Carbon Stores 2
Geography: Edexcel A Level, topic 8.1.2
Geological Processes that Release Carbon
Carbon can be released into the atmosphere via the rock cycle.
Chemical weathering of rocks
- Chemical weathering is the wearing away of rock by chemical reactions, causing material to dissolve through solution, hydrolysis and oxidation.
- Slightly acidic rain (a carbonic acid) forms from carbon dioxide in the atmosphere being dissolved into rainwater.
- When acidic rain hits carbon-rich rocks (e.g. limestone) it can dissolve material and form calcium carbonate.
- These dissolved materials are then transported down rivers and deposited into the sea, forming into sedimentary rock.
Volcanic out-gassing
- Extreme heat from tectonic processes leads to sedimentary rock undergoing chemical changes, causing CO2 to be released into the atmosphere.
- Volcanic activity happens at two types of plate boundaries:
- Constructive plate boundaries, where two plates move apart.
- Destructive subduction zones, when an oceanic plate subducts under a continental plate.
- Volcanic activity at these plate boundaries causes CO2 to be released in out-gassing.
- Out-gassing is common in geothermal locations like New Zealand.
Test yourself on Carbon Stores 2
What is released into the atmosphere in out-gassing from volcanoes?
The Process of Chemical Weathering