1.4: Activity 1C - Earth Cycles

In the Earth System, energy and matter are exchanged by cycles, connections, between the spheres. In this activity we will explore the hydrologic (water) cycle, Wilson cycle, Milankovitch cycles, and biogeochemical cycles like the carbon, nitrogen and sulfur, and phosphorus cycles.

The Hydrologic (Water) Cycle

The hydrologic cycle involves the continuous circulation of water in the Earth-Atmosphere system. At its core, the water cycle is the motion of the water from the ground to the atmosphere and back again. Of the many processes involved in the hydrologic cycle, the most important are, evaporation, transpiration, condensation, precipitation, and runoff.

Figure 1.4: Earth's water is always in movement, and the natural water cycle (hydrologic cycle), describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye or over millions of years.

Movement of the tectonic plates through time to rift continents. This cycle initiates with a continental rift which breaks up a continent, and leads to the formation of an ocean basin between two lithospheric plates.

Figure 1.5: An overview of the Wilson Cycle. Movement of the tectonic plates through time to rift continents. This cycle initiates with a continental rift which breaks up a continent and leads to the formation of an ocean basin between two lithospheric plates.

Milankovitch Cycles

Milankovitch cycles are related to Earth’s place in space, sometimes referred to as the exosphere. The shape of Earth's orbit (eccentricity), angle Earth's axis is tilted with respect to Earth's orbital plane (obliquity), and the direction Earth's axis of rotation is pointed (precession).

Figure 1.6: Milankovitch cycles, including the 1) shape of Earth’s orbit, known as eccentricity; 2) angle Earth’s axis is tilted with respect to Earth’s orbital plane, known as obliquity; and 3) direction Earth’s axis of rotation is pointed, known as precession.

Biogeochemical Cycles

A biogeochemical cycle is a pathway by which a chemical substance moves through biotic (biosphere) and abiotic (geosphere, atmosphere, and hydrosphere) compartments of Earth. These cycles include the carbon, nitrogen and sulfur, and phosphorus cycles.

Carbon Cycle

Figure 1.7: An overview of Earth's carbon reservoirs and the pathways between those reservoirs.

Nitrogen Cycle

Figure 1.8: An overview of Earth's nitrogen reservoirs and the pathways between those reservoirs.

Sulfur Cycle

Figure 1.9: An overview of Earth's biogeochemical cycling of sulfur.

Phosphorus Cycle

Figure 1.10: An overview of Earth's phosphorus reservoirs and the pathways between those reservoirs.

Activity:

1. Select a cycle from those listed above. Search the internet for information regarding your cycle.

a. Which spheres do you think your cycle connects?

b. How do you think this cycle is important to geology?

Attributions

• Figure 1.4: “The Water Cycle” (Public Domain; Howard Perlman and John Evans, USGS)
• Figure 1.5: Derivative of “Rock Cycle in Wilson Cycle” (CC-BY-SA 4.0; Fabirichter via Wikimedia Commons) by Chloe Branciforte.
• Figure 1.6: “Milankovitch Cycles and Their Role in Earth's Climate” (Public Domain; NASA/JPL-Caltech)
• Figure 1.7: “Carbon in Deep Earth” (CC-BY-SA 4.0; Mice of Mu via Wikimedia Commons)
• Figure 1.8: “Nitrogen Cycle” (Public Domain; EPA)

• Figure 1.9: “Sulfur Cycle” (CC-BY-SA 4.0; GeoscienceHd via Wikimedia Commons)
• Figure 1.10: “Phosphorus Cycle”; (CC-BY-SA 3.0; Bonniemf via Wikimedia Commons)