Fossil Fuels
<p>The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.<sup id="cite_ref-2" class="reference"><a href="https://en.wikipedia.org/wiki/Fossil_fuel#cite_note-2">[2]</a></sup> Fossil fuels contain high percentages of <a href="https://en.wikipedia.org/wiki/Carbon" title="Carbon">carbon</a> and include <a href="https://en.wikipedia.org/wiki/Petroleum" title="Petroleum">petroleum</a>, <a href="https://en.wikipedia.org/wiki/Coal" title="Coal">coal</a>, and <a href="https://en.wikipedia.org/wiki/Natural_gas" title="Natural gas">natural gas</a>.<sup id="cite_ref-3" class="reference"><a href="https://en.wikipedia.org/wiki/Fossil_fuel#cite_note-3">[3]</a></sup> Other commonly used derivatives include <a href="https://en.wikipedia.org/wiki/Kerosene" title="Kerosene">kerosene</a> and <a href="https://en.wikipedia.org/wiki/Propane" title="Propane">propane</a>. Fossil fuels range from <a href="https://en.wikipedia.org/wiki/Volatility_%28chemistry%29" title="Volatility (chemistry)">volatile</a> materials with low <a href="https://en.wikipedia.org/wiki/Carbon" title="Carbon">carbon</a>:<a href="https://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">hydrogen</a> ratios like <a href="https://en.wikipedia.org/wiki/Methane" title="Methane">methane</a>, to liquids like petroleum, to nonvolatile materials composed of almost pure carbon, like <a href="https://en.wikipedia.org/wiki/Anthracite" title="Anthracite">anthracite</a> coal. Methane can be found in <a href="https://en.wikipedia.org/wiki/Hydrocarbon" title="Hydrocarbon">hydrocarbon</a> fields either alone, associated with <a href="https://en.wikipedia.org/wiki/Oil_field" title="Oil field">oil</a>, or in the form of <a href="https://en.wikipedia.org/wiki/Methane_clathrates" class="mw-redirect" title="Methane clathrates">methane clathrates</a>.
The theory that fossil fuels formed from the <a href="https://en.wikipedia.org/wiki/Fossil" title="Fossil">fossilized remains</a> of dead plants<sup id="cite_ref-4" class="reference"><a href="https://en.wikipedia.org/wiki/Fossil_fuel#cite_note-4">[4]</a></sup> by exposure to heat and pressure in the Earth's crust over millions of years<sup id="cite_ref-5" class="reference"><a href="https://en.wikipedia.org/wiki/Fossil_fuel#cite_note-5">[5]</a></sup> was first introduced by <a href="https://en.wikipedia.org/wiki/Georgius_Agricola" title="Georgius Agricola">Georgius Agricola</a> in 1556 and later by <a href="https://en.wikipedia.org/wiki/Mikhail_Lomonosov" title="Mikhail Lomonosov">Mikhail Lomonosov</a> in the 18th century.</p>