancakes brown
and make your champagne bubble.
If you squeeze me, I'll pop.
If you look at me, you'll pop.

Can you answer the riddle?