Imagine our world millions of years ago. The land looked very different. The oceans were full of life.
The oceans held tiny plants and bugs. We call the plants phytoplankton. We call the bugs zooplankton.
These tiny things were smaller than a grain of sand. You would need a microscope to see them. They floated everywhere in the sea.
The sun shone brightly on the ancient oceans. The tiny plants caught the sunlight. They used the light to make food.
This process is called photosynthesis. The plants trapped the sun energy inside their tiny bodies. It was like charging a tiny battery.
The tiny bugs ate the tiny plants. The bugs took the sun energy for themselves. The energy moved up the food chain.
Life in the ancient ocean was busy. Trillions of these tiny plants and bugs lived and grew. The water was a giant soup of life.
But these tiny living things did not live forever. Their lives were very short. They eventually died in the water.
The dead creatures stopped floating. Their tiny bodies slowly sank. They fell deep down to the bottom of the sea.
It rained dead plants and bugs on the ocean floor. This happened every day for millions of years. A thick layer of bodies formed.
Dead things usually rot and disappear. Bugs and bacteria eat them. This requires oxygen from the air or water.
But the deep ocean floor was special. The water at the very bottom had no oxygen at all. We call this an anoxic zone.
The tiny bodies did not rot because there was no oxygen. They just piled up in the dark. The pile grew thicker and thicker.
Rivers kept flowing into the oceans. The rivers carried dirt and sand and mud from the land. This dirt slowly sank to the bottom too.
The mud fell right on top of the dead plants and bugs. It covered them up like a heavy blanket. They were trapped in the dark.
More time passed. Millions of years went by. More sand and mud piled up on top of the old mud.
The layers of dirt grew incredibly heavy. The weight pushed down very hard on the bottom layers. This created intense pressure.
The heavy pressure squeezed the mud. The intense squeezing turned the mud into solid rock. We call this shale rock.
The dead plants and bugs were stuck inside the rock. They were locked in tiny spaces. They could not escape.
The earth is very hot deep inside. The rock got hotter as it sank deeper. It heated up like an oven.
The trapped bodies felt the heavy pressure. They also felt the baking heat. This combination changed them completely.
The tiny bodies stopped being plants and bugs. They slowly melted into a dark waxy substance. Scientists call this substance kerogen.
Kerogen is the first step in making oil. It is a solid material. It holds all that ancient sun energy tight.
The earth kept pushing the rocks deeper. The temperature kept going up. The oven got much hotter over time.
The temperature reached a magic number. It hit around two hundred degrees Fahrenheit. This is called the oil window.
If the rock stayed too cool then the kerogen did nothing. It just stayed as a solid wax. Nothing would change.
If the rock got too hot then the kerogen burned up. It would turn into dry natural gas. The oil would be lost forever.
Something amazing happened inside the magic oil window. The solid kerogen melted into a thick dark liquid. This liquid is crude oil.
The oil was born deep underground. It was made of carbon and hydrogen. It was packed with ancient trapped sunlight.
The oil did not stay in one place. The heavy rocks above kept pushing down. The earth squeezed the oil like a sponge.
Oil is lighter than water. It always wants to float up. It began a long journey toward the surface of the earth.
The oil moved through the solid rock. Some rocks have tiny holes inside them. These holes are called pores.
Sandstone is a good example. It looks solid but acts like a hard sponge. The oil crept slowly upward through these tiny pores.
The oil traveled for thousands of years. It moved up inch by inch. It tried to reach the open air above.
The oil sometimes made it all the way up. It bubbled out onto the ground. This created sticky black pools on the surface.
But most of the oil hit a wall. It ran into a different kind of rock. This rock had no holes at all.
We call this solid rock a caprock. Salt rock or thick clay makes a good caprock. The oil could not pass through it.
The oil was completely trapped. It gathered under the solid rock roof. A massive underground pool of oil formed in the dark.
The oil waited there for millions of years. Dinosaurs walked on the earth above it. Mountains grew and fell down. The oil stayed hidden.
Fast forward to a few hundred years ago. Humans lived on the earth. We needed energy to run our new machines.
We used wood and coal for a long time. Then we discovered the hidden oil. This liquid held incredible power.
Humans built giant drills. We drilled deep holes into the ground. We punched right through the solid caprock.
The trapped oil was under high pressure. The oil rushed up the pipe when the drill broke through. It burst out of the ground.
Humans figured out how to clean the black oil. We cooked it in huge factories. We turned it into gasoline and plastic.
This ancient energy changed everything. It powered cars and airplanes and giant ships. It made the whole world move faster.
A single gallon of gas holds amazing energy. It takes millions of tiny dead plants to make one drop. It is concentrated ancient sunlight.
You use old energy when you ride in a car. The engine burns the gasoline. It releases the power trapped long ago.
But burning this ancient oil causes a big problem. It releases dirty gases into the air. This gas is called carbon dioxide.
The tiny plants took carbon from the air long ago. They buried it deep underground. We are putting it back into the sky.
This extra gas acts like a warm blanket. It wraps around the earth. It makes our whole planet too hot.
We call this global warming. It changes the weather everywhere. It makes the ice melt and the seas rise up.
We used the earth savings account very fast. We burned millions of years of oil in just one century. We cannot make more oil.
Now humans face a huge challenge. We must find new ways to get energy. We need power from the wind and the sun.
We must leave the rest of the oil in the ground. We have to learn to power our world safely. We must protect our home.
Oil is simply the ghost of ancient oceans. It is buried sunlight that helped humans grow. Now this ancient power threatens our future. We must outgrow it.