New Discovery Helps Decode The Mystery of Heat Loss from Earth’s Crust

The discovery of a new type of ‘hydrothermal vent system’ has helped explain the long observed disconnect between the theoretical rate at which the Earth’s crust is cooling at seafloor spreading ridge flanks, and actual observations. The credit for the detection goes to scientists at the National Oceanography Centre (NOC) and the University of Southampton, UK. Scientists have always predicted more number of certain locations on the Earth’s crust than the known mechanisms, to fully explain the current rate of cooling of earth’s interior and this newly invented hydrothermal vent system may well be the answer.
The phenomenon which makes these vent systems different is that the source of heat driving them comes from hot rock pushed towards the seabed by low angle faults, called tectonic spreading centres, rather than volcanic heat from magma chambers.

The new class of venting was discovered at the Von Damm Vent Field in the Caribbean during an expedition on board the Royal Research Ship, James Cook. The team used sonar on the autonomous-sub, Autosub6000, to map the vent field before sending down a remotely operated vehicle (ROV) to collect samples of hydrothermal fluids and minerals. Multi-beam sonar on this ROV was also used to produce a map with a resolution so high it could pick out individual pebbles on the sea floor.


The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, the deepest spreading centre on Earth,13 km west of the axial rift. The heat flux at the VDVF measured at 487±101 MW, is comparable to the most powerful magma-driven hydrothermal systems known, and may represent a significant mode of off-axis oceanic crustal cooling not previously recognized or accounted for in global models.

Scientists expect this new type of vent system to be found in tectonic seafloor spreading sites across the globe.
The world class marine technology is also what led to the discovery, which had remained elusive until now as the spreading sites are almost invisible to the traditional ways of searching for hydrothermal vents, and the process driving them was not understood fully.

The investigation of chemistry and the minerals obtained from the vents revealed that they were much different from what we obtain from any other known vents. The unusual mineralogy of the VDVF results from mixing between moderate-temperature vent fluid and cold seawater. As a result, the fifty metre tall mounds and chimneys were formed largely of a magnesium-rich mineral, talc, rather than the more usual iron and copper sulphides.

In addition, the vents release over a one thousand kilograms per second of fluid at 215°C, which carries hundreds of megawatts of heat out of the crust. No wonder accounting for such a major flux of heat and chemicals it has important implications for the balance of magnesium and calcium in seawater, which might have also played a significant role in past climatic conditions.

With this discovery; the phenomenon of much intrigue to the scientific world, of how heat and chemistry is transferred from inside the Earth’s crust is solved. Consequently it will also mean that the ocean models of magnesium and calcium budgets will need to be updated which could lead to more accurate insights into Earth’s past climate. The research was published in #-Link-Snipped-#.

Source: Latest News | National Oceanography Centre