Fossil Fuel Formation

How fossil fuels were formed:

<span class='figure-reader-id'>Stage 1</span> During the Paleozoic (pay-lee-ah-ZOE-ik) Era, which lasted from about 540 million years ago to about 250 million years ago, land that included North Dakota was covered by shallow seas. <span class='figure-reader-id'>Stage 2</span> Plant life grew along the edges of the seas, and the first forests appeared. The first four-legged animals also developed during this time. As algae, plankton and other organisms died, they accumulated in the sediment at the bottom of the sea. <span class='figure-reader-id'>Stage 3</span> Each time the seas would recede (go back), decayed matter from the living things would be left behind. <span class='figure-reader-id'>Stage 3</span> Each time the seas would recede (go back), decayed matter from the living things would be left behind. <span class='figure-reader-id'>Stage 3</span> Each time the seas would recede (go back), decayed matter from the living things would be left behind. <span class='figure-reader-id'>Stage 3</span> Each time the seas would recede (go back), decayed matter from the living things would be left behind. <span class='figure-reader-id'>Stage 4</span> Over millions of years, layer after layer of decayed plant and animal matter built up. <span class='figure-reader-id'>Stage 4</span> Over millions of years, layer after layer of decayed plant and animal matter built up. <span class='figure-reader-id'>Stage 5</span> Fast-flowing rivers carried and deposited sand, silt, and clay into the area. <br /> These sediments (small pieces of rock and dirt carried by water) were also piled into layers. <span class='figure-reader-id'>Stage 6</span> The pieces of sediment were pressed together and formed sedimentary (sed-ah-MEN-ter-ee) rocks. <span class='figure-reader-id'>Stage 6</span> The pieces of sediment were pressed together and formed sedimentary (sed-ah-MEN-ter-ee) rocks. <span class='figure-reader-id'>Stage 7</span> As decayed plants and animals became trapped in the sedimentary layers, heat and the weight of the sediments pressed them into material, which millions of years later became fossil fuels (petroleum, natural gas, and coal).
  
 
  • Petroleum and natural gas were created from very tiny plants and animals that had lived in oceans, or seas. Coal formed from plants that grew on land.
    • Hundreds to thousands of feet of earth continued to cover the dead plants and animals over the millions of years when the seas kept advancing and receding.
    • Even after the seas were gone, weight from the layers above continued to press down.
      • Heat and pressure "cooked" the organic materials into the liquid called petroleum.
      • The enormous weight and pressure together with very high heat created natural gas.

 

  • The rocks that contain coal in our area were formed millions of years later than the rocks that contain petroleum and natural gas.