Conclusion

Conclusion: Could tectonics control biodiversity?

Tectonics not only destroys life but it creates it. The creation, alteration and destruction of new ecological niches instigate changes in both biotic and abiotic variables. Changes in abiotic variables such as precipitation, sunlight, pH, temperature, nutrient availability, salinity, wind, and available oxygen occurs as a result of climatic change. Processes in the geosphere e.g. tectonic movement, which affects the flow of the hydrosphere and the atmosphere, can instigate this climatic change. The nature of both ocean and atmospheric flow regimes regulate the climate in both marine and terrestrial environments so as they change the climate changes too. Uplifting topography or closing and opening of seaways can have massive implications on the hydrosphere. Tectonics can also facilitate the eruption of magma, which has major implications on the hydrosphere as demonstrated by some of the examples previously discussed in our blog (Siberian Traps). We have seen throughout our previous blog posts that ecosystems have had and still have complex relationships and responses to major tectonic events.

Tectonics is presumably responsible for the generation of our early earth atmosphere, which protects us from short wave radiation from the sun. Igneous processes release gases such as CO2, CH4, and H2O. These gases are major constituents of earth’s atmosphere. CO2 was abundant from magmatic processes because carbon is incompatible with silicate minerals. Carbon dioxide is therefore left out of the crystallisation processes so are extruded in a gaseous form. Water is also incompatible with silicate minerals so are erupted as steam. In the past, after it was capable of cooling it was able to condense and form a liquid, which allowed the establishment of significant volumes of water on earths surface e.g. oceans. The oceans were unable to previously form because abundant magmatic processes kept earth to hot so restricted water to existing only as a vapour. Tectonic action also supports the idea that life developed in the oceans and moved onto more stable crust supposedly generated by plate collision. These are important examples of how tectonics established suitable conditions to found the formation of life. 

Hydrogen, oxygen, nitrogen, phosphorous and sulphur are the elements that support the basic chemistry of all life. Prof. Tilman Spohn believes that tectonics could be accountable for the replenishment of nutrients to the top surface.  All the nutrients that support primitive life on the top surface have to be replenished somehow or the top surface will become depleted. The nutrient cycling that occurs in conjunction with action in the geosphere could be partially responsible for that. For example the recycling of carbon (carbon cycle) from the atmosphere through the processes of subduction and related volcanism could mean that without tectonics a crucial link in the carbon cycle is gone. Also the high temperatures on Venus are assumed to be a result of the lack of tectonics, which has given rise to the greenhouse effect.  Could this be the reason behind the presumed absence of life on Venus?

With all these variables important to life and their partial dependency on tectonics and/or tectonics related processes, could the creation of suitable conditions for life be a function of tectonics? If so, it may not be wrong to assume that life could not be possible without tectonics.

Josephine Turnbull & Rosie Hebden