methane

• Methane comes from leaks from oil reservoirs and coal seams due to the decomposition of plants.  
• Methane hydrates are found under the ocean and in permafrost. 
• CO2 released from volcanoes reacts with water in the atmosphere and forms a weak carbonic acid. Plants draw it into the soil and it enters the bedrock causing chemical weathering - carbonation and hydrolysis. Carbonate ions run off into the oceans where it is removed from the water by corals and bivalves. Over time it is deposited on the sea floor as limestone. Limestone on the sea floor is subducted and is erupted as magma. 
• During the carboniferous large plants evolved and their roots broke apart the bedrock and exposed more rock to chemical weathering. This meant there was less CO2 and caused a glaciation. 
• 65 ma CO2 levels fall due to mountain formations that increased rates of chemical weathering.