Two mammoth-shaped bodies exist in the Earth’s mantle’s lowest sector beneath Africa and the Pacific region around the Earth’s core and take up 3 to 9 percent of Earth’s total volume.
Thank you for reading this post, don't forget to subscribe!The core of Earth remains hidden to human perception unless you survive molten-death or fight through underground human populations. To examine Earth beneath its surface scientists use seismic tomography and its dependence on earthquake activities.
The occurrence of earthquakes produces seismic waves that spread themselves across every directional axis. Surface measurements of seismic waves generate compositions of the Earth’s internal structure. Different densities between rocks and liquids inside the Earth cause seismic waves to travel at different speeds therefore enabling scientists to identify the materials through which the waves pass.
During the late 1970s scientists made an unexpected discovery of two unusually gigantic features which scientists named large low shear velocity provinces (LLSVPs). Waves move through “blobs” more dilatorily than in the surrounding lower mantle regions.
Earth science researchers confirmed long ago that these islands sit precisely between mantle and core regions. Study co-author Arwen Deuss from Utrecht University confirmed this finding through her statement
The LLSVPs have hot temperatures which cause seismic waves to move more slowly in the same way hot weather affects human running speed.
The under-African geological feature Tuzo stands as about 800 kilometers (497 miles) high equivalent to 90 Mount Everests.
Scientists were uncertain about these structures because they could not determine whether they lasted for millions or billions of years while in existence there or existed only briefly during specific time periods according to Deuss. These two substantial islands exist within a deadzone of tectonic plates that were carried there through the natural geological process of ‘subduction.’ During this method one tectonic plate descends beneath another until it completely sinks thousands of kilometers beneath Earth’s surface.
So, what are they? At this moment scientific understanding about this matter remains incomplete despite the few well-founded explanations existing. The objects surpass mantle density so scientists believe they contain different materials yet the actual composition remains unknown. Scientists believe that LLSVPs exist because oceanic crust material has been continuously sinking into the mantle since the beginning of geological time. Scientific theories about LLSVPs include two possible explanations – one more serious than the other.
Scientists believe Theia was a planet comparable to Mars which collided with Earth 4.5 billion years ago to generate the large amount of space debris that ultimately became the Moon. A suggestion exists that these blobs represent material from Theia which mixed with Earthen materials through the powerful planetary collision. Scientists modeled Theia’s survival under conditions where its mantle required density enhancements between 1.5% to 3.5% for survival in 2021.
A new investigation of the blobs was conducted through advanced research techniques by the same scientific team.
Research teams integrated “damping” seismic wave measure to their studies after investigation of the decline in wave strength that occurs while waves propagate through Earth’s interior. The study investigated both the tone detuning and sound volume variations for its necessary analysis and findings according to co-author Sujania Talavera-Soza of Utrecht University. The LLSVP showed minimal damping effects which produced a loud sonic profile when we played the tones there. The graveyard of cold slabs presented high damping that made the tones produce very soft sounds. The upper mantle showed the expected results with its hot conditions that caused wave damping.
Temperature serves as an insufficient factor to account for complete differences in wave speed. Team members indicate that grain sizes in the material matter significantly more than its overall volume.
The subducting tectonic plates which end up in slab graveyards develop small grain dimensions as a result of their deep Earth journey. The size of grains directly influences the number of boundaries and thus grains within the material as explained by co-author Ulrich Faul from MIT. The slab graveyard contains numerous grain boundaries between grains which explains why damping occurs more frequently because waves dissipate energy as they intersect those boundaries. LLSVPs must contain enormous grains since they demonstrate minimal damping features.
