What is The steep area where oceans rapidly get deeper?

Why don't aircraft fly over the Sahara desert? Important monuments in Indiana? The primary economic activity in the Rocky Mountains West before the Civil War was what? What is the source of the Nile river and in what counrty is this lake found? What type of structure is burj khalifa? When will which will fall for you part 40 come out? What is the name of the long skinny lake contained within Russia? Where does the water come from in the dead sea and what are the names of the rivers that flow into the dead sea? What are the physical characteristics of the Eiffel Tower? Is most of the world's water in lakes and rivers? In what country is Lake Balkhash? Types of human activities in hot deserts? How do you put diesel additive in? What presidential monument is carved into the Native American black hills? A keep or what stood in the middle of a courtyard surrounded by walls? What is cross bridge formation? What will best help determine the direction of heat flow in a system? What causes the deflection of ocean currents and wind belts? What was the Grand Canyon like 100 years ago? What toxics were dumped in the Love Canal?