We can get a rough estimate of how fast the rift zone in the atlantic ocean is moving the continents of south america and africa apart simply by assuming that 240 million years ago natal, brazil, and douala, cameroon, occupied the same neighborhood. these cities are presently 5000 km apart. how fast would they have to be moving, on average, to reach their present separation? express your result in cm/year.
b. another way to estimate the same quantity is by analyzing the convection cells in the mantle. if we assume that the convection cells are circular in shape with a diameter of 700 km, and that it takes 100 million years for a piece of rock to complete a trip around a cell, how fast is the rock traveling? how does this value compare to your previous results