Coal takes tens or even hundreds of millions of years to form. It starts out as living plants that turn into fossils over time.
People have been burning coal for thousands of years. Since the Industrial Revolution, coal has become a major source of both electricity and global warming. But how does coal get there? Scientists can learn about the past and what will happen when different kinds of coal burn by looking at how coal forms.
In a process called “coalification,” swamp plants are buried, pressed down, and heated until they turn into sedimentary rock. This makes coal. James Hower, a petrologist at the University of Kentucky, told Live Science that coal is just plants that have turned into rock. He said that these fossils of plants were made by “a lot of geological accidents.”
Living plants are the first step in making coal. “The tree can be hurt by fire or by insects as long as it is still alive,” Hower said. “The coal record will show all of these things,” Hower said that pollen, leaves, roots, and even bug poop found in coal can be used to figure out what ecosystems were like in the past. Fire damage, for example, can tell us about the weather in the past.
Next, plants die. Hower said, “If the coal is kept in any way, that tells you something about the environment as a whole.” Because mountain slopes and deserts aren’t good places for peat to grow, it’s unlikely that plants there will turn into coal.
“A very, very high percentage of the coals we see out there came from swamps,” Hower said.
This is because plants that die in wetlands are covered with water and can’t get oxygen. So, they don’t rot as quickly as they would if they were on dry ground. Instead, plants grow in layers on the wet bottom of the swamp, making peat. That peat, which is sometimes a precursor to coal, has a long history of its own. It is home to insects, fungi, bacteria, and even tree roots that grow underground. All of these things help break down plants in a process called beatification. Hower said that each layer of coal could be the result of tens, hundreds, or even thousands of years.
Minerals that come from water seeping into peat or from chemical reactions are also caught in coal. Hower said that the rare earth elements in the fire clay coal in eastern Kentucky came from a volcano eruption millions of years ago. The U.S. Department of Energy is now funding technologies to pull these elements out of coal waste so they can be used in solar panels, windmills, and batteries.
But there are also problems with the minerals in coal. For example, peat that has been near seawater often has more sulphur in it. High-sulfur coals may be more likely to catch fire on their own in mines, and they may also be linked to heart disease. Both mining coal and breathing coal smoke are generally dangerous, but high-sulfur coals may be even more likely to do so.
This is because plants that die in wetlands are covered with water and can’t get oxygen. So, they don’t rot as quickly as they would if they were on dry ground. Instead, plants grow in layers on the wet bottom of the swamp, making peat. That peat, which is sometimes a precursor to coal, has a long history of its own. It is home to insects, fungi, bacteria, and even tree roots that grow underground. All of these things help break down plants in a process called beatification. Hower said that each layer of coal could be the result of tens, hundreds, or even thousands of years.
Minerals that come from water seeping into peat or from chemical reactions are also caught in coal. Hower said that the rare earth elements in the fire clay coal in eastern Kentucky came from a volcano eruption millions of years ago. The U.S. Department of Energy is now funding technologies to pull these elements out of coal waste so they can be used in solar panels, windmills, and batteries.
But there are also problems with the minerals in coal. For example, peat that has been near seawater often has more sulphur in it. High-sulfur coals may be more likely to catch fire on their own in mines, and they may also be linked to heart disease. Both mining coal and breathing coal smoke are generally dangerous, but high-sulfur coals maybe even more likely to do so.
