4. Compare and contrast the rate of sea floor spreading along the Mid-Atlantic Ridge and East Pacific Rise.

The Mid-Atlantic Ridge runs down the center of the Atlantic Ocean. ... The rift valley is 1 to 3 km deep, about the depth and width of the Grand Canyon. In contrast, the East Pacific Rise spreads fast at rates of 6 to 16 cm per year (more than 20 cm per year in the past).

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many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.