Question

for energy. when fossil fuels burn, they undergo a chemical reaction known as combustion. during a combustion reaction, a carbon - based fuel source, like the methane found in natural gas, reacts with oxygen gas (o₂) in the air to produce carbon dioxide gas (co₂) and water vapor (h₂o). this reaction releases heat energy, which humans use to power vehicle engines and to generate electricity at power plants.
coal seams in a rock face in utah
volcanic activity also releases carbon stored below earths surface into the atmosphere. when they erupt, volcanoes release lava, ash, and gases, including co₂. over earths history, volcanic activity has emitted a large amount of co₂ into the atmosphere.
however, the amount of co₂ emitted by volcanoes each year is small compared to the amount emitted by fossil fuel combustion. for example, the 1980 eruption of mount saint helens in washington state released 10 million tons of co₂ into the atmosphere over 9 hours. by comparison, human activities emit that same amount of co₂ in just 2.5 hours.
the 1980 eruption of mount saint helens
identify whether each process stores or releases carbon. complete the table.

	stores carbon	releases carbon
limestone formation
volcanic activity
fossil fuel combustion
fossil fuel formation

Explanation:

Step1: Analyze Limestone Formation

Limestone forms from the accumulation of calcium carbonate - rich materials (like shells of marine organisms). Carbon is incorporated into the limestone structure, so it stores carbon. So for Limestone formation, we check the "Stores carbon" circle.

Step2: Analyze Volcanic Activity

From the text, volcanic activity releases carbon (in the form of \(CO_2\)) from below Earth's surface into the atmosphere. So for Volcanic activity, we check the "Releases carbon" circle.

Step3: Analyze Fossil Fuel Combustion

The text says that during fossil fuel combustion (like burning natural gas), carbon - based fuels react with oxygen to produce \(CO_2\) (releasing carbon). So for Fossil fuel combustion, we check the "Releases carbon" circle.

Step4: Analyze Fossil Fuel Formation

Fossil fuels form from the burial and decomposition of organic matter over millions of years, where carbon is stored in the fuel (like coal, oil, gas). So for Fossil fuel formation, we check the "Stores carbon" circle.

Answer:

Process	Stores carbon	Releases carbon
Volcanic activity	$\circ$	$\circ$ (checked)
Fossil fuel combustion	$\circ$	$\circ$ (checked)
Fossil fuel formation	$\circ$ (checked)	$\circ$