Volcanic Event Transformed Oceanic Plate Beneath Pacific Ocean

Topic: Earth Science

Scientists discovered that a massive volcanic event 110-120 million years ago changed an entire oceanic plate beneath the Pacific Ocean. The team led by Azusa Shito used seismic waves to study the deep structure of the Ontong Java Plateau and found evidence of vertical intrusions and chemical changes in the rock. Their findings suggest that magma rising from deep inside Earth altered the plate's chemistry.

The largest oceanic plateau on Earth, the Ontong Java Plateau (OJP), lies beneath the western Pacific Ocean. It was formed approximately 110-120 million years ago during a period of extraordinary submarine volcanism. This event is considered the largest volcanic outpouring known in Earth's history.

A research team led by Lecturer Azusa Shito of Okayama University of Science studied the deep structure beneath the OJP using seismic waves. They found evidence of vertical intrusions, called dikes, which are formed when molten rock forces its way through cracks and then cools inside them. Large groups of these intrusions can preserve a record of intense volcanic activity long after the magma has solidified.

The team also detected unusually low seismic wave speeds within the plate. This suggests that magma rising from deep inside Earth did not simply pass through the plate, but likely changed its chemical composition as well.

Why It Matters

This discovery is important because it helps us understand how massive volcanic events can affect our planet's environment and climate. It may also have contributed to mass extinctions by changing ocean chemistry, climate, and the amount of oxygen available in seawater.

Key Facts

• The Ontong Java Plateau was formed approximately 110-120 million years ago during a period of extraordinary submarine volcanism.
• The largest volcanic outpouring known in Earth's history occurred at this time.
• A research team led by Lecturer Azusa Shito studied the deep structure beneath the OJP using seismic waves.
• They found evidence of vertical intrusions, called dikes, which are formed when molten rock forces its way through cracks and then cools inside them.
• The team also detected unusually low seismic wave speeds within the plate.

Key Terms

Dike

A vertical intrusion of molten rock that forms when magma pushes through cracks in the Earth's crust.

Mantle plume

A column of unusually hot material moving upward through the Earth's interior.

Implications

This discovery is important because it helps us understand how massive volcanic events can affect our planet's environment and climate. It may also have contributed to mass extinctions by changing ocean chemistry, climate, and the amount of oxygen available in seawater.