Problem 1
How many seconds would it take an echo sounder's ping to make the trip from a ship to the Challenger Deep \((10,994\) meters and back? Recall that depth \(=1 / 2(1500 \mathrm{~m} / \mathrm{sec} \times\) echo travel time).
Problem 5
Briefly explain why the ocean floor generally gets deeper the farther one travels from the ridge crest.
Problem 8
Propose one or two ideas to explain why some continental rifts evolve into active plate boundaries while others do not.
Problem 10
Explain this statement: The oceans are at least 4 billion years old, but the oldest ocean basin is only about 200 million years old.
