C rock layers... hope this helped
Ronald Reagan who was the 40th president and earned the title in his 8 years of serving as president
The name for such a hole is "caldera" which is a word of Spanish origin meaning "a pot" or a "cooking pot" (thing of cauldron!) - and this word is used because it resembles the shape of this hole.
Often the Calderas are filled with water forming lakes and often there is an island in the middle of the water.
Answer:
its the world's longest unfortified border :))
A. Based on the location of the Mesopotamia, it always flooded anually.
