Question

what caused the enlargement of atlantic ocean​

Answer 1

The Atlantic Ocean is still growing now, because of sea-floor spreading from the mid-Atlantic Ridge, while the Pacific Ocean is said to be shrinking because the sea floor is folding under itself or subducting into the mantle.

Answer 2

Atlantic ocean is expanding due to formation of new crust at the mid-Atlantic ridge and westward motion of the North American Plate.

Explanation:

• As the Atlantic Ocean spreads, the tectonic plates beneath the Americas, Europe, and Africa are being pushed apart. What's pushing the plates apart, according to new research:
• At an undersea ridge in the centre of the Atlantic, material from deep beneath the Earth is rushing upward.
• Further eastward movement of the Eurasian Plate, which is sliding over the Pacific Plate and minor plates sinking in the Pacific Ocean.