Earth's Atmosphere and Ocean Formation Sequence

The formation of Earth's key components followed a specific timeline:

• Atmosphere Formation: The earliest atmosphere likely formed shortly after Earth's accretion, primarily through volcanic outgassing, releasing gases like water vapor, carbon dioxide, and nitrogen.
• Ocean Formation: As the young Earth cooled, the abundant water vapor in the atmosphere condensed and fell as rain, accumulating over millions of years to form the first oceans. This process occurred after a substantial atmosphere was established.
• Plant Life Evolution: Photosynthetic organisms, including early plants, evolved much later, dependent on the presence of liquid water (oceans) and a suitable atmosphere.

Based on this sequence, the atmosphere developed first, followed by the oceans.

Therefore, the ocean formed after the atmosphere.