Why does semi arid climate exist?

Will the Louvre give permission to who ever needs it to find out if the Holy Grail is in fact buried underneath the inverted pyramid? Why does dante choose a frozen lake to represent the worst part of hell? Why does West Virginia own the Ohio River? How does the sea erode? Why is the zebra mussel so successful in the Great Lakes? How much of sea water is water? What cuts down trees and increases erosion because there are no plants to block the wind and water runoff? What happens when the Atlantic Deep Water meets the Antarctic Bottom Water? Does ocracoke light flash or rotate? Where are the six Legoland Thrme Parks? What is the function of superior colliculus? Does the couch have to be centered on the wall to hang pictures or does the pictures have to be centered on the wall? What happens if you don't eject your ipod? How many cm tall is the empire state buliding? When was Allan D. Emil Memorial Award created? Who went with sir Edmund Hillary when he climbed mount Everest? How many of species of animals live on the blackland prairies? What is the difference between landmark and famous site? Which river was Sutters Mill located? What drives creatuers into the forest?

Why does semi arid climate exist?