“Did the Atlantic close and then reopen?” That was the question posed in a 1966 article by Canadian geophysicist J. Tuzo Wilson.
The answer? Yes, millions of years ago. And it was the breakup of the supercontinent Pangea, which began about 180 million years ago, that began to create the Atlantic Ocean basin as we know it today.
The surface of the Earth is made up of intersecting tectonic plates. For much of our planet’s history, these plates have been colliding with each other, forming chains of mountains and volcanoes, and then pulling apart, creating oceans.
When Pangea existed, it would have been possible to walk from what we now know as Connecticut or Georgia in the United States to what is now Morocco in Africa. Geologists don’t know what causes the continents to break up, but we do know that when the break up occurs, the continents thin out and separate. Magma gets into continental rocks.
The oldest portions of the crust of the Atlantic Ocean lie off North America and Africa, which were adjacent to Pangea. They show that these two continents separated about 180 million years ago, forming the North Atlantic Ocean basin.
The rest of Africa and South America separated about 40 to 50 million years later, creating what is now the South Atlantic Ocean basin.
Magma flows upward from below the ocean floor in the Mid-Atlantic Ridge, creating a new crust where the plates separate. Some of this oceanic crust is younger than you or me, and more is being created today. The Atlantic continues to grow.
Winds and currents
Once the ocean basin was formed after the breakup of Pangea, the water came in thanks to rain and rivers. The winds began to move the surface water.
Thanks to the uneven heating of the Earth’s surface and its rotation, these winds blow in different directions. Earth is warmer at the equator than near the poles, which sets the air in motion. At the equator, the planet’s heat causes humid air to heat up, expand, and rise. Cold, dry, heavier air descends in the polar regions.
This movement creates “cells” of rising and falling air that control global wind patterns. The rotation of the Earth dictates that different parts of the globe travel at different speeds. At one pole, an air molecule would simply spin, while an air particle at the equator in Quito, Ecuador, would travel 12,742 kilometers in a single day.
This different movement causes the air cells to break. For example, in Hadley’s cell, tropical air, which rose at the equator, cools in the upper atmosphere and descends to about 30 degrees north and south latitude, near the northern and southern ends of Africa.
Earth’s rotation spins this downward air, creating trade winds that flow east-west across the Atlantic and back to the equator. At higher latitudes in the North and South Atlantic, the same forces create mid-latitude cells with winds blowing from west to east.