Question

Describe two ways in which the biosphere has influenced the composition of Earth’s crust.

Short answer

Example 1: In a process known as photosynthesis, simple algae turned ${\mathrm{CO}}_2$and ${\mathrm{H}}_2\mathrm{O}$into organic compounds and ${\mathrm{O}}_2$. The oxygen content of the atmosphere increased.

Example 2: Organic carbon locked in subterranean deposits (in the form of ancient plants and animals) degraded into coal and petroleum.

Step-by-step solution

Biosphere

The biosphere is a worldwide ecosystem made up of living species (biota) and non-living (abiotic) components that give energy and nutrients to them.

Explanation

Solid, liquid, and gaseous, or lithosphere, hydrosphere, and atmosphere, make up the Earth's crust. The term "biosphere" refers to all life systems that have ever existed on the planet. The crust's composition was naturally influenced by the evolution of the biosphere.

Example 1: First organisms appeared $500$million years after the formation of rocks and the filling of ocean basins with water. Within a billion years, those creatures evolved into basic algae capable of obtaining metabolic energy from photosynthesis by converting ${\mathrm{CO}}_2$and ${\mathrm{H}}_2\mathrm{O}$into organic compounds and oxygen. Oxidation became the dominant source of free energy in the crust and biosphere as the atmosphere became richer in ${\mathrm{O}}_2$.

Example 2: As the Earth's crust evolved, a large amount of organic carbon was "locked" in subsurface deposits. The compounds began to decompose when they were buried deeply, in the absence of oxygen, and at high pressure and temperature—ancient vegetation became coal, and animals buried in the same conditions became petroleum.