Good Riddles

Question: You walk down a path through the woods everyday. You always walk by one particular large rotting log which weighs over a ton. The next day you notice that there is another large log underneath the familiar one that you've never seen before. How did it get there?

Question: Which thing that comes once in a year, twice in a week?

Question: What is older than Obama, sits still as stone, but in some people's eyes is more appreciated than the president's home ? Hint: HIS nickname has Two words and starts with H and the second with A.

Question: I have existed for centuries, but last only a month. What am I?

Question: A chicken gives meat and egg while cow gives us milk. Find another who gives us all these?