Researchers Find Huge Prehistoric Seafloor That Sank Beneath the Pacific Ocean

Researchers have detected what they believe to be an ancient seafloor beneath the Pacific Ocean. Scientists from the University of Maryland have possibly discovered remnants of a prehistoric seafloor that got plunged beneath the Earth's depth around the age of dinosaurs, SciTech Daily reported. This revelation has shocked the scientific community as it raises questions regarding the Earth’s interior structure. The findings associated with the discovery have been published as a study in the journal Science Advances.

Site of Discovery

The lost seafloor has been estimated to be in the 'mantle transition zone,' an area that separates the upper mantle from the lower mantle, Daily Mail reported. It is located at the East Pacific Rise, a tectonic boundary on the floor of the southeastern Pacific Ocean. Researchers believe that the ancient sea floor was likely broken off from a large tectonic plate after which it slipped into the depths of Earth. Scientists discovered in their analysis that the structure was comparatively thicker and cooler than the surrounding areas.

"This thickened area is like a fossilized fingerprint of an ancient piece of seafloor that subducted into the Earth approximately 250 million years ago,"  lead author, and geology postdoctoral researcher, Jingchuan Wang, of the University of Maryland said. According to researchers, the seafloor could also aid experts in understanding the unconventional structure of Pacific Large Low Shear Velocity Province (LLSVP), a structure present in  Earth’s lower mantle which is allegedly split by a slab, SciTech Daily reported.

Seismic Imaging

Researchers applied innovative seismic imaging techniques to analyze the mantle transition zone, SciTech Daily reported. "You can think of seismic imaging as something similar to a CT scan. It’s basically allowed us to have a cross-sectional view of our planet’s insides," Wang said.

"Usually, oceanic slabs of material are consumed by the Earth completely, leaving no discernible traces on the surface. But seeing the ancient subduction slab through this perspective gave us new insights into the relationship between very deep Earth structures and surface geology, which were not obvious before."

The research team believed that the seafloor had been subducted, at the beginning of the research. Subduction is a process that occurs in the event of one tectonic plate sliding beneath another, which leads to the recycling of surface material back into Earth’s mantle. Researchers examined how seismic waves interacted with different layers and created a detailed map of the structures present within the mantle. 

Discovery Opens up New Questions

Researchers in their analysis discovered that the materials in the mantle transition zone moved slower than expected, Daily Mail reported. "We found that in this region, the material was sinking at about half the speed we expected, which suggests that the mantle transition zone can act like a barrier and slow down the movement of material through the Earth," Wang explained.

The study noted that the unusual thickness of the seafloor could be because of the presence of colder material in that area. They believe it implied that oceanic slabs got stuck halfway through their path while sinking within the mantle. This assertion challenges the conventionally held belief amongst experts that oceanic slabs are completely consumed by the Earth during subduction.

The experts associated with the revelation believe that it is a huge step in understanding how deep earth influences the structures present on Earth's surface, SciTech Daily reported. "Our discovery opens up new questions about how the deep Earth influences what we see on the surface across vast distances and timescales," Wang added. 

The Phoenix Plate

The findings have made the research team conclude that the seafloor was part of Phoenix plate, a tectonic plate that once dominated the Pacific Ocean, Daily Mail reported. They believe that when the Phoenix plate was sinking, it transferred cooler material from the ocean floor into the hot mantle. This created a cold thermal signature that the study detected through their proceedings.

The research team wants to extend the area of their examination, to put into place a detailed map of ancient subduction and upwelling zones. Upwelling occurs when subducted material heats up and rises to Earth's surface.