Photosynthesis indirectly affects the lithosphere by linking it to the biosphere through carbon dioxide (CO2) cycling.
The Connection: Photosynthesis and Lithospheric Processes
While photosynthesis primarily occurs in the biosphere, its influence extends to the lithosphere through several key mechanisms. The reference material explains this interaction clearly:
- CO2 Pulses and Plate Tectonics: Photosynthesis connects the Earth's crust and biosphere by impacting CO2 levels. This connection becomes clear through plate tectonic activity. When tectonic plates collide, CO2 is released.
- Source of CO2: This CO2 released during collisions does not come out of nowhere. It originates from the oxidation of buried organic matter. This organic matter is the remains of organisms that performed photosynthesis and stored carbon. The process of sulfate reduction in subduction zones is also involved.
In short, the carbon initially captured by plants during photosynthesis is stored in the earth's crust in the form of organic matter. When tectonic plates interact, some of this organic matter is oxidized, releasing CO2 back into the atmosphere, which may then be used again in the biosphere during photosynthesis. The cycle is continuous.
The Indirect Influence
Here is a breakdown of how photosynthesis’ influence on the lithosphere is indirect:
- Carbon Sequestration: Photosynthesis initially removes CO2 from the atmosphere and incorporates it into organic matter. A portion of this organic matter eventually gets buried and becomes part of the lithosphere (e.g. fossil fuels).
- Organic matter storage in the Earth's crust: This matter, initially made possible through photosynthesis, is then part of geological processes.
- CO2 Release: Tectonic activity causes the oxidation of this buried organic matter, releasing CO2 back into the atmosphere. This CO2 can then be used by photosynthetic organisms.
- The Cycle Continues: The continuous cycle of carbon transfer between the lithosphere, biosphere and atmosphere is driven by both photosynthesis and geological processes.
Practical Insights
- Fossil Fuels: A significant amount of the lithosphere's carbon is in the form of fossil fuels (coal, oil, and natural gas), derived from ancient photosynthetic organisms.
- Carbonate Rocks: Some of the carbon captured by photosynthesis also ends up in carbonate rocks.
Conclusion
Photosynthesis, through its role in the carbon cycle, plays an important, yet indirect, part in lithospheric processes via carbon storage and the release of CO2 during tectonic activity.
