Cretaceous Greenhouse World

Article | Updated 7 years ago

In the Late Cretaceous, around 94 million years ago, the Earth experienced extreme global warming.

During this time the ocean floor changed greatly as the continents drifted apart. This increased plate movement and produced a surge in volcanic activity, both on the land and on the ocean floor. The increase in young and hot oceanic crust and a rise in water temperature resulted in a major sea level rise. A massive release of carbon dioxide (CO₂) from volcanoes and sea level rise are intimately linked to the vast oil and gas fields that date to this time.

Volcanic eruptions change the climate

Carbon dioxide was released in vast quantities by volcanoes erupting during this time. The rising sea and warmer climate flushed nutrients into the oceans. On the ocean floor, volcanic eruptions pumped iron and other micro-nutrients into the water. This resulted in enormous blooms of floating microscopic plants (called phytoplankton), while on the land the plants grew faster and both these events added more oxygen into the atmosphere. The high levels of oxygen in the atmosphere led to frequent and very hot wildfires across the planet. 

Generating oil and gas

The greenhouse conditions ended as volcanic activity slowed and blooms of phytoplankton reduced levels of carbon dioxide in the atmosphere. As these blooms died, the oceans were depleted of oxygen. The build up of organic material on ocean floors during this period is the source of much of the world’s oil and gas that today we are so dependent on.