When Were the Atlantic and Pacific Oceans Separated by Land?
ES2307  Observing Changes in Isotope Ratios over Time

By analyzing microfossils from sediment cores, scientist have been able to track the ratio of oxygen isotopes on both sides of the Isthmus of Panama. Changes in the ratio of isotopes indicate how salinity levels in the Caribbean and Pacific changed over time.

  !   Examine the graph carefully to interpret how salinity changed over time.

3. Describe the changes in salinity in the Caribbean Sea and the Pacific Ocean from six to two and a half million years ago (mya).

Movement of land masses and uplift of submerged land between Central and South America from 6 million years ago to 2.5 million years ago.

What triggered the change in ocean chemistry?

  !   Click the image to see an animation showing plate tectonic movements over the same time period.

4. Why do you think the ocean chemistry changed?


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